mildenhall hub heat network opportunities · mildenhall hub heat network opportunities ramboll 40...

Intended for

West Suffolk Partnership

Document type

Final Report

Date

May 2016

MILDENHALL HUB HEAT NETWORK

OPPORTUNITIES

MILDENHALL HUB

HEAT NETWORK OPPORTUNITIES

Ramboll

40 Queen Square

Bristol BS1 4QP

T +44 (0)117 929 5200(0)117 929 5200

F +44 (0)117 929 523944 (0)845 299

1610

Revision 3

Date 16/05/2016

Made by Sophie Cator and Gemma Giribet

Checked by Robin Glendinning

Approved by Anthony Riddle

Description Report

Ref 1620001100

Document ID 581652-1 / WSHNO-14-001

Version 3

Heat Network Opportunities

CONTENTS

Glossary 1 Executive Summary 3 1. Introduction and Background 1 1.1.1 Objectives 2 1.1.2 Strategic Background and Policy 2 1.1.3 Previous Work Undertaken 3 2. Energy Demand Mapping 5 2.1 The Study Area 6 2.2 Heat Demand 7 2.2.1 Methodology 7 2.2.2 Existing Buildings 9 2.2.2.1 Town Centre 9 2.2.2.2 Industrial Estate 9 2.2.3 New Development 11 2.2.3.1 Mildenhall Hub Site 11 2.2.3.2 Other Planned Developments 12 2.2.4 Heat Demand Summary 14 2.3 Cooling Demand 17 2.3.1 Methodology 17 2.3.2 Cooling Demand Summary 17 2.4 Power Demand 19 2.4.1 Methodology 19 2.4.2 Existing Buildings 19 2.4.3 Mildenhall Hub 20 2.4.4 Electricity Demand Summary 20 3. Energy Supply Opportunities 22 3.1 Existing Supply Assets 22 3.2 Future Supply Assets 23 3.3 Potential Supply Assets 23 3.3.1 Gas CHP 25 3.3.2 Biomass 25 3.3.3 Absorption Chillers 26 3.3.4 Solar Thermal Panels 26 3.3.5 Industrial Heat Recovery Using Heat Pumps 27 3.3.6 Water Source Heat Pumps 27 3.3.7 Energy Centre Options 28 4. Heat Network Opportunity Appraisal 31 4.1 Identification of Opportunity Areas 31 4.1.1 Heat 31 4.2 Heat Network Routing Strategy 33 4.3 List of Identified Opportunities 35 4.4 Opportunity Appraisal 36 4.4.1 Mildenhall Hub 38 4.4.2 Northern Light Industrial Area 39 4.4.3 Mildenhall Hub with Extension to Light Industrial Area 41 4.4.4 Summary 42 5. Energy Masterplanning for Preferred Opportunities 43 5.1 Energy Demand Assumptions 44 5.1.1 Mildenhall Hub Concept Design Alterations 44 5.1.2 Heat Demand Assessment 45


5.1.3 Electricity Demand Assessment 47 5.1.4 Project Phasing 47 5.2 Energy Supply Assumptions 48 5.2.1 Overview of General Assumptions for All Scenarios 48 5.2.2 Solar PV 50 5.2.3 Gas CHP 51 5.2.4 Biomass Boiler 53 5.2.5 Water Source Heat Pump 55 5.2.6 Solar Thermal 57 5.2.7 Ground Source Heat Pump 59 5.3 Modelling Results 61 5.3.1 Results without Solar PV 61 5.3.1.1 Economics 61 5.3.1.2 Carbon 62 5.3.2 Results with Solar PV 63 5.3.2.1 Economics 63 5.3.2.2 Carbon 63 5.3.3 Sensitivity Analysis 65 5.3.4 Summary of Modelling Results 69 6. Project Outline RisK assessment 70 6.1 Technical Risks 70 6.2 Commercial Risks 71 6.3 Financial Risks 72 6.4 Planning Risks 73 6.5 Risk Register 74 7. Conclusions, Recommendations and Next Steps 75 7.1 Conclusions 75 7.2 Recommendations 76 7.3 Next Steps 76 7.3.1 Business Model and Business Case 76 7.3.2 Ensuring Correct Design Standards are adopted 76 7.3.3 Safeguarding Wider Network Demand 76 7.4 Summary Implementation Plan 77

TABLES

Table 1: Contents of Report Sections ......................................................... 2 Table 2: Benchmarks Used for Mildenhall Hub and other New Development

Sites ..................................................................................................... 8 Table 3: Expected Floor Areas for Mildenhall Hub (Autumn 2015) ................ 11 Table 4: Planning Applications Considered within the Heat Map ................... 12 Table 5: Summary of Key Figures of Planning Applications .......................... 12 Table 6: Heat Demand for New Developments ........................................... 12 Table 7: Mildenhall Heat Demand summary .............................................. 14 Table 8: Mildenhall Cooling Demand ......................................................... 17 Table 9: Summary of Existing Power Demands .......................................... 19 Table 10: Estimated Annual Power Demand for the Mildenhall Hub .............. 20 Table 11: Extract from Technology Options Appraisal ................................. 24 Table 12: RHI Support for Biomass .......................................................... 25 Table 13: Energy Centre Locations Appraisal ............................................. 29 Table 14: List of Identified Opportunities .................................................. 35 Table 15: Common Assumptions for Opportunity Models ............................. 37


Table 16: Key Metrics for Opportunity MH001 to MH005 ............................. 38 Table 17: Key Metrics for Opportunity MH006 to MH007 ............................. 40 Table 18: Key Metrics for Opportunity MH008 to MH009 ............................. 41 Table 19: Options Appraisal Summary ...................................................... 42 Table 20: Floor Areas per Building for Mildenhall Hub ................................. 44 Table 21: Key CHP Parameters ................................................................ 51 Table 22: Capital Costs for CHP Option ..................................................... 51 Table 23: Key Biomass Boiler Parameters ................................................. 53 Table 24: Capital Costs for Biomass Option ............................................... 54 Table 25: Key WSHP Parameters ............................................................. 55 Table 26: Capital Costs for WSHP Option .................................................. 56 Table 27: Solar Thermal Case Key Parameters .......................................... 57 Table 28: Capital Costs for Solar Thermal Option ....................................... 58 Table 29: GSHP Option Key Parameters .................................................... 60 Table 30: Capital Costs for GSHP Option ................................................... 60 Table 31: Summary of Economic Results .................................................. 61 Table 32: NPVs at 6% and 10% Discount Rates ......................................... 61 Table 33: Carbon Savings for Mildenhall Energy Supply Options .................. 62 Table 34: Summary of Economic Results with PV ....................................... 63 Table 35: NPVs at 6% and 10% Discount Rates ......................................... 63 Table 36: Carbon Savings for Mildenhall Energy Supply Options .................. 63 Table 37: Sensitivity of Schemes to RHI Reduction .................................... 65 Table 38: Sensitivity of Economics to Leisure Centre Heat Sale Price ............ 68 Table 39: Risk Register for Mildenhall Hub ................................................ 74

FIGURES

Figure 1: Two Study Areas Considered for Heat Network Opportunities .......... 1 Figure 2 Network Route Diagram from 2013 Feasibility Study ....................... 4 Figure 3: Mildenhall Hub Site and Study Area ............................................. 6 Figure 4: Screenshot of Local Authority Billing Data .................................... 7 Figure 5: Photograph from Mildenhall Industrial Estate (taken during Ramboll

site visit) ............................................................................................... 9 Figure 6: Concept Diagram for Mildenhall Hub ........................................... 11 Figure 7: Estimated Heat Demand for Planned Developments ...................... 13 Figure 8: Estimated Heat Demands for Mildenhall Hub ................................ 15 Figure 9: Estimated Heat Demands within the Study Area ........................... 15 Figure 10: Mildenhall Heat Demand .......................................................... 16 Figure 11: Estimated Cooling Demand of Mildenhall Study Area ................... 18 Figure 12: Mildenhall Hub Estimated Electricity Demand ............................. 20 Figure 13: Mildenhall Hub Power Demand Estimate .................................... 21 Figure 14: Screenshot from DECC Public Database ..................................... 23 Figure 15: Environment Agency Air Pollution Map of Mildenhall .................... 27 Figure 16: River Lark Heat Capacity (courtesy of DECC National Heat Map) ... 28 Figure 17: Council Owned Land in Mildenhall ............................................. 30 Figure 18: Image of Mildenhall High Street (courtesy of Google Maps) ......... 31 Figure 19: Image of the light-industrial area (taken by Ramboll during a site

visit). ................................................................................................... 32 Figure 20: Extracts from Network Route Analysis ....................................... 33 Figure 21: MH001 Opportunity Boundary .................................................. 38 Figure 22: MH007 Industrial Area Opportunity ........................................... 39 Figure 23: MH008 Opportunity Area ......................................................... 41 Figure 24: Indicative Design Option for Mildenhall Hub ............................... 44 Figure 25: Annual Heat Demand by Building Type ...................................... 45


Figure 26: EnergyPRO Annual Heat Demand Profile for Mildenhall Hub.......... 46 Figure 27: EnergyPRO Weekly Heat Demand Profile (Jan) ........................... 46 Figure 28: Predicted Daily Electricity Profile for Mildenhall Hub .................... 47 Figure 29: Solar Irradiation Data for Mildenhall .......................................... 50 Figure 30: Example Weekly Profile of Supply Asset Contributions ................. 51 Figure 31: Contribution of Supply Assets to Heat Demand for Biomass Option

........................................................................................................... 53 Figure 32: Photographs of the River Lark (courtesy of Ramboll) ................... 55 Figure 33: Contribution of Supply Assets to Heat Demand for WSHP Option .. 56 Figure 34: Contribution of Solar Thermal Supply Assets to Heat Demand in

Summer ............................................................................................... 57 Figure 35: Contribution of Solar Thermal Supply Assets to Heat Demand in

Winter .................................................................................................. 58 Figure 36: Screenshot from UK Soilscapes Map ......................................... 59 Figure 37: Contribution of Supply Assets to Heat Demand for GSHP Option ... 60 Figure 38: Effect of Removing RHI from Project Cash Flow .......................... 65 Figure 39: Graph of 25 year IRR Varying with Cost of Heat ......................... 66 Figure 40: Graph of 40 year IRR Varying with Cost of Heat ......................... 66 Figure 41: Effect of Varying Capital Costs on Project 25 year IRRs ............... 67 Figure 42: Effect of Varying Capital Costs on Project 40 year IRRs ............... 67

APPENDICES

Appendix 1 Energy Demand Map Data

Appendix 2 Technology Options Appraisal


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GLOSSARY

AQMA Air Quality Management Area

Barg Gauge Pressure Unit (bar)

BaU Business as Usual

BGS British Geological Survey

CAPEX Capital Expenditure

CEVAP Church of England Voluntary Primary School

CHP Combined Heat and Power

CHPA Combined Heat and Power Association

CHPQA Quality Assurance Scheme for Combined Heat and Power

CIBSE Chartered Institution of Building Services Engineers

Coolth Cooling delivered by chilled water loop

CoP Coefficient of Performance

CoP Coefficient of Performance

DECC Department of Energy and Climate Change

DEFRA Department for Environment, Food and Rural Affairs

Delta T The temperature difference between water flowing in the flow and return

sections of the network.

DHN District Heating Network

DNO Distribution Network Operators

EMP Energy Masterplan

ERF Energy Recovery Facility

ESCo Energy Services Company

FHDCLP Forest Heath District Council Local Plan

FiT Feed-In Tariffs

GFA Gross floor area

GIS Geographical Information System

GSHP Ground Source Heat Pump

GWh Gigawatt hour

HIU Heat Interface Unit

HNDU Heat Network Delivery Unit

HRSG Heat Recovery Steam Generator

HTHW High Temperature Hot Water

IES-VE Integrated Environmental Studies - Virtual Environment

IRR Internal Rate of Return

kWth Kilowatts (thermal)

LECs Levy Exemption Certificates

LLPG Local Land and Property Gazetteer

LTHG Low temperature heat generators

LTHS Low Temperature Heating System

LTHW Low Temperature Hot Water

MTHW Medium Temperature Hot Water

MWe Megawatts (electrical)

MWh Megawatt hour

MWth Megawatts (thermal)

NA Not Applicable

NHM National Heat Map

NPV Net Present Value

O&M Operation & Maintenance

OCGT Open Cycle Gas Turbine

OFGEM Office of Gas and Electricity Markets


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OPEX Operational Expenditure

PSV2 Public Service Village 2

PV Photovoltaic

REPEX Reinvestment Expenditure

RHI Renewable Heat Incentive

SAP Standard Assessment Procedure

SBEM Simplified Building Energy Model

WRAP The Waste and Resources Action Programme

WSHP Water Source Heat Pump


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EXECUTIVE SUMMARY

Ramboll was commissioned by St

Edmundsbury Council and Forest Heath

District Council, hereafter known together as

West Suffolk, to complete a study into the

opportunity for heat networks and

decentralised low carbon energy at two

locations.

The two study areas are the Mildenhall Hub

site in Mildenhall and the Public Service

Village 2 (PSV2) site in Bury St Edmunds.

This report was prepared on behalf of Forest

Heath District Council and presents the

results from the study into the Mildenhall

Hub.

RECOMMENDATIONS AND

CONCLUSIONS OF WORK UNDERTAKEN

There is opportunity to supply the various

areas within the proposed Mildenhall Hub

from a lower carbon technology than natural

gas boilers. However, there is not currently

any potential for a district heating network

extending from the Mildenhall Hub. This is

primarily due to low existing heat demand

density in Mildenhall and a lack of plans for

substantial new development.

Analysis was conducted to assess the

potential for a standalone heat network

within the Mildenhall industrial estate. The

project economics were found to be

extremely poor and therefore it was not

considered as an opportunity.

The analysis showed that ground source

heat pump (GSHP), combined heat and

power (CHP) and biomass could be suitable

primary supply technologies for the

Mildenhall Hub.

In order for a scheme to be considered

viable under public sector leadership, the

lowest hurdle IRR was set at 4%.

The GSHP scenario generates attractive

economic results with the IRR over 25 and

40 years estimated to exceed 14%.

However, the scheme’s feasibility would be

heavily affected by any changes to the

current RHI tariffs.

Gas CHP also returned attractive economic

results, with IRRs estimated at 11% for both

25 and 40 year project lifetimes. This

technology benefits from not being

dependent on RHI, but it exhibits a high

sensitivity to heat sale price.

The biomass case is likely to deliver

significant CO2 savings. However the

economic results show that this solution may

only be attractive for a public led project.

It is recommended that these three options

are considered in more detail at feasibility

stage. It is essential that further information

regarding the energy demands of the

Mildenhall Hub is made available before this

takes place.

ENERGY MAPPING AND ASSESSMENT OF

SUPPLY ASSETS

The first phase of the work was to map the

major heat, cooling and electricity demands

of the Mildenhall Hub and surrounding areas.

Three major clusters of energy demand were

identified at the Mildenhall Hub, northern

light industrial area and town centre. These

areas presented the greatest opportunity for

district heating or cooling.

No existing assets were identified that might

be able to supply energy into a network. A

The purpose of this study was to

establish opportunities for district

heating in Mildenhall and to

determine the most appropriate

primary supply technology for the

Mildenhall Hub development.

The work consisted of energy

mapping, opportunity

identification and techno-

economic analysis of the preferred

opportunity.


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technology options appraisal was carried out

in order to present a shortlist of energy

supply technologies that would be suitable

for the scale of demand and environmental

conditions in Mildenhall.

The technologies considered appropriate for

inclusion in the next project phase were gas

CHP, heat-only biomass, water-source heat

pumps (WSHP), GSHPs and solar thermal

panels.

IDENTIFIED OPPORTUNITIES

The process of opportunity identification

involved a combination of qualitative and

quantitative factors including:

energy demand density

proximity to identified supply assets

number of public buildings

potential anchor loads

barriers to construction

Once opportunities were identified, possible

heat network routes were assessed.

Nine heat network opportunities were

identified for high level modelling.

Project

Ref. Project Name

Estimated

25 yr IRR

MH001 Mildenhall Hub Gas

CHP 15%

MH002 Mildenhall Hub

Biomass 9%


WSHP 6%


Solar Thermal 9%


GSHP 7%

MH006 Mildenhall Industrial

Area CHP NA

MH007 Mildenhall Industrial

Area Gas Biomass -9%

MH008 Mildenhall Hub +

Industrial Area NA

MH009 Mildenhall Hub +

Industrial Area -6%

The project key performance indicators

(KPIs) of the opportunities were presented

to West Suffolk for comment and to confirm

Ramboll’s recommendations for preferred

opportunities.

Following the initial opportunities appraisal,

five opportunities were selected for further

analysis. Each opportunity features the

same heat load, but with different supply

technologies. The opportunities are listed as

follows:

1. MH001 Mildenhall Hub supplied by gas

CHP

2. MH002 Mildenhall Hub supplied by

biomass boilers

3. MH003 Hub supplied by a WSHP

4. MH005 Hub supplied by solar thermal

panels

5. MH006 Hub supplied by a GSHP

TECHNO-ECONOMIC ASSESSMENT OF

PREFERRED OPPORTUNITY

The first stage in the techno-economic

modelling process was to re-evaluate the

energy demand assessment based on up to

date information.

Following this, energy profiles were created

using EnergyPRO software which enabled

the sizing of various technology options. An

economic assessment was then undertaken

to determine the performance of each of the

supply options. The results of this

assessment are shown below

Supply

Technology

Estimated

25 yr IRR

Estimated 25

yr NPV

Gas CHP 11% £250,100

Biomass 9% £376,700

WSHP 5% £133,800

Solar

Thermal

NA -£555,400

GSHP 14% £997,500

At the request of Forest Heath District

Council, each of the scenarios was modelled

with the addition of a solar PV array to the

project energy flows and economics.

The results of the study were as follows:


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Supply

Technology

Estimated

25 yr IRR

Estimated 25

yr NPV

Gas CHP 10% £361,900

Biomass 10% £569,800

WSHP 6% £336,800

GSHP 14% £1,171,400

The integration of a Solar PV installation was

found to result in improvements both in

terms of economics and carbon emissions

savings for CHP, biomass, WSHP and GSHP

scenarios.

A sensitivity analysis was carried out to

assess the impact any changes of key

parameters on the economics of each

option.

Without the revenue from the RHI, the

WSHP and biomass projects are no longer

viable. The IRR of the GSHP reduces

significantly and the economics are unlikely

to be attractive except for a public led

scheme. The CHP scheme is not affected by

RHI.

