IAC Chiller

8/3/2019 IAC Chiller

1/30

A Chilled Water System Analysis Tool

for Industrial Assessments

Chiller System Optimization & Energy

Efficiency Workshop

September 2003

Presented by Michael SocksUMass Industrial Assessment Center


2/30

The Industrial Assessment Center

at UMass-Amherst The IAC performs no-cost, on-site energy efficiency,

waste reduction, and productivity improvementassessments for small and mid-size manufacturers

Client Characteristics:1) SIC Code 2000-3999

2) Annual energy bills of $100,000 to $2,000,000

3) Gross annual sales less than $100 million

4) Fewer than 500 employees at the plant site5) No in-house staff to complete a similar assessment


3/30

Summary of Operating Cost

Reduction MeasuresEquipment-based Opportunities

Replace the chiller

Install NG or absorption chillers (Hybrid)

Install HX to recover condenser heat

Store thermal energy for peak use


4/30


Reduction MeasuresControl-based Opportunities

Optimize chiller sequence

Raise chilled water temperature setting Lower condenser cooling water temperature

Use variable speed capacity control

Use 2-speed or VSD control of tower fans Use VSD control of pump flow

Use free cooling


5/30


Reduction MeasuresLoad-based Opportunities

Use chilled water efficiently

Distribute chilled water efficiently

Use optimal coil or heat exchanger size/design


6/30

Purpose: Reduce the energy consumption of installed

chilled water systems

Goal: Create a simple but useful software tool for

analyzing potential energy savings in chilled water

systems

Program Introduction


7/30

Chilled Water System (Water-Cooled)

Condenser

1

Evaporator

Compressor

32

4

Expansion

Valve

Cooling Tower

Cooling Load

CHILLER LOOP

HEAT REJECTION LOOP

HEAT GAIN LOOP

Cooling Tower

Pump

Supply

Pump

Cooling TowerFan


8/30

Chilled Water System (Air-Cooled)

Air-Cooled

Condenser

1

Evaporator

Compressor

32

4

Expansion

Valve

Cooling Load

CHILLER LOOP

HEAT GAIN LOOPSupply

Pump

Fan


9/30

Program Description

Visual Basic Executable Program

User is prompted for system information

Program analyzes the existing system User is prompted for changes to system

Program analyzes the proposed system

Program presents savings results


10/30

Program Overview: Input

Basic System Data:

Number of chillers (up to 5)

Chilled water supply temperature

Geographic location

Condenser cooling method (water or air)


11/30


If chiller condensers are water-cooled:

Condenser cooling water supply temperature

(if constant) WB to cooling water temperature differential

(if variable)

Cooling Tower Data

(# towers, # cells/tower, motor hp, # motor speeds)


12/30


If chiller condensers are air-cooled:

Cooling air design temperature

Average annual ambient air temperature(if indoor air is used for cooling)

DB to condenser temperature differential

(if outdoor air is used for cooling)


13/30


Pump Data:

Fixed or variable flow pumping

Flow rate [gpm/ton]

Nominal pump efficiency [%]

Nominal motor efficiency [%]


14/30


Chiller Data:

Chiller compressor type

Chiller capacity

Chiller full load efficiency (if known)

Chiller age


15/30


Energy Cost Data:

Average electricity cost [$/kWh]

Average NG cost [$/MMBtu]

System Control Data:

System operating schedule

System loading schedule


16/30

Program Overview: Cost Reduction

Cost Reduction Measures to Consider:

Increase chilled water supply temperature

Decrease chiller condenser temperature

Upgrade to 2-speed or variable speed tower fan motors

Upgrade to variable speed pump motor control Replace chillers (use more efficient or NG units)

Replace refrigerant

Install VSD on chiller compressor motor (centrifugal only)

Use free cooling Sequence chillers


17/30

Program Overview: Output

Output Information:

Annual chiller energy consumption (kWh and/or MMBtu)

and cost

Annual cooling tower energy consumption (kWh) and cost Annual pump energy consumption (kWh) and cost

Total annual energy consumption and cost


18/30

Program Overview: Output

Chiller energy may be viewed by:

Chiller

Load

Cooling tower energy may be viewed by:

Wet-bulb temperature group

Pump energy may be viewed by:

Chiller


19/30

ExampleLets run an example . . .

(3) 200 ton water-cooled chillers (centrifugal)

44 F chilled water temperature

Located in Boston, Massachusetts

Condenser cooling water is held constant at 85 F

(1) 2-cell tower with 15 hp 2-speed motors

Chilled water flow is constant [2.4 gpm/ton]

Condenser water flow is constant [3.0 gpm/ton]

Electricity is $0.06 per kWh

Operates 24/7 and serves an air-conditioning load

Install VSDs on each chiller compressor motor


20/30

Example: Input Screen


21/30

Example: Output Screen

Output Summary:

Chillers: 2,187,676 kWh (92%)

Tower: 4,768 kWh (< 1%)

Pumps: 193,934 kWh (8%)

Total Energy: 2,386,378 kWh

Total Cost: $143,183


22/30

Example: Operating Cost Reduction

Opportunities Screen

Operating Cost

Reduction Measure:

Install a VSD oneach Centrifugal

Compressor Motor


23/30

Example: Savings Screen

Savings Summary:

598,797 kWh/yr

$35,928/yr


24/30

Case Study: Application

Manufacturer of laminated circuit boards useschilled water for process cooling and spaceconditioning

Process Cooling

Laminating oven cool-down cycle Plating fluid temperature control

Space Conditioning

~ 50,000 ft2

clean rooms Office and manufacturing floor air conditioning


25/30

Case Study: System Specs

Chilled Water System Summary (2) 250-ton helical rotary chillers (1997)

(2) 350-ton helical rotary chillers (2001)

45F chilled water; 2.4 gpm/ton

75F condenser water; 3.0 gpm/ton

(4) cooling towers; (3) 15-hp fans each (2-speed)

Operates 24/7 year-round

Free cooling is used when possible


26/30

Case Study: System Loading

Typical Loading Schedule

20% load for 25% of year




Note: These are average system loads.

Individual chiller loading will differ.


27/30

Case Study: Results


28/30

Case Study: Prediction vs. Actual

Without Using Free Cooling 3,478,905 kWh actual

3,436,931 kWh predicted

Difference: 41,974 kWh (-1.2%)With Free Cooling

489,054 kWh and $41,570 actual savings

608,720 kWh and $51,744 predicted savings

Difference: 119,666 kWh and $10,174 (+24%)


29/30

Case Study: Other Observations

Chiller and pumping

energy decrease by

approximately 22%

Tower energy increases by

approximately 63%


30/30

Closing Comments

The Program IS NOT intended to determine systemenergy use down to the kWh or MMBtu

Program IS intended to direct analysis effort towardthe most promising cost reduction opportunities

I need your help to make this program better:1) Download the program from www.ceere.org

2) E-mail questions, suggestions, errors, etc. to me [email protected]

Any questions?

Documents

IAC Chiller