Rigs were used to drill over 370 boreholes 250 metres deep under the University of Toronto's campus. Water will be circulated through this system, taking excess heat from buildings in the summer and storing it underground for use to heat the building ventilation systems in the winter.David Lee/University of Toronto
The University of Toronto is building Canada’s largest urban geo-exchange system underneath its St. George Campus to heat and cool several of its century old buildings in downtown Toronto.
The system, also called a ground source heat pump, is expected to reduce the school’s annual greenhouse gas emissions by 15,000 tonnes when it is up and running in 2024. The initiative is part of the university’s Landmark Project, which aims to revitalize and reduce the environmental footprint of the late 1890s-buildings, among the oldest in the city.
“The goal is making heritage buildings more efficient than they were ever imagined to be,” said Scott Mabury, the vice-president of operations and real estate partnerships, adding that he hopes builders across the country eventually see the project as proof that the carbon footprint of old structures can be manipulated.
“This geo-exchange system will help us have a much lighter touch on the world, and if we can do it here, we can do it anywhere.”
The system will help regulate the temperature of more than 15 buildings through a network of heat pumps extracting and storing heat from the ground. In the summer, it will strip excess heat from the buildings and store it inside a closed-looped, 200-kilometre-long underground network of U-shaped tubes filled with glycol and water. The heat will then be pumped back into those buildings during the colder months. The annual reduction in carbon emissions will be equivalent to taking 3,260 gas-powered cars off the road.
The price tag for the system is not yet known, but Mr. Mabury said the donations pot is quickly growing: More than 3,800 donors have already given almost $15-million to the Landmark Project, including a $250,000 gift from the University of Toronto Students’ Union and another $1-million from the alumni association.
“Never have we had a project that has had that breadth and depth of donations,” Mr. Mabury said.
U of T’s chief operating officer of property services and sustainability, Ron Saporta, who is overseeing the construction, said he expects to see a payback in 15 years. Geo-exchange systems have higher upfront costs than traditional heating and cooling systems but offer a significant reduction in utility and maintenance fees. Plus, the life expectancy of such a system is at least 50 years – double that of traditional chillers and boilers.
“We just hit our 200th anniversary at U of T, we plan to be here for at least 200 more, so long-term investments are of interest,” Mr. Saporta said.
There are approximately 100,000 geo-exchange systems in operation in Canada. Early versions were installed as far back as 1992, at the Father Michael McGivney Catholic Academy in Markham, Ont., gradually finding application in larger and larger buildings – the biggest system in the country is at Vancouver International Airport and cut its yearly emissions by as much as 35 per cent.
U of T, meanwhile, is popularizing their use in urban environments. Geo-exchange systems already heat and cool major buildings on the school’s Scarborough and Mississauga campuses.
Mr. Saporta said adapting the old St. George campus buildings to new heat pumps can take a lot of work, as it involves updating electrical panels and mechanical systems. But those issues won’t be as burdensome to the building process as supply chain disruptions and other pandemic complications. On some days during the Omicron wave, 30 per cent of construction workers would be absent from work after being exposed to the virus.
The most obvious challenge that comes with nestling a 200 kilometre-long network of heating pipes inside Canada’s busiest city, however, is space. Jim Wallace, a professor emeritus of mechanical and industrial engineering in the faculty of applied science and engineering at U of T, said most geo-exchange systems expand underground horizontally, but on the St. George campus, the surrounding buildings make that impossible. So instead of digging shallow, long trenches, he explained, urban heat pumps have to be installed vertically by digging deep wells.
Dr. Wallace is no stranger to the method of digging deep – the first researcher to prove geo-exchange systems can be suitable in cold Canadian soils was his colleague and mentor, Frank Hooper, also a professor emeritus of mechanical and industrial engineering at the university. Back in 1952, Dr. Hooper and his research team proved Ontario’s relatively stable temperature of 10 to 12 C 200 metres down created appropriate conditions for transferring heat through fluid circulating in underground pipes.
Dr. Hooper died last May but not before becoming known as a pioneer of ground source heat pumps.
With excitement, Dr. Wallace has been watching the heat pump gain acceptance.
“This complex vertical well-drilling system is a lovely, sophisticated design,” he said, adding that his late colleague’s ideas played an indirect role in rendering the project possible.
“It’s serendipitous that it’s being built here, right where one of the pioneers of geo-exchange had worked. Frank would be proud.”
Editor’s note: An earlier version of this article incorrectly said the buildings were 200 years old.
Interested in more stories about climate change? Sign up for the Globe Climate newsletter and read more from our series on climate change innovation and adaption.