The CHP, biomass and WSHP scenarios were

found to be very sensitive to the heat sale

price when compared to the GSHP option.

In a similar way to the heat sale prices,

changes in project CAPEX reduce the IRRs

for the WSHP scenario to an unattractive

level. However the CHP, biomass and GSHP

scenarios appear to remain feasible even

with a 20% cost increase.

RISK ASSESSMENT

An outline risk assessment was undertaken

for the preferred project opportunities. A

number of key risks were identified;

Accuracy of heat demand data

Hub heating system design

Ground conditions

Properties of the River Lark (WSHP

option only)

Operating costs higher than expected

These risks will require further consideration

during the next phase of the project

NEXT STEPS

Based on the conclusions and

recommendations of the study, a number of

next steps can be identified as follows:

1. West Suffolk to present the results of the

study to council members to ensure

support for the proposed low carbon

solution and to raise awareness of the

project.

2. A full business case should be produced

following a detailed feasibility exercise

once there is more certainty regarding

the design of the Hub.

3. The results of the study must be

provided to the Mildenhall Hub Design

Team to enable them to incorporate it

into the designs and adopt appropriate

heating systems.


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1. INTRODUCTION AND BACKGROUND

Ramboll was commissioned by St Edmundsbury Council and Forest Heath District Council,

hereafter as West Suffolk, to complete a study into the opportunity for heat networks and

decentralised low carbon energy at two locations.

West Suffolk is planning work with other public sector organisations to bring together a number

of public services, such as council offices, education and leisure, within the towns of Mildenhall

and Bury St Edmunds onto single sites. The two study areas are:

Mildenhall Hub site in the town of Mildenhall. This development will be led by Forest Heath

District Council

Public Service Village 2 (PSV2) site in the town of Bury St Edmunds. This development

will be led by St Edmundsbury Borough Council.

Figure 1: Two Study Areas Considered for Heat Network Opportunities

This report presents the results from the study into the Mildenhall Hub.


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1.1.1 Objectives

The aims of the study were set out in the invitation to quote as:

to identify and evaluate the feasibility of options for on-site low carbon heat and

power

to explore preferred options to gain support by key stakeholders

to establish the outline financial cases to take forward preferred options to the next

stage of wider project development

These objectives were maintained throughout the course of the work.

The report comprises the following sections:

No. Section Title Contents

2 Energy Demand Mapping An overview of energy demands within the study

area and mapping outputs. A summary of the

methodology.

3 Energy Supply Mapping An overview of existing, future and potential energy

supply assets within the study area and technology

options appraisal.

4 Heat Network Opportunity

Appraisal

A high level review of potential decentralised energy

opportunities including key metrics for each possible

scheme.

5 Energy Masterplanning for

Preferred Opportunity

A techno-economic assessment of the preferred heat

network opportunity.

6 Project Outline Risk assessment A risk register for the project to date, including

potential mitigation measures.

7 Conclusions, Recommendations

and Next Steps

A series of conclusions and recommended actions

following the results of the study.

Table 1: Contents of Report Sections

1.1.2 Strategic Background and Policy

Heat networks projects can be highly complex to deliver due to many interrelated commercial,

financial, technical and planning factors including:

1. inherent economic value and commercial risk 2. complexity of stakeholder relationships/appetites for involvement 3. councils capacity and appetite for involvement as a delivery partner and in some cases

conflicting commercial and strategic objectives for proposed projects

4. strength of local planning policy

Successful delivery through to procurement will require a scheme that is aligned to the Council’s

drivers, aspirations and capacity, and ability to deliver. It must be financially viable and

deliverable under the preferred delivery model as well as being attractive to a range of

stakeholders including developments, existing key anchor load and potential delivery partners.

The councils of St Edmundsbury and Forest Heath have created the partnership, West Suffolk, to

deliver effective development to a high standard of sustainable design. At the time of writing,


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measures had already been taken in the form of two previous studies, one of which was

conducted by Ramboll in 2013.

The successful bid to the Heat Network Delivery Unit (HNDU) demonstrates the will of the councils to implement successful district heating schemes and meet their objectives for sustainable development. HNDU can support the Councils from heat mapping through to detailed project development.

The West Suffolk Strategic Plan 2014-2016 provides an indication of the main motivators for the Councils. District heating is relevant to two out of three of the priorities set out in the document:

The promotion of energy efficiency measures is one of the actions listed to achieve Priority 1

– Increased Opportunities for Economic Growth.

Alleviation of fuel poverty is encompassed in Priority 3 – Homes for Our Communities, which

can often be achieved through district heating schemes.

In addition to the Strategic Plan priorities, the West Suffolk Sustainability Strategy (Dec 2013) sets out the range of issues which the councils wish to influence at a local level through appropriate use of services.

A mixture of technical and social issues is identified in the Sustainability Strategy. The desire to contribute to the carbon reduction target of a 60% reduction in CO2 against the 2004 baseline can be assisted through use of district heating and cooling. We propose to refer back to this target when reporting the potential CO2 savings of opportunities identified in the

energy masterplanning exercise. Social issues are also identified; primarily the problem around fuel poverty and the need for affordable warmth. It is proposed that reductions in the business as usual heat prices will be incorporated into the study to demonstrate economic viability

whilst taking into account affordable energy prices.

Planning policies are recognised by the councils as a tool to present the case for sustainability. Further ways in which planning policies can be used to help progress the identified district heating opportunities are outlined in section 7.

1.1.3 Previous Work Undertaken

In July 2011, St Edmundsbury Borough Council commissioned a report titled ‘Investigating Decentralised Energy in Bury St Edmunds’. The report provided a technical evidence base to support local authority actions and planning policies for decentralised energy. It also provided a technical and financial options appraisal to help inform policy making and investment decisions in decentralised energy (heating, cooling and electricity) projects in Bury St Edmunds and their potential to be delivered to existing and

planned mixed development in the town over the next 20 years. The study did not constitute a complete technical and financial feasibility study; rather it identified which options were worth taking to the next stage. One of the identified options focused on Bury Leisure Centre in Western Way and proposed further investigation around the potential to develop a district heating scheme around anchor loads in close proximity to the Leisure centre.

On the basis of that study, St Edmundsbury Borough Council and its project partners decided to

commission this feasibility study for a decentralised energy scheme based around Bury Leisure

Centre which Ramboll undertook in 2013.


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The objectives of the feasibility study were to evaluate options for a decentralised energy project

opportunity based around Bury Leisure Centre. The brief was to identify an opportunity that was

financially viable, capable of delivering CO2 reductions in line with Suffolk’s targets under its

Creating the Greenest County programme and affordable to the project stakeholders.

Figure 2 Network Route Diagram from 2013 Feasibility Study

The study found that:

A potential case existed whereby Bury Leisure Centre exports heat to a network that is

separately developed by the project stakeholders, but that the margin on buying and selling

of heat for supply into the network was likely to be low, generating low IRR’s for the project

stakeholders.

The economic case for connecting St Edmundsbury CEVAP School and King Edward IV School

to the identified heat network opportunity was poor.

Options for implementing solar PV, biomass heating and solar thermal were worth further

consideration, given that reasonably attractive IRRs were identified.

However, no further investigation was carried out following the study.


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2. ENERGY DEMAND MAPPING

This section provides an overview of heat, cooling and power demand within the study area. The

aim was to produce energy maps and databases suitable for use in identifying and assessing heat

network opportunities in Mildenhall.

As heat supply strategy was the main objective of the study, developing heat maps was the

primary focus of the energy mapping phase of work. Cooling was assessed at high level in order

to identify any opportunities for combined heating and cooling networks. Finally the map of

electricity demand was developed to establish any opportunities for private wiring of electricity

that could be supplied by supply assets such as combined heat and power (CHP) engines or solar

photovoltaic (PV) panels.

To support this phase of works West Suffolk provided the following information:

In Excel format:

National Heat Map (NHM) Data

Gas and electricity billing records for municipal buildings

Local Land and Property Gazetteer (LLPG).

ArcGIS Layers:

Background Mapping – Ordnance Survey MasterMaps,

Planning Application information

Forest Heath District Council Local Plan

Council owned land.

Links to the planning portal were also provided in addition to a number of general background

documents.

The following sections summarise the identified heat, cooling and power demands identified

within the study area.


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2.1 The Study Area

The study considers a 1 km “buffer area” around the Mildenhall Hub site. This was deemed by the

Forest Heath District Council and Ramboll to be an appropriate area to encompass major

opportunities.

Mildenhall Hub aims to concentrate public facilities in one location that are currently scattered

across the town and that are either reaching the end of their lives or are in need of

refurbishment. Converging public services buildings is intended to improve public access, service

delivery and efficiency.

The Mildenhall Hub project is currently under design with Mildenhall College Academy, Forest

Heath District Council, Anglia Community Leisure, Suffolk County Council, Suffolk Police and

Crime Commissioner/Suffolk Constabulary and West Suffolk Clinical Commissioning Group. Other

public services in town such as the library service, are considering taking part of Mildenhall Hub.

The Hub envisions a range of public services working collectively and collaboratively with

communities and sharing spaces.

Figure 3 shows the location of the Mildenhall Hub site and surrounding buffer area. The boundary

includes the town centre and the industrial estate to the north, in addition to potential areas of

new development to the south and east.

Figure 3: Mildenhall Hub Site and Study Area


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2.2 Heat Demand

A heat demand map was created to include existing and planned buildings within Mildenhall Hub

and the buffer area. The sub-sections below outline the methodology used to map the heat

demands for existing buildings, the Mildenhall Hub development and other planned

developments.

2.2.1 Methodology

Due to the fact that the NHM data is defined within these building type categories, multiple

records are often present for within the same building. For example where a shop and dwelling

are present in the same building two records are located in the same building.

Therefore, the information provided by the NHM was aggregated by location; aggregating the

multiple heat demands into a single point and assigning them the category with the highest heat

demand of the building.

It is important to note that the NHM data is likely to be overestimating the industrial heat loads.

This is due to the fact that the buildings often have large floor areas, but only localised heating

which is not reflected in the benchmarks. This is explored further in section 4.

Any records below 100,000 kWh were then filtered out of the heat map. A load below this

threshold would typically have a heat exchanger of the order of 50 kW, which is relatively small

and from experience on other projects loads smaller than this will not in themselves form the

basis for an energy network. These smaller loads could potentially be connected to a network

already under development and depending on the proximity of the network connection they may

serve to improve the project economics. However, designing networks specifically to serve these

loads may reduce the overall economic returns. These smaller connections should be considered

on a case by case basis in the next phase of works.

The Council also provided gas and electricity billing data from 2014/2015 for Local Authority

buildings in Bury St Edmunds, which was included in the heat map. When there were data points

from both the NHM and billing data, the NHM records were replaced.

The gas data was factored using an estimated boiler efficiency of 80%. The figures were degree

day corrected based on the region’s 20-year average in order to take account of annual weather

variations.

Figure 4: Screenshot of Local Authority Billing Data


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Following the inclusion of the billing data an exercise was carried out to estimate the heat

demand of existing buildings that appeared to be of interest, but were not included in the NHM or

billing data. Buildings which may present significant heat demands such as hotels and nursing

homes were identified through a desktop assessment of the study area maps. The heat demand

was estimated using the floor areas extracted from the OS maps and CIBSE benchmarks1.

Three benchmarking methods were applied to estimate the heat demand for the Mildenhall Hub

development:

CIBSE benchmarks for existing buildings were adjusted to take into account the

potential higher energy efficiency of new buildings.

A combination of energy modelling outputs (SAP, SBEM and IES-VE) from Ramboll’s

experience in energy strategies in addition to CIBSE data was used. This was corrected to

reflect expected improvements under future updates to the building regulations.

Benchmarks were formulated to reflect separately 2010 Building Regulations and the

2013 Building Regulations amendments.

The billing data for existing public buildings which are due to be moved to the new

site was assessed to give an indication of the likely requirements of the new buildings.

Reduction in demand due to the improved thermal efficiency of buildings was taken into

account during this exercise.

In a similar way to the proposed Mildenhall Hub buildings, heat demands for other planned

developments within the buffer area were calculated using benchmarks including a combination

of energy modelling outputs (SAP, SBEM and IES-VE) from Ramboll’s experience in energy

strategies in addition to CIBSE data which was corrected to reflect expected improvements under

future updates to the building regulations.

Building Type Energy Demand

(kWh/unit)

Units

Government Buildings 74 sqm

Police 157 sqm

Leisure Centre 141 sqm

Health 93 sqm

Library 60 sqm

Education - primary 60 sqm

Education - academy 58 sqm

Fire Department 206 sqm

Public access 104 sqm

Residential 5,840 House

Residential 3,760 Flat

Commercial Offices 12.3 Sqm

Table 2: Benchmarks Used for Mildenhall Hub and other New Development Sites

A full table of point heat demands is presented as Appendix 1. The sections below outline a

number of key heat load opportunities in further detail.

1 Energy Efficiency in Buildings. CIBSE Guide F


9

2.2.2 Existing Buildings

2.2.2.1 Town Centre

The town centre has a mix of residential building with several small hotels, small shops and some

public buildings. In general terms, the heat loads in Mildenhall, especially in the town centre, are

small and many of them are estimated to be around 100 MWh.

Billing data was available for Mildenhall Swimming Pool, the Forest Heath District Council offices

and Mildenhall Depot. However, these services were intended for relocation to the Hub.

2.2.2.2 Industrial Estate

Based on NHM data, the industrial estate in the north of the town centre appeared to feature high

energy demands per building and a considerable number of buildings exceeding the 100 MWh

threshold.

In order to ascertain the buildings which were likely to have wet heating systems compatible with

DH, Ramboll undertook a visual analysis of the buildings in the area firstly using publicly available

tools such as Google Maps, Google Street View and Bing Maps. Following this a site visit was

undertaken to confirm the conclusions.

The majority of the buildings were observed to be warehouses with small retail frontages, offices

or workshops. It was also noted that the industrial estate was generally low in development

density.

Specific examples of businesses include:

Nestor UK Ltd – Pharmaceutical

Gerda – Manufacturer of fire safety and security products and services.

Electronic Metal Work Services – Manufacture of sheet metal components and assemblies,

powder coat or stove enamelling and silk screen printing,

Mildens Garage – Repairing and maintenance of cars and vans,

English Architectural Glazing – Design and manufacturing cladding packages,

JEB Engineering Design Limited – Provider of individual components through complex

assemblies,

Thoroughbred – Industrial doors,

Complete Office Solutions Ltd. – Office supplies and furniture.

Figure 5: Photograph from Mildenhall Industrial Estate (taken during Ramboll site visit)


10

The analysis of the industrial estate also included identification of the buildings with stacks and,

therefore, the buildings that are likely to feature gas boilers. This assessment is associated with a

margin of error due to the fact that stacks may also be related to process or ventilation systems.

However, it was deemed to be an appropriate starting point for the heat demand assessment.

One particular building of interest within the industrial estate was Witton Chemical Company Ltd.

Their manufacturing site features a range of batch reactors, centrifuges, driers and storage

vessels that are used for the production of a range of chemical types. The heat demands for the

site are served by a steam based system due to the temperature requirements of the processes

undertaken.

It is important to note that, as described in the methodology in section 2.2.1, industrial loads

within the NHM are often found to be overestimated. Therefore as part of the Opportunity

Appraisal conducted in section 4, further investigation was required into the exact businesses

present and the likelihood of them presenting an opportunity for decentralised energy networks.


11

2.2.3 New Development

2.2.3.1 Mildenhall Hub Site

Figure 6 shows the concept drawing provided by the Forest Heath District Council which gave an

indication of floor areas to enable the benchmarking process. This concept layout was based on

the 2014 business plan.

Figure 6: Concept Diagram for Mildenhall Hub

Category Floor Area

(m2)

Government buildings 3,096

Police 306

Leisure Centre 4,075

Health 409

Library 250

Education – primary school 170

Education - academy 0

Fire Department 234

Public access 360

Table 3: Expected Floor Areas for Mildenhall Hub (Autumn 2015)

The total annual heat demand for the site was estimated to be 1,818 MWh. A breakdown by

building function is presented in Table 7.

Following the heat mapping exercise and opportunity analysis (section 4), the concept

diagram was updated and new floor areas were provided in January 2015. This affected the

predicted heat loads.

The new heat demand estimates were not included in this heat mapping section as the

project had progressed to techno-economic modelling stage. However, a revision of the heat

demand was carried out in advance of the techno-economic modelling for preferred

opportunities. This is presented in section 5.1.2.


12

2.2.3.2 Other Planned Developments

Forest Heath District Council Local Plan (FHDCLP) envisions for Mildenhall a town centre with a

broad range of retail and services and plans the allocation of new residential areas to meet the

needs of the local people. Two residential allocations are situated in the north-east limit of the

study area and the Town Centre area close to the Mildenhall Hub.

Figure 7 shows the principal allocations includes in the FHDCLP. The expansion of the industrial

area, recreational space and other community services are also shown.

Four planning applications were found to be of interest within the study area. At the time of

writing three of the applications had been granted whereas the Mildenhall Community Centre was

approved with conditions.

The table below shows the planning applications with significant/major developments that are

located in the Study Area buffer.

Table 4: Planning Applications Considered within the Heat Map

Information was gathered from the planning documents to establish dwelling numbers and floor

areas allocated to each use type within the developments as shown below:

Table 5: Summary of Key Figures of Planning Applications

The benchmarked heat demands are presented in Table 6 and Figure 7.

Table 6: Heat Demand for New Developments

Code Application number

Application Main characteristics

FHDCPA01 F/2012/0531/FUL Approved with conditions

Construction of a new community building (following demolition of existing community building) and erection of 20 dwellings (18 affordable and 2 market rented)

FHDCPA02 DC/14/2320/FUL Granted Erection of 9 No. dwellings and 1 No. B1 office unit

FHDCPA03 DC/13/0927/OUT Granted Residential development of up to 78 dwellings with creation of new vehicular access

FHDCPA04 DC/15/0452/FUL Granted Proposed conversion and alterations to the existing White Hart public House with new build construction to the rear to form 12N o. dwellings for affordable rent

Code Residential

Commercial Offices (m2) Community Centre (m2) No Houses No Flats

FHDCPA01 20 0 0 216

FHDCPA02 8 1 57.8 0

FHDCPA03 78 0 0 0

FHDCPA04 4 8 0 0

Code Residential Heat

(kWh) Commercial Offices

Heat (kWh)

Community Centre Heat

(kWh)

Total Heat (kWh)

FHDCPA01 116,800 0 2,657 119,457

FHDCPA02 50,480 711 0 51,191

FHDCPA03 455,520 0 0 455,520

FHDCPA04 48,404 0 0 48,404


13

Figure 7: Estimated Heat Demand for Planned Developments


14

In addition to the Local Plan and Planning Application information, the RAF Mildenhall site was

also considered to be of interest. The RAF currently operates a station located outside of the

study area to the north. In January 2016 it was announced that operations at RAF Mildenhall

would cease and the site would become available for other uses. It is expected that all military

personnel will have left the site by 2022.

