chiller plants for tropical climates - airah · 2014-09-09 · chiller plants for tropical climates...

Chiller Plants for Tropical Climates Today’s Agenda Chiller developments VSD advantages YMC2 Technology Chiller plant optimization Series counter-flow configuration Opportunities from ‘de-coupling’ Multi CHW loop applications Efficiency possibilities Example project

YMC2 – YORK® State of the Art Magnetic Centrifugal Chillers

AIRAH 2014

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Control, monitor, and communication

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In recent decades, significant gains in chiller efficiency at full & part load through advances in HX, compressor, motor, driveline, and economizers.

The biggest single efficiency gain has been at reduced ‘lift’ condition with the adoption of the variable speed drive.

YK YMC2


Despite using more environmentally benign, yet less efficient refrigerants, chiller efficiency has improved significantly

Reduces inrush current to < than FL amps (soft start)

Corrects power factor close to unity

Reduces utility demand

Regulates compressor speed to provide the most efficient chiller operation, reducing energy consumption


VSD technology benefits

High efficiency permanent magnet motor

Latest Generation VSD

Frictionless magnetic bearings

Direct drive compressor

Oil free design


Recent technology introduction Variable speed magnetic bearing oil free centrifugal chillers

Load% LWT EWT COP EWT COP COP COP % % 100 6.7 29.4 6.46 29.4 6.46 6.28 6.60 2.1 5.0 90 6.7 29.4 6.54 27.2 7.05 7.05 7.43 5.6 5.6 80 6.7 29.4 6.52 25.0 7.55 7.99 8.41 11.5 5.5 70 6.7 29.4 6.44 22.8 7.83 9.09 9.66 22.8 6.2 60 6.7 29.4 6.25 20.5 8.12 10.34 11.23 38.6 9.0 50 6.7 29.4 6.14 18.3 8.18 11.72 13.12 61.1 13.0 40 6.7 29.4 5.75 18.3 7.55 11.31 12.79 89.5 13.0 30 6.7 29.4 5.28 18.3 6.77 10.34 11.96 76.1 15.7 20 6.7 29.4 4.46 18.3 5.55 9.30 10.31 85.9 10.9 15 6.7 29.4 3.96 18.3 4.88 8.25 8.60 75.7 4.0

At AHRI “relief “ conditions At constant conditions

YK VSD

YK CSD

YMC2

VSD YK

CSD YMC2

VS YK CSD

YMC2

VS YK VSD


Comparing fixed speed to variable speed technology

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YK CSD Constant CEFT YK CSD AHRI Relief YK VSD AHRI Relief YMC2 AHRI Relief

Chillers operate for 85% of the time within this capacity range


VSD chillers perform best with condenser water “relief”

How to effectively apply high efficiency VSD chillers to HVAC systems

in tropical climates?


Design Performance

Chiller58%

Tower5%

Fans24%

Pumps13%

One of the most ‘constant’ tropical climates is Singapore. What levels of plant efficiency can be achieved where operating conditions have limited variance ?

Measure & Verify

Optimize System

Automate System

Apply components effectively, optimally

Select components effectively, optimally

Design system infrastructure to maximize efficiency potential

Operating Decisions

Design Decisions

Maintain

Efficient chillers are a great foundation, but optimization is a process


Apply variable speed drives Chillers Pumps Tower Fans Reduce “lift” lower CW temperatures higher CHW temperatures Reduce pump energy wide delta T variable flow Efficient chiller staging energy based vs load based

The key functional components of chiller plant optimization are the same irrespective of jobsite location


Lower tower water temps

Higher chilled water temps

Limited opportunity at design condition. Some opportunity when at off-design.

Significant opportunity with HT CHW, chiller arrangement,and airside design

AND


All chillers benefit from reduced “lift”…..especially VSD chillers. How to achieve reduced ‘lift’ in tropical climates ?

Supply

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Johnson Controls - Proprietary & Confidential

Every 1 deg C of ‘lift’ reduction improves VSD chiller efficiency by 3-6%

depending on the technology


One has to ‘create’ the optimum operating environment

Every 1 deg C counts !

Conventional design @ “ASIA” conditions

Pressure

Enthalpy

Lift

12° C 6° C

32 ° C 95° F 35° C

37° C


The cooling tower is the most effective heat transfer device in the system

32 - 37 deg C OR 30 - 35 deg C

Design Condition

Can we lower tower water temps ?

