Outdoor Ice Season and Energy Savings
A timing based approach to energy savings and
ice quality improvement at Toronto's 49 Outdoor
Ice Rinks
Prepared by Corey Chivers for the Centre for Local Research Into Public Space
CELOS
Toronto's Outdoor Ice Rinks at a Glance



Toronto has more outdoor
compressor cooled ice rinks
than any city in the world
4 outdoor rinks at central
locations and 45 outdoor rinks
scattered in neighbourhoods
throughout the city
Ice rinks provide a much
needed social gathering space
during the winter months
Source: www.cityrinks.ca
Watching the Rinks



For over 10 years, CELOS has been keeping a
close eye on Toronto's outdoor rinks
One thing that we have consistently noticed
(and have been told by rink users across the
city) is that ice surfaces seem to deteriorate in
the spring despite air temperatures still being
fairly cold.
We wondered, what is going on here?
Dispelling Misconceptions


The rink hotline at Dufferin Grove AIR receives
dozens of calls a day during warm spells asking
“is there any ice left?”
What makes Toronto's outdoor ice rinks so
special is that they don't leave it up to Mother
Nature to keep them frozen...
Warm air – Skate On!
Rinks: Giant Refrigerators


The rinks work just like your
kitchen refrigerator (sort of...)
Big electrically driven
compressors cool ammonia,
which in turn cools a salt
brine or glycol solution.
Rinks: Giant Refrigerators


Electrically driven pumps
pump that cold brine through
a series of tubes underneath
the ice surface
This process removes heat
from the ice slab keeping the
rink frozen
Saving Energy


In 2000, City Council voted for
an environmental plan (EP),
meant to reduce communitywide carbon dioxide emissions
by 20% by 2005 (from 1990
levels), and also to reduce
energy use by 15% in all its
departments.
In 2002 the City hired
CINERGY Solutions to
undertake a $10.2 million
energy retrofit of the city's
arenas and rinks.
Source: toronto.ca
Saving Energy without Spending Money


CELOS recommends opening the rinks during
the weeks of the year that are best suited to
outdoor artificial ice
This will save energy costs and deliver better
ice to Toronto's skaters
Better Ice, Happier Skaters
The Season


Since amalgamation, the rinks have been
opening later and later in the year, shifting the
rink season toward the spring months.
Not only is this not ideal from an energy
perspective, but census counts of skaters
carried out at Dufferin Rink over the past four
years show a marked decline in interest in
skating in March.
Modelling the effects of temperature and sun on
energy consumption and ice quality


Cooling load depends on the ambient air
temperature as well as the radiative heating
contribution from the sun
The relative contributions of each were modeled
mathematically over the period of November 1st
to March 31st
Results


When sun and average air temperature are
taken together, we see that the compressors
must work beyond their capacity to keep ice
after March 1st.
It can also be seen that ice is more viable
throughout the month of November than in
March.
Compressor Load
For average air temperatures and constant ice thickness (4cm)
160
% of load required for hard ice
140
120
100
80
60
40
31-Mar
21-Mar
11-Mar
1-Mar
19-Feb
9-Feb
30-Jan
20-Jan
10-Jan
31-Dec
21-Dec
11-Dec
1-Dec
21-Nov
11-Nov
1-Nov
Figure 1
Results


We then ran the model to compute the
maximum temperature for each day of the
season at which skateable ice could exist.
Figure 2 shows this curve compared with the
average daily temperatures (from Environment
Canada).
Maximum possible air temp for hard ice VS Average Daily Temperatures
Results
12pm: Nov - March (Average Cloud Cover)
15.0
Temperature (degrees C)
10.0
5.0
Maximum Temp for Ice
AverageDailyTemp
0.0
-5.0
-10.0
-15.0
28-Apr
8-Apr
19-Mar
27-Feb
7-Feb
18-Jan
29-Dec
9-Dec
19-Nov
30-Oct
10-Oct
Figure 2
What's going on?



During the winter months the sun stays low in
the sky throughout the entire day.
For this reason, there is drastically less solar
input than there is in the summer. (In fact, this
is why we have summer and winter!)
Let's take a look at what happens when we
rerun the model to simulate all overcast days...
Maximum possible air temp for hard ice VS agerage daily temperature
12pm: Nov - March (overcast)
25
Temperature (degrees C)
20
15
Maximum Temp for
Ice
10
AverageDailyTemp
5
0
-5
25-Mar
16-Mar
7-Mar
26-Feb
17-Feb
8-Feb
30-Jan
21-Jan
12-Jan
3-Jan
25-Dec
16-Dec
7-Dec
28-Nov
19-Nov
10-Nov
1-Nov
Figure 3
A Closer Look
Hourly Maximum Air Temperature for Hard Ice
November 1st - 3rd
35.0
30.0
Temperature (degrees C)
25.0
20.0
15.0
10.0
5.0
Figure 4
0.0
The sun is our culprit!



Outdoor ice rinks can hold ice at almost 20৹C in
overcast skies in December.
Providing you've got a cloudy day, the time
interval over wich ice can be held in air
temperatures over 15 degrees is November 1st
to February 9th.
The capacity to hold ice is drastically reduced
beyond March 1st (for both sunny and overcast)
Are Outdoor Rinks Doomed?


These results have interesting implications for
those who would suggest that outdoor ice rinks
are on their way out in the face of climate
change.
Even with an increase in average air
temperatures, the outdoor compressor cooled
rink will live on!
Recommendations


Operate the city run outdoor ice rinks from the
First of November to the end of February
This will result in:

Energy savings

Better ice over the entire season

Happier skaters
Further Measures for Easy Energy
Savings


Ice thickness is directly related to energy
consumption
According to a study by Marbek Engineering,
reducing depth 12mm will result in an average
reduction of 6,000 kwh/yr/refrigeration plant for
seasonal rinks.
Ice thickness vs Energy Consumption
Adapted from: Manitoba Hydro, URL: http://www.hydro.mb.ca/
Produced By The Centre For Local Research
Into Public Space
© CELOS, Toronto 2008