Suggestions have been made for 4,000 new homes and 100,000 m2 of employment land at the

site, which would present a significant opportunity for decentralised energy networks. Although

the project was at too early a stage to consider as part of this report, it is important to note the

plans in the event that it presents an opportunity in future.

2.2.4 Heat Demand Summary

Figure 10 shows the point load heat map for the Mildenhall Hub and surrounding study area. This

includes both existing buildings and heats loads estimated for Mildenhall Hub and the new

development areas.

The mapped heat demand data is presented below in Table 7, Figure 7 and Figure 8.

Building Type Number of Buildings

Sum of Heat Demand (kWh)

Mildenhall Hub

Government Buildings 1 269,700

Recreational 1 679,100

Health 1 449,200

Education 1 12,100

Fire Station 1 56,900

Central Hub 1 44,000

Education (Sixth Form

College) 1 306,700

Rest of Study Area

Commercial Offices 3 1,362,000

Education 3 254,700


Health 3 32,100

Hotels 7 209,100

Industrial 54 13,296,900

Recreational 1 13,700

Residential 2 27,900

Retail 5 631,500

Transport 11 3,589,300

Planning Applications 4 540,600

TOTAL 108 22,700,000

Table 7: Mildenhall Heat Demand summary


15

Figure 8: Estimated Heat Demands for Mildenhall Hub

Figure 9: Estimated Heat Demands within the Study Area

It is again important to note that the NHM data is likely to be overestimating the industrial heat

loads and therefore they were revised at opportunity identifications stage.


16

Figure 10: Mildenhall Heat Demand


17

2.3 Cooling Demand

A cooling demand map was created including existing buildings, the Hub site and other planned

developments for the purpose of identifying the potential for combined heat and cooling

networks.

2.3.1 Methodology

The potential cooling demands of existing buildings was estimated by applying CIBSE cooling

benchmarks to floor areas extracted from the OS map data.

It is important to note that at this stage of energy assessment the cooling map shows the

potential demands based on building type. The existing cooling technology within the buildings is

not taken into consideration, but should be investigated as part of the next project stage.

The buildings located in the light-industrial area north of the town centre were also included in

the cooling benchmarking although only those considered offices were gauged. No other cooling

demands were identified in the area where warehouses and workshops are the most predominant

building types. The benchmarks for these offices are probably overestimated since it is unlikely

that the whole building area is potentially cooled.

The cooling demands of the buildings planned in Mildenhall Hub were estimated by applying

cooling benchmarks to the quoted floor areas as established in the business case. The cooling

benchmarks for new buildings include internal modelling (SAP, SBEM, and IES) and corrected

CIBSE data to reflect expected improvements of the updates to the building regulations.

Cooling demand was estimated for the planned developments identified in section 2.2.3.2. The

calculation methodology was similar to that used for the proposed buildings within the Mildenhall

Hub development, using benchmarks based on floor area, internal modelling and adjusted CIBSE

data. Since it is estimated that residential buildings do not have cooling demands, the new

developments, which are mainly residential developments, do not present cooling demand.

2.3.2 Cooling Demand Summary

Figure 11 shows the mapped cooling demands for Mildenhall Hub and the surrounding study

area.

The summary of the estimated cooling demands for the Mildenhall Hub and, other proposed and

existing buildings within the study area are as follows:

Building Type Number of

Buildings

Sum of Cooling Demand

(kWh)

Government buildings 5 211,133.6

Commercial Offices 35 461,138.6

Mildenhall Hub


Public Access 1 11,160

TOTAL 3,101,115

Table 8: Mildenhall Cooling Demand


18

Figure 11: Estimated Cooling Demand of Mildenhall Study Area


19

2.4 Power Demand

The power demand was considered due to the fact that the site electricity requirement is relevant

to certain low carbon technologies such as CHP, where there is potential for electricity to be

privately wired to buildings.

Private wiring involves the distribution of decentralised generated power to one or a number of

consumers via a privately owned distribution network. Distribution of power via a private wire

does not utilise infrastructure owned by National Grid or distribution network operators (DNOs).

For low voltage power generated by a CHP the electricity demand must be suitably close or the

network losses become significant. This is due to the fact that the conductor (network) losses

which arise from distribution of power are proportional to current and length of the network; for a

fixed voltage, line resistance and therefore conductor losses increase with distance.

Conductor losses can be reduced by decreasing the current. This can be achieved by increasing

the distribution voltage using a step-up transformer or a high voltage generator. However, the

additional capital cost associated with both of these approaches would normally be inhibiting for

small-scale CHP. As a result of this, throughout the analysis it was noted that private wire supply

would only be viable in the immediate vicinity of supply assets.

2.4.1 Methodology

The electricity demand for each building within the hub was estimated using a combination of

Ramboll’s in-house modelling results and CIBSE benchmarks2.

For new developments, in a similar way to the heat demand estimates, when using CIBSE

benchmarks, the electricity was factored down by 35 % to account for improvements to building

standards. This figure was approximated through energy modelling in previous buildings projects.

2.4.2 Existing Buildings

Only the buildings that were taken into account in the heat demand mapping previously (heat

demands higher than 100 MWh) were benchmarked and had their electricity demand estimated.

The higher electricity demands correspond to retail buildings mostly located in the town centre

and near to the Mildenhall Hub site. A summary of the power demands excluding the new

buildings in the Hub within the study area is presented in Table 9.

Building Number of

Buildings

Annual Power

Demand (kWh)

Commercial Offices 35 2,082,190


Health 11 269,700

Hotels 20 730,250

Industrial 18 1,236,390

Nursing homes 2 104,590

Retail 115 15,394,200

Table 9: Summary of Existing Power Demands

2 Energy Efficiency in Buildings. CIBSE Guide F


20

2.4.3 Mildenhall Hub

The estimated power demand for the new Mildenhall Hub site is presented in Table 10.

Building Annual Power Demand

(kWh)

Government buildings 36,117.63

Police 10,465.00

Recreational3 270,136.60

Health 18,154.50

Education 548,476.50

Central Hub 47,624.13

Commercial Offices 930,974.35

Table 10: Estimated Annual Power Demand for the Mildenhall Hub

It should be noted that the mapped demand points are shown further apart than the buildings in

the massing concept diagram in order to make them clearer.

Figure 12: Mildenhall Hub Estimated Electricity Demand

2.4.4 Electricity Demand Summary

Figure 13 shows a map of the estimated annual electricity demands within the study area.

3 Includes library and leisure


21

Figure 13: Mildenhall Hub Power Demand Estimate


22

3. ENERGY SUPPLY OPPORTUNITIES

This section presents the assessment of potential energy supply assets in the study area. The

magnitude of heat and/or electricity available in combination with the location of the supply is

taken into account in the assessment of potential DH opportunities.

The supply assets were considered in three categories:

Existing – operational supply assets

Future - planned supply assets

Potential – opportunities for the creation of new supply assets specifically to supply a

decentralised energy network

A heat supply opportunity database was created which contains information about existing and

future heat supply assets which could potentially feed district heating networks within the study

area. Each supply asset was identified through the use of one or more of the following resources

as part of Ramboll’s desktop research:

DECC High Level Water Source Heat Map

National Heat Map

OFGEM accredited Renewable Obligation sites

DECC CHP development map

WRAP database for ERF’s

Biomass energy centre website

DECC Restats website

Environment Agency website

ADE database of District Heating Installations

Visual Inspection of the area on Bing and Google maps

Reports from previous studies undertaken

Local planning applications

BGS Geothermal mapping

Potential energy supplies were considered through a technology options appraisal, which is

outlined in section 3.3.

3.1 Existing Supply Assets

The investigation into existing supply assets was carried out predominantly using the DECC public

energy supply database and CHP Focus database. The data was filtered to show all installations

within West Suffolk.

In particular, the assets that were of interest would be existing CHP or biomass installations with

the potential for exporting heat. Additionally the presence of water treatment works or landfill

sites may provide opportunities.


23

Figure 14: Screenshot from DECC Public Database

The assessment showed that no existing supply assets are situated within the Mildenhall Hub

study area. Therefore any decentralised energy networks would have to be supplied by future

installations or purpose-built supply assets.

3.2 Future Supply Assets

Through a review of the available data sources and an assessment of planning applications it

became apparent that there are no planned energy supply assets within the study area.

Correspondence with Forest Heath District Council confirmed that there were no available

opportunities at present. Therefore focus was placed on the potential for creation of new supply

assets.

3.3 Potential Supply Assets

This section presents the results of a review of the potential supply technologies that could feed

heat, coolth and or power into the district energy networks. Appropriate technologies have been

identified on the basis of the presence of a suitable resource or clear suitability of a site to a

particular technology.

A full qualitative technology options appraisal was conducted and is presented as a table in

Appendix 2. The list of criteria included in the appraisal included, but was not limited to:

Fuel source and fuel risk

Security of supply

Site requirements

Technology and planning risks

CO2 reduction potential

Transportation

Environmental impacts

Timeframe for delivery

Capital and operational costs

Revenue potential

Overall financial performance and funding opportunities.

Based on the assessment of each of these criteria for a number of supply technologies, a

conclusion was drawn regarding whether the technology should be considered as part of the

opportunity appraisal. A summary of the findings of this assessment is shown in Table 11 below.


24

Technology CO2 Abatement Potential Revenue Potential General

Consider in

Opportunity

Appraisal?

Gas Combined Heat and

Power Plant

Medium as part of technology mix if operating on

Natural Gas.

Heat and power sales Low risk, well proven technology at the scale of

the project. Reasonable financial performance

expected.

Yes

Dual fuel boiler Low Heat sales only Low risk and low cost, but low carbon reduction

potential.

No

Biomass heating High on individual technology basis. Medium as

part of technology mix.

Heat sales and RHI Reasonable financial performance expected.

Low risk technology as long as fuel supply is

secured.

Yes

Biomass CHP Steam

cycle

High Heat and power sales and RHI Not considered commercially viable at this

scale.

No

Organic Rankine Cycle High Heat and power sales and RHI Marginal financial performance at this scale. No

Gasification CHP High Heat and power sales and RHI Technology not established at this scale. No

Anaerobic Digestion

with CHP

High on individual technology basis. Medium as


FiT(<5MW), RHI, heat and power

sales

Unlikely to be commercially viable at this scale. No

Waste Incineration CHP High Heat and power sales and RHI Not an appropriate scale for the site. No

Bio liquid CHP High on individual technology basis. Medium as


Heat and power sales High fuel prices reduce economic viability. No

Absorption chiller Carbon emissions savings are sensitive depending

on the fuel source of the heat production

Coolth sales Requires low cost heat to be financially viable. Yes

Solar Thermal Panels High Heat sales and RHI Reasonable payback expected. Large area

required.

Yes

Ground Source Heat

Pump/Heat Store

Medium - as part of site wide heat network Heat sales and RHI Reasonable payback expected but can only

deliver low grade heat.

Yes

Water source heat

pumps

Medium - as part of site wide heat network Heat sales and RHI Reasonable paybacks expected. Nearby source

has been identified.

Yes

Air source heat pumps Medium - as part of site wide heat network Heat sales and RHI Poor payback expected. No

Industrial heat recovery Medium to high - as part of site wide heat network Heat sales and RHI Good payback if suitable source identified. Yes

Deep geo borehole Medium Heat and power sales and RHI Not suitable at this scale. No

Table 11: Extract from Technology Options Appraisal


25

3.3.1 Gas CHP

Gas engine CHP was considered as a lower carbon heat. CHP engines use natural gas from the

gas network to generate electricity and make use of the remaining thermal energy that would

otherwise be wasted. This technology can potentially reduce a building’s carbon footprint

resulting from energy use when compared to importing electricity from the grid and generating

heat in fossil fuel fired boilers.

The heat output from a CHP could be used to supply the Mildenhall Hub or DHN in addition to the

electricity output could be sold to the grid or retailed through a bilateral contract.

CHP engines are available to suit a wide range of heat and electricity demands and can be

installed on a modular basis to match the phased development of a heat network.

3.3.2 Biomass

Biomass fuel, supplied in the form of wood chip or pellets, may be a suitable fuel to generate

heat and power at the site. Biomass boilers are becoming increasingly popular in the UK due to

their strong green credentials, the simplicity of the technology and the relatively cheap fuel costs.

Renewable biomass fuels are produced from sustainably grown trees that are cut down and

processed into either chip or pellet form.

The size of boiler selected for the scheme is affected by two main factors:

the base load heat demand of the network

the optimisation of revenue through the Renewable Heat Incentive (RHI) scheme

Consideration of thermal store / buffer vessel size should also be included when sizing biomass

boilers.

The current levels of non-domestic RHI for biomass installations with an accreditation date on or

after 1st January 2016 are shown in Table 12. Please note these figures are revised by the

Government regularly and current trends suggest these could be reduced.

Installation Type Applicable Size Tier RHI Support

(p/kWh)

Small commercial

biomass Less than 200 kWth

1 3.76

2 1.00

Medium commercial

biomass

≥200 kWth

<1 MWth

1 5.18

2 2.24

Large commercial

biomass ≥1 MWth NA 2.03

Table 12: RHI Support for Biomass

For commercial biomass systems with a capacity below 1 MWth, the RHI is awarded in two tiers.

Tier one applies to the useful heat output supplied to a qualifying demand up to that which is

equivalent to the biomass boiler running at full load for 1314 hours. Tier two applies for any heat

output that is supplied to a qualifying demand above that equivalent to 1314 full-load running

hours

The logistics of supply and storage of the biomass fuel are an important consideration when

determining viability technology. Biomass fuel is normally delivered by trucks. This will impact on

transport planning issues as well as limit the distance from which biomass fuel can economically


26

and sustainably be supplied. Research into available biomass supplies surrounding Mildenhall

should be carried out at feasibility stage.

Sufficient secure storage space is required at sites using biomass boilers. Sizing of fuel stores

needs to take into consideration economies of scale and security of supply, land take and

planning limitations. In addition, the energy density of different biomass fuels will impact the fuel

store size requirement. To put this in context, biomass pellets have a higher energy density and

are easier to handle than wood chips. This means that the fuel store size requirement and

associated capital cost is lower but this can be offset by the significantly high fuel purchase price.

These issues must be considered in greater detail at feasibility stage.

Air quality management areas (AQMAs) can present a barrier to the implementation of biomass if

restrictions to emissions are in place. However, an assessment of the study area using the DEFRA

AQMA database4 has shown the site does not fall into an AQMA. Forest Heath District Council has

confirmed this.

3.3.3 Absorption Chillers

Absorption chillers produce coolth by using high temperature water or steam to raise the

temperature of a cooling circuit for heat rejection and lower the temperature of a chilled water

circuit used for cooling.

Several factors must be taken into account when considering this technology:

Presence of a suitable heat source – coefficient of performance (CoP) for absorption

chillers decreases with lower heat source temperature

Nature of the load –A reasonably stable base load is required as absorption chillers

are not suited to modulation

Availability space – Absorption chillers are large

Safety of refrigerant – Some absorption chillers use ammonia which will have

stringent health and safety requirements

3.3.4 Solar Thermal Panels

Solar thermal panels present the opportunity to significantly reduce carbon emissions. Typically a

solar thermal system would be sized to supply only the hot water demand and therefore must be

implemented as part of a mix of technologies.

Solar thermal panels require a significant amount of space unaffected by shading from nearby

buildings. Consideration must be given to issues relating to visual pollution and planning

restrictions.

Payback times are expected to be reasonable due to the revenues available through government

funding. The technology is currently eligible to receive RHI funding at a rate of 10.16 p/kWh for

collectors with an installed capacity of less than 200 kWth. This translates into a collector size of

up to 282 m2 [5].

4 http://uk-air.defra.gov.uk/aqma/local-authorities?la_id=105 5 International Energy Agency’s Solar Heating and Cooling Programme (IEA SHC)


27

3.3.5 Industrial Heat Recovery Using Heat Pumps

The Environment Agency interactive air pollution map6 was used to identify buildings with

particularly high emissions which might indicate the presence of a stack with the potential for

heat recovery. For the Mildenhall area the Witton Chemical Plant was identified as shown by the

red circle in Figure 15.

Figure 15: Environment Agency Air Pollution Map of Mildenhall

Ramboll conducted a site visit to Mildenhall in November 2015 to assess the opportunities for

industrial waste heat recovery in further detail. It was found that the stack at the plant was too

small to present any opportunity. Furthermore, it is know that the site specialises in small batch

production runs. The batch nature of the processes means that there is no opportunity here to

implement a heat recovery asset that can provide a stable heat supplier to any potential DHN. No

further sources of waste heat were identified and therefore this supply opportunity was excluded

from the study.

3.3.6 Water Source Heat Pumps

The River Lark flows to the south of the Mildenhall Hub site. The National Heat Map was used to

assess the heat capacity of the river. The map shows a capacity between 950 kW and 2,400 kW

6 http://maps.environment-agency.gov.uk/wiyby/wiybyController?x=357683.0&y=355134.0&scale=1&layerGroups=default&

ep=map&textonly=off&lang=_e&topic=airpollution


28

Figure 16: River Lark Heat Capacity (courtesy of DECC National Heat Map)

In order to fully quantify the heat resource for a project, information on river depths and flow

rates are required. This should be progressed during a subsequent feasibility phase should

WSHPs be deemed a viable opportunity.

The current levels of non-domestic RHI for WSHP installations with an accreditation date on or

after 1st January 2016 are 8.84 p/kWh at Tier 1 (up to 1,314 run hours) and 2.64 p/kWh for Tier

2.

3.3.7 Energy Centre Options

An investigation was carried out into the areas in which to locate potential new energy centres.

