introduction to improving energy efficiency in chiller...

©© Hudson TechnologiesHudson Technologies1

Introduction to Improving Energy Efficiency in Chiller Systems

Riyaz Papar, PE, CEMDirector, Global Energy ServicesHudson Technologies Company

[email protected]

November 2013


Acknowledgments

Texas Industries of the Future (TXIOF) Texas State Energy Conservation Office (SECO)

Energy Industries in Ohio

Joe Longo & Derrick Shoemake, Hudson Technologies


Webinar Agenda

The Systems Approach

Fundamentals of Refrigeration

Chiller Plant Actual Operating Performance

Predictive and Preventive Maintenance BestPractices

Energy Conservation Measures (ECMs)

Conclusions


Chiller System Energy Cost?Chiller System Energy Cost?

1,000 Refrigeration Tons chiller plant load Chiller System performance = 0.75 kW/ton Bundled power cost = $0.085/kWh

-

100,000

200,000

300,000

400,000

500,000

600,000

4 months 6-8 months All year round

Operating hours

Ope

ratin

g C

ost (

$)



Establish current system conditions, operating parameters, and system energy use

Investigate how the total system presently operates

Identify potential areas where system operation can be improved

Analyze the impacts of potential improvements to the plant system

Implement system improvements that meet plant operational and financial criteria

Continue to monitor overall system performance


A Chilled Water Plant Systems Approach


Energy Reliability Maintenance Productivity Quality Cost avoidance Emissions reductions

Main Driving Force for Change


Fundamentals of Refrigeration


The Refrigeration Cycle

0 25 50 75 100 125 150101

102

103

h [Btu/lbm]

P [p

sia]

105°F

40°F

0.2 0.4 0.6 0.8

R134a

Compression

Condensation / SubCooling

Ev aporation (Boiling)

Expansion

State Point


Single Stage Chiller System

Condenser

Compressor

Evaporator

HGBP

HGBP

Cooling Water

Chilled Water

(Hot Gas ByPass)


A Centrifugal Chiller

Evaporator (Chiller Barrel)

Condenser

Compressor

A Water-Cooled Chiller System


Two Stage Chiller System

Condenser

Compressor

Evaporator

HGBP

HGBP

Cooling Water

Chilled Water

Economizer(Hot Gas ByPass)


LiBr-Water Absorption Chillers


The Air, Water and Refrigerant CycleThe Air, Water and Refrigerant Cycle



Chiller Plant - Actual Operating Performance


Chiller Capacity

Definition of Refrigeration Ton (RT) The amount of thermal energy to be

removed from 1 Ton (2,000 lbs) of water at 32°F to make it into ice at 32°F in one day (24 hr) is known as 1 RT

1 RT = 12,000 Btu/hr = 3.517 kW

Chiller capacity (size or tonnage) is the amount of full load cooling capacity provided by the chiller at certain design conditions


Chiller Performance Metrics

Most standard rating in the US - kW/RT (hp/RT) Amount of compressor power (kW or

hp) required to produce 1 RT of cooling or refrigeration

)( )( /

RTLoadCoolingkWPowerCompressorRTkW


Chiller ID: Chiller #6 Chiller Manufacturer: ZZZZZZZ

Year Commissioned: 1990 Chiller Type: Constant Speed Centrifugal

Model Number: XXXXXXXXXX Serial Number: AAAAAAAA

Refrigerant Type: R-134a Capacity (Tonnage): 2,000

Efficiency (kW/Ton): 0.625 IPLV / NPLV: .541

Full Load Amps (FLA): 198 Volts: 4160

Evaporator Entering Water Temperature: 54.37°F Evaporator Leaving Water Temperature: 44°F

Condenser Entering Water Temperature: 85°F Condenser Leaving Water Temperature: 94.4°F

Evaporator Delta Temperature: 10.37°F Condenser Delta Temperature: 9.4°F

Evaporator GPM: 4,627 Condenser GPM: 6,000

Evaporator Pressure Drop (psig): 9.9 Condenser Pressure Drop (psig): 8.1

Chiller Full Load Design Specifications

Obtained from the Chiller Manufacturer


Overall Chiller Plant Performance

Information required Total tonnage Total kW

Compressor Power Pumping Power Cooling Tower Fan Power Other (as defined in the scope)

m

n

TonsChiller

kWePerformancPlant


Overall Chiller Plant Performance


Chiller Plant Efficiency Metrics

Overall chiller plant performance Total tonnage Total kW (including chillers and auxiliaries)

Individual chiller efficiency Chiller tonnage Compressor kW

Individual Chiller Lift Lift is defined as the difference between the refrigerant

saturated condensing and evaporating temperatures

Individual compressor isentropic efficiency Suction and discharge temperatures Suction and discharge pressures

Individual heat exchanger effectiveness Approach temperatures T on chilled water and cooling tower water


