For Ice Rinks, Pools

2015 ASHRAE TECHNOLOGY AWARD CASE STUDIES
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A CO2 refrigeration system is the centerpiece
of the renovation of the
225,000 ft2 (21 000 m2) Dollarddes-Ormeaux Civic Centre. CO2
is used to heat the stands of the
civic center’s three ice rinks,
with the CO2 coils installed
directly into the system’s air
ducts.
FIRST PLACE
COMMERCIAL BUILDINGS, OTHER INSTITUTIONAL, EXISTING
CO2 Showcase
For Ice Rinks, Pools
BY KATERI HEON, ING., MEMBER ASHRAE; PIETRO GUERRA, ING., ASSOCIATE MEMBER ASHRAE
BUILDING AT A GLANCE
Optimizing energy consumption was the main focus of
Dollard-des-Ormeaux the Dollard-des-Ormeaux Civic Centre renovation. The
Civic Centre
Location: 12001 Salaberry, Dollard-desOrmeaux, Québec, Canada
Owner: Municipality of Dollard-des-Ormeaux
Principal Use: Multiple municipality services: city hall, public library, ice rinks
and pools
Includes: City hall, public library, 3 ice rinks,
2 pools, a small gym and cultural center
Employees/Occupants: About 115 employees
and 4,000 to 5,000 visitors per week
Gross Square Footage: 225,000
Conditioned Space Square Footage: 225,000
Substantial Completion/Occupancy: September 2012
energy-efficiency program was built on the CO2 refrigeration system, which provides increased cooling power
for the ice surfaces and heats the building with heat
recovered from the refrigeration system compressors.
Prior to this project, electric baseboards and coils were
used to heat the entire Centre.
The project has become a showcase project for CO2
refrigeration systems and energy-efficiency measures
such as new dehumidifiers for the building’s three pools
and the addition of variable air volume units and occupancy sensors in parts of the building.
Occupancy: 100%
National Distinctions/Awards: Energia 2014 from
AQME (Association québecoise pour la
maitrise de l’énergie); Grand prix du
génie québécois de l’AICQ (Association
des ingénieurs conseils du Québec)
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Kateri Heon, ing., is an engineer and Pietro Guerra, ing., is the mechnical department director for Les Services Exp in
Montréal.
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2015 ASHRAE TECHNOLOGY AWARD CASE STUDIES
ABOVE The facility houses city hall, a public
library, ice rinks and pools.
LEFT Insulated CO2 piping brings heat to the
ice rink dehumidifier at right on the roof. The
bare pipes are for heat rejection in the fluid
cooler at left.
The 225,000 ft2 (21 000 m2) facility includes three NHLsize ice rinks with team, referee, and machinery rooms,
shared corridors, stands and other installations adjacent to
the ice rinks; two swimming pools (one 25 m [82 ft] pool),
changing rooms, lifeguard office, filtration and machinery
rooms; gym and fitness room; and Dollard-des-Ormeaux
City Hall, Public Library and Cultural Centre.
Energy Study
An extensive energy-efficiency study of the Centre’s
systems was performed at the beginning of the project.
It included:
•• Hourly simulations for each ice rink and estimates
of heat rejection potential for a typical year, based on the
use of three refrigerants (ammonia, CO2 and R-507A);
•• Hourly simulations to establish dehumidification
and heating needs for the pools;
•• Calculation of the amount of heat that could be recovered from dehumidifiers and used to heat pool water
and pool areas;
•• Complete annual simulation, using DOE software,
for other rooms of the Centre to assess hour-by-hour
heating needs for specific areas.
Integration of the collected data allowed the facility’s
different heating needs (air and pool/domestic water)
to be matched to the amount of energy rejected by the
refrigeration system.
Advantages of CO2
What immediately emerged from these studies was
that CO2 offered significant advantages for the project,
compared to ammonia. This is despite ammonia compressors having an average coefficient of performance
(COP) value of 3.45, which is considered excellent for
the temperature requirements associated with an ice
rink. Ice rink refrigeration systems typically release
heat through a glycol loop that cools the compressors
and can reject heat in several heating coils or through
heat pumps in the building. Because CO2 refrigeration
systems operate at very high pressure and, therefore, at
high temperature, it is possible to reject the heat from
the refrigeration system into a high-temperature water
loop (160°F to 180°F [71°C to 82°C]).
At the Dollard-des-Ormeaux Civic Centre, the hightemperature loop heated by energy recovered from the
CO2-based refrigeration system contributes to heating
pool water, domestic hot water and two small glycol
loops that provide heating for the players’ locker rooms,
and the main pool area and changing rooms.