Focus was placed primarily on Council owned land and that of major stakeholders. Figure 17

indicates council owned land within Mildenhall and shows two locations considered within the

industrial estate which include:

Mildenhall Depot in Holborn Ave, which features a large parking area which may be

suitable for an Energy Centre for a potential network in the industrial area (1)

The area next to St Johns Close Post Office, which is Council Owned and part of a

redevelopment area (planning application F/2012/0531/FUL) where there is a Community

Centre planned among other buildings (2).

It should be noted that the economic performance of WSHPs and biomass boilers are heavily

dependent on support from the Renewable Heat Incentive (RHI). The level of support

available for these technologies may be subject to change to future government spending

reviews. This is a risk for project development as if there is a cut in support the projects may

no longer achieve the economic results presented here.


29

Location Ownership Space Availability

Access for construction and maintenance

Proximity to energy demand

AQMA restrictions

Mildenhall Hub Site

Forest Heath District Council

High Good access from Queensway

Central to new development heat demand

None

Industrial Area Council Owned Land

Forest Heath District Council

Medium Access from industrial estate

Within industrial estate, but low heat demand density.

None

Table 13: Energy Centre Locations Appraisal


30

Figure 17: Council Owned Land in Mildenhall


31

4. HEAT NETWORK OPPORTUNITY APPRAISAL

This section presents a series of opportunities for heat networks and decentralised energy which

were identified using the energy maps created in section 2.

Potential opportunities were identified taking into account, but not limited to, the following

criteria:

energy demand density

proximity to identified supply assets

number of public buildings

potential anchor loads

barriers to construction

4.1 Identification of Opportunity Areas

Energy demand density is a key criterion in the validity of heat networks and decentralised

energy supply. For this reason it was the first stage in identifying opportunities.

The following sub-sections present the observation of energy demand clusters and assess their

feasibility at a high level in terms of the other criteria listed above.

4.1.1 Heat

Three areas of high heat demand density were identified on the Mildenhall Heat Demand Map

including the Mildenhall Hub site, Mildenhall Industrial Estate and the Town Centre.

All three of these potential opportunity areas of high heat demand density were assessed during

a site visit carried out in November 2015.

The heat loads in the Town Centre were found to be small pubs and shops which were not

deemed to be appropriate for connection to a heat network. This was due to the fact that the cost

of network construction in urban areas is high and it is highly unlikely that the heat loads would

be sufficient to yield high enough heat sale revenues to pay back the cost. In addition the cost of

retrofitting and connecting existing buildings would present a barrier.

Figure 18: Image of Mildenhall High Street (courtesy of Google Maps)

As stated in section 2.2.2.2, NHM data typically overestimates light industrial heat demands and

observations made during Ramboll’s site visit to the light industrial area confirmed that this

was likely to be the case. However, a number of buildings were seen to have flues indicating the


32

presence of boilers and thus wet heating systems. These buildings were deemed appropriate to

include within a heat network opportunity, but a re-assessment of the estimated heat demand

was conducted. The heat loads were reduced by 20%-70% depending on the number of buildings

connected to the network. This exercise was based on Ramboll’s experience of actual data from

previous projects.

The light industrial area is entirely privately owned and therefore consumer uptake and the

choice of delivery vehicle would present an additional challenge to the project. Furthermore,

since the buildings are privately owned by a wide range of organisations it is likely to be difficult

to establish a commercial arrangement. Potential consumers would have to be strongly

incentivised to connect through the use of low heat prices against the business as usual case.

Figure 19: Image of the light-industrial area (taken by Ramboll during a site visit).

The Mildenhall Hub is comprised of exclusively public building uses and therefore Forest Heath

District Council is likely to be able to drive a low carbon project forward successfully.

Within the Mildenhall Hub, the proposed leisure facility would act as an anchor load due to the

relatively constant heat demand required to heat the pool and changing areas.

It was concluded that heat networks should be considered separately in the two locations

(Mildenhall Hub and the industrial area) with a view to connecting them either from the outset or

at a later phase.

As no existing supply assets were identified in either of these areas, purpose-built energy supply

facilities would be considered. The most appropriate location would sit within the Mildenhall Hub

as it is understood that the project is at a sufficiently early stage of development to incorporate

an energy centre into the design.


33

4.2 Heat Network Routing Strategy

Once opportunities were identified, possible heat network routes were assessed. Networks were

routed through council owned green spaces, car parks and other available open areas wherever

possible. Where this was not possible the network was routed along public roadways.

Forest Heath District Council provided GIS layers containing information regarding the constraints

that needed to be taken into account and where possible avoided while developing potential

network routes. This GIS data included information on:

Conservation Areas,

Protected Areas (including Local Nature Reserves, Archaeological Sites, and Sites of Special

Scientific Interest amongst others)

Councils owned land

Planning applications.

Other constraints and opportunities such as railway networks and the existence of underpasses

on the routes were also considered in order to minimise cost and inconvenience. These barriers

and opportunities were assessed as part of a desktop study using resources such as Google Maps

and Bing Maps.

The diagram in Figure 20 presents a selection of locations observed during the site walkover.

Brief descriptions are included below.

Figure 20: Extracts from Network Route Analysis


34

1. Queensway – This is the main route for traffic across the Town. Traffic management would be

a consideration should heat network infrastructure be constructed here.

2. Riverbank – Only one barrier appeared to be present on the route from the River to the

Mildenhall Hub, which was a public footpath. The route would be largely soft dig which results

in lower capital expenditure.

3. South of Hub – As above, to the south of the Hub site the only major consideration is the

public footpath.

4. Church Walk – This is the main pedestrian route from the Mildenhall Hub site to the town

centre.

5. A1101 – This is the main road running through Mildenhall and provides the primary link

between the town centre and industrial estate. Traffic management would be a consideration

should heat network infrastructure be constructed here.

6. Mildenhall Industrial Estate – This primarily privately owned and therefore agreements with

landowners would be necessary in order to deploy heat networks. In addition, traffic

management would be necessary should heat network infrastructure be constructed here.


35

4.3 List of Identified Opportunities

Table 14 lists the eight opportunities identified and considered for initial assessment.

MH001 to MH005 consider the Mildenhall Hub development only, with a series of supply options.

MH006 to MH007 consider the industrial area opportunity and MH008 to MH009 assesses a

connection between the two areas.

Project Ref. Project Name Description

MH001 Mildenhall Hub Gas CHP Mildenhall Hub heat loads only supplied by

natural gas CHP. Potential for private wiring

of electricity.

MH002 Mildenhall Hub Biomass As MH001 with a heat-only biomass boiler.

MH003 Mildenhall Hub WSHP As MH001 with a water source heat pump.

MH004 Mildenhall Hub Solar Thermal As MH001 with solar thermal panels.

MH005 Mildenhall Hub GSHP As MH001 with a ground source heat pump.

MH006 Mildenhall Industrial Area CHP The light industrial area heat loads supplied

by a CHP engine.

MH007 Mildenhall Industrial Area Gas

Biomass

The light industrial area heat loads supplied

by a heat-only biomass boiler.

MH008 Mildenhall Hub + Industrial

Area

The Mildenhall Hub and light industrial area

connected and supplied by a single CHP

energy centre.

MH009 Mildenhall Hub + Industrial

Area

The Mildenhall Hub and light industrial area

connected and supplied by biomass boilers

in a single energy centre.

Table 14: List of Identified Opportunities


36

4.4 Opportunity Appraisal

The following sub-sections present each of the nine opportunities in further detail and show

estimated key metrics for each proposed scheme. Comparison of these metrics enables the

prioritisation of opportunities for progression to masterplanning stage and more detailed analysis.

The opportunity appraisal was intended to narrow down the list of opportunities to the

most viable options to take forward to techno-economic feasibility through a high level

assessment of likely energy flows and costs. It is not intended to comprise a techno-

economic analysis in itself.

Table 15 presents assumptions made as part of the modelling process that were common to each

opportunity.

Variable Assumption

Heat Sale Prices In each case the heat sale price for public buildings was based on

WSC’s current gas costs7 and an assumed boiler efficiency of 80%. The

value used was 5.26p/kWh which encompasses both the unit rate and

standing charge.

Electricity Sale Prices Were calculated depending on the assumed availability of private wire

vs. grid sales. Private wire price was set at Forest Heath District

Council’s avoided electricity cost of 12 p/kWh. Grid sale was set at 4.5

p/kWh.

RHI Revenue The RHI does not account for degression over the project lifetime at

opportunity modelling stage and is therefore considered to be a best

case scenario. RHI is in accordance with 2016 tariffs8.

CAPEX Capital expenditure was based on Ramboll’s supplier database which

encompasses values from previous project experience.

Cost of Gas The cost of gas figures for the CHP cases and for the top up boilers

were taken from DECC’s most recently published energy price figures9.

At this stage energy price inflation was not taken into account.

7 Applying an assumed gas boiler efficiency of 80%. 8 Ofgem, “Tariffs that apply for Non-Domestic RHI for Great Britain”, https://www.ofgem.gov.uk/environmental-programmes/non-

domestic-renewable-heat-incentive-rhi/tariffs-apply-non-domestic-rhi-great-britain

It is important to note that the high level opportunity appraisal does not take project

phasing into account.

All heat loads connections and capital expenditures are assumed to take place in project

year 1. This is due to the fact that the opportunity appraisal is intended as an initial

screening process.

The preferred option(s) taken forward to full techno-economic analysis in section 5 will

include detailed phasing assumptions where relevant.


37

OPEX Operational costs were based on Ramboll’s supplier database which

encompasses values from previous project experience.

REPEX A value of 25 % every 20 years was assumed for gas boilers and a

value of 20 % every 25 years for thermal storage. Reinvestment costs

for primary supply technologies are stated within the sections below.

Carbon Factors The carbon savings were calculated using DECC’s most recent

emissions factors10. At opportunity mapping level the predicted changes

to electricity emissions over time was not taken into account and 2016

values were used. At masterplanning level in section 5 the emissions

are modelled in further detail.

Thermal Storage Thermal store sizes are based on an equivalent of 2.5 hours of the full

output of the primary supply technology.

Table 15: Common Assumptions for Opportunity Models

The cost of carbon abatement is calculated as the total capital expenditure (CAPEX) divided by

the estimated tonnes of CO2 saved over the project lifetime.

In each case a single energy centre location is assumed. A multi-energy centre option was not

explored primarily because the scheme is not big enough to justify it. There would be minimal

operational benefit and the capital and O&M costs to the project would be higher.

The following sub-sections present the results of the opportunity appraisal. Again it is

emphasised that this exercise was not intended to comprise a techno-economic analysis in itself;

it was a high level assessment to narrow down the number of scenarios to be taken forward to

full masterplanning and techno-economic analysis.

9 DECC, “Gas and electricity prices in the non-domestic sector”, https://www.gov.uk/government/statistical-data-sets/gas-and-

electricity-prices-in-the-non-domestic-sector 10 Table 1 and Table 2a. https://www.gov.uk/government/publications/valuation-of-energy-use-and-greenhouse-gas-emissions-for-

appraisal


38

4.4.1 Mildenhall Hub

This opportunity includes the energy loads

within the Mildenhall Hub development only.

This includes the Mildenhall Academy 6th form

that exists on the site.

As each “building” proposed is connected by a

central hub, it is assumed that there will be a

centrally located energy centre and the heat

distribution system will form part of the

building design. Therefore no heat network

pipe costs were considered. However, it should

be noted that the type of primary supply

technology will affect the required energy

centre size. The implications of this are

considered in section 5.

Figure 21: MH001 Opportunity Boundary

Thermal storage is proposed to optimise the outputs of the primary supply technologies. Storage

was initially sized to equate to 2.5 hours of output equivalent to the capacity of the primary

supply asset. For example the thermal store associated with a 300 kW biomass boiler would be

750 kWh.

In the CHP case, it was assumed that 75% of the electricity generated by the CHP could be

private wired to the Mildenhall Hub. This assumption was based on the expectation that the heat

and electricity demands are likely to be of similar orders of magnitude and also due to the fact

that the student accommodation should provide a suitably diverse demand profile. The

assumption was explored in further detail at detailed techno-economic modelling stage.

Table 16 shows the key metrics for this opportunity.

Network Reference MH001 MH002 MH003 MH004 MH005

Primary heat supply

technology Gas CHP Biomass WSHP Solar GSHP

Supply Asset Capacity 200 kWe 350 kWth 300 kWth 200 kWth 175 kWth

Total Network length 0 m 0 m 442 m 296 m 100 m

Total project CAPEX £0.6 M £0.5 M £1.0 M £792k £0.7 M

Annual Operating

Costs (incl. Fuel) £105 k £55 k £37 k £48.5k £55 K

Annual revenue from

heat sales £111 K £100 K £100 k £92 k £92 K

Annual revenue from

electricity sales £121 K NA NA NA NA

Annual revenue from

RHI NA £39 K £61 k £49 K £23 K

Annual CO2 Savings 125 tonnes 400 tonnes 240 tonnes 130 tonnes 120 tonnes

Estimated Non-

Discounted IRR 15% 9% 6% 9% 7%

Table 16: Key Metrics for Opportunity MH001 to MH005


39

4.4.2 Northern Light Industrial Area

This scenario encompasses the industrial area in the north, connecting mainly industrial buildings

but also the Great Heath Primary School, the Mildenhall Lodge Care Home and some Commercial

Offices and Retail buildings, providing some variability to the heat demand in the area.

Only the most potentially likely industrial buildings to have a potentially sufficient heat demand

are connected to this network. In order to establish which buildings were most likely to connect,

an assessment of the existing stacks was conducted as described in section 2.2.2.2. Once

connections were identified, a review of the heat loads was conducted to refine the NHM data.

This resulted in a reduction of the total heat demand when compared to the figures presented in

section 2.2.

The opportunity for combined heat and cooling was considered in this case as the energy

mapping exercise showed this area to present a possible cluster of cooling load. However, upon

further investigation no building use types were identified that are deemed to have sufficient

cooling load to justify a establishing a district cooling network.

A number of industrial buildings were selected to connect to the DHN along with other relevant

assets. These other assets comprise a potential new development that includes a new community

centre and 20 new dwellings with a total annual heat demand around 7,570 MWh.

It is unlikely that any private wire opportunities would be possible to private organisations due to

the complexity of the commercial arrangements and high capital cost in comparison to the

available revenue. Therefore all electricity is assumed to be sold to the grid.

Figure 22: MH007 Industrial Area Opportunity


40

The opportunity modelling results are shown in Table 17.

Network Reference MH006 MH007

Primary heat supply technology Gas CHP Biomass

Supply Asset Capacity 400 kWe 750 kWth

Total Network length 3,255 m 3,255 m

Total project CAPEX £4.3 M £4.1 M

Annual Operating Costs (incl. Fuel) £227 K £104 K

Annual revenue from heat sales £160 K £160 K

Annual revenue from electricity sales £99 K NA

Annual revenue from RHI NA £83 K

Annual CO2 Savings 100 tonnes 600 tonnes

Estimated Non-Discounted IRR NA -9%



41

4.4.3 Mildenhall Hub with Extension to Light Industrial Area

This scenario considers a heat network connecting the Northern Industrial Area and Mildenhall

Hub. The total annual heat demand is estimated to be 8,570 MWh.

The chosen technology to assess this opportunity was a biomass fired boiler due to the fact that

for the Hub-only scheme it showed a combination of reasonable rates of return and a relatively

low cost of carbon abatement. If this opportunity was found to be viable, alternative supply

opportunities would be investigated at the Masterplanning stage.

It was assumed that the CHP could supply 80% of the Mildenhall Hub’s electricity, but that the

remainder would be sold to the grid.

This option uses a 1.5MW biomass boiler with a thermal store. Peaking and backup heat supply

would be provided by natural gas boilers.

Figure 23: MH008 Opportunity Area

Network Reference MH008 MH009

Primary heat supply technology Gas CHP Biomass

Supply Asset Capacity 750 kWe 999 kWth

Total Network length 4,700 m 4,700 m

Total project CAPEX £5.9 M £5.4 M

Annual Operating Costs (incl. Fuel) £389 K £165 K

Annual revenue from heat sales £256 K £256 K

Annual revenue from electricity sales £263 K NA

Annual revenue from RHI NA £110 K

Annual CO2 Savings 80 tonnes 800 tonnes

Estimated Non-Discounted IRR NA -6%



42

4.4.4 Summary

Table 19 below shows a summary of the key indicators of the eight opportunities for the

Mildenhall study area that have been assessed during the options appraisal. The simple payback

field is highlighted to indicate the opportunities expected to generate positive rates of return.

As stated previously, it should be emphasised that this summary of opportunities is intended to

narrow down a high number of opportunities and is therefore presented at high level only.

Section 5 presents a full techno-economic analysis.

Opportunity CAPEX Annual O&M

Costs

Annual

Revenue

Estimated

IRR

Net Impact

on Carbon

Emissions

MH001 £0.6 M £105 K 232 K 15% 125 tCO2e/yr

MH002 £0.5 M £55 K 139 K 9% 400 tCO2e/yr

MH003 £1.0 M £37 K 161 K 6% 240 tCO2e/yr

MH004 £0.8 M £49 K 141 K 9% 130 tCO2e/yr

MH005 £0.7 M £55 K 115 K 7% 120 tCO2e/yr

MH006 £4.3 M £227 K £259 K NA 100 tCO2e/yr

MH007 £4.1 M £104 K £243 K -9% 600 tCO2e/yr

MH008 £5.9 M £389 K £519 K NA 80 tCO2e/yr

MH009 £5.4 M £165 K £366 K -6% 800 tCO2e/yr

Table 19: Options Appraisal Summary

Five options were found to be likely to generate a positive return on investment and these were

taken forward for a more detailed energy economic assessment the next project phase. The

supply technologies in these cases were:

biomass

gas CHP

WSHP

GSHP

solar thermal

The standalone network in the light industrial area to the North was not found to be viable. This

was predominantly due to the low heat demand density.

The connection of the Mildenhall Hub to the Northern light industrial area via a DH network was

deemed to be unfeasible. This was attributed to the low heat demand density in combination with

the high heat network infrastructure cost associated with connecting the two areas.


43

5. ENERGY MASTERPLANNING FOR PREFERRED

OPPORTUNITIES

The project key performance indicators (KPIs) resulting from the opportunity modelling were

presented to the Council for comment and to confirm Ramboll’s recommendations for preferred

opportunities. This section explores the preferred opportunities in further technical and economic

detail.

