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Nov.24 2011, Summary of CIMCO ice-making responses:
1. With ideal environmental conditions and the correct equipment, ice can be made in the latter half of November
2. To avoid the radiant heat gain, making ice at night is ideal
3. There is nothing to my knowledge that says the sensible [ambient] temperature canít be greater than 10 degC. This is the average temperature in an insulated indoor arena
posted November 16, 2010
There's a lot of confusion about the factors that go into deciding on opening and closing dates for outdoor rinks, so we thought we'd ask an expert.
CIMCO (an acronym for Canadian Ice Machine Company, formed in 1913) has a support contract for 18 of Toronto's outdoor rinks in the west end of the city. They visit each of these rinks twice a day when they operate, and built many of them. So they know their business.
I spoke to David Sinclair of CIMCO (He's the Toronto Branch Manager) about factors effecting the outdoor rink season, and he had a lot of interesting information and insights.
He confirmed that the main factor for deciding outdoor ice viability was "radiation load" (direct or indirect sunlight). The lowest effect of this was in the 12 weeks from the start of December to the end (third week) of February. He noted however that on a sunny day even during this winter period, direct sunlight reflecting from white boards around the ice could cause ice near the boards to become soft.
Operating rinks before and after this Dec - Feb period could be done, he said, particularly before sunrise and after sunset. During the day, it depends a bit on luck. Cloud cover helps, whereas bright sunshine can compromise the ice. And yes, cold ambient temperature helps a bit, but is not the main factor.
This being the case, rinks like Nathan Philips Square which is shielded from the sun by the Sheraton Centre Hotel to its south, have a huge advantage. Another way to extend the life of an outdoor rink would be to place a tent over it. This would allow the rink to operate from even late October he said. Of course such a structure has its own problems and a great deal of expense.
Ice could be formed in the night even at 10 degrees celsius he said, and the compressors have no problem dealing with that (outdoor rink compressors are designed for more capacity than indoor rink compressors). It's the daytime and the angle of the sun that is the main factor.
Ambient temperature, according to Sinclair, is very much a secondary factor. Consider the temperature in indoor rinks, he said, which is often 10-12 degrees celsius. So outdoor rinks can be quite successful at those temperatures, as long as sunlight is not a factor.
Sinclair also had a number of insights about ice quality, which is often not as good in outdoor rinks for a number of reasons. For one thing, most outdoor rinks are often only flooded once a day (with a Zamboni), he said, whereas indoor rinks are routinely treated every hour. Also humidity can be controlled indoors, but not outdoors, so one can get frost on outdoor rinks which can compromise the ice quality. Rain can be a factor, particularly early or late in the season, softening the ice. Finally, as mentioned before, ice near white boards around hockey rinks if they reflect light can compromise the ice around the boards.
So the bottom line:
Outdoor rinks are run most efficiently in December, January, and first three weeks of February. They can be opened in mid November and the last week of February, but they require a bit more maintenance (and therefore expense) during this early and late period, and there is the risk of poor ice mid-day if they are effected by direct sunlight (or extreme warm temperatures). In the absence of sunlight issues, temperatures of 10-12 degrees are not a problem, even during ice formation.
[Editor's note: as a practical matter, we find that the sun really isn't a problem in the last half of November (it's pretty close to the winter solstice). On the other hand the sun can start softening the ice from mid-February on.]
For more information on weather and the ice, see Outdoor Rinks And Weather
Q: I went by Dufferin Rink earlier today, and found that the ice was good, but the ice was wet on the north side of both the pleasure and hockey sections (but dry in the south sides), more wet in the hockey section (all presumably owing to the sideboards reflecting radiation - but even in overcast conditions??). I believe the temperature was about 7C today, and overcast. Is this what you would expect under optimal conditions (ie good ice maintenance, good compressor system performance)?
A: The answer to your question is, yes. Hereís the rational. Sensible temperatures in indoor arenas in summer conditions is typically 10 deg.C. If you recall, indoor arenas that operate in the summer require the same capacity as outdoor rinks in the winter. So considering the sensible loads are roughly equal, the air temperature wouldnít be a factor in this case. However as discussed earlier, the radiant heat load is a rinkís greatest load. The radiant load exists when itís daylight (cloudy or sunny). The other factor that affects the ice is humidity. Moisture in the air that condenses and freezes releases heat in the process. Itís called the Latent heat of Fusion and itís a real load to the ice sheet. Itís the opposite effect of boiling where heat is added to change the state of liquid water to water vapour. The Latent Heat of Fusion @ 32 deg.F is 144 BTU/lb = the heat that is released when water changes from a liquid to a solid. As warmer air can hold more moisture, the effect on the ice is greatest at this time of year. When the air temperature is low (January), the humidity is also low and so is the latent heat load. Indoor arenas compensate by dehumidifying to eliminate a large part of this load but can still operate with sensible temperatures in the 10 deg. C. range. Unfortunately we havenít found a way of dehumidifying the great outdoors!
Q: By way of comparison, what is the prescribed and actual ambient temperature in indoor rinks? Does this vary with season and type of activity? For example is the ambient indoor temperature warmer in Sept/Oct and March/April for indoor rinks to save energy, or is it warmer for pleasure skates than for hockey sessions? Does the ice ever (or is it allowed to) get wet in indoor rinks?
A: The temperature of indoor arenas do fluctuate depending on the building construction and the outdoor temperatures. A newer arena that is better insulated will typically have indoor temperatures of 10 degC in the summer and 7-8 degC in the winter. Poorly insulated buildings (Scarborough Heron Park for example) gets downright cold in the winter as the temperature drops with the outdoor ambient. Since the arena environment is controllable (no sun load and humidity controlled), the quality of indoor ice (ie wet ice) should never be an issue. Indoor ice quality is always better than outdoor ice.
We also asked the Toronto Energy & Waste Management Office about ambient temperature of indoor rinks:
A: Ambient temperature in the stands for a recreational hockey rink does not have a comfort standard. It is sometimes as high as 17 C. For energy conservation, it should be kept between 10įC and 15įC.
There are two issues with temperature. Too high causes excessive refrigeration use and fog which causes both the refrigeration plant and the dehumidifiers to work harder.
[Our] preference is to have no heating in the stands.