A 50-foot wide hole excavated 150-feet into bedrock below a six-level underground parkade in downtown Toronto will serve as a “thermal well” filled with 8.5 million litres of Lake Ontario water to heat and cool downtown buildings.
Lined with concrete, the giant watertight cistern will employ Enwave Energy’s innovative low-carbon heating/cooling system to provide energy to buildings, including a seven-building development, where it is under construction, called The Well at Front Street and Spadina Avenue.
To cool buildings in the summer, Enwave Energy will cool water in the cistern from its Deep Lake Water Cooling (DLWC) system at night and feed that water to buildings to provide cooling in the daytime, Carson Gemmill, director of engineering at Enwave, says.
Commissioned in 2004, Enwave’s DLWC displaces about 55 MW of energy a year from the grid. It is used to condition the air of about 75 mixed-use buildings in downtown Toronto.
Enwave will also use the well’s water in a separate hot water loop in tandem with heat exchangers to warm building interiors in winter, Gemmill says.
Longer term, heat will be drawn via heat pumps from waste energy sources such as data centres, he points out.
The waste-heat energy captured from buildings through cooling them is a source for low-carbon heat that Enwave can use to service buildings for heating, he adds.
The costs of pumping the water as cooling energy to the network of buildings is “significantly lower” when compared to the cost of operating in-house cooling equipment in each building, he says.
Enwave’s technology is in a “closed loop system” — meaning lake water from the tank gets charged with heating or cooling buildings and then is returned for reuse to the well.
The size of the cistern was determined by the need for heating/cooling demand for the growing downtown area, which includes (over 20 buildings) in Enwave’s western expansion corridor running from University Avenue to Bathurst Street between Adelaide Street and Front Street.
The giant water storage tank’s concrete lining was done by forming contractor C&M McNally Engineering Corp.
“Co-ordinating the construction of this (the well or storage tank) along with construction of this seven-building development above it and around it has required significant co-operation between all the development partners, and multiple consultants and contractors,” Gemmill adds.
Enwave’s director of engineering says while there might be several systems using thermal energy storage in North America, he is not aware of any that have gone underground on such a large urban commercial scale.
He says Enwave’s system helps developers meet the Toronto Green Standard, the city’s sustainable design requirements for new developments. The standard defines the energy and carbon requirements of buildings.
Allied Properties and RioCan are the commercial developers of The Well in Toronto’s core. It includes more than one million square feet of office space and upwards of 400,000 square feet of retail and features about to 1.5 million square feet of residential developed by Tridel.