Predictive & Preventive Maintenance BestPractices


First Things First First Things First –– Fluid ManagementFluid Management

Understanding “Cause” and “Effect” is very important for Root Cause Analysis

This enhances system reliability and reduces unplanned shutdown

Significant savings in Maintenance costs Most Maintenance BestPractices are testing-

based Refrigerant, Oil and Water Testing Rotating equipment monitoring

Vibration analysis

Eddy-current testing

In chiller systems, contaminants affect efficiency & capacity Chemistry Based Solutions


Blood ChemistryBlood Chemistry


Chiller ChemistryChiller Chemistry


Refrigerant Analysis CriteriaRefrigerant Analysis Criteria

Moisture Oil Particulate Chlorides Acid Purity Non-Condensables Other Contaminants


Nonferrous cutting wearNonferrous cutting wear Severe sliding wearSevere sliding wear

Copper alloy Copper alloy sliding wearsliding wear

Nonferrous cutting wearNonferrous cutting wear

FerrographyOil Analysis


Water Testing and Analysis

Cooling Tower Water testing and analysis Open loop – evaporation of water Control of corrosion, scale and biological activity Material of construction plays a very important role Testing conducted for pH, TDS, Conductivity, Hardness,

Alkalinity, Chlorides, Silica, Bacteria, etc.

Chilled Water testing and analysis Closed loop – generally less issues Lower temperatures

Working with a water chemist / treatment company Periodic testing program


Energy Conservation Measures (ECMs)


3 Methods of Maximizing Chiller Plant Efficiency

Preventive Identify problems before they become expensive

(cost avoidance) Maintain optimum chiller plant efficiency

Restorative Identify heat transfer problems, i.e., off-design

water flow, fouling or scaling, etc. Remove non-condensable gases Maintain proper refrigerant levels

Opportunity Identify optimal chilled water set points Proper chiller sequencing and load balancing Proper tower basin water management Peak demand management Condition-based maintenance versus scheduled

preventive maintenance


List of ECMs

Implement ECWT management Optimize settings for ChWST Eliminate all refrigerant leaks Maintain design water flow rates

in evaporator / condenser Eliminate refrigerant stacking Remove non-condensable gases

and moisture Reclaim refrigerant

No

Cos

t / L

ow C

ost

EC

Ms


List of ECMs (continued)

Clean fouled and scaled heat exchangers

Sequence multiple chillers to optimize efficiency

Maintain compressor isentropic efficiency

Improve drive efficiency Investigate application of variable

frequency drives Undertake peak load management

strategy Install water-side economizers

Med

ium

Cos

tE

CM

sH

ighe

r C

ost

EC

Ms


Implement ECWT Management

ECWT – Entering Cooling Water Temperature

Approach The approach is the difference in temperature between

the cooled-water temperature and the entering-air wet bulb temperature

Since the cooling towers are based on the principles of evaporative cooling, the maximum cooling tower efficiency depends on the wet bulb temperature of air

Wet Bulb Wet bulb temperature is the lowest temperature that

can be reached by the evaporation of water only It is determined by the atmospheric pressure, ambient

temperature and the relative humidity


Concept of Lift


80°F ECWT drops to 70°F ECWT

kW/ton drops from 0.7 to 0.47 (33% improvement)

Implement ECWT Management


Optimize Settings for ChWST

ChWST – Chilled Water Supply Temperature

Approach / RAT The approach (RAT) is the difference in temperature

between the chilled-water supply temperature and the refrigerant saturated temperature in the evaporator

It provides the driving force to transfer the heat from the water to the refrigerant

Load control Cooling required is controlled by bypassing chilled

water flow Alternate methodology – variable pumping

Primary Secondary


Optimize Settings for ChWST

0.3

0.325

0.35

0.375

0.4

0.425

0.45

0.475

41 42 43 44 45 46 47

CWST (°F)

Chi

ller P

erfo

rman

ce (k

W/R

T)


Clean Fouled and Scaled Evaporator

Fouling in the evaporator / cooler Refrigerant-side Water-side

Refrigerant-side fouling – Excess Oil

Refrigerant-side fouling – Water

Water-side fouling High makeup (leaks) in the closed loop system Iron fouling from corrosion, microbiological growth and

scale due to insufficient chemical protection


Fouled/Scaled EvaporatorFouled/Scaled Evaporator

Iron Oxide ScaledCondition

After tube brushing


Fouled/Scaled CondenserFouled/Scaled CondenserMarch

July

Sept


Reclaim Refrigerant

Over time and operations, the refrigerant in the chiller gets contaminated and results in Fouling of heat exchangers Reductions in heat transfer coefficients

The process of recovering the refrigerant and bringing it back to AHRI-700 specification standard is known as “Reclamation”

Reclaiming a refrigerant improves overall operating performance and in most cases increases chiller tonnage (capacity)

