chilled water thermal energy storage –– an alternative to ... water storag… · –– an...

FEFPA Summer 2015

Chilled Water Thermal Energy StorageChilled Water Thermal Energy Storage an Alternative to Static Icean Alternative to Static Ice

Chilled Water TES an Alternative to Static IceRouleau, Roman, Ellis 7 July 2015

Presentation By:Presentation By:

Marc Rouleau, PEMarc Rouleau, PEExecutive Director of Facilities Management,District School Board of Collier County

Adrian Roman, RA, AIAAdrian Roman, RA, AIADistrict Architect / Facilities Planning and Design,District School Board of Collier County

Lawrin T. Ellis, PE, LEED AP,Lawrin T. Ellis, PE, LEED AP, CxACxAPrincipal / Senior Mechanical Engineer,TLC Engineering for Architecture


Presentation OutlinePresentation Outline Introduction to Thermal Energy

Storage (TES) Basic Design of Chilled Water

Storage Systems Tank Location Construction of Chilled Water

Storage Tank Operation of Chilled Water Storage

Systems Economic Comparison of Chilled

Water vs. Static Ice


Introduction to Thermal Energy StorageIntroduction to Thermal Energy StorageThermal Energy Storage (TES)

Basic Concept TES Systems remove heat from or add heat to astorage medium for use at another time

Most Common Application is Comfort Cooling Energy is Charged, Stored, and Discharged - Can be Daily, Weekly,

or Seasonally Storage unit is Ton-hour Means to Reduce Total Utility Bill and/or Size of Equipment

Applications that Benefit from TES Loads are Cyclical Energy Costs are Time-Dependent (Time-of-Use Rate) Utility Rebates or Economic Incentives for Load-Shifting Equipment

Focus on Static Ice and Chilled Water Storage


Introduction to Thermal Energy StorageIntroduction to Thermal Energy StorageThermal Energy Storage (TES) - Static Ice

Typical Storage Medium Water, due to High Latent Heat Capacityof 144 Btu/lb

Latent Technology achieves capacity through change of state fromSolid to Liquid during Melt process

Typically Requires about 1.455 ft3 ice per ton-hour of cooling Example 5,000 ton-hours Cooling requires 7,275 ft3 ice (roughly

54,420 gallons/water)


Introduction to Thermal Energy StorageIntroduction to Thermal Energy StorageThermal Energy Storage (TES) - Chilled Water

Typical Storage Medium Water, specific heat of 1 Btu/lbF Sensible Technology achieves capacity through high specific heat of

water Requires about 10.66 ft3 water per ton-hour (at 20 Degrees Delta T) Example 5,000 ton-hours Cooling requires 53,300 ft3 water (roughly

398,725 gallons/water)


Design of Chilled Water Storage SystemsDesign of Chilled Water Storage SystemsTypes of Chilled Water Storage Systems

Simplest Form Series Storage Tank Effective at reducing on-peak electric demand Drawbacks Tendency for stagnation, Higher leaving water

temperatures



Multiple Tanks Parallel Storage Tanks Minimizes stagnation associated with Series Tank Drawbacks Need accurate means of measuring tank volume,

Complex Controls to ensure proper sequencing



Most Common Stratified Storage Tanks, System Preferredby Collier County Schools

Exploits tendency of warm and cold water to stratify Drawbacks Requires specifically engineered diffusers

designed to promote stratification


Design of Chilled Water Storage SystemsDesign of Chilled Water Storage SystemsStratified Storage Tanks - Understanding Thermocline

Naturally occurring change in density of water between 44-54degrees.

Thermal layer separating warmer water at top from coolerwater at bottom.

Design of Stratification Diffusers optimized to maintainThermocline.


Design of Chilled Water Storage SystemsDesign of Chilled Water Storage SystemsStratified Storage Tanks Tank Sizing Estimates

Building/Campus Load Profile Summer Peak Full Storage Shift TES Covers Load (Typical Operation) Total Capacity based on Ton-Hours Shifted



Building/Campus Load Profile Summer Peak Part Storage Shift TES Covers Peak Loads, Alternate

Approach to Full Shift



Florida Power and LightTime of Use Tariff Summer and Winter PeakPeriods

TES Operates During On-Peak Periods to MinimizeEnergy Costs



Tank Storage Volume Calculation using Figure of Merit FOM of Sizing Estimates is approximately 0.9 (90%)

Given FOM, Total Ton-Hrs and Tank Differential Temperature,solve of Volume Using:

Note: Specific Gravity of Water at 50F is approximately 1.0.