CO2 can be circulated in the building, as opposed to
ammonia, which is too toxic. CO2 is not a highly viscous
fluid, and the high operating pressure of the system
means it can easily be moved. Given these advantages,
CO2 was used to heat the stands of the Centre’s three ice
rinks, with CO2 coils installed directly in the system’s
air ducts. This method avoided having to provide the
pumping power required for a glycol loop and optimized
the efficiency of the exchange.
And, like ammonia, CO2 has little impact on the
environment.
Ventilation System
The ventilation systems for Ice Rink 1 and 2 had been
replaced two years prior to the renovation. Provisions
for additional glycol heating coils had been made at
that time. Consequently, work on these systems simply
consisted of adding CO2 recovery coils. Since the third
ice rink is the most used during the summer, its ventilation system was replaced by a ventilation unit with a
desiccant wheel dehumidifier. In addition to the CO2
heating coils used for the stands, another CO2 heating
coil was used to reactivate the desiccant wheel, which
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2015 ASHRAE TECHNOLOGY AWARD CASE STUDIES
allowed heat rejection to be used to dehumidify the ice
rink.
Refrigeration System
The CO2 refrigeration system is comprised of two
groups of compressors, each having 105 ton (369 kW)
capacity. Three independent systems could have been
installed, but this would have required a more powerful
system for the third ice rink, which is operational yearround. Additionally, given the city’s desire to alternate
use of the rinks during the summer to facilitate maintenance, it was decided to cool a shared brine distribution
system in lieu of installing three independent systems.
With its thermodynamic properties, CO2 operates in
the transcritical zone of the pressure/enthalpy curve for
refrigerants when its temperature exceeds 88°F (31°C). It
is therefore neither liquid nor gas when in the transcritical state. When air temperature is above 86°F (30°C) in
the summer, the CO2 has to operate at very high pressure
and cannot be further cooled by outside air, which results
in much poorer compressor performance than in colder
periods and COPs as low as 1.6 at 95°F (35°C). By comparison, an ammonia compressor cooled by an evaporative
condenser in the summer would have a 3.45 COP.
Heat Rejection Recovery
The refrigeration system rejects a significant amount
of heat because heat rejection includes the cooling load
transformed into condensation combined with the heat
rejection from the compressors. The highest temperature
heat rejection (220°F [104°C]) of desuperheating, which
accounts for more than 40% of emissions, was used to heat
a water loop to 180°F (82°C). After having rejected part of
the heat to the water loop, the system rejects the excess
heat–around 120°F (49°C) at that point—into the coils used
to heat the stands of the three arenas. Temperature in the
stands is maintained at 55°F (13°C).
This project is the first in North America to use direct
heat recovery with CO2 coils for heating and dehumidifying an arena. In the summer, when refrigeration needs
are high and heating needs are low, using heat rejection
to dehumidify arenas is an ideal application because the
compressors reject a significant quantity of heat. In the
winter that waste energy can be used to heat the building’s indoor air instead of dehumidifying it.
While it is very efficient, direct heat recovery presents unique difficulties that must be addressed. To
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ensure project safety, the building team coordinated
the requirements of the Régie du bâtiment du Québec
(RBQ), which enacts construction, safety and professional qualification standards, with Canadian Standards
Association’s Standard CSA B52-2005, Mechanical
Refrigeration Code, which sets the maximum refrigerant
quantities per occupied space, allowing the building to
exceed the standard’s requirements.
Inside the Centre, the stands were the only areas big
enough to satisfy CSA B52-2005 code requirements for
direct heating with CO2 coils. The ventilation system
is installed on the roof of the ice rink, and the coils are
installed outside. The installation specs for the coils
stated that the coils’ U fittings were to be located outside
the ducts, but inside the insulation. These fittings are
the most likely leak points for coils, and if they were to
fail, the refrigerant would spill outside, posing no threat
to the occupants of the arena.
Storage areas under the stands are ventilated to avoid
problems caused by condensation and odors and are
heated by a CO2 coil installed directly in the ventilation
system. This type of coil installation was permitted in this
case, because those spaces are ventilated, exhausted and
locked, and therefore off limits to the general public.
A centralized control facility allowed the City of Dollarddes-Ormeaux to refine sequences and optimize the use of
heat emissions as the Centre’s needs changed during the
first year of operation. As a result, accumulating domestic
hot water during the night has been prioritized when a
number of ventilation systems are shut down.
