ASHRAE Journal - March 2015 - 79

2015 ASHRAE TECHNOLOGY AWARD CASE STUDIES

ABOVE Westhills Recreation Centre's NHL size

indoor ice rink.

LEFT VFD-driven high efficient ammonia

compressors provide refrigeration for the ice
rinks in winter and building air conditioning
in summer.

The outdoor ice rink was designed with embedded
refrigeration piping for winter ice and water fixtures to
convert it into a children's splash park in summer, making
use of the same footprint for both summer and winter.

Eliminating Fossil Fuels
The city of Langford, located on Vancouver Island, has
among the highest natural gas prices in North America.
The project objective was to eliminate natural gas consumption for all heating, hot water and dehumidification loads while minimizing electrical consumption
year-round. In fact, the building does not use fossil
fuels at all except in the kitchen, which does use natural gas. And, it was determined during the preliminary
design phase that the quantity of heat rejected from the
refrigeration to service the three ice surfaces would be
more than enough to satisfy all of the heating loads with
extra heat that could be shared with a nearby housing
community.
The challenge was to ensure that there was heat available between compressor run cycles and during the
colder periods of the year when the refrigeration was
running less. The outdoor ice rink offered an interesting
energy balance opportunity in Langford's mild winter by
providing additional waste heat during the peak heating
season, just when it was needed most.
To ensure that there would be no periods between
refrigeration run cycles without heat being available, two
approaches where taken. The refrigeration compressors
and brine pumps were equipped with variable speed
drives. The variable speed drives, controlled by the computer control system, were programmed to operate the
compressors at their lowest permissible speed while precisely maintaining the temperature setpoint.
This strategy provided a number of benefits. The compressors always operated at their maximum coefficient of

performance (COP) due to the higher saturated suction
temperatures and lower saturated condensing temperatures while running at low speeds. The centrifugal brine
pumps were also modulating their speed and taking
advantage of the Pump Affinity Law, resulting in reduced
electrical consumption. The main objective of perpetuating the heating cycle was also met as the compressor run
cycles were much longer throughout the day.
A system also had to be designed that would have heat
available during colder periods and when the night set
back control strategy would shut the compressors off. To
achieve this, we required some form of thermal storage.
A cost effective solution was to use the ice rink sub-floor
heating system for thermal storage.
Traditionally, ice rink sub-floor heating systems would
operate at 40°F (4.5°C) to prevent frost heaves caused by
long-term refrigeration operation. To minimize any
impact to the ice surface as a result of higher sub-floor
temperatures, we installed 6 in. (150 mm) of R-5 insulation board between the ice pad and the heating floor,
and around the outside walls. This enabled the temperature of the sub-floor to be increased to 75°F (24°C). This
"geothermal system on steroids" was cost effective to construct because the civil work, piping mains, pumps and
half the insulation would have been required anyway for a
traditional sub-floor heating system.
During the winter, 100% of the refrigeration waste
heat is harvested with an energy recovery condenser,
which is able to provide 82°F (28°C) glycol temperature
while maintaining 85°F (30°C) condensing temperature. The warm 82°F (28°C) glycol from the energy
recovery condenser directly provides radiant heating
throughout 19,000 ft2 (1765 m2) of public space.
The concrete floors are maintained at 72°F to 74°F
(22°C to 24°C), which provides an excellent level of
comfort. In mid-winter, an energy recovery heat pump
MARCH 2015

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