Five opportunities were selected for further analysis. Each opportunity features the same heat

load, but with different supply technologies. The opportunities are listed as follows:

1. MH001 Mildenhall Hub supplied by gas CHP

2. MH002 Mildenhall Hub supplied by biomass boilers

3. MH003 Hub supplied by a WSHP

4. MH005 Hub supplied by solar thermal panels

5. MH006 Hub supplied by a GSHP

At the request of Forest Heath District Council, all scenarios were modelled with and without the

addition of solar photovoltaic (PV) panels, with the exception of the solar thermal case.

The first stage in the analysis was to enter the energy demand data for the Mildenhall Hub and

establish the ‘business as usual’ (BaU) or ‘do nothing’ scenario, which enabled the calculation of

relative carbon and cost savings of the four low carbon options against the scenario where only

natural gas fired boilers are installed.

Following this, heat supply information for the five low carbon energy supply options was entered

into an EnergyPRO model to generate results which indicate the economic and carbon potential.

EnergyPRO creates hourly annual demand and supply profiles to enable accurate calculation of

economic and carbon results.


44

5.1 Energy Demand Assumptions

Due to the fact that the plans for the Mildenhall Hub were evolving during the time of writing,

changes were being made to the concept design as the opportunity modelling was conducted.

Therefore, before conducting the techno-economic analysis for preferred opportunities,

the energy demand estimates from section 2 were revised to ensure the most up to

date information was being used and thus the results would be presented to the

highest possible degree of accuracy.

5.1.1 Mildenhall Hub Concept Design Alterations

A revised business case with more detail on the design was issued in January 2016 by the

Developer with alterations to the previous concept design. The new design maintained the

existing Sixth Form College building and concentrated the other services into two adjacent

buildings. Figure 24 shows the revised layout. The corresponding floor areas are presented in

Table 20.

The main building has Public Access that functions as a hall and hub for the building. This public

access area includes a reception, offices, health centre, library, café, and pre-school. This

building also incorporates spaces for meeting and conference rooms, an academy (with changing

rooms), a wet and dry leisure centre, a kitchen and plant rooms.

The fire and police stations would share another building within the site with common facilities.

Figure 24: Indicative Design Option for Mildenhall Hub

Building Function Floor Area (m2)

Public Access 2,029

Shared meeting space and hall 646

Education Provision 8,420

Education Changing Room Provision 222

Kitchen and Plant Rooms 350

Leisure Centre 4,155

Fire & Police Station 250

Table 20: Floor Areas per Building for Mildenhall Hub


45

5.1.2 Heat Demand Assessment

Due to the fact that further information was made available by the Forest Heath District Council

regarding the possible area schedule of the Mildenhall Hub, the benchmarking exercise outlined

in section 2.2.3 was repeated using the new values.

It is important to note that the updates to the area schedule were not retrospectively included in

the opportunity modelling stage as the work had already been completed. The opportunity results

in section 4.4 are based on the previous schedule.

Figure 25 shows the updated breakdown of the heat demand with respect to the building use

class and the end use of the heat energy. Education and Leisure (leisure classed as

“Recreational”) building types are expected to be the largest energy consumers in the Hub.

Figure 25: Annual Heat Demand by Building Type

The peak diversified demand for the Mildenhall Hub was calculated to be just less than 1.1 MW.

The annual demand from this building was calculated as 1,940 MWh.

The heat demand profile for the Hub was assessed in combination with degree day profiling to

develop a detailed picture of heat demand across the year. Diversification of demand profiles was

also accounted for at this stage.

Hourly energy demand profiles were constructed for the Mildenhall Hub using EnergyPRO based

on the various use types. It was assumed that the public offices would close at the weekend, but

that the leisure centre and library as well as the central Hub would remain open.

Figure 26 shows the modelled annual heat consumption for the Mildenhall Hub.


46

Figure 26: EnergyPRO Annual Heat Demand Profile for Mildenhall Hub

An example heat demand profile for a typical week in January is shown in Figure 27. As the

profile is taken from the winter months the graph represents some of the peak annual heat load

values.

Figure 27: EnergyPRO Weekly Heat Demand Profile (Jan)


47

5.1.3 Electricity Demand Assessment

As part of the detailed energy assessment for techno-economic modelling, predicted electricity

profiles were analysed to enable a more accurate estimation of the proportion of electricity that

could be private wired rather than sold to the grid.

As no predicted half hourly data was available from the Developer at the time of writing, a likely

daily electricity profile was constructed based on actual half hourly data profiles obtained from

Ramboll’s other Local Authority masterplanning projects. Given that the largest proportion of the

Hub is made up of public offices and educational facilities, the profile was taken from a similar

large public facility.

The profile was then scaled in accordance with the difference in total electricity demand of the

Mildenhall Hub and the sample building. The weekday profile is shown in Figure 28.

Figure 28: Predicted Daily Electricity Profile for Mildenhall Hub

The profile clearly shows a steady daytime load of over 400 kW and overnight base load of 70

kW.

During the weekend the profile would be expected to reduce due to the lack of occupancy in the

offices and schools. However the leisure facility and library would remain open which represent a

total of about 15% of the annual electricity load. Therefore a daytime increase would still be

expected over the weekend of at least 100 kW.

5.1.4 Project Phasing

Limited information regarding project timescales was available at the time of writing. From the

Developer’s initial project plan it was apparent that construction was sue to start in September

2017, with completion in December 2018. As there was no indication that the construction of

various areas of the Hub would be phased, it was assumed that the entire heat demand for the

project would therefore be available at the start of 2019.


48

5.2 Energy Supply Assumptions

Five different primary supply technologies were considered. The sub-sections below present an

overview of the modelling assumptions including the required sizing of each supply asset, capital

and operational costs, carbon emissions and also key practical considerations.

5.2.1 Overview of General Assumptions for All Scenarios

There are a number of overarching assumptions for each modelled scenario:

The BaU case was assumed to be a communal plant room solution with gas fired boilers. The

BaU cost of gas in all cases was assumed to be the average value observed in the Forest Heath

District Council billing data which was calculated to be 4.2 p/kWh.

Due to the fact that the BaU scenario also involves a single plant room solution, the costs of

construction for the plant room/energy centre at the Mildenhall Hub would be absorbed into the

development costs (as it would be required in any case) and they are therefore not included in

the capital costs for any scenario. The stated “energy centre and plant” costs for each option

include major plant items, other equipment (pumps, heat exchangers, etc.) and balance of plant.

Specific cost quotations were not obtained for this analysis at masterplanning level. The assumed

plant and network capital costs were based on Ramboll’s database of historic supplier data

and benchmarking and it is recommended that a cost consultant be commissioned at feasibility

stage to conduct a detailed evaluation of project costs. Specific annual costs are presented for

each scenario in the sub-sections below.

Reinvestment costs for each system were also included in the model. They are based on

Ramboll’s previous experience on existing projects in the UK and Denmark. Plant reinvestment

costs have been calculated based on:

10% reinvestment over a 25 year reinvestment cycle for the thermal store

50% reinvestment over a 20 year reinvestment cycle for the gas boilers

50% reinvestment over a 15 year reinvestment cycle for the CHP engines

50% reinvestment over a 15 year reinvestment cycle for the biomass boilers

50% reinvestment over a 15 year investment cycle for heat pumps.

Reinvestment for the balance of plant is assumed to be covered under the on-going operation

and maintenance costs.

In a similar way to the capital cost estimates, O&M costs were taken from Ramboll’s database of

historic supplier data and benchmarking. Specific annual costs are presented for each scenario in

the sub-sections below.

The electricity costs for the heat pumps were taken from DECC’s most recently published

energy price figures11.

The cost of gas figures for the CHP cases and for the top up boilers were taken from DECC’s

most recently published energy price figures12. It was assumed that if the Council runs plant to

supply the whole Hub site, they would be able to obtain a more favourable rate which has been

11 DECC, “Gas and electricity prices in the non-domestic sector”, https://www.gov.uk/government/statistical-data-sets/gas-and-

electricity-prices-in-the-non-domestic-sector 12 DECC, “Gas and electricity prices in the non-domestic sector”, https://www.gov.uk/government/statistical-data-sets/gas-and-

electricity-prices-in-the-non-domestic-sector


49

factored into the scheme economics. Gas supplied to the CHP engine was assumed to be exempt

from CCL.

The sale price of heat from each supply asset is based on the BaU gas value with an applied

boiler efficiency of 80%. 5% of the cost was deducted to represent an incentive against the BaU.

Avoided boiler maintenance and replacement costs were accounted for at a rate of 0.15 p/kWh.

The resulting heat sale price was calculated to be 5.26 p/kWh.

RHI revenue is set in accordance with 2016 tariffs13. In the first instance the 2016 tariff values

are applied to the first 20 years of each of the relevant modelling scenarios. As part of the

sensitivity analysis degression of the RHI over time is assessed.

Carbon emissions factors were taken from DECC’s most recently published figures14. Gas was

assumed to have a constant emissions factor of 0.184 tonnes CO2/kWh. Electricity was assumed

to change over time in accordance with DECC’s estimates, starting with a generation-based grid

average value of 0.273 tonnes CO2/kWh in the first operational year of 2019.

13 Ofgem, “Tariffs that apply for Non-Domestic RHI for Great Britain”, https://www.ofgem.gov.uk/environmental-programmes/non-

domestic-renewable-heat-incentive-rhi/tariffs-apply-non-domestic-rhi-great-britain 14 Table 1 and Table 2a. https://www.gov.uk/government/publications/valuation-of-energy-use-and-greenhouse-gas-emissions-for-

appraisal


50

5.2.2 Solar PV

As previously stated, each model was tested with and without the addition of a roof-mounted

solar PV array, in order to test the effects on the economics if a solar PV scheme was included as

part of the low carbon decentralised energy project.

The scheme was sized taking two main factors into consideration; the available roof space and

the FIT tariff bands.

In order to remain just within the 150 kW to 250 kW band with a total panel area of 1,690 m2

was required, which corresponds to approximately 248 kW.

The total floor area of the Mildenhall Hub was expected to be over 16,000 m2. Assuming the

entire building is three storeys15 the roof space is therefore expected to be approximately 5,300

m2. Even allocating 50% of this to buildings services (e.g. ventilation systems) and allowing for

panel spacing would leave sufficient space for the 1,690 m2 of panel area calculated above.

In the biomass, WSHP and GSHP cases it is assumed that the Mildenhall Hub consumes the entire

electricity output from the solar PV installation. For the CHP case it is assumed that 75% would

be consumed by the Mildenhall Hub with the remaining 25% exported to grid.

Based on the typical levels of solar irradiation in Mildenhall throughout the year, the annual

electricity output of the panels was estimated to be 229 MWh.

Figure 29: Solar Irradiation Data for Mildenhall

PV pricing forecasts were obtained from the 2012 DECC Solar PV cost update16, which presents

the likely reduction in panel costs over a 20 year period.

OPEX assumptions were taken from the most recent Government cost statistics17

15 This is a general assumption as no information was available. 16 Solar PV Cost Update, Parsons Brinkerhoff for the Department of Energy and Climate Change, May 2012 17 “PV Cost Update”, https://www.gov.uk/government/statistics/pv-cost-update


51

5.2.3 Gas CHP

The Gas CHP scenario would involve the use of a 358 kWth CHP engine fuelled by natural gas. The

sizing was optimised to ensure annual full load equivalent running hours of at least 4,500 hours

and a contribution to total annual heat demand in the region of 60%.

The CHP engine would operate in combination with natural gas boilers supplying a total back up

and peaking capacity of approximately 1.1 MW.

Accumulator thermal storage can provide significant operational benefits to gas engine CHP

schemes. The optimal size of thermal store will depend on a trade-off between capital cost and

operational cost savings. The modelling carried out at this stage has assumed a capacity based

on 2.5 full load output of the CHP engine. In this case the thermal storage capacity was

calculated to be 900 kWh which corresponds to a water volume of 31 m3.

Table 21 shows the key parameters of this scenario:

Parameter Value

CHP Capacity 358 kWth

Gas Boiler Capacity 2 No. 550 kWth

Thermal Store Capacity 0.9 MWh

Annual CHP Electricity Output 1,008 MWh/yr

Annual CHP Heat Output 1,520 MWh/yr

Annual Boilers Heat Output 420 MWh/yr

Table 21: Key CHP Parameters

The contribution of the CHP engine and boilers to the heat demand for a sample week in January

is shown in the figure below. The thermal store is not shown on the graph due to the fact that it

acts to store and release energy, but it is not a supply asset.

Figure 30: Example Weekly Profile of Supply Asset Contributions

The capital cost estimates are shown in Table 22 below.

Item Cost

Energy Centres and Plant £228 K

Thermal Store £43 K

External pipework and trenching NA

Contractor and Design £40 K

Total £311 K

Table 22: Capital Costs for CHP Option

The operational cost considerations for this scenario consist of the gas cost and on-going O&M.

Annual O&M for the energy centre and plant was included at just under £10 K per annum.


52

Revenues are obtained through the sale of heat and electricity. Based on the constructed profiles

in section 5.1.2, it was assumed that electricity could be private wired to the Mildenhall Hub at a

rate of 12 p/kWh for approximately 75% of the time. The remaining 25% of the electricity would

be sold to the grid at 4.5 p/kWh.


53

5.2.4 Biomass Boiler

The biomass heating option would involve the installation of a biomass boiler in the energy

centre. For this option, a single 550 kW biomass fired boiler was selected along with a 1,100 kW

of gas fired boilers for provision of back up and peaking capacity.

During any subsequent feasibility and design phases, it may be decided to remove the

requirement to provide gas fired back up and peaking boilers. This would remove the need for a

gas connection and the cost savings would contribute to offsetting the additional cost associated

with biomass heating. The impact of this has not been assessed in this report.

A thermal store was included as part of the biomass option to:

act as a buffer vessel

improve response of the biomass boilers

reduce inefficient short cycling of biomass boiler

provide peak heat supply capacity

The thermal store capacity was sized based on 2.5 full load output of the biomass boiler. This is

equivalent to of 1.38 MWh which corresponds to an approximate volume of 47 m3.

The key figures for the biomass operation are shown in Table 23 below.

Parameter Value

Biomass Fired Boiler Capacity 550 kWth

Gas Fired Boiler Capacity 1,100 kWth


Annual Biomass Heat Production 1,920 MWh/yr

Annual Natural Gas Heat Production 20 MWh/yr

Table 23: Key Biomass Boiler Parameters

Figure 31 below shows how the biomass boiler, thermal store and gas fired boilers could operate

and contribute to annual heat demand for the Mildenhall Hub. As the graph presents only heat

generation assets, the thermal store is not directly represented. However, the operation of the

thermal store can be seen where the area under the heat demand curve appears to be unfilled.

Figure 31: Contribution of Supply Assets to Heat Demand for Biomass Option


54

A breakdown of the estimated project costs is shown in Table 24.

Item Cost



External pipework and trenching N/A


Total £767 K

Table 24: Capital Costs for Biomass Option

The operational costs in this scenario include the biomass fuel, natural gas and on-going O&M. It

is assumed that the biomass fuel will take the form of wood chip. In this case it was decided that

chip would be favourable to wood chip due to the fact that it is considerably cheaper than pellets.

A disadvantage of wood chip is that it requires a relatively large storage area; however it was

assumed that sufficient space could be incorporated into the Mildenhall Hub design due to the

large land area covered by the site.

The cost of wood pellets included in the model was £110 per tonne. This figure was based on

quotations obtained for similar past projects.

In addition to revenue from heat sales, it was assumed that all heat produced by the biomass

boilers was eligible for RHI payments according to 2016 tariff rates for biomass under 999 kW.

This corresponds to figures of 5.24 p/kWh and 2.27 p/kWh for Tier 1 and Tier 2 respectively.

As projects such as this often rely heavily on RHI revenues, the sensitivity of the project

economics to this factor is analysed in section 5.3.3.


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5.2.5 Water Source Heat Pump

Since the internal heating system of the Mildenhall Hub is yet to be designed, there is an

opportunity to include a low temperature space heating system that is suited to low temperature

heat sources such as heat pumps (water source and ground source) and solar thermal collectors.

Low temperature space heating includes technologies such as under floor heating or oversized

radiators. These have much higher heat transfer surface areas than traditional systems which

mean the circulating fluid within the system can be cooled further thereby releasing more of the

heat content. This means lower heating system operating temperatures can be used (35 °C – 60

°C on the flow depending on floor construction). Lower heating system operating temperatures

may also allow a greater range of pipework materials to be used.

The proposed energy supply technology for this option is a 550 kW WSHP. This option would

involve installing a heat loop within a deep section of the River Lark approximately 450 m to the

south of the proposed Mildenhall Hub site.

The river was observed during Ramboll’s visit to the site in autumn 2015 and photos are shown

below. If this project is selected for progression to feasibility stage, depth and temperature

measurements must be taken to assess the heat availability in further detail. At masterplanning

stage the limited information represents a risk to the project.

Figure 32: Photographs of the River Lark (courtesy of Ramboll)

The heat pump unit would be located within the Hub’s boiler house and connected to the river

loop via insulated pipework buried in the ground. Also located within the boiler house would be

two 550 kW gas fired boilers to provide back up and peaking capacity.

A thermal store is included to assist in balancing of heat demand, increase utilisation of the

WSHP installation and reduce heat required from the gas fired boiler plant. The thermal store was

sized at 47 m3 which corresponds to a capacity of approximately 1.38 MWh.

The key energy production figures for this scenario are shown in Table 25 below.

Parameter Value

WSHP Capacity 550 kW

Gas Fired Boiler Capacity 1,100 kW


Annual WSHP Heat Production 2,000 MWh

Annual Natural Gas Heat Production 55 MWh

Table 25: Key WSHP Parameters


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Figure 33 shows how the WSHP and gas fired boilers are expected to operate and contribute to

the heat demand for the Mildenhall Hub.

Figure 33: Contribution of Supply Assets to Heat Demand for WSHP Option

The capital costs for this scenario are shown in Table 26. The WSHP option requires pipework to

connect the heat pump units with the heat recovery loops. This cost is included under external

pipework and trenching.

Item Cost



External pipework and trenching £316 K


Total £1,493 K

Table 26: Capital Costs for WSHP Option

The operational costs consist of electricity to run the heat pump, gas for the peaking boilers and

on-going O&M. Annual maintenance costs were approximated to be £3,300 per annum.

In addition to revenue from heat sales, it was assumed that all heat produced by the WSHP was

eligible for RHI payments at the 2016 tariff rates. At the time of writing the values were currently

set at 8.95 p/kWh at Tier 1 and 2.67 p/kWh at Tier 2 for all capacities.