Periodic sampling and testing of refrigerants in chiller systems is key to ensuring that the chiller chemistry is well maintained Analogous to maintaining water chemistry in boilers


Reclaim Refrigerant

Presence of Oil in refrigerant

Particulate in refrigerant

Moisture in refrigerant


SUMMARY of RESULTS & COST SAVINGS

Tons = 1,502 [RT]

compHP = 1,219 [HP]

SteamRate = 12.02 [lb/hr-HP]

NC% = 0.0 [%] Superheat Capacity Penalties

Total System

Cost ($) NC Penalty ($)

678,871 0

Evaporator Condenser System

Evaporator

%Capacity Loss (RT)

2.8 0.1

2.6 2.3

13.1 0.0 13.1

BalanceSystem = 0.0 [%]

BalanceEvap = 0.0 [%]

BalanceSubCooler = ???? [%]

SteamCost = 14.48 [$/1000lb]

Hours = 4,000 [Hr]

SUMMARY of RESULTS & COST SAVINGSTotal System

2.3

2.6

Component Balances

LFC = 0.80 [kW/ton]

2,002 [RT]

2,360 [HP]

12.03 [lb/hr-HP]

Annual Energy Costs

RefrigerantDesign F/LDesign:

Currently Used:

R134a

R134a

Potential Savings OpportunitiesPressure Ratio (current):

New Ratio

Savings (%)

HPTon = 0.81 [BHP/RT] 1.18 [BHP/RT]

1,502 [RT]

1,503 [HP]

Design P/L

1.001 [HP/Ton]

Reclaim Refrigerant

Impact of Oil, Particulate & Moisture in refrigerant on energy efficiency & costs

Impa

ct o

n C

apac

ity


Eliminate Refrigerant Stacking

Refrigerant stacking impacts heat transfer efficiency in both the evaporator and condenser - higher kW/Ton and energy costs

Leads to reduced compressor capacity

Chiller surging or stalling

Shut down on low refrigerant temperature (pressure)


Refrigerant Stacking

RaiseECWT


Sequence Multiple Chillers to Optimize Efficiency

All chillers will have an optimal operation range (best efficiency point)

When multiple chillers are operating, the overall plant’s composite operating curve maybe very different from the individual chiller’s curve

It is important to know how each of the chillers operate under different load conditions

Pick the best chiller operating combination for the current operating conditions – Dynamic Optimization problem (NOT Easy)


Investigate Application of Variable Frequency Drives (VFD)

Replacing old chillers with newer energy efficient systems –most new packaged chillers will come with a VFD option

VFDs take advantage of lower ambient temperatures (lower lift) and correspondingly lower cooling loads (lower refrigerant flow rates)

VFD pumps and fans can play a very important role in reducing total system energy consumption

VFD efficiency is extremely high (99%) and more importantly, it offers a benefit on the drive side by providing Soft start capability Power factor correction


Comparison of Constant Speed & VFD Chiller Performance

0.3

0.35

0.4

0.45

0.5

0.55

0.6

0.65

0.7

0.75

20 30 40 50 60 70 80 90 100

Cooling Load (%)

Chi

ller P

erfo

rman

ce (k

W/R

T)

Constant SpeedVariable Frequency


Install Water-side Economizers

This ECM is applicable only in certain geographical areas but can have a huge impact on energy savings

Installing a water-side economizer allows for “free cooling” during times of the year when the outdoor ambient conditions allow for very low wet-bulb temperatures

The cooling tower water provides all (or some portion) of the chilled water plant load and reduces the amount of chillers required


Undertake a Peak Load Management Strategy

Peak demand charges can become excessive depending on chiller plant management and operational strategy

There are 3 ways to manage peak demand regarding chillers Thermal energy storage Optimize chiller efficiency to lower kW usage of running

chillers Take a chiller off-line


Conclusions


Next Steps

Develop a simple schematic of your Chiller Plant / Refrigeration system and define the boundaries

Use a systems approach to complete an initial assessment to understand operations and load profile

Undertake a simple gap analysis to identify any potential improvement opportunities

Evaluate each ECM and prioritize based on quantified savings opportunities

Put a program in place to ensure that there is proper Predictive and Preventive Maintenance BestPractices

Implement an effective Chiller Plant Performance Monitoring, Diagnostics and Optimization system


1-Day Training Workshop

Introduction to Energy Efficiency in Chiller Plant Systems

December 17, 20138 am – 4 pm

Houston Business RoundTable5213 Center StreetPasadena, TX 77505

Facilitator: Riyaz Papar, PE, CEMHudson Technologies Co.

Registration Information:Kathey Ferland

Texas Industries of [email protected]

http://TexasIOF.ceer.utexas.edu


Contact Information

Technical InformationRiyaz Papar, PE, CEM

Hudson Technologies [email protected]

http://www.hudsontech.com

Program InformationKathey Ferland

Texas Industries of [email protected]

http://TexasIOF.ceer.utexas.edu

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