Design of Chilled Water Storage SystemsDesign of Chilled Water Storage SystemsStratified Storage Tanks Estimating Tank Geometry

Tall, Slender Tanks are Preferred to Optimize Thermocline andMinimize Footprint

Where practical, Tank Height should be greater than highestair vent in Chilled Water Lines Prevents Drainback

Quick Formula for Tank Sizing:Volume, gallons = 5.875D2H

whereD = Inside Tank Diameter, Feet

H = Height of Water, Feet

Assuming 750,000 gallons (6,583 Ton-hrs at 14 Degree Delta T) andDiameter of 50 feet, Height of Water is approximately 51.06 feet.


Tank LocationTank LocationAfter tank sizing estimates - but prior to construction -

determine tank location

Location can have a profound impact on cost, campusappearance and your relationship with the community

Determining location is a balancing act school needs,cost, community concerns


Tank LocationTank LocationFirst step Review Local Ordinances

Height restrictions Aesthetic limitations Prohibited structures Florida Statutes 1013.37(1)(a) and Florida Building Code 423.2.2

exempts District from compliance with local Ordinances


Tank LocationTank LocationNext Determine optimal location(s)

Distance from chiller plant and buildings Tank can act as chiller plant sound block Shield tank with buildings May be limited by retention areas, sporting fields, easements, terrain

features, buried utilities


Tank LocationTank Location Conduct Internal Review

Generate renderings All proposed locations Highlight potential visual impacts Illustrate plan to eliminate or minimize visual impacts

Review locations with Principal and other stakeholders (maintenance,facility manager)


Tank LocationTank LocationRenderings may look like this view from above


Tank LocationTank LocationWith ground level views


Tank LocationTank Location


Tank LocationTank LocationMeet with local officials and community members

Review HVAC system and main components HVAC Impact on student health and comfort Review utility rate structures Introduce concept of chilled water thermal energy storage Chilled water storage benefits

Lower electric bill more than $5,000/month Extend life of chiller plant

Review scope of work Present renderings to illustrate visual impact

Emphasize reduced impact using paint and landscaping


Chilled Water Storage Tank ConstructionChilled Water Storage Tank ConstructionStratified Storage Tanks

Common construction for Tanks Steel and Pre-stressed Concrete

Pre-stressed Concrete mostCommon for Larger Systems

Typical Construction Concrete Base, Steel Diaphragm Wall with

interior/exterior shotcrete on pre-stressed reinforcement (inside andoutside),

Concrete Dome with InteriorInsulation,

Exterior insulation, Exterior finish EIFS or Aluminum

Siding


Chilled Water Storage Tank ConstructionChilled Water Storage Tank ConstructionStratified Storage Tank Concrete Base


Chilled Water Storage Tank ConstructionChilled Water Storage Tank ConstructionStratified Storage Tank Steel Diaphragm


Chilled Water Storage Tank ConstructionChilled Water Storage Tank ConstructionStratified Storage Tank - Steel Diaphragm, Readyfor Shotcrete


Chilled Water Storage Tank ConstructionChilled Water Storage Tank ConstructionStratified Storage Tank Exterior Shotcrete


Chilled Water Storage Tank ConstructionChilled Water Storage Tank ConstructionStratified Storage Tank Interior Prep/Shotcrete


Chilled Water Storage Tank ConstructionChilled Water Storage Tank ConstructionStratified Storage Tank Installation of Dome


Chilled Water Storage Tank ConstructionChilled Water Storage Tank ConstructionStratified Storage Tank Interior with Dome and Diffuser


Chilled Water Storage Tank ConstructionChilled Water Storage Tank ConstructionStratified Storage Tank Exterior Finish Installation


Chilled Water Storage Tank ConstructionChilled Water Storage Tank ConstructionStratified Storage Tank Exterior Finish, Painted Siding


Chilled Water Storage Tank ConstructionChilled Water Storage Tank ConstructionStratified Storage Tank FillEr Up!