57

5.2.6 Solar Thermal

This scenario involves the installation of solar thermal collectors on south easterly sections of the

roof of the Mildenhall Hub buildings.

The solar thermal collector installation was sized with a total area of 282 m2, equivalent to

around 200 kWth of peak heat supply capacity. This is the maximum installation size that is

currently supported under the RHI.

This option includes a 17 m3 thermal store to assist in supply and demand balancing.

In the UK, the performance of solar thermal collectors is highly seasonal. Two 550 kWth gas

boilers were included within this option to ensure adequate heat is provided when the solar

thermal system is unable to meet the peak demand. These boilers shall also provide back-up

capacity and would be located in the boiler house with the thermal store.

The key energy production figures for this scenario are shown in Table 27 below.

Parameter Value

Solar Thermal Capacity 200 kW



Annual Solar Thermal Heat Production 167 MWh

Annual Natural Gas Heat Production 1,773 MWh

Table 27: Solar Thermal Case Key Parameters

Figure 34 and Figure 35 below show how the solar thermal collector and gas fired boilers are

expected to operate and contribute to the weekly heat demand for the Mildenhall Hub in summer

and winter respectively. Due to the heavily seasonal nature of the technology, the gas boilers can

be seen to produce almost all of the required heat in the winter months.

Figure 34: Contribution of Solar Thermal Supply Assets to Heat Demand in Summer


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Figure 35: Contribution of Solar Thermal Supply Assets to Heat Demand in Winter

The estimated capital costs for this scenario are presented in Table 28.

Item Cost



External pipework and trenching N/A


Total £682 K

Table 28: Capital Costs for Solar Thermal Option

The operating costs include the cost of gas and the on-going O&M.

In addition to revenue from heat sales, it was assumed that all heat produced by the solar

thermal collectors was eligible for RHI payments at 2016 rates of 10.28 p/kWh.




59

5.2.7 Ground Source Heat Pump

The final option is the installation of a GSHP. Similarly to the WSHP option, this technology is

suited to low temperature space heating systems such as under floor heating, which should be

considered during the design phase of the Mildenhall Hub.

For this option a 550 kWth GSHP is proposed. The ground loop would be installed in trenches

within the grounds of the Hub and Sixth Form College. Once installed, the ground above the

ground loop can be utilised for a variety of recreational purposes. The ground loop would be

connected to the heat pump unit that would be located in the boiler house.

The thermal conductivity of the soil into which the ground loop is installed will influence the

required length and therefore cost of the collector. Dry, loose soil such as loams, sand and gravel

are freely draining and will trap air. This means the thermal conductivity for these soil types will

be low which will increase the collector length requirement for a given heat pump output.

Clay, silty and saturated soils have much higher thermal conductivities which will reduce the

required collector length for the same heat pump output. Furthermore, sandy or loamy soils that

are saturated will have a significantly higher thermal conductivity that when dry. Thermal

conductivity also varies by bedrock type which will influence the length and number of boreholes

required for vertical ground loop installations.

The UK Soilscapes map18 (extract shown in Figure 36 below) identifies the soils around the

Mildenhall Hub as being freely draining lime-rich loamy soils. Consequently, it is likely the length

requirement for the ground loop will be significant on a meter per heat pump kW output basis.

Figure 36: Screenshot from UK Soilscapes Map

Also located in the boiler house would be two 550 kW gas fired boilers to provide back up and

peaking capacity. A thermal store is included to assist in balancing of heat demand, increase

utilisation of the GSHP installation and reduce heat required from the gas fired boiler plant.

The key energy production figures for this scenario are shown in Table 29.

18 http://www.landis.org.uk/soilscapes/ NOTE: Soilscapes was used for high-level observations only. Soilscapes is not intended as a

means for supporting detailed assessments, such as land planning applications or site investigations; nor should it be used to support

commercial activities.


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Parameter Value

GSHP Capacity 550 kW



Annual GSHP Heat Production 1,900 kWh

Annual Natural Gas Heat Production 14 MWh

Table 29: GSHP Option Key Parameters

Figure 37 below shows how the GSHP, thermal store and gas fired boilers could operate and

contribute to the heat demand for a week in January when the load is at its highest.

Figure 37: Contribution of Supply Assets to Heat Demand for GSHP Option

The GSHP scenario involves pipework to connect the heat pump units with the heat recovery

loops. This cost is included under external pipework and trenching.

Item Cost



External pipework and trenching £220 K


Total £919 K

Table 30: Capital Costs for GSHP Option

The operational expenditure in this case consists of the electricity required to run the heat pump,

natural gas for the boilers and on-going O&M costs. Maintenance costs were included at a rate of

£3,300 per annum.

In addition to revenue from heat sales, it was assumed that all heat produced by the GSHP was

eligible for RHI payments at the 2016 tariff rates. These are the same as the RHI levels for

WSHPs at 8.95 p/kWh and 2.67 p/kWh for Tier 1 and Tier 2 respectively.




61

5.3 Modelling Results

As previously stated, the techno-economic analysis was conducted using EnergyPRO software. A

model was built for each of the five energy supply options for the Mildenhall Hub.

The results were compared according to the following key performance indicators:

Internal rate of return (IRR)

Net present value (NPV) at a 3.5% discount rate19

CO2 savings against BaU.

The models have been assessed over a 25-year and 40-year project lifetime.

The lowest IRR hurdle rate considered for project viability is 3.5 % to 4.0 % which is in line with

the lowest acceptable values for public borrowing. However, should the Council wish to work in

partnership with a private ESCo IRRs in excess of 10 % would have to be achieved. These rates

were taken into account when evaluating the economic results.

The first operational year of the project was taken to be 2019, as this was the date presented in

the Developer’s indicative project plan.

5.3.1 Results without Solar PV

5.3.1.1 Economics

The table below presents a summary of the key economic results for each of the five

opportunities without the addition of solar PV. It is colour coded whereby the IRRs are green

in excess of 10% and yellow in excess of 4 %.

Opportunity CAPEX IRR 25 yrs 25 yr NPV @

3.5% DR IRR 40 yrs

40 yr NPV @

3.5% DR

CHP £310,500 11% £250,100 11% £387,300

Biomass £766,500 9% £376,700 9% £493,100

WSHP £1,492,400 5% £133,800 6% £368,100

Solar Thermal £682,300 NA -£555,400 -7% -£519,000

GSHP £918,300 14% £997,500 15% £1,249,400

Table 31: Summary of Economic Results

Table 32 presents the NPVs at 6% and 10% discount rates.

Opportunity 25 yr NPV @

6% DR

25 yr NPV @

10% DR

40 yr NPV @

6% DR

40 yr NPV @

10% DR

CHP £131,600 £12,500 £193,900 £31,300

Biomass £172,700 £1,077,900 £226,700 -£36,900

WSHP -£117,500 -£536,800 -£8,700 -£380,800

Solar Thermal -£537,500 -£536,800 -£520,800 -£531,800

GSHP £650,600 £268,700 £767,600 £305,000

Table 32: NPVs at 6% and 10% Discount Rates

19 DR set at the lowest project hurdle rate


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Two of the scenarios stand out as the most viable; the CHP and GSHP options. The IRR of 14% in

the GSHP case is highly likely to be attractive to private energy services companies, should

Forest Heath District Council not wish to take on the costs and operation of the project

themselves.

The IRRs of 11% in the CHP case are attractive enough for a public sector led project and are

also likely to attract private investment should the Council seek it.

The biomass scenario is also found to generate positive returns, with IRRs at 9% for 25 and 40

year lifecycles. This is sufficient to be considered viable for a publicly led project.

The WSHP scenario returns positive IRRs of 5% and 6% over 25 and 40 years respectively. This

shows that the project is likely to be viable if led by Forest Heath District Council. The high

capital costs are the reason for the relatively low returns when compared to the GSHP case, and

if these could be brought down the economics would look significantly more attractive.

Contrary to the findings of the opportunity assessment in section 4, the solar thermal scheme

was not found to be viable. This is most notably due to the fact that the detailed seasonal energy

profiling carried out in EnergyPRO provided a more comprehensive overall figure for the

contribution of heat to the system from the collectors.

5.3.1.2 Carbon

The CO2 savings for each of the four options against the BaU case have been calculated using the

EnergyPro model and are shown in Table 33 below. The CO2 savings calculated here are based on

heat use only and do not account for electricity consumption of the customers. Please note the

carbon figures quoted do not account for grid decarbonisation.

Opportunity

Annual CO2

savings

(tonnes)

CO2 savings over

25 yr lifetime

(tonnes)

Carbon intensity

(kg.CO2/MWh)

Cost of CO2

abatement20

(£/tonne CO2)

CHP 115 2,883 198 £108

Biomass 376 9,396 50 £82

WSHP 391 9,779 40 £153

Solar Thermal 40 1,009 223 £676

GSHP 402 10,046 37 £91

Table 33: Carbon Savings for Mildenhall Energy Supply Options

The results show that the GSHP, WSHP and biomass scenarios are likely to result in significant

CO2 savings when compared to the BaU. The cost of carbon abatement in the biomass, GSHP and

CHP cases is relatively low at £82, £91 and £108 per tonne respectively over a 25 year project

lifetime.

20 Over 25 year lifetime


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5.3.2 Results with Solar PV

5.3.2.1 Economics

The table below presents a summary of the key economic results for each of the four

opportunities with solar PV. Please note that the solar PV scenario is excluded from the solar

thermal case since it is assumed that there will be insufficient roof space for both installations.

Opportunity CAPEX IRR 25 yrs 25 yr NPV @

3.5% DR IRR 40 yrs

40 yr NPV @

3.5% DR

CHP £477,100 10% £361,900 11% £592,500

Biomass £933,100 10% £569,800 10% £778,800

WSHP £1,658,900 6% £336,800 7% £653,800

GSHP £1,084,900 14% £1,171,400 14% £1,535,100

Table 34: Summary of Economic Results with PV

Table 35 presents the NPVs at 6% and 10% discount rates.

Opportunity 25 yr NPV @

6% DR

25 yr NPV @

10% DR

40 yr NPV @

6% DR

40 yr NPV @

10% DR

CHP £498,200 £319,800 £603,900 £352,000

Biomass £1,053,800 £747,800 £1,149,400 £776,700

WSHP £1,494,800 £1,114,900 £1,639,900 £1,097,100

GSHP £1,673,200 £1,218,100 £1,842,100 £1,270,500

Table 35: NPVs at 6% and 10% Discount Rates

The inclusion of a solar PV installation has a positive effect on the performance of the four

scenarios modelled. Both 25 year and 40 year NPV are improved by between £100k-200k and

200k-£285k respectively. For the CHP scenario, solar PV has the least effect since this option

includes two forms of competing on-site power generation. Solar PV has the most benefit for the

biomass and WSHP scenarios where IRRs are improved by one percentage point.

5.3.2.2 Carbon

The CO2 savings for the modelling scenarios which include PV are shown below. Conversely to the

assessment of the scenarios without PV, the carbon savings analysis presented in below also

account for electricity consumption of the customers in the Hub.

Opportunity

Annual CO2

savings

(tonnes)

CO2 savings over

25 yr lifetime

(tonnes)

Carbon intensity

(kg.CO2/MWh)

Cost of CO2

abatement21

(£/tonne CO2)

CHP 143 3,578 183 £133

Biomass 404 10,103 148 £92

WSHP 419 10,486 134 £158

GSHP 430 10,753 138 £101

Table 36: Carbon Savings for Mildenhall Energy Supply Options

21 Over 25 year lifetime


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In all cases the inclusion of solar PV increases the annual CO2 savings by 28 tonnes per year.

Similarly, the carbon intensity increases for all cases, except CHP, when compared to the without

PV assessment since electricity consumption related CO2 emissions are now accounted for.

However, biomass, WSHP and GSHP continue to achieve significant CO2 emissions savings when

compared to the CHP case.


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5.3.3 Sensitivity Analysis

The results of the Mildenhall Hub energy model are sensitive to a number of key assumptions.

Consequently, the EnergyPRO model was re-run to assess the impact any changes of these key

parameters on the economics of each option. The parameters assessed in the sensitivity analysis

are discussed below.

The sensitivity analysis was conducted on the models excluding the effects of solar PV in order to

put focus on the heat supply asset.

Renewable Heat Incentive

There is currently a great deal of uncertainty regarding the future of support for renewable heat

technologies under the Renewable Heat Incentive. During the Governments Autumn Statement

released on 25th November 2015 it was announced that the RHI scheme would be extended to

2020/21. However, the security of the current tariffs is still uncertain.

The implication of the above on four of the proposed energy supply options for the Mildenhall Hub

is that value of payments from the RHI could be reduced or removed completely.

Firstly the best and worst cases were compared. These were considered to be the 2016 tariffs

compared to no RHI whatsoever. The results are shown in Figure 38.

Figure 38: Effect of Removing RHI from Project Cash Flow

It is clear that without support from the RHI the biomass and WSHP are no longer viable. The IRR

of the GSHP option is significantly reduced from 20% to 4%.

Given the dramatic difference in IRRs with and without RHI, the results were tested again with

reductions in RHI revenue of 10% and 50%. The results for a 25 year project lifetime are

presented in Table 37.

Scenario Base Case IRR -10 % RHI -50 % RHI

Biomass 9% 8% 2%

WSHP 5% 4% -4%

Solar Thermal NA NA NA

GSHP 14% 13% 8%

Table 37: Sensitivity of Schemes to RHI Reduction

-15%

-10%

-5%

0%

5%

10%

15%

20%

Biomass WSHP Solar Thermal GSHP

IRR

ove

r 4

0 Y

ears

RHI

No RHI


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Heat Sale Price

The assumed total heat sale price was varied by +/- 10% and 20% in order to observe the

change in IRR. The variation was applied to the entire price including standing charges.

Figure 39 shows the results of the analysis.

Figure 39: Graph of 25 year IRR Varying with Cost of Heat

Figure 40: Graph of 40 year IRR Varying with Cost of Heat

It can be seen that the CHP scenario is most heavily dependent on the heat sale price. An

increase of 10% or 20% makes the scheme significantly more attractive, but an equivalent

reduction results in the scheme IRRs appear to be borderline. The high dependence on heat sale

price can be attributed to the fact that the heat revenue in this case makes up a greater

proportion of the total cash flow than in the other scenarios.

The GSHP option maintains attractive rates of return even with a 20% reduction in heat sale

price.


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The results show that for the WSHP and biomass options a 10% or 20% reduction in heat sale

price reduces the IRR to a point where the viability of the project would be questioned. In the

case of the biomass scenario a 20% reduction results in a low rate of return.

Over a 25 year project lifetime the solar thermal does not return a positive IRR even with an

increase of heat sale price of 20%. Over 40 years an increase of 20% results in a positive IRR,

but the value is still not significant enough to be considered attractive.

Project Capital Costs

Sensitivity was also carried out on the project capital costs. This was deemed necessary due to

the fact that capital costing of the project opportunities was carried out based on Ramboll’s

experience in the low and zero carbon energy market in the UK, which were not confirmed with

the market specifically for this project.

The impact of altering the costs by +/- 10% and 20% for each opportunity is shown in Figure 41.

Figure 41: Effect of Varying Capital Costs on Project 25 year IRRs

Figure 42: Effect of Varying Capital Costs on Project 40 year IRRs

Even with a 20% increase in capital costs the GSHP scenario remains viable with IRRs exceeding

11%.


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The CHP option maintains IRRs of approximately 7-9% when presented with an increase in

capital cost. This is still considered to be sufficient for a publicly led scheme.

The capital cost increases bring the biomass scenario’s rates of return down to 6% which is could

be attractive for a public led project. However, a 20% reduction in the estimated costs results in

the IRR exceeding 10% for both 25 and 40 year lifetimes, which significantly increases the

appeal of the scheme.

In a similar way to biomass, the sensitivity of the WSHP scheme to capital cost is significant due

to the borderline nature of the modelling results. A reduction in cost results in the rates of return

reaching values which are more likely to be considered for implementation, but any increase in

costs reduces the project IRRs down to unattractive levels.

In the case of the proposed solar thermal scheme, even a 20% reduction in the estimated capital

expenditure is not sufficient for a positive rate of return.

Leisure Centre Heat Sale Prices

Following completion of the techno-economic analysis phase, the Council stated that an

additional risk had arisen in the form of the heat sale price to the leisure centre portion of

Mildenhall Hub.

Due to amendments to the size and staffing of the proposed leisure facility, it was deemed likely

that they would receive a significant discount to the heat sale price or even free heat. Therefore

analysis was conducted to establish the effect of this on the project economics.

Firstly it should be noted that the total estimated revenue from heat sales to the leisure facility in

the base scenarios was over £30 K per annum. This represents approximately 30% of the total

heat sale revenue and is therefore a significant factor in the economic results.

The two scenarios with the most attractive economic results were assessed: CHP and GSHP. The

leisure centre heat sale revenue was removed from the project cash flow to demonstrate the

worst case scenario. The results of the sensitivity analysis are presented in Table 38.

Scenario

Base IRR 25 Yrs

25 Yr IRR

without LC

Revenue

Base IRR 40 Yrs

40 Yr IRR

without LC

Revenue

CHP 11% -9.1% 11% -6.9%

GSHP 14% 9.8% 15% 10.1%

Table 38: Sensitivity of Economics to Leisure Centre Heat Sale Price

The results show that in the CHP case, the results are heavily affected by the loss of revenue and

the project is no longer viable. This is due to the fact that the annual operating margin in this

case is only marginally more than the amount of heat sale revenue from the leisure centre under

the base case.

In the case of the GSHP the scheme was still found to be viable without the leisure centre heat

sale revenue, despite the reduction in IRR of over 4%. This is due to two key factors: firstly, the

GSHP IRRs were well above the hurdle rate to begin with and so a reduction would have to be

significant to reduce viability. Secondly the annual operating margin in the base was well in

excess of the value of the leisure centre base case heat sale revenue and therefore the scheme is

still paying back at a reasonable rate.


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5.3.4 Summary of Modelling Results

The results from the technical modelling, economic assessment, carbon assessment and

sensitivity analysis can be summarised as follows:

The results show that GSHP and gas CHP technology are the most promising options for

energy supply at the Mildenhall Hub development in terms of economics alone.

WSHP and biomass options also return reasonable IRRs and are considered to be viable

for a publically led project.

The GSHP, WSHP and biomass options result in the greatest CO2 savings and were found

to have the lowest cost of carbon abatement.

