iac chiller
TRANSCRIPT
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A Chilled Water System Analysis Tool
for Industrial Assessments
Chiller System Optimization & Energy
Efficiency Workshop
September 2003
Presented by Michael SocksUMass Industrial Assessment Center
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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
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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
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Summary of Operating Cost
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
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Summary of Operating Cost
Reduction MeasuresLoad-based Opportunities
Use chilled water efficiently
Distribute chilled water efficiently
Use optimal coil or heat exchanger size/design
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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
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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
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Chilled Water System (Air-Cooled)
Air-Cooled
Condenser
1
Evaporator
Compressor
32
4
Expansion
Valve
Cooling Load
CHILLER LOOP
HEAT GAIN LOOPSupply
Pump
Fan
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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
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Program Overview: Input
Basic System Data:
Number of chillers (up to 5)
Chilled water supply temperature
Geographic location
Condenser cooling method (water or air)
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Program Overview: Input
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)
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Program Overview: Input
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)
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Program Overview: Input
Pump Data:
Fixed or variable flow pumping
Flow rate [gpm/ton]
Nominal pump efficiency [%]
Nominal motor efficiency [%]
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Program Overview: Input
Chiller Data:
Chiller compressor type
Chiller capacity
Chiller full load efficiency (if known)
Chiller age
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Program Overview: Input
Energy Cost Data:
Average electricity cost [$/kWh]
Average NG cost [$/MMBtu]
System Control Data:
System operating schedule
System loading schedule
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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
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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
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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
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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
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Example: Input Screen
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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
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Example: Operating Cost Reduction
Opportunities Screen
Operating Cost
Reduction Measure:
Install a VSD oneach Centrifugal
Compressor Motor
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Example: Savings Screen
Savings Summary:
598,797 kWh/yr
$35,928/yr
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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
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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
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Case Study: System Loading
Typical Loading Schedule
20% load for 25% of year
30% load for 25% of year
40% load for 25% of year
50% load for 25% of year
Note: These are average system loads.
Individual chiller loading will differ.
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Case Study: Results
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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%)
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Case Study: Other Observations
Chiller and pumping
energy decrease by
approximately 22%
Tower energy increases by
approximately 63%
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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?