Tower water does not have to be held constant

Energy efficiency ratio = 7.5 kW / 875 kWr = 117

250 ton tower super low noise tower

Conventional design = approach 5-7 deg C Optimized design = approach 3-4 deg C


Singapore Building Operation Profiles can take some advantage of ambient wet bulb relief

Source: ASHRAE IWEC Weather Bin Data

Singapore tower water will achieve 3 deg C of relief with 5 deg C of relief available for 24/7 systems

ASHRAE 32.8db / 27.3wb


Can we raise CHW temps ?

Conventional coil design = 2.5 m/s Face velocity & approach 6-7 deg C Optimized coil design = < 2.0 m/s Face velocity & approach 3-4 deg C

Chiller HX approach temperatures <= >1 deg C


13 deg C air off coil = 9 deg C CHW @ 4 deg C approach

Design delta T 5.5C 7.5C 9.5C % Flow reduction 0 2/7.5 =27% 4/9.5 = 42%

Wide delta T chilled water systems save significant pump energy, but to use ‘similar’ CHW coils, the chillers must work harder.

12.5 / 7.0 deg C

13.5 / 6.0 deg C

14.5 / 5.0 deg C


Can we widen the CHW temperature range to 8-10 deg C?

Using 9 deg C CHW & 10 deg C delta T will need different AHU CHW coils

air ON db 25 air ON wb 18.5 air OFF db 13 Air Qty l/s 5,000

Increasing face area and reducing coil velocity is key to equivalent energy performance


What is the impact to the AHU CHW coil with 9 deg C CHW temp and 10 deg C delta T ?

Smaller CHW pipes

Smaller CHW valves and fittings

Reduced thermal insulation area

Smaller CHW pumps, motor kW, and VSD’s

Smaller CHW pump electrical requirements

Smaller chiller electrical requirements

1st cost economics of a 9 /19 deg C CHW system

Savings Costs Larger AHU coil HX areas and

rows to achieve equivalent energy performance

If the additional coil area cannot be accommodated in AHU height, the AHU footprint will increase


9 deg C 14.0 deg C 19 deg C

30 deg C 32.5 deg C 35 deg C

Lift is reduced 2.5 degrees C Lift is reduced 5.0 degrees C

VPF

VPF = variable primary CHW flow & fixed delta T

Wide CHW delta T best suits Series Counter-flow chillers


Series Counter-Flow chillers further reduce lift

9 14 19

30 32.5 35

Series counter flow YMC2 performance at Singapore conditions (office hours)

1645 kWr 1520kWr

Load% CHW in CHWint CHWout CWin CWint CWout UP

COP DN

COP SYS COP

100 19 13.8 9 30 32.4 35 8.75 7.83 8.29

90 19 13.8 9 29.4 31.6 33.9 9.33 8.14 8.70

80 19 13.8 9 28.8 30.7 32.8 9.96 8.49 9.20

70 19 13.8 9 28.2 29.9 31.7 10.56 8.79 9.63

60 19 13.8 9 27.6 29.1 30.7 10.95 8.92 9.88

50 19 13.8 9 27 28.2 29.5 11.42 8.92 10.07

40 19 13.8 9 27 28 29.1 10.95 8.43 9.58

30 18.5 13.6 9 27 27.7 28.5 10.02 7.46 8.60

20 15.4 12.1 9 27 27.5 28.1 6.83 5.38 6.04


Load% YK YMC2 S/C 100 6.46 8.29 28% 90 6.54 8.70 33% 80 6.52 9.20 41% 70 6.44 9.63 50% 60 6.25 9.88 58% 50 6.14 10.07 65% 40 5.75 9.58 66% 30 5.28 8.60 48% 20 4.46 6.04 35%

YK CSD at AHRI

constant CW YMC2 S/C at 9 deg C & 30 deg C

with 3 deg C CW relief


How does optimized series counter flow YMC2 efficiency compare to conventional Singapore design with YK CSD ?

Chiller energy reduced on weighted average by 55% !

The bulk of operating hours

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YK CSD Constant CEFT YMC2 SCF Office


How has performance improved over conventional design ?

Compared to constant speed chillers

at AHRI constant condenser water

conditions

CHW pump energy savings 35 %

YMC2 S/C chillers 28-66 % more efficient

Energy economics of a 9 /19 deg C S/C CHW system

Savings Costs Marginally higher design flow

pump pressures with series HX

Note : pressures are reduced at . . part load with variable flow

Marginally greater tower fan energy to leverage the 3 deg C reduction in CW temperature

Note: tower efficiency is an order of magnitude greater than chillers

YMC2 S/C chillers 28% more efficient at design

YMC2 S/C chillers up to 66% more efficient at reduced load & lift YMC2 S/C chillers 55% more efficient on weighted average


19 C

9 C 14 C

HT CHW loop

VPF

Typical system = CHW VAV AHU’s


Are there more efficiency gains to be found ? Can we go higher than 9 deg C CHW ?