Utility Costs Coordination:Meet early with local water purveyorto establish sewer credits for wateruse during construction and tank fill.Temporarily install dedicated watermeter.

Water Treatment Coordination:Account for adding inhibitor andbiocide to full tank prior to finalconnection to chilled water piping.

Tank Settlement Survey:Allow 4-6 weeks for tank settlementfollowing fill. Verify with survey,minimum of three points on tank.


Operation ofOperation of Static Ice TESStatic Ice TESMain Components in a Static Ice TES

Chillers, 25% Glycol Brine Solution Nominal 23F Operation Static Ice Tanks Glycol /Chiller Loop Pumps Glycol Make-up/Mixing Tank Heat Exchanger Three-Way Isolation/Diverting Valves Ice Farm Piping and Low Temp Insulation (3-Inch Nominal)


Operation ofOperation of Static IceStatic IceCentral Energy Plant with Static Ice TES


Operation ofOperation of Static Ice TESStatic Ice TES


Operation ofOperation of Static ice TESStatic ice TES


Operation ofOperation of Static Ice TESStatic Ice TES


Operation of Chilled Water StorageOperation of Chilled Water StorageMain Components in a Chilled Water TES

Chillers, Water - Nominal 42F Operation Chilled Water Storage Tank Chiller Loop Pumps Two-Way Isolation Valves Storage Tank Piping with Standard Temp Insulation (2-Inch Nominal)


Operation of Chilled Water StorageOperation of Chilled Water StorageCentral Energy Plant with Chilled Water StorageTES


Operation of Chilled Water StorageOperation of Chilled Water Storage


Operation of Chilled Water StorageOperation of Chilled Water StorageComparison of Chiller Performance Air Cooled

Nominal 500-Ton Air Cooled Chiller, 25% Glycol Brine Solution Chilled Water Supply Temp 23F Operation during Ice Make Mode: Chiller Capacity

352 Tons, Chiller Efficiency 1.24 kW/Ton at 80F Ambient Chilled Water Supply Temp 40F Operation during Chiller Mode: Chiller Capacity

477 tons, Chiller Efficiency 1.13 kW/Ton at 85F Ambient

Nominal 500-Ton Air Cooled Chiller, Water Chilled Water Supply Temp 42F Operation during Chilled Water Storage Charge

Mode: Chiller Capacity 518 Tons, Chiller Efficiency 1.03 kW/Ton at 80F Ambient Chilled Water Supply Temp 42F Operation during Chiller Mode: Chiller Capacity

503 tons, Chiller Efficiency 1.10 kW/Ton at 85F Ambient

Chiller Capacity/Efficiency Comparison Additional 166 TonsCapacity and 0.21 kW/Ton Efficiency Gain in Chilled Water Charge vs.Ice Make Modes


Operation of Chilled Water StorageOperation of Chilled Water StorageComparison of Chiller Performance Water Cooled

Nominal 500-Ton Water Cooled Chiller, 25% Glycol Brine Solution Chilled Water Supply Temp 23F Operation during Ice Make Mode: Chiller Capacity

374 Tons, Chiller Efficiency 0.835 kW/Ton at 80F Entering Condenser Water Chilled Water Supply Temp 40F Operation during Chiller Mode: Chiller Capacity

480 tons, Chiller Efficiency 0.661 kW/Ton at 85F Entering Condenser Water

Nominal 500-Ton Water Cooled Chiller, Water Chilled Water Supply Temp 42F Operation during Chilled Water Storage Charge

Mode: Chiller Capacity 500 Tons, Chiller Efficiency 0.488 kW/Ton at 80FEntering Condenser Water

Chilled Water Supply Temp 42F Operation during Chiller Mode: Chiller Capacity 480 tons, Chiller Efficiency 0.541 kW/Ton at 85F Entering Condenser Water

Chiller Capacity/Efficiency Comparison Additional 126 TonsCapacity and 0.281 kW/Ton Efficiency Gain in Chilled Water Chargevs. Ice Make Modes