Solar thermal technology was found to be inappropriate for the site. Even with increases

in heat sale price and reductions in the estimated capital expenditure, the scheme does

not appear to generate attractive rates of return.

The integration of a Solar PV installation was found to result in improvements both in

terms of economics and carbon emissions savings for CHP, biomass, WSHP and GSHP

scenarios.

Without the revenue from the RHI the WSHP and biomass projects are no longer viable.

The IRR of the GSHP reduces significantly and the economics are unlikely to be attractive

except for a public led scheme. The CHP scheme is not affected by RHI.

The CHP, biomass and WSHP scenarios were found to be very sensitive to the heat sale

price when compared to the GSHP option.

In a similar way to the heat sale prices, changes in project CAPEX reduce the IRRs for the

WSHP scenario to an unattractive level. However the CHP, biomass and GSHP scenarios

appear to remain feasible even with a 20% cost increase.

The implications of these results on the next steps for Forest Heath District Council are presented

in section 7.


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6. PROJECT OUTLINE RISK ASSESSMENT

This section presents an outline risk assessment for the preferred project opportunity outlined in

section 5. A number of key risks were identified relating to four main aspects of project

implementation: technical, commercial, financial and planning.

A risk register was created and is presented in Table 39. Each of the identified risks is

summarised below.

6.1 Technical Risks

Accuracy of Heat Demand Estimates

The Mildenhall Hub project is within the early phases of the development process and the design,

size and layout is potentially subject to significant change. The energy demand assessment has

been undertaken using the concept layout and floor areas current at the time of the analysis.

Consequently, there is a significant risk that the energy demands of the Hub will change which

will jeopardise the validity of the assumptions, analysis and conclusions presented in this report.

In order to mitigate against this risk, the energy demand and supply assessment should be

revisited in detail once the outline and detailed design for the Mildenhall Hub has been fixed.

Hub heating system design – i.e. traditional opposed to low temp system

The heat supply options assessed during the energy master plan for Mildenhall include low

temperature heat generators (LTHG) such as WSHP and GSHP. These produce heat at a

temperature of up to 45 °C and are best suited to low temperature heating systems (LTHS), such

as underfloor heating or modern, high surface area heat emitters (radiators). In order to protect

against legionella, DHWs systems supplied by LTHGs require supplementary heating. This is

normally provided by electrical heating elements located within DHW storage tanks or traditional

fossil fuel fired or electric low temperature hot water (LTHW) boilers.

Traditional LTHW heating systems are operated at much higher temperatures than LTHS,

typically between 70 °C and 80 °C. In order to be compatible with LTHW heating systems, the

temperature of the heat output from LTHS would need to be increased by an auxiliary heat

source such as gas fired or electric boilers. This will increase heating energy usage and

associated costs of the Hub as well as decreasing potential carbon savings, thereby significantly

reduces the benefit of utilising LTHGs

Heat sources that produce LTHW, such as natural gas fired CHPS and biomass fired boilers, are

compatible with both LTHS and LTHW heating systems.

There is a risk that the final Mildenhall Hub design includes a LTHW heating system that is not

compatible with, and will therefore exclude, LTHGs as potential heat supply assets. Since the

Mildenhall Hub project is currently in the concept design phase there is an opportunity to ensure

a LTHS is implemented into the final design. This will mitigate against this risk and ensure the

Hub’s heating system is flexible and compatible with both LTHG and LTHW heat sources.

Ground conditions As discussed in section 5.2.7, the ground conditions around the Mildenhall Hub will dictate the length requirement and associated cost of the ground loop as well as the quantity of heat than can be safely extracted on an annual basis. The heat extraction potential, and ground loop requirements and costs presented in this report are based on high level assumptions. There is a


71

risk that these assumptions do not reflect the actual requirements for the Mildenhall Hub GSHP option. Consequently, there is a risk that the ground loop needs to be significantly larger than estimated in this report in order to achieve the same stated heat pump output. This would increase the capital costs and therefore affect the economic performance of the GSHP option. In addition, local soil conditions may restrict the quantity of heat that can be extracted locally, meaning the heat pump size is over estimated and a greater reliance on fossil fuel back up plant will be necessary.

In order to mitigate against this risk during future feasibility phases, it is recommended that a

ground condition survey is undertaken to accurately determine heat loop requirements and costs,

as well as determine the quantity of heat that can be sensibly extracted annually. Properties of River Lark

The heat that can be extracted from a body of water by a WSHP is a function of the flow rate and

volume of the pool in which the coil is situated. The Environment Agency place strict limitations

on allowable temperature changes to a water body that result from water and heat extraction /

discharge in order to protect the ecology. This will place a limit on the allowable heat extraction

from the River Lark by the potential Mildenhall Hub WSHP and will be particularly relevant in

periods of low flow such as during the summer months.

There is a risk that the annual heat output estimated during the EnergyPro modelling analysis for

the Mildenhall Hub has been overestimated. This will increase the heat output required from the

fossil fuel fired back up plant.

In order to mitigate against this risk, it will be necessary to undertake a detailed river survey and

formal discussions with the Environment Agency during any subsequent feasibility phase to

determine maximum permissible annual heat extraction from the River Lark.

6.2 Commercial Risks

Commercial Arrangement and Delivery Vehicle

If the project developed into a wholly private sector based scheme, the Local Authority would not

have any control over how scheme developed and there is a risk that the private sector may not

grow the scheme to its full potential. If the project remains wholly Local Authority led, they

remain in full control, but also take on full developmental and operational risk.

Whichever delivery route is taken forward Forest Heath District Council will need to procure the

scheme through the private sector since it won’t have the necessary expertise to develop or

operate the scheme alone. The Local Authority will need technical, commercial and legal support

through this process so that it can secure the best partnering arrangement in its interests and

those of the local community.

Policy Assumptions made in the analysis were based on policy at the time of writing. The Government’s policies and incentives are subject to change and this presents an on-going risk to the project. A specific example of this is the uncertainty around RHI. There is a risk that the tariff may reduce or be removed completely over time thus providing the system operator with lower revenue. The impact of this is explored in more detail in section 5.3.3.


72

Development Risk

Programme delay presents a further development risk, in addition to difficulties encountered by

Forest Heath District Council in planning.

Operational Risk

The operating cost may be higher than expected due to the following issues occurring:

high heat losses

high return temps

high heat purchase / generation costs

high maintenance costs

lower than expected operating margins

lower volume of heat sales

poor take up

Consideration could also be given to adopting a tariff structure that incentivises retrofitting

measures that address heating system return temperatures.

6.3 Financial Risks

Development and operational costs

The development and operational costs presented in this report are derived from similar projects

using Ramboll’s database. These costs are highly project specific and will be dependent on how

the energy system is designed, procured and operated.

There is a risk that these costs have been underestimated or overestimated which will affect the

economic performance of the five options assessed. In order mitigate against this risk, a detailed

assessment of the development and operational costs should be undertaken for the options taken

forward to the detailed feasibility stage.

Capital Costs

The capital costs used within this study are based on Ramboll’s database of historic supplier data

and benchmarking. Specific quotations were not obtained and there is a risk that the stated

capital costs are underestimated or overestimated. This will affect the validity of the analysis

undertaken and the arrived conclusions.

In order to mitigate against this risk it is recommended that a cost consultant is commissioned to

conduct a detailed evaluation of project costs as part of any future development phases.

Unknown Future Project Expansion

The extent and nature of the future developments surrounding the Mildenhall Hub is unknown. It

is therefore difficult to future proof the Hub’s energy plant to supply a future district heating

network of unknown size. Oversizing the energy centre for potentially future will add significant

risk to the economic performance of the Mildenhall Hub energy scheme.

This risk would be considered especially high since it is likely that the land surrounding the Hub

will be developed into low density housing. The options for future proofing the Mildenhall Hub

Energy Scheme for potential future expansion are discussed in more detail in section 7.3.3.


73

6.4 Planning Risks

Restrictions on River Lark

In order to protect the ecology of water bodies, the Environment Agency place strict limitations

on temperature changes that arise from water and heat extraction / discharge. This could

potentially limit the quantity of heat that can be extracted by a WSHP located at the Mildenhall

Hub. This is discussed in more detail in section 6.1. In addition, the Environment Agency may be

unwilling to grant a licence to extract heat from the River Lark. Should this option be taken

forward to detailed feasibility it is recommended that early discussions are held with the

Environment Agency to determine the licence requirements and any restrictions that could apply.


74

6.5 Risk Register

Table 39: Risk Register for Mildenhall Hub

Risk No. Risk description Potential impact (including on cost and

schedule)

Impact (low

1- high 4)

Likelihood

(low 1-

high 4)

Current Risk

Rating

Mitigation to date Mitigation

Achieved Date

Further Action Action Owner

1 Accuracy of estimated heat demand Business case affected by variation in

heat sales.

2 3 6 All available information used and

comparisons made to similar buildings.

Jan-2016 At the next project stage the heat demand

calculations should be revised as new design

information becomes available.

Local Authority

/ Consultant

2 Hub heating system design Business case and technical viability. 3 1 3 Assumptions regarding heating system

expectations clearly stated in EMP report.

Jan-2016 Importance of appropriate heating system must be

emphasised throughout ongoing design stages.

Local Authority

/ Consultant

3 Ground conditions Presence of low conductivity soil will

increase collector loop length and

therefore cost

3 3 9 UK soil map consulted Jan-2016 Detailled soil investigations to be undertaken during

the design phase if GSHP selected

Local Authority

/ Consultant

4 Properties of River Lark (WSHP only) unsuitable for WSHP Technical and economic viability. 3 3 9 River observed during site visit. Nov-2015 Gather data from Environment Agency on

temperature, flow rate and depth and feasibility

stage.

Local Authority

/ Consultant

5 Uncertainty around commercial arrangement There may be additional costs to the

project or extensions to timescale

depending on chosen arrangement.

1 2 2 NA NA Conduct detailed business case and soft market

testing to deduce preferred commercial arrangement

and its effects on project,

Local Authority

/ Consultant

6 Assumptions around incentives are subject to uncertainty

and government policy

Business case, reduction removal of

incentives will impact business case and

project viability

2 2 4 Cost of heat has been modelled with and

without RHI, a conservative value has been

assumed in the modelling

Jan-2016 Status of Incentives to be kept under review

throughout feasibilty stage and on a continuous basis

as the project develops

Local Authority

/ Consultant

7 Development risk (change to master plan) Changes to heat load affect business case

and technical viability.

3 1 3 Sensitivity analysis carried out to show

effects of reduced load.

Jan-2016 Review project economics whenever significant

changes are made to development plans.

Local Authority

8 Operating costs higher than expected Business case 2 3 6 O&M costs based on previous projects. Jan-2016 Gather further data from suppliers at fasibility stage. Local Authority

/ Consultant

9 Development, investment and operational costs are

subject to uncertainty and will change as the project

develops

Business case, impact on NPVs, IRRs 2 2 4 Costs based on data from previous projects Jan-2016 Continued refinement of design assumptions and

improved cost estimates at feasibility stage. Engage a

cost consultant at delivery stage.

Local Authority

/ Consultant

10 Capital cost are higher than BaU case. Project fails to get funding, not

developed, opportunity lost

1 3 3 Sensitivity analysis carried out to quantify

risk.

Jan-2016 Feasibility work should include detailed cost

research.

Local Authority

/ Consultant

11 Current assumptions don't allow for future expansion of

network i.e. to new developments which are not

currently known and planned. This may reduce the long-

term business case for investment beyond what has been

proposed here.

Business case. Project is limited in its

ability to expand beyond the Hub, new

developments cannot connect.

2 2 4 There are currently no planned

developments of scale in Mildenhall. Design

for low temperatures in new development

could liberate network capacity.

Jan-2016 Consider potential for decentralised supplies feeding

into a larger network. Blanked connections sized for

Hubs full load should be included on the heating

system header to allow connection to any future DHN

or Energy Centre.

Local Authority

/ Consultant

12 Air quality management (CHP and Biomass only) If further measures are required to

address emissions the business case ,ay

be affected.

3 1 3 No AQMA regulations currently in place in

Mildenhall.

Jan-2016 Review status at design stage. Local Authority

/ Consultant

13 Environment agency and use of River Lark (WSHP only) Potential restrictions to use of river may

limit viability.

4 2 8 NA NA Conduct full investigation at feasibility stage. Local Authority

/ Consultant

Planning

Mitigation & ActionRisk Identification Risk Assessment

Commercial

Financial

Technical


75

7. CONCLUSIONS, RECOMMENDATIONS AND NEXT STEPS

This section outlines the conclusions, recommendations and next steps for West Suffolk, resulting

from the techno-economic analysis and risk appraisal.

7.1 Conclusions

The results of the study suggest that that under the assumptions of the techno-economic model,

the GSHP options is the most economically attractive. However, it is important to note that the

project is heavily reliant in the availability of RHI revenue at its current rates and sudden removal

of the RHI scheme may render the project unfeasible. Therefore moving forward with this

technology should only be done following further research into the Government’s plans for the

continuation of current incentives. Increasing the assumed capital expenditure by 20% or

reducing the assumed heat sale price by 20% does not drive down the project IRRs to an

unattractive level.

The gas CHP case was found to be the second most attractive technology option in terms of

economics, achieving an IRR of approximately 11%. However, the project economics are very

sensitive to the heat sale price and therefore the business case should be reassessed upon

further investigation into the commercial arrangements. A positive aspect of CHP is that it is not

affected by changes to RHI revenue.

Biomass has the potential for significant carbon savings when compared to the CHP and solar

thermal options. However, the economic results show that this solution may only be attractive for

a public led project. For this reason any variation in the heat sale and CAPEX assumptions was

found to be a deciding factor in the validity of the scheme.

The results of the WSHP show that the economic performance of this solution is marginal and

only likely to be attractive for a public led project. The capital expenditure was found to be higher

than all other scenarios mostly due to the requirement for pipe infrastructure between the river

and the plant room. This may present an additional barrier to implementation.

The solar thermal option was not found to be feasible in any case. The sensitivity analysis

showed that even improvements to the heat sale prices and capital costs could not bring the

project economics up to an acceptable level.

The integration of a Solar PV installation will increase the capital outlay for the project. However,

solar PV was found to result in small improvements both in terms of economics and carbon

emissions savings for CHP, biomass, WSHP and GSHP scenarios.

Overall, three out of the five scenarios stood out as being valid energy solutions for

the Mildenhall Hub: GSHP, gas CHP and heat-only biomass.

Each of the options was found to be sensitive to changes in key project variables

and therefore further investigation is required to establish the single preferred

scheme for Forest Heath District Council to implement.


76

7.2 Recommendations

It is recommended that Forest Heath District Council progresses all three of the preferred options

of GSHP, CHP and biomass to feasibility stage.

A presentation of the energy masterplanning results should be given to all relevant stakeholders

to gauge interest in the proposed schemes and obtain feedback on how each technology might or

might not be appropriate for their requirements. Stakeholder engagement is crucial at the

earliest project stages to ensure opportunities or barriers are not overlooked.

Further techno-economic modelling must be conducted when more accurate information is

available regarding the final masterplan for the Mildenhall Hub. At present the energy demand

information is not deemed to be accurate enough to clearly state feasibility.

7.3 Next Steps

7.3.1 Business Model and Business Case

There is a great deal more work to be done around technical, financial and commercial analysis

and de risking of the project before it can progress to business case.

To progress the project further, will require a detailed business case that should include financial

modelling as stated above, and also consideration of appropriate procurement, delivery and

governance options for the project. This should include the relative advantages and

disadvantages of each option, together with identification of the preferred course of action.

7.3.2 Ensuring Correct Design Standards are adopted

The design of the internal heating systems at the Mildenhall Hub will have a significant impact on

the operational capacity and efficiency of the primary supply technology.

The final Hub design should incorporate appropriate internal heating system designs to ensure

flow and return temperatures are compatible with the primary supply technology. Forest Heath

District Council, through their Planning and Building Control departments, should ensure that

systems are being designed, installed and commissioned appropriately.

Although no new developments were identified as part of this EMP, new developments may

emerge in future within the vicinity of the network. If this is the case then appropriate design

standards should be considered so that opportunities for connection are not missed.

7.3.3 Safeguarding Wider Network Demand

Since the extent and nature of the future developments around the Mildenhall Hub is unknown, it

is difficult to future proof the Hub’s energy plant to supply a future district heating network.

Furthermore, oversizing the energy plant would add cost to the project and therefore will put the

economic performance of the Hub’s energy strategy at risk. This risk is considered high as it is

likely that the land surrounding the Hub will be developed into low density housing which rarely

has an economic case for the establishment of a district heating network. However, the following

measures will provide some flexibility and facilitate development of a district heating network.


77

1. Provide sufficient space within the Energy Centre to locate an additional future boiler. The

headers within the energy centre should include blank connections for an additional heat

supply asset. This will also facilitate the connection of temporary boilers for use during any

major outage (major boiler or CHP service) or reworking of the energy centre.

2. The headers within the energy centre should include a set of connections through which the

full heat demand of the Mildenhall Hub can be provided. This would allow the Hub to be

connected to a future district heating network should any opportunity arise.

3. The energy centre should be located and designed such that heat supply assets can be

removed and relocated to a future energy centre. This would enable the boilers to be utilised

as part of a future district heating network should any opportunity arise.

