Ammonia Use In Central Chilling Plant
for Comfort Cooling and More
J. Michael Whitcomb, P.E.
Energy Manager
Montgomery College
ASHRAE Member
June 2008
Salt Lake City
Presentation
Overview
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Introduction to Montgomery College
Decisions Made – Why Ammonia?
Central Plant Experience
Conclusions
Questions
Montgomery
College
• Three Campuses, 43 Buildings, 1.9 Million
GSF, Montgomery County, Maryland
• 65,000 Credit & Non-Credit Students or
9,000 Full Time Equivalent Students.
• $6.1 Million Utility Budget
• 4 Central Plants with Ammonia Chillers
and Ice Storage
Why Ammonia
(Early 1990s)
• Electric Utility Demand Side Management
& Rebate Programs
• Energy Efficiency Programs
• Utility Master Planning Recommended
Central Plant Cooling & Ice Storage
• Montreal Protocol & Refrigerant
Management
Typical Ice Thermal Storage
Demand Management Load Profile
Why Ammonia
Refrigerant?
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Low Temperature, High Efficiency
Natural Refrigerant, Long History
ASHRAE Std 15 & 34 – Ammonia OK
Zero Ozone Depletion Potential(ODP)
Zero Global Warming Potential(GWP)
Low Total Equivalent Warming
Impact(TEWI)
Low Temperature, High Efficiency
Ammonia’s Long
History
Early Compressor
Technology
ANSI/ASHRAE Standard 34
Designation and Safety Classification of
Refrigerants
• Ammonia
– Inorganic Compound
– R-717
– Safety Group B2
ANSI/ASHRAE Standard 15 – Safety
Standard for Refrigeration Systems
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Public Assembly Occupancy
Indirect Closed System
Limited Refrigerant Charge – (HX Selection)
Low Probability System
Refrigerant Detectors
Vent Fans
Water Spray Chamber-(College Option)
Safety Reliefs Vent to Roof
Central Plant Experience
• Currently have 4 plants, 8 Ammonia
Rotary Screw Chillers & Ice Storage
• Total 3,380 Tons of Chiller Capacity
• 14,446 Ton-hrs Ice Storage Capacity
• Time Span Early 1990s to 2007
• Located in Basement of Occupied
Buildings
• Shell & Tube HX vs Plate & Frame HX
Central Plant Experience(cont’d)
• Constant Speed Electronic Starters vs
Variable Speed Drives(VFD)
• Installed Water Spray Chambers on
Exhaust Fans as a Precaution
• Early Machines Designed as R-717/R-22
as a “Fall Back Precaution”
• Flexibility in Size & Configuration
• Industrial Strength Machines
• Open Drive Noise but Accessible
All Central Plants In Occupied
Buildings
Retrofit & New Construction
Ice Storage Outside & Inside
Early 1990s to Present Compressors
Typical Chiller
Assembly
Starters
Constant Speed Electronic vs
Variable Speed Drives
Shell & Tube vs
Plate & Frame
• 2 Degree(F)
Approach
• Less Refrigerant
• More Capacity
• Lower Horsepower
• Steel Vs Copper
Plant Ventilation & Water Spray
Standard Cooling Tower Condenser
Configuration With Additional
Heat Rejection From Oil Cooler
Compressor Discharge Temperatures
Require Heat Rejection To Cooling Tower
Building Automation
Controls Integration
Recent Green Building
Interest
• U.S. Green Building Council LEED Rating
System
– Energy Efficiency & Demand Management
– Ozone Depletion Potential(ODP)
– Global Warming Potential(GWP)
– Total Equivalent Warming Impact(TEWI)
Conclusions
• Life Cycle Cost Effective
• Operationally Successful
• 16 Year Successful Central Plant Demand
Management Strategy
• Ammonia Refrigeration Successful and
Environmentally Acceptable Method of
Supplying Low Temperature and Normal
Temperature Refrigeration
• More Information:
http://www.montgomerycollege.edu/Departments
/facilitiesca/energy_management.htm
Questions?