The most efficient HVAC systems treat the latent loads separately “De-coupling”

Cooling Load Component Latent Sensible

Conduction thru walls, roof etc

Solar radiation

Lights

People

Equipment (some…most is sensible)

Infiltration

Ventilation

System heat gains


Typically @ 14 degrees C CHW

One HVAC system performs all dehumidification

One HVAC system performs only sensible cooling

De-coupled

A typical application that de-couples loads is a chilled beam system


DOAS

+ Chilled Beam

Typically @ 6 degrees C CHW

16 C

6 C 11 C

LT CHW loop (S/C chillers)

VPF VPF 18 C

14.0 C

ACB HT CHW loop

Plant room Plant room

DOAS supplies dry cool primary O/A to the active chilled beams


What can a CHW system look like for a chilled beam application ?

16 C

6 C 11 C

LT CHW loop (S/C chillers)

VPF

Plant room

VPF 18 C

14.0 C

ACB HT CHW loop

Plant room

DOAS with cascade reduction in primary air temp


Efficiency is improved further where a % of O/A load is removed by the HT loop

19 C

9 C 14 C

VAV AHU(s)

CHW loop

VPF

DOAS pre-conditions the O/A supplied to the zone VAV AHU’s

With a VAV system space dew point control is not as critical.

VPF 19 C

14 C


Similar methodology applied to a VAV system

Load% YK YMC2 s/c YMC2 100 6.46 8.29 28% 9.20 90 6.54 8.70 33% 9.77 80 6.52 9.20 41% 10.37 70 6.44 9.63 50% 10.95 60 6.25 9.88 58% 11.38 50 6.14 10.07 65% 11.68 40 5.75 9.58 66% 11.20 30 5.28 8.60 48% 10.34 20 4.46 6.04 35% 8.45

Office profile

HT YMC2 delivers weighted average 79% improvement over base design

YK CSD at AHRI

constant CW

YMC2 S/C at 9 deg C YMC2 at 14 deg C

42% 49% 59% 70% 82% 90% 95% 95% 89%

Office profile


What efficiency levels can the HT loop chiller deliver ?

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YK CSD Constant CEFT YMC2 Evap 14/18C YMC2 SCF Office


With dual loops, plant performance can be further improved

Where 30 % load is transferred to the HT loop , cooling efficiency is improved a further 8%

Example of Dual CHW loop project


JEM Project Singapore

Multi stage

fresh air treatment

Dual CHW

loops

Elevated CHW temps

Series

counter-flow LT chillers

Wide delta T

LT loop

Greenmark ‘Platinum’ rating @ 0.55 kW/Ton = 6.4 plant COP

Low temp loop = 9/18 deg C with 2 S/C York YK CSD chiller pairs

High temp loop = 15/20 deg C with 2 x York YK VSD chillers


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24-26 22-24 20-22 18-20 16-18 < 16

% O

pera

tion

Hou

rs

Wet-bulb Temperature oC

Source : YorkCalc Energy Analysis Database


66% hrs

Cairns has a greater potential for condenser water relief

Cairns 24Hrs Weather Bin Profile

What about Australia ?

Johnson Controls PowerPoint Guidelines | February 8, 2008 36

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YMC2 performance at 14C CHW Constant ECWT 29.4C Constant ECWT26C Constant ECWT 24C Constant ECWT 22C Constant ECWT 20C


With a 14 deg C HT loop YMC2 chiller 66% of the run hours can be at 12-21 COP !

What efficiencies can a YMC2 HT loop chiller deliver in Cairns ?

Very few chillers can operate continuously with 14 deg C CHW & 20 deg C CW

YMC2

YK

Refrigerant level control Motor cooling technologies

Variable orifice expansion

High Efficiency VSD or VSD magnetic bearing chillers

Raise CHW supply temperatures

Wide delta T CHW with series counter-flow chiller arrangement

Re-evaluate design approach temperatures

cooling towers are efficient and low cost

lower face velocity coils

De-couple and condition outside air loads separately

Dual HT & LT CHW loops with cascade coils & ‘low lift’ VSD chillers

For Consideration


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chiller plants for tropical climates - airah · 2014-09-09 · chiller plants for tropical climates...

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