Similarly, to optimize recovery, the 400 kW electric
water heater operating by 100 kW stages for the pools runs
only at night to keep them at their hottest setpoint. During
the day, the water heater is turned off, and the recovery
hot water loop keeps the pools within the operating range
most of the day. In January, the water heater typically has
to start up again only in the afternoon, providing significant energy savings and greatly reducing demand.
Beginning in March, the water heater is no longer
required, and the pools are heated day and night by the
heat recovery systems. Moreover, pool maintenance is
conducted in September, when the pools are completely
drained. During the filling process, demand for heating
is high because of the staging required to avoid damaging
the finish on the pools. When the pools are filled coincides with the refrigeration system rejecting a lot of heat
due to high exterior temperatures, and the Centre’s other
2015 ASHRAE TECHNOLOGY AWARD CASE STUDIES
heating needs are limited. This was identified during the
pre-project study, and the heat exchanger for the pool
water has been sized accordingly. Nevertheless, monitoring system data by the Center’s employees and optimizing the control sequences to maximize heat recovery in
that period have been key in reducing electric heating.
Other Energy-Efficiency Measures
The following energy-efficiency measures were implemented in addition to heat recovery from the compressors:
•• Four-pass brine distribution reduces by more than
50% the brine pump power compared to the old twopass distribution;
•• Low-e ceiling above the skating rinks dramatically
limits the radiative heat exchange between the hot ceiling and the cold ice surfaces;
•• T5HO efficient lighting above the skating rinks and
LED in the Centre;
•• Increased water storage using an existing 160 gallon
(600 L) tank to accumulate preheated domestic hot water;
•• New dehumidifiers for the pools, which use heat
pipes to preheat entering air, and an energy recovery
system to heat the air and the pool water using the heat
rejected from the dehumidification process;
•• Sensitive energy recovery at the exhaust vents for
the arena and pool changing rooms to preheat fresh air;
•• Variable air volume units and occupancy sensors
for the City Hall council chamber and changing room
showers;
•• Optimizing the existing air-conditioning system for
City Hall by replacing the old constant air volume condenser with a new multiple stage condenser; and
•• Optimization of controls and review of operating
sequences for all systems, to maximize energy efficiency.
Environmental Impact
Aside from energy efficiency, the city was also looking for
a low environmental impact solution. The environmental
impact of refrigeration systems that use CO2 is 1,800 times
less than those using R-22 (the existing refrigerant in the
building) and 3,900 times less than some HFC refrigerants.
Furthermore, refrigerant leaks are minimized. The previous system let almost 50% of the R-22 refrigerant leak into
the atmosphere each year. The new system will result in the
elimination of 905 metric tons CO2 equivalent of previously
released global warming and ozone contamination.
Using CO2 also meant not having to install a water
TABLE 1 Energy costs before and after refrigeration system renovation project.
ANNUAL CONSUMPTION
(KWH)
COST/YEAR
($)
(KWH/FT 2)
Prior to Renovation
(2007 to 2008 Average)*
14,040,600
794,360
62.4
Post Renovation
(Sept. 2012 to Oct. 2013)
9,340,600
547,360
41.5
Savings
4,700,000
247,000
20.9
*2009 and 2010 consumption was a little higher due to urgent winter repairs and were not used
for the analysis.
cooling tower. The high temperature operation of CO2
means that a dry cooler can evacuate the excess heat even
in the summer. The city saves drinkable water and avoids
having to use chemicals to maintain a water tower.
Cost Effectiveness
Total cost of the project, before taxes, was $6.5 million.
Approximately $2,175,967 went to implement efficiency
measures while other expenses included upgrading the
rink refrigeration system, the pool dehumidifiers and
several ventilation systems that required replacement.
Implementation of recovery and energy savings measures reduces current annual overall consumption by
4.7 million kWh, which translates in annual savings of
more than $247,000, a 31% cost reduction from the previous baseline (Table 1).
Achieving a return on investment will take approximately 8.3 years, excluding subsidies. The project has
benefited from the federal government excise taxes
reimbursement program, which helps cities do road
network and energy-efficiency projects.
As a result of the energy measures and choice of a
natural refrigerant, the project received a $95,000 subsidy through the Optimization Program for Refrigeration
Systems (OPTER) program from the Québec government and a $1.2 million subsidy through the Programme
Bâtiments of Hydro-Québec. These subsidies reduced
the return on investment period from 8.3 years to
approximately 3.9 years.
Conclusion
The Dollard-des-Ormeaux Civic Centre sets an example of how efficient, safe and environmentally friendly
CO2 can be used in existing buildings, and demonstrates
that municipalities can help fight global warming and
have a positive impact on the environment while driving
technological progress.
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