Concrete Progress: Chilling in Toronto

Concrete Progress is an ongoing series of columns by Peter Brewitt devoted to exploring America’s infrastructure. It is part of Orion’s two-year Reimagining Infrastructure project.

Some of us live in the outdoor oven of Arizona. Some, in the face-numbing cold of Vermont, or the heavy sweaty boil of east Texas. But no matter where we live in America, we all manage to wear the same clothes to the office. Indoors, it’s always California: mild and pleasant, nine to five, all year long. Climate control is almost as crucial to modern life as clean water or the internet, but until the 1930s, people had to rely on fans, windows, and siestas to get through the summertime. That was before air conditioning. Now two-thirds of American households and pretty much all white-collar businesses have them.

But most people don’t think about the incredible amount of energy it takes to constantly suck, say, twenty degrees of heat out of the air. Air conditioning consumes 5 percent of all the electricity used in the United States per year. That works out to 100 million tons of CO2. But in the modern world, AC is pretty well non-negotiable. Imagine your office without air conditioning in August—you’d sweat like a slab of unrefrigerated cheddar cheese.

I found an innovative answer to this dilemma over the border in Toronto. The city’s summer temperatures are in the mid-seventies, the same as in the northern tier of the United States. Toronto’s the fourth-biggest city in North America, and its municipal cooling needs are immense.

For a long time, Toronto’s AC worked like anywhere else’s, using industrial refrigerants and electricity from the grid. But in the 1940s, an engineer named Bob Tamblyn began to think about the enormous supply of frigid water in Lake Ontario, sitting there like an heirloom in the basement. Deep in the lake, the temperature is thirty-nine degrees. Water that cold is dense, so it stays there, hundreds of feet below the surface. Can’t we, he wondered, use this to cool us down?

We can. Water does a great job of moving heat around, which is, of course, why people sweat. If you build a closed pipeline looping water through and between buildings, it’ll essentially let those buildings sweat, pulling their heat away and down the pipe. But you need to absorb the loop’s heat and keep the water cool for its return to the buildings. That’s where the lake comes in.

It took some engineering, but Bob Tamblyn’s idea came to fruition in the 1990s. Enwave Energy Corporation, which was jointly owned by the city and the Ontario Municipal Employees Retirement System, built just such a system in downtown Toronto, near the rink where the Maple Leafs skate. The loop started working in 2004.

In September, during my cross-country road trip, I went to see it for myself. Enwave (which was bought by Brookfield Asset Management last year) gave me a tour of Toronto’s cooling facility. After a quick look at a schematic of the pipelines, we descended into the system.

The John Street Pumping Station is like some James Bond-style industrial complex, fluorescent lights and concrete corridors, jungles of blue piping and massive heat exchangers, where you can just imagine Daniel Craig (or, if you prefer, Sean Connery) stalking a Canadian super-villain. Immense pipes four feet across run down the walkways, and when I put my hand on them I could feel the thrum of living water coursing from the lake to the city. Smaller pipes set the different routes of lake water and city water, which flow through exchangers to process Toronto’s heat. With the exception of a small chilling system, which runs during the hottest and most humid conditions, it all happens without artificial refrigerants and with 10 percent of the electricity demands of a normal system.

Since you’re probably wondering, here is how it works:

A set of gigantic pipes sucks in the thirty-nine-degree lake water. This water shoots along to an Energy Transfer Station—this is where I was. There it meets the giant closed loop bringing in heat from the city. Loop water (which comes in around fifty-six degrees) and lake water run through heat exchangers, with the lake water sucking in heat from the loop before joining Toronto’s municipal drinking water. The heat only raises the lake water’s temperature to about fifty-four degrees, which is plenty cold for household purposes. Inside the heat exchanger, the lake water and loop water are separated by a series of metal plates—these are what conduct the heat. The two streams never physically mix.

The now-chilled loop water runs up and cools clients’ buildings in downtown Toronto. The deep water cooling system cuts more than 87,000 tons of CO2 per year, as well as hundreds of tons of pollutants like nitrogen and sulfur dioxide. The system cools sixty-two buildings, and counting.

Can it expand? People use air conditioning pretty much everywhere, but not too many places have deep lakes handy. However, plenty of cities are on the ocean. Honolulu is developing its own system right now. While they need to dispose of the warmed ocean water—you can’t drink it—consider the potential for deepwater systems in cities from Seattle to Miami. Perhaps they, too, can find a way to organize a low-pollution, low-carbon municipal air-conditioning system. Pretty cool.

Peter Brewitt has wondered about infrastructure ever since a flood kept him away from three days of kindergarten. He’s currently at work on a PhD at the University of California, Santa Cruz, where he’s researching the ways people restore and remake their environments.


  1. Interesting, after looking into this I learned that there’s also a project like this in Ithaca, NY, that cools buildings for Cornell U and other buildings:

    “Cornell University’s Lake Source Cooling System uses Cayuga Lake as a heat sink to operate the central chilled water system for its campus and to also provide cooling to the Ithaca City School District.[4] The system has operated since the summer of 2000 and was built at a cost of $55–60 million. It cools a 14,500 ton (51 megawatt) load.”

  2. Hi John. I saw that about Cornell. It really does seem like these systems can be built in lots of places. Maybe we’ll see them elsewhere…

  3. Leave it to the brilliant people of Toronto to come up with yet another innovative design to mitigate greenhouse gas emissions!

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