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.