7.4 Summary Implementation Plan


78

APPENDIX 1

ENERGY DEMAND MAP DATA


79

HEAT

Address Postcode Building Type Heat Demand

(kWh) Source

1 Breck Gardens IP28 7AU Residential 138,754 National Heat Map filtered and aggregated

Plot 6 Land At Queensway Farm Queensway

Residential 136,595 National Heat Map filtered and aggregated

Mildenhall College - Sheldrick Way IP287JX Education 306,739 National Heat Map filtered and aggregated

Mildenhall Hub - Sheldrick Way

Central Hub 44,087 Mildenhall Hub benchmarked

Mildenhall Hub - Sheldrick Way

Government

Buildings 269,706 Mildenhall Hub benchmarked

Mildenhall Hub - Sheldrick Way IP287JX Police 56,891 Mildenhall Hub benchmarked

Mildenhall Hub - Sheldrick Way IP287JX Recreational 679,113 Mildenhall Hub benchmarked

Mildenhall Hub - Sheldrick Way IP287JX Health 44,912 Mildenhall Hub benchmarked

Mildenhall Hub - Sheldrick Way IP287JX Education 12,127 Mildenhall Hub benchmarked

Mildenhall Hub - Sheldrick Way IP287JX Library 17,833 Mildenhall Hub benchmarked

Mildenhall Hub - Sheldrick Way IP287JX Education 606,497 Mildenhall Hub benchmarked

Wamil Court Wamil Way IP28 7JU Health 447,978

National Heat Map filtered and

aggregated

17 Mill Street IP287DP Hotels 188,430 Estimated using CIBSE TM46

Mildenhall Swimming Pool Recreation Way IP287HG Government Buildings 815,767 Billing data from the Council

32 St Andrews Street IP287HB Retail 234,980 National Heat Map filtered and aggregated

25 The Bell Hotel High Street IP287EA Hotels 201,630 Estimated using CIBSE TM46

Flat 2 14 Mill Street IP28 7DP Retail 102,899 National Heat Map filtered and aggregated

Second Floor 8 Breckland House Churchyard IP287EE Health 104,190


aggregated

2 A Mill Street IP28 7DP Hotels 207,484 National Heat Map filtered and aggregated

Flat 14 A High Street IP28 7EQ Hotels 249,494 National Heat Map filtered and aggregated

14 Market Place IP287EF Hotels 183,760 National Heat Map filtered and aggregated

15 Market Place IP287EF Retail 158,951 National Heat Map filtered and


80


(kWh) Source

aggregated

Spar Stores Market Place IP28 7EF Hotels 121,391


aggregated

5 King Street IP287EZ Commercial Offices 159,193 National Heat Map filtered and aggregated

Flat 4 5 Police Station Square IP28 7ER Hotels 115,456 National Heat Map filtered and aggregated

Fire Station North Terrace IP287AA Government Buildings 146,806

National Heat Map filtered and aggregated

Mildenhall Police Station Kingsway IP287HS Government Buildings 146,806


97 Kingsway IP287HS Transport 216,352 National Heat Map filtered and aggregated

Top Flat 6 Kingdom Hall Of Jehovahs Witnesses North Terrace IP28 7AA Industrial 266,915


Forest Heath District Council College Heath Road IP287EY Government Buildings 104,999 Billing data from the Council

Flat Mildenhall Social Club Recreation Way IP28 7HG Recreational 131,682


aggregated

48 50 Kingsway IP287HR Government Buildings 146,806


Land Adjacent Great Heath Cp School St Johns Close

Education 136,468 National Heat Map filtered and aggregated

143 St Johns Close IP287NX Health 541,200 Estimated using CIBSE TM46

77 Merlin House Fred Dannatt Road IP287RD Transport 548,011


aggregated

Unit 3 30 Hampstead Avenue IP287AS Transport 155,311 National Heat Map filtered and aggregated

Cedar Lodge Chiswick Avenue IP287BD

Government

Buildings 22,971 Billing data from the Council

Unit B 83 James Carter Road IP287DE Industrial 236,260 National Heat Map filtered and aggregated

Plot 74 Fred Dannatt Road

Industrial 241,922 National Heat Map filtered and aggregated




Retail 187,266 National Heat Map filtered and


81


(kWh) Source

aggregated

Unit 23 James Carter Road IP287DE Industrial 241,922


aggregated

Unit 27 James Carter Road IP287DE Industrial 241,922 National Heat Map filtered and aggregated


Plot 60 James Carter Road






Unit 17 Hampstead Avenue IP287AS Industrial 241,922


aggregated

Unit 12 Plot 24 Hampstead Avenue IP28 7AS Industrial 745,398 National Heat Map filtered and aggregated

Rd Castings Leyton Avenue IP287BL Industrial 1,590,040 National Heat Map filtered and aggregated

Unit A 53 Leyton Avenue IP287BB Transport 182,561 National Heat Map filtered and aggregated

Plot 58 Finchley Avenue

Transport 194,484 National Heat Map filtered and aggregated


Industrial 241,922


aggregated

Unit 10 Leyton Avenue IP287BL Industrial 249,330 National Heat Map filtered and aggregated

Unit 8 Leyton Avenue IP287BL Industrial 241,922


aggregated




82


(kWh) Source

Plot 44-45 Leyton Avenue

Industrial 241,922


aggregated

Plot 14 Finchley Avenue IP287BG Industrial 148,558 National Heat Map filtered and aggregated

Plot 7 Holborn Avenue

Industrial 241,922


aggregated

Plot 8 Holborn Avenue IP287AN Transport 408,668


aggregated



95 Hampstead Avenue IP287AS Industrial 241,922 National Heat Map filtered and aggregated

11 B Finchley Avenue IP287BG Industrial 241,922 National Heat Map filtered and aggregated

11 B Finchley Avenue IP287BG Transport 149,522 National Heat Map filtered and aggregated


Plot 88 James Carter Road

Commercial Offices 114,881 National Heat Map filtered and aggregated

38 Southgate Avenue IP287AT Industrial 241,922 National Heat Map filtered and aggregated

Mildenhall Monumentals 37 Southgate Avenue IP287AT Industrial 241,922 National Heat Map filtered and aggregated

36 Southgate Avenue IP287AS Industrial 241,922 National Heat Map filtered and aggregated


40 Hampstead Avenue IP287AS Industrial 241,922


aggregated



aggregated

94 C Hampstead Avenue IP287AS Industrial 241,922 National Heat Map filtered and aggregated



aggregated

Plot 52 Chiswick Avenue

Industrial 241,922 National Heat Map filtered and


83


(kWh) Source

aggregated

F W Cocksedge & Sons Ltd 25 Hampstead Avenue IP287AS Retail 179,199


aggregated

Safepac House Field Road IP287AP Transport 421,243 National Heat Map filtered and aggregated





Unit B 18 Delmore House Chiswick Avenue IP287AY Industrial 241,922 National Heat Map filtered and aggregated

Delmore House Chiswick Avenue




Plot 53 Chiswick Avenue IP287AY Transport 191,822 National Heat Map filtered and aggregated


Industrial 259,244


aggregated



56 Chiswick Avenue IP287AY Industrial 241,922 National Heat Map filtered and aggregated



St Marys Primary School North Terrace IP287AB Education 150,245 National Heat Map filtered and aggregated

College Heath Middle School Girton Close IP287PT Education 274,752


aggregated

Plot 52a Chiswick Avenue IP287AY Industrial 241,922 National Heat Map filtered and aggregated

Logika House 2 Holborn Avenue IP287AN Industrial 241,922


aggregated

Unit 10 Chiswick Avenue IP287AY Industrial 241,922 National Heat Map filtered and aggregated

Unit 9 Chiswick Avenue IP287AY Industrial 241,922 National Heat Map filtered and aggregated


84


(kWh) Source

31 Southgate Avenue

Industrial 241,922


aggregated

30 A Hampstead Avenue IP287AS Transport 193,307 National Heat Map filtered and aggregated

32 Southgate Avenue IP287AT Industrial 241,922


aggregated

27 28 Hampstead Avenue IP287AR Industrial 206,087


aggregated

Silverline Office Equipment Ltd James Carter Road IP287DE Industrial 241,922 National Heat Map filtered and aggregated

Plot 57 Finchley Avenue IP287BG Industrial 241,922 National Heat Map filtered and aggregated

Nestor Uk Ltd Chiswick Avenue IP287AX Commercial Offices 52,294 Benchmarked

Nestor Uk Ltd Chiswick Avenue IP287AX Transport 621,570 National Heat Map filtered and aggregated


85

COOLING

Address Building Type Postcode Cooling Demand

(kWh)

British Red Cross Recreation Way Commercial Offices IP287HG 11,787

24 Swallow Mead Farm Worlington Road Commercial Offices IP287DY 12,370

31 Wamil Way Commercial Offices IP287JU 5,556

Beeches Moat The Street Commercial Offices IP286AW 4,967

13 Mill Street Commercial Offices IP287DW 13,295

47 Lloyds Tsb Bank High Street Commercial Offices IP287DZ 15,698

46 St Andrews Street Commercial Offices IP287HB 13,526

27 29 Barclays Bank High Street Commercial Offices IP287EA 7,287


Second Floor 8 Breckland House Churchyard Commercial Offices IP287EE 7,364

34 High Street Commercial Offices IP287EA 11,486


11 Market Place Commercial Offices IP287EF 5,839

20 B Market Place Commercial Offices IP287EF 8,290

5 King Street Commercial Offices IP287EZ 26,008

1 Police Station Square Commercial Offices IP287ER 1,743

2 The Forge Cottage High Street Commercial Offices IP287EJ 1,553

Springvale Police Station Square Commercial Offices IP287ER 3,120

The Court House Queensway Government Buildings IP287EW 18,780

Fire Station North Terrace Government Buildings IP287AA 13,044

Mildenhall Police Station Kingsway Government Buildings IP287HS 23,140

Mildenhall District Office Government Buildings IP287EY 148,775

16 Mill Street Commercial Offices IP287DP 1,275

48 50 Kingsway Government Buildings IP287HR 7,394

Radio Base Station 18 A Chiswick Avenue Commercial Offices IP287AY 5,025


86

Address Building Type Postcode Cooling Demand

(kWh)

Cedar Lodge Chiswick Avenue Commercial Offices IP287BD 32,809

Unit 1g Plot 84 Gregory Road Commercial Offices IP287DF 2,740

Merlin Park Fred Dannatt Road Commercial Offices IP287RD 7,947

Unit 21 James Carter Road Commercial Offices IP287DE 7,447

Unit 4 Wallis Court James Carter Road Commercial Offices IP287DD 21,037

Plot 88 James Carter Road Commercial Offices

48,505

First Floor Front 26 Hampstead Avenue Commercial Offices IP287AS 22,414

Unit 15 Chiswick Avenue Commercial Offices IP287AY 8,579

Nestor Uk Ltd Chiswick Avenue Commercial Offices IP287AX 17,050

M And M Leisure Field Road Commercial Offices IP287AL 24,453

Beatrice Carter Place Field Road Commercial Offices IP287AL 24,068

Plot 1 Holborn Avenue Commercial Offices

29,531

Mildenhall Hub Government Buildings

4,613

Mildenhall Hub Central Hub - Public Access

11,160


87

ELECTRICITY

Address Building Type Postcode Power Demand (kWh)

Worlington Hall Hotel Mildenhall Road Hotels IP288RX 97,853

The Walnut Tree Newmarket Road Hotels IP288RU 35,266

Milden Court Hereward Avenue Health IP287LP 28,407

34 Market Place Retail IP287EQ 60,864

British Red Cross Recreation Way Commercial Offices IP287HG 48,671

26 C Worlington Road Retail IP287DY 47,928

24 Swallow Mead Farm Worlington Road Commercial Offices IP287DY 51,077

20 Cameron Mews Mill Street Hotels IP287DP 32,614

31 Wamil Way Commercial Offices IP287JU 22,941

Wamil Court Wamil Way Nursing home IP287JU 84,548

42 Queens Arms Queensway Hotels IP287JY 20,277

Barton Hall The Street Nursing home IP286AW 20,041

Bell Cottage Bell Lane Hotels IP286AJ 3,629

The Bell Bell Lane Hotels IP286AJ 11,319

Beeches Moat The Street Commercial Offices IP286AW 20,508

17 Mill Street Hotels IP287DP 137,232

Riverside Clinic Vets 15 Silver Lodge Mill Street Health IP287DP 11,347

13 Mill Street Commercial Offices IP287DW 54,897

11 Mill Street Retail IP287DP 66,344

5 A Mill Street Retail IP287DP 205,976


47 Lloyds Tsb Bank High Street Commercial Offices IP287DZ 86,426

The Pavilion Recreation Way Health IP287HG 50,127

32 St Andrews Street Retail IP287HB 699,204


25 The Bell Hotel High Street Hotels IP287EA 100,270

27 29 Barclays Bank High Street Commercial Offices IP287EA 40,118

13 St Andrews Street Hotels IP287HB 21,534


22 St Andrews Street Retail IP287HB 24,968

37 B High Street Retail IP287EA 125,904

37 A High Street Retail IP287EA 68,184

37 High Street Retail IP287EA 143,976



88



Second Floor 8 Breckland House Churchyard Commercial Offices IP287EE 40,543

30 High Street Retail IP287EQ 78,240





23 A High Street Retail IP287EA 51,464


22 26 High Street Retail IP287EQ 108,224

20 Tigers Head High Street Hotels IP287EQ 24,917



14 High Street Hotels IP287EQ 39,941


1 2 Market Place Retail IP287EF 185,320

4 Market Place Retail IP287EF 113,472


7 Market Place Health IP287EG 44,894

9 Market Place Hotels IP287EF 7,022

9 A Market Place Retail IP287EF 37,752

33 A Market Place Retail IP287EF 122,184

29 B Market Place Retail IP287EF 129,480




21 The White Hart Hotel High Street Hotels IP287EA 32,434

10 Market Place Health IP287EF 20,007


11 Market Place Commercial Offices IP287EF 32,146









89








20 B Market Place Commercial Offices IP287EF 45,637

7 King Street Retail IP287EZ 201,432

39 King Street Retail IP287EZ 35,848

54 Kingsway Retail IP287HR 131,480

5 King Street Commercial Offices IP287EZ 143,186

1 King Street Health IP287ES 15,788

9 Maids Head Kingsway Hotels IP287HN 39,637

7 Police Station Square Retail IP287ER 39,216

6 Police Station Square Retail IP287ER 67,960

4 5 Police Station Square Hotels IP287ER 21,034

1 Police Station Square Commercial Offices IP287ER 9,597

12 C High Street Hotels IP287EQ 11,778

12 B High Street Retail IP287EQ 74,480

12 A High Street Retail IP287EQ 80,928



1 New Street Retail IP287EN 46,024



2 The Forge Cottage High Street Commercial Offices IP287EJ 8,548

Springvale Police Station Square Commercial Offices IP287ER 17,178

3 High Street Retail IP287EJ 189,240

1 Manor Court High Street Retail IP287EH 57,192










90


North Terrace Garage North Terrace Retail

317,208

The Court House Queensway Government Buildings IP287EW 50,889

Fire Station North Terrace Government Buildings IP287AA 35,346

Mildenhall Police Station Kingsway Government Buildings IP287HS 62,701

Ambulance Station Chestnut Close Health IP287NL 24,885

103 Half Moon Inn Kingsway Hotels IP287HS 27,023

9 Brandon Road Retail IP287HZ 42,996

Mildenhall Health Clinic Chestnut Close Health IP287NL 56,696

Holiday Accomodation 23 North Terrace Hotels

24,302

1 Market Street Retail IP287ES 80,400

Mildenhall District Office Government Buildings IP287EY 320,937

16 Mill Street Commercial Offices IP287DP 7,020

48 50 Kingsway Government Buildings IP287HR 20,036

Mildenhall Tyre 3 Field Road Retail IP287AF 55,308

143 St Johns Close Retail IP287NX 106,284

Unit C 81 Fred Dannatt Road Retail IP287RD 176,496

Ro 25a Hampstead Avenue Retail IP287AS 254,504

Radio Base Station 18 A Chiswick Avenue Commercial Offices IP287AY 20,748

Cedar Lodge Chiswick Avenue Commercial Offices IP287BD 31,976

85 Gregory Road Retail IP287DF 540,504

Unit 1g Plot 84 Gregory Road Commercial Offices IP287DF 11,314

Unit 1h Plot 84 Gregory Road Retail IP287DF 27,808

Unit 1i Plot 84 Gregory Road Retail IP287DF 27,984

Unit 1e Plot 84 Gregory Road Retail IP287DF 23,344

Unit 1c Plot 84 Gregory Road Retail IP287DF 19,116

Unit 1a Plot 84 Gregory Road Retail IP287DF 28,104

Unit A 83 James Carter Road Commercial Offices IP287DE 94,881

82 A James Carter Road Retail IP287DE 62,280

82 D James Carter Road Retail IP287DE 110,416

5 Merlin Park Fred Dannatt Road Retail IP287RD 94,112






Merlin Park Fred Dannatt Road Commercial Offices IP287RD 32,812

Plot 70 Fred Dannatt Road Retail

777,400


91


Unit 1-5 65 James Carter Road Retail IP287DE 57,408

Unit 3 65 James Carter Road Retail IP287DE 57,832

Unit 4 James Carter Road Retail IP287DE 54,696

Unit 21 James Carter Road Commercial Offices IP287DE 30,749




Unit 19 Hampstead Avenue Retail IP287AS 187,264

Unit 20b Leyton Avenue Retail IP287BL 184,860

Unit B 53 Leyton Avenue Retail IP287BL 342,212

47 Leyton Avenue Retail IP287BL 241,144

Unit 11 Leyton Avenue Retail IP287BL 59,452





Plot 43a Leyton Avenue Retail IP287BL 183,764

L G Aves And Son Finchley Avenue Retail IP287BG 132,504

Unit 4 Wallis Court James Carter Road Commercial Offices IP287DD 86,862

Plot 88 James Carter Road Commercial Offices

200,279

Unit 7 Chiswick Avenue Retail IP287AY 290,248

F W Cocksedge & Sons Ltd 25 Hampstead Avenue Retail IP287AS 1,003,816

First Floor Front 26 Hampstead Avenue Commercial Offices IP287AS 92,547

Field Road Service Station Field Road Retail IP287AL 42,440

Unit 15 Chiswick Avenue Commercial Offices IP287AY 35,424

14 Chiswick Avenue Retail IP287AY 87,112

Plot 18a Chiswick Avenue Retail

125,432

Nestor Uk Ltd Chiswick Avenue Commercial Offices IP287AX 70,400

M And M Leisure Field Road Commercial Offices IP287AL 100,966

Unit 1 Holborn Avenue Retail IP287AN 292,752

Unit 2 Holborn Avenue Retail IP287AN 190,144

Crossways North Terrace Health IP287AE 7,718

1 St Johns Close Retail IP287NT 17,724

Beatrice Carter Place Field Road Commercial Offices IP287AL 99,379

84 Field Road Health IP287AL 9,834

Unit 8 Chiswick Avenue Retail IP287BD 183,480

Plot 1 Holborn Avenue Commercial Offices

121,933


92



Swimming Pool Recreational

234,619

Mildenhall Hub Government Buildings

36,118

Mildenhall Hub Police

10,465

Mildenhall Hub Health

18,155

Mildenhall Hub Education

548,477

Mildenhall Hub Central Hub

47,624

Mildenhall Hub Leisure Centre

270,137

Mildenhall Hub Commercial Offices

930,974


93

APPENDIX 2

TECHNOLOGY OPTIONS APPRAISAL


94


95


96

mildenhall hub heat network opportunities · mildenhall hub heat network opportunities ramboll 40...

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