How Toronto's skating rinks stay frozen when temperatures rise

Ever wonder how rinks stay chilled on balmy winter days? It's all due to refrigeration technology.

Ever wonder how rinks stay chilled on balmy winter days? It's all due to cool technology

Nathan Phillips Square is one of Toronto's 52 outdoor skating rinks. (David Donnelly/CBC)

With highs of anywhere from 2 to 4 C throughout the week, it almost feels like spring in Toronto right now. But there's still plenty of time to skate at a local rink.

That's because there's technology beneath your blades keeping the ice frozen — even when temperatures rise.

So how does that all work, exactly?

The cool technology behind skating rinks

Richard Ubbens, director of parks for the city, says there are refrigeration systems in place for the city's 52 outdoor rinks.

"The pads are full of pipes that carry refrigeration fluids through them and we have a series of compressors and circulating pumps and coolers," he explains.

According to the Centre for Local Research into Public Space, also known as CELOS, artificial ice rinks are able to keep ice frozen in air temperatures up to 15 C if the sun isn't too strong.

Rink compressors vary between 100 and 200 horsepower each, CELOS notes. These compressors push brine or a glycol solution through a big tank of cooling ammonia, and then out into the "extensive grid of PVC pipes underneath the concrete floor of the rink."

The cold liquid brings the whole massive slab of concrete to below freezing — which means water on top forms a layer of ice. 

Toronto's skating season typically lasts from around late November to March. That's usually when the sun gets too hot to handle. (Nikita Sursin/Shutterstock)

'It's like a giant refrigerator'

"The brine liquid in the pipe grid circulates back into a large pipe in the 'header trench' right next to the building, underneath where everybody stands when the zamboni is doing ice maintenance," CELOS explains online.

"From there the brine gets pushed back into the compressor room, where it passes through the freezing-cold ammonia tank, and out again into the pipes under the concrete, and so on."

When you see how it's built, "it's like a giant refrigerator," Ubbens said.

But when summer sun finally arrives, it's a bit much for the refrigeration systems to handle. That's why the skating season typically lasts from around late November to March — so better lace up a few more times before the spring.

"The ice has to be hard enough to skate on," Ubbens said. "As soon as it gets too soft, that's when we have to close the ice pad because it's not safe."

With files from Metro Morning