Evaporative-Cooled vs. Air -Cooled Chillers: Kirtland AFB

17 Pages·2011·0.57 MB·English

by  Joseph Adjei

Evaporative-Cooled vs. Air-Cooled Chillers:
Kirtland AFB Case Study
www.amec.com
DISCUSSION TOPICS

Brief Overview of Air-Cooled and Evaporative-Cooled Condenser
Technologies

Pros and Cons

Scope and Results of Kirtland AFB Study

Conclusions and Recommendations

Q&A
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AIR-COOLED CONDENSER BASICS

Refrigerant hot gas is cooled and
condensed in Air-to-Refrigerant Heat
Exchanger (coil).

Air-Cooled Condenser efficiency
depends on ambient air dry bulb
temperature, i.e. the higher OAT is, the
more power is required to compress
hot gas in order to condense it into
liquid.
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EVAPORATIVE-COOLED CONDENSER
BASICS

Treated water is sprayed over condenser
coil. Part of water is evaporated thus
lowering surface temperature of the
condenser and the air drawn across it.

Remaining water is collected in drain pan
and recirculated back to sprayer.

Make-up city water is added to replace
evaporated water.

Refrigeration system efficiency is increased
by 25-50% compared to air-cooled due to
lower vapor compression pressure, thus
reducing compressor‘s energy.
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AIR-COOLED AND EVAPORATIVE-COOLED
CONDENSER COMPARISON

PROS OF AIR-COOLED vs. EVAPORATIVE-COOLED:

Smaller cabinet

Lighter weight

No condenser water piping and treatment

Lower equipment cost

Lower maintenance cost

No water consumption for condenser operation

PROS OF EVAPORATIVE-COOLED vs. AIR-COOLED:
20-40% lower electrical consumption of the chiller
Quieter operation
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KIRTLAND AFB ENERGY STUDY
OBJECTIVE:

Increase the energy efficiency of existing facilities on various Air
Force Bases in order to reduce the building annual operating cost.
STUDY SCOPE:

Evaluate life cycle costs of replacement of existing Air-Cooled
Chillers with Evaporative-Cooled Chillers at seven (7) buildings.

Life Cycle Cost Analysis compared costs associated with
Evaporative-Cooled Chillers against Status Quo (air-cooled chillers),
and included:
Capital Cost Estimate (material and labor) at +/-30% accuracy.
Maintenance Cost analysis.
Operating Cost Analysis (electricity and water).
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KIRTLAND AFB ENERGY STUDY RESULTS
CAPITAL COST COMPARISON FOR EVAPORATIVE AND AIR-
COOLED CHILLERS
BUILDING CHILLER EVAPORATIVE-COOLED AIR-COOLED
NO. TONNAGE CHILLERS CHILLERS
1005 60 $178,000 $74,000
20140 60 $178,000 $74,000
322 70 $204,000 $84,000
1017 90 $262,000 $113,000
20222 100 $279,000 $130,000
20361 165 $389,000 $176,000
472 250 $471,500 $235,000
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KIRTLAND AFB ENERGY STUDY RESULTS
ANNUAL OPERATING COST COMPARISON FOR EVAPORATIVE
AND AIR-COOLED CHILLERS
ELECTRICITY CITY WATER AND
CHILLER MAINTENANCE
KWh x 1,000 / COST SEWER
TONS (chiller only)
(chiller only) (chiller only)
EVAP- AIR- EVAP- AIR- EVAP-
AIR-COOLED
COOLED COOLED COOLED COOLED COOLED
60 49 / $3,920 28 / $2,240 $0 $323 $1,600 $2,000
60 49 / $3,920 28 / $2,240 $0 $323 $1,600 $2,000
70 56 / $4,480 30 / $2,400 $0 $353 $1,600 $2,000
90 34 / $2,720 16 / $1,280 $0 $196 $2,400 $3,200
100 66 / $5,280 39 / $3,120 $0 $463 $2,400 $3,200
165 102 / $8,160 56 / $4,480 $0 $665 $2,400 $3,200
250 200 / $16,000 108 / $8,640 $0 $1,260 $2,400 $3,200
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KIRTLAND AFB ENERGY STUDY RESULTS
10- YEAR LIFE CYCLE COST COMPARISON FOR EVAPORATIVE
AND AIR-COOLED CHILLERS
LCC OF COST RATIO OF
LCC OF AIR-
BLDG CHILLER EVAPORATIVE- AIR-COOLED /
COOLED
NO. TONNAGE COOLED EVAP-COOLED
CHILLERS
CHILLERS CHILLERS
1005 60 $301,000 $201,000 67%
20140 60 $301,000 $201,000 67%
322 70 $350,000 $233,000 62%
1017 90 $462,000 $293,000 64%
20222 100 $513,000 $335,000 65%
20361 165 $757,000 $557,000 74%
472 250 $1,386,000 $1,191,000 86%
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KIRTLAND AFB ENERGY STUDY RESULTS
10- YEAR LIFE CYCLE COST COMPARISON FOR EVAPORATIVE
AND AIR-COOLED CHILLERS
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