Economics of Chilled Water vs. Static IceEconomics of Chilled Water vs. Static IceSystems Economics Comparison First Costs

Gulf Coast High School, Laurel Oak Elementary School Static Ice at both Schools - GCHS Water-Cooled Plant, LOES Air Cooled Plant Both Plants in CIP for Maintenance Replacement Alternate Option to Provide Centralized Plant with TES Feasibility Study



GCHS/LOES Direct Replacement CEP First Cost Comparisons Pricing Estimates for Replacing Each Plant with Similar Equipment and Replacing Ice

at Each School Alternate to Provide Centralized Campus Chilled Water Plant Considered Air-

Cooled and Water-Cooled Options

Direct Replacement of Systems at GCHS (Including Ice) - $1,667,150 Two Nominal 450-ton Ice Chillers; One Nominal 215-ton Base-load Chiller; 4,850 Ton-

hours TES Static Ice

Direct Replacement of Systems at LOES (Including Ice) - $ 618,325 Two Nominal 170-ton Ice Chillers; 2,500 Ton-hours TES Static Ice

Total Direct Replacement Cost Estimate - $ 2,285,475



GCHS/LOES Centralized CEP First Cost Comparisons Alternate to Provide Centralized Campus Chilled Water Plant Considered Air-

Cooled and Water-Cooled Options Added Additional 5-Percent Capacity in TES for Future Campus Growth, Additional

Chiller Redundancy for TES Charging

Centralized CEP with Redundancy and Chilled Water Storage Three Nominal 500-ton Chillers, 7,700 Ton-hrs of Chilled Water TES

First Cost Estimate for Air Cooled Chiller Plant - $ 2,373,925

First Cost Estimate for Water Cooled Chiller Plant - $ 2,985,750






Centralized CEP with Redundancy and Chilled Water Storage Three Nominal 500-ton Chillers, 7,700 Ton-hrs of Chilled Water TES

First Cost Estimate for Air Cooled Chiller Centralized Plant with ChilledWater Storage vs. Direct Replacement - $ 88,150

First Cost Estimate for Water Cooled Centralized Plant with ChilledWater Storage vs. Direct Replacement - $ 700,275






Total Estimated Cost for Static Ice Bank Replacement - $ 735,000

Total Estimated Cost for Chilled Water Storage Tank - $ 913,000

Net Add for Chilled Water Storage Tank - $ 178,000

Estimated FPL Incentive Payment - $ 633,600


Economics of Chilled Water vs. Static IceEconomics of Chilled Water vs. Static IceSystems Economics Comparison Energy Costs

Total Plant Efficiency Direct Replacement Water Cooled Ice Chillers at GCHS Nominal 1.29 kW/ton (Includes Cooling Tower

Make-up Water) at 630 Chiller Tons for Ice Make Air Cooled Ice Chillers at LOES Nominal 1.34 kW/ton at 240 Chiller Tons for Ice

Make

Total Plant Efficiency Centralized CEP with Chilled Water Storage Water Cooled Water Chillers Nominal 0.95 kW/ton (Includes Cooling Tower Make-

up Water) at 1,000 Chiller tons for Tank Charge Air Cooled Water Chillers Nominal 1.14 kW/ton at 1,000 Chiller tons for Tank

Charge



Total Plant Energy Direct Replacement, GCHS Water Cooled Ice Chillers at GCHS 630 Chiller Tons for Ice Make with 4,850 Ton-

hrs of Ice Storage; Nominal Charge Time of 7.7 Hours At 1.29 kW/ton, 630 Chiller Tons for 7.7 Hours Rough Energy Estimate using FPL

GSLDT-1, $ 2,584 Demand Charge and $ 272 Energy Charge

Total Plant Energy Direct Replacement, LOES Air Cooled Ice Chillers at LOES 240 Chiller Tons for Ice Make with 2,500 Ton-hrs of

Ice Storage; Nominal Charge Time of 10.4 Hours At 1.34 kW/ton, 240 Chiller Tons for 10.4 Hours Rough Energy Estimate using FPL


