City of Toronto and Enwave aim to expand Deep Lake Water Cooling (DLWC ) system with $100 million project


By John Devine

Special to Ontario Construction Report

A system that uses cold water from Lake Ontario to cool more than 80 downtown Toronto buildings is the subject of an environmental assessment aimed at expanding its capacity, to provide air conditioning to even more properties and people.

The roughly $100 million project is targeted to be operational for the 2023 cooling season, and the sustainable energy project will be supported by $10 million in federal funding, through the Low Carbon Economy Fund, according to project details.

Since 2002, the City of Toronto and Enwave have operated under an existing Energy Transfer Agreement (ETA) that facilitates the transfer of cooling energy from the City’s water infrastructure into Enwave’s District Energy System, through heat exchangers.

Although the system has the capacity to meet current demands, Enwave anticipates close to 35 percent increase in its customers’ cooling demands in the near future. There is opportunity for the City and Enwave to amend the Energy Transfer Agreement and expand the Deep Lake Water Cooling (DLWC ) system to meet the cooling demand in a mutually beneficial way. The assessment will examine the proposed expansion of the DLWC supply, according to the City.

“As Toronto grows over the next 20 years, Enwave is committed to making our city more resilient by providing innovative, sustainable heating and cooling in support of the City’s growth,” said Carlyle Coutinho, president and Chief Operating Officer, Enwave Canada.

So, how does the current system work? Well, Enwave provided these details:

  • The City’s Island Water Treatment Plant (Island WTP) draws cold water from three intake pipes that extend deep into Lake Ontario.
  • Before entering the City’s distribution system, the treated water passes through Enwave’s Energy Transfer Station (ETS).
  • There, heat exchangers transfer thermal energy from the district cooling water loop to the cold drinking water. The re-chilled cooling water is circulated through a closed loop running throughout downtown to provide cooling to buildings, and then Enwave recycles the heat, returning the warm water to the ETS to repeat the process.

According to Enwave, the expansion of the DLWC system would involve slip-lining and extending up to two existing inactive shallow intake pipes at the Island WTP deep into Lake Ontario to a depth with constant cold water supply. The new intake pipe(s) would be inter-connected with the three existing intake pipes at the Island WTP. Raw water would be conveyed from the new