Hybrid Refrigeration
System with Desiccant
Dehumidifiers in an
Ice Rink
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The ice
rink uses a CHP (Cooling, Heating, and Power) system that offers significant
energy savings through the useful recovery of heat generated during energy
conversion. The refrigeration system consists of two electric motor-driven
8-cylinder reciprocating compressors, one motor-driven 16-cylinder
reciprocating compressor, and one natural gas engine-driven 16-cylinder
reciprocating compressor.
Super Rink Layout
The basic system design involves chilling
calcium chloride brine to -9.8ºC to freeze the ice sheets. Heat is recovered
from engine jacket cooling water and from engine exhaust and is used to preheat
the reactivation air for four desiccant units (one per ice sheet) for
dehumidification and to preheat boiler feed water for heating rooms in the
facility.
The range
of possible savings for the hybrid gas-electric heat recovery refrigeration and
dehumidification system is great, depending upon the use of off-peak rates and
on the percentage of time the electric engines and the gas engines are
operating. The system is currently saving the rink approximately $27,000 (USD)
annually in energy costs. The system was monitored and savings were verified by
the CDH Energy Corporation in conjunction with the Industrial Center, Inc.,
which has partnered with the U.S. Department of Energy's Office of Power
Technologies. The Office of Power Technologies facilitates the research and
development of CHP technology.
Actual recovered thermal energy for 1999 from the
refrigeration system totaled approximately 3,200 MMbtus.
Boiler gas use was reduced by .18 MMBtu per 1 MMBtu of engine gas consumption, resulting in a heat
recovery system efficiency of approximately 18%.
Technical data
The
refrigeration system consists of two electric motor-driven 8-cylinder
reciprocating compressors, one motor-driven 16-cylinder reciprocating
compressor, and one 16-cylinder natural gas engine-driven reciprocating
compressor. The R-22 refrigeration compressors, operating at -12ºC suction
temperature, allow the chiller to supply brine at -9.8ºC to the rinks, with a total
capacity of 495 tons. Heat from the engines is recovered to preheat boiler
water for space heating to regenerate four desiccant units that dehumidify and
heat the rink areas. A plate and frame heat exchanger is used to transfer
engine jacket water heat to the heat recovery loop, and a combination exhaust
silencer/heat recovery exchanger provides additional energy to the recovery
loop.
Energy data
Actual recovered thermal energy for 1999 from the
refrigeration system totaled approximately 3,200 MMbtus.
Boiler gas use was reduced by .18 MMBtu per 1 MMBtu of engine gas consumption, resulting in a heat
recovery system efficiency of approximately 18%.
Economic data
The
incremental cost of the hybrid heat recovery refrigeration system is roughly
$73,000 (USD). Annual energy cost savings because of engine heat recovery and
because natural gas is less expensive than electricity totaled about $27,000
(USD) annually, creating a simple payback of 2.7 years.
Contacts:
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Schwan’s Super Rink 763-785-3687 763-785-5650 (fax) http://www.superrink.org |
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