Total Energy Cost Estimate, Per Ice Bank Charge DirectReplacement for GCHS/LOES

Demand Charge - $ 3,607 (Monthly) Energy Charge - $ 417 / Charge



Total Plant Energy Centralized CEP, Water Cooled At 0.95 kW/ton, 1,000 Chiller Tons for 7.7 Hours Rough Energy Estimate using FPL


Total Plant Energy Centralized CEP, Air Cooled At 1.14 kW/ton, 1,000 Chiller Tons for 7.7 Hours Rough Energy Estimate using FPL


Centralized Water Cooled vs. Direct Replacement Approximately $ 586 / Month Demand Savings Approximately $ 99 / TES Charge Energy Savings

Centralized Air Cooled vs. Direct Replacement Approximately $ 18 / Month Demand Costs Approximately $ 36 / TES Charge Energy Savings


Economics of Chilled Water vs. Static IceEconomics of Chilled Water vs. Static IceSystems Economics Comparison Life Cycle Costs

Comparison of Direct Replacement vs. Centralized CEP with ChilledWater Storage

25-Year Life Cycle Cost Analysis Assumptions Replacement of Air-Cooled Chillers at Year 15 Replacement of Static Ice Banks at Year 17 Maintenance Costs Energy Costs Water and Water Treatment Costs for Water Cooled Plants

LCCA for Direct Replacement at GCHS - $ 8,920,694 LCCA for Direct Replacement at LOES - $ 5,427,270

Combined LCCA for Direct Replacement - $ 14,347, 964


Economics of Chilled Water vs. Static IceEconomics of Chilled Water vs. Static IceSystems Economics Comparison Life Cycle Costs

Comparison of Direct Replacement vs. Centralized CEP with ChilledWater Storage

25-Year Life Cycle Cost Analysis Assumptions Replacement of Air-Cooled Chillers at Year 15 Maintenance Costs Energy Costs Water and Water Treatment Costs for Water Cooled Plants

LCCA for Centralized Water Cooled Plant - $ 8,853,915 LCCA for Centralized Air Cooled Plant - $ 13,827,641


Economics of Chilled Water vs. Static IceEconomics of Chilled Water vs. Static IceSystems Economics Comparison 25-Year LCCAOwnership and Operating Costs, Including TES

Centralized Air Cooled CEP vs. Direct Replacement - $ 520,323 Centralized Water Cooled CEP vs. Direct Replacement - $ 5,494,049

Centralized Water Cooled vs. Air Cooled - $ 4,973,726


Economics of Chilled Water vs. Static IceEconomics of Chilled Water vs. Static IceSystems Economics Comparison 25-Year LCCAOwnership and Operating Costs, Including TES

Chilled Water Storage is Viable Economic Alternative to Static Ice forLong-term Ownership

First-Cost Differences between Chilled Water Storage vs. Static IceDiminish as TES Storage Capacity Increases Economy of Scale

Around 10,000 Ton-hrs of Storage, Costs are almost Identical


Economics of Chilled Water vs. Static IceEconomics of Chilled Water vs. Static IceComparative Costs for Current Installations

Gulfview Middle School Tank Construction Cost - $ 452,000 FPL Incentive - $ 209,760 Cost Difference - $ 242,240 Annual Energy Cost Savings - $ 50,000 Payback Approximately 5 Years

Pelican Marsh Elementary School Tank Construction Cost - $ 791,660 FPL Incentive - $ 231,840 Cost Difference - $ 559,820 Annual Energy Cost Savings Waiting on Complete Year of Data

Corkscrew Elementary/Middle Schools Tank Construction Cost - $ 966,018 FPL Incentive - $ 380,640 Cost Difference - $ 588,378 Annual Energy Cost Savings Waiting on Complete Year of Data


SummarySummary Introduction to Thermal Energy

Storage (TES) Basic Design of Chilled Water

Storage Systems Tank Location Construction of Chilled Water

Storage Tank Operation of Chilled Water Storage

Systems Economic Comparison of Chilled

Water vs. Static Ice


Questions?Questions?

chilled water thermal energy storage –– an alternative to ... water storag… · –– an...

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