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Energy Optimization of a LargeCentral Plant Chilled Water System

Riyaz Papar, PE, CEMHudson Technologies Company

Harold Myart, PE, CEMMark Krawczyk, PE, CEM

Freescale Semiconductor, Inc.

Texas Chemical Council Seminar

June 09, 2009


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Agenda Objectives

System Description

Data Collection & Models

System Optimization Opportunities

System Optimization Results

Conclusions


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Objectives Conduct a chilled water system Energy

Savings Assessment (ESA) using a Systems

Approach at the Oak Hill Plant site

Identify (and quantify) chilled water plant

energy savings opportunities

Assist plant personnel to gain familiarity with

certain bestpractices and to continue toidentify energy efficiency improvementopportunities at the site


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System PFD

1 62 3 4 5

1 2 3

Water Chillers (42F)

Glycol Chillers (32F)

Air Coils

Air Coils


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Identified Chiller Plant BestPractices Site-level integrated chilled water and glycol loops

High efficiency two-stage centrifugal chillers for base load and screwmachines to provide for swing capacity

Use of variable speed drives on the secondary pumping loop

Use of variable speed drives on the condenser water pumps

Use of two-speed fans on the cooling towers

Significant instrumentation, data monitoring and controls

Use of real-time data for tracking efficiency metrics (kW/ton) and aHistorian for analysis

Good periodic maintenance practices for equipment (oil analysis,cleaning of heat exchanger tubes, eddy current testing, etc.)

Periodic calibration of all critical instrumentation


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Load Profile

-

2,000

4,000

6,000

8,000

10,000

9/5/07 10/25/07 12/14/07 2/2/08 3/23/08 5/12/08 7/1/08 8/20/08 10/9/08

42FChillerPlantLoad(RT)

1

2

3

4

5

6

NumberofOperatingChillers


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Chilled Water Plant Efficiency

0.400

0.450

0.500

0.550

0.600

0.650

0.700

0.750

0.800

9/5/07 10/25/07 12/14/07 2/2/08 3/23/08 5/12/08 7/1/08 8/20/08 10/9/08

OverallPlant

Efficiency(kW/RT)


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Chilled Water Plant Efficiency

0.6230.7040.6500.6770.7050.5410.597Efficiency (kW/RT)

2,144591561599610511553Power (kW)

3,428846863887868944924Load (RT)

8,7502,5916,3366,8772,6337,4587,469Operating hours

OverallPlant

654321Chiller #


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Chiller Efficiency

0.50

0.55

0.60

0.65

0.70

0.75

0.80

0.85

0.90

68 70 72 74 76 78 80 82

Condenser Water Temperature (F)

ChillerEffi

ciency(kW/RT)


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Chiller Efficiency

0.40

0.45

0.50

0.55

0.60

0.65

0.70

0.75

0.80

39.0 40.0 41.0 42.0 43.0 44.0 45.0 46.0 47.0

Chilled Water Supply Temperature (F)

ChillerEffi

ciency(kW/RT)


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Energy Savings Opportunity Reduce condenser water temperature

Condenser water maintained currently at 75F

Controlled by two-speed fans

Typically, 10% energy used by fans, 20% bypumps and 70% by compressor

Compressor kW/RT increases with highercondenser water temperature

Float condenser pressure for maximum savings

Implementation to lower condenser water to 70F Potential savings ~7%


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Energy Savings Opportunity Constraints / Precautions - Reduce condenser

water temperature

Check manufacturers recommendations 65Fminimum condenser water temperature

Refrigerant Stacking issues

Concerns about leaks in low pressure (R123)chillers


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Energy Savings Opportunity Reduce number of operating chillers

-

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

09/05/07 10/25/07 12/14/07 02/02/08 03/23/08 05/12/08 07/01/08 08/20/08 10/09/08

ChillerTons

(RT)

Actual P lant Load

Operating Capacity

Ex cess Ca pacity

\


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Energy Savings Opportunity Increase primary chilled water flow through chillers

Design rating is based on 42F chilled water, 85Fcondenser water and 100% load (Tons)

But this happens for 1-3% of the operating hours

Chiller has a lot more capacity at off-design conditions

Implement Variable Primary Flow and increase chilledwater flow

Chiller moves to full-load conditions and kW/RT reduces

Preliminary estimates ~5-10% energy savings Constraints / Precautions

Pumping power capability

Compressor horsepower limitation


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Energy Savings Opportunity Implement SMART algorithm to reset chilled water

supply temperature

1F increase in chilled water supply temperature leadsto a reduction of 0.015 kW/RT

DAS has information on chilled water flow control valve

positions of almost all the air-handling units Automatically increase chilled water supply temperature

till a control valve reaches 80% open

Currently, done on a manual basis

Constraints / Precautions

Dynamic flow issues

Will have to ensure no hunting


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BestPractices Implement real-time calculation of chiller

efficiencies and trending

Will provide information for further optimization All the data is already available

Implement a Chiller Chemistry program Fluids Refrigerant, Oil and Water should be tested

every six months

An engineering analysis combining all these results

Root-cause analysis

Best Predictive Maintenance can be done online


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Energy Savings Opportunities

N5,000NC0NCImplement a Chiller Chemistry PM program

N25,000NANANAImplement real time monitoring and add trendingof efficiency

MNCNC0NCImplement SMART algorithm to reset chilledwater supply temperature

M25,00020,0000315,000Transfer load from the 32F glycol loop to the42F chilled water loop

N10,00060,0000930,000Increase primary chilled water flow through thechillers

N25,00091,00001,400,000Reduce number of operating chillers

N40,00053,0000815,000Reduce condenser water temperature

ThermskWhPB

ProjectCost ($)

CostSavings ($)

Energy Savings

Opportunity

*NA Not Applicable**NC Not Calculated (See write up for details)


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Conclusions Instrumentation & monitoring of critical

parameters was key for optimization of thechilled water plant

A Systems Approach is needed for optimizing

any energy system

Typically, chilled water and refrigeration

systems are neglected in plants but they offersignificant energy savings potential


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Acknowledgments Kathey Ferland

TX Industries of the Future

Paul Lloyd & Dean BlackmanFreescale Semiconductor, Inc.


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Discussion & Questions

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