Toronto is Canada’s largest city and continues to grow at a staggering rate. This rapid growth comes with both opportunities and challenges. Economic growth exerts more pressure on Toronto’s already constrained electricity grid and makes it harder to reduce total greenhouse gas (GHG) emissions. However, it also provides Toronto with the scale and resources to invest in transformative strategies.

Addressing climate change is a key priority for the City, and its climate change action plan, titled “TransformTO”. Through TransformTO, the City has committed to reducing GHG emissions by 65% by 2030 and 80% by 2050 compared to 1990 levels. Since 60% of GHG emissions in Toronto are generated by buildings, the City has identified thermal energy networks as a critical strategy to meet its goals.

Since the 80s, the primary means of cooling buildings were chiller systems that used chlorofluorocarbon (CFC) refrigerants, chemicals that are particularly harmful to the ozone layer. Deep Lake Water Cooling (DLWC) has been evaluated as a system to improve the environmental performance of Toronto's energy network in the 90s, when the City experienced a water quality issue as the Zebra mussels infested the City’s potable water intake pipes from Lake Ontario, fouling the water and causing undesirable odours.

DLWC is a system that would use cold water from the depths of Lake Ontario to supply cooling to buildings in the downtown core instead of refrigerant-driven chillers. Installing very deep raw water intake pipes could both address the water quality issue caused by zebra mussels and provide a source of water that remains a consistent, cold temperature year-round to support DLWC. Commissioned in 2004, DLWC is an example of a circular city strategy that has provided and continues to create value for the City of Toronto, its citizens, and the natural environment.

DLWC now serves over 70 buildings in downtown Toronto, displacing 1391 kg of CFC’s, 61 MW of peak electricity demand, 75% of total cooling-related electricity consumption, and related GHG emissions. Looking forward, plans for DLWC continue to support the City’s long-term goals. The next step in the evolution of DLWC will be the backbone for low-carbon heating as well as cooling.

Additionally, DLWC has generated significant additional benefits since its implementation.

• DLWC reduces cooling tower use, saving potable water consumption and related energy used in the treatment process.

• DLWC has contributed to economic development in the City by retaining money spent on energy within the local economy and establishing a centre for innovation in district energy in Toronto. Over the past 10 years, over $116 million of capital has been invested in expansions of the DLWC distribution network.

• DHR has the potential to reduce GHG emissions by a projected 37,000 tCO2e per year relative to that produced by conventional natural-gas fired boilers, provide a new model for low-carbon heating in Canada, and foster further economic development for the City.

Photo by Sandro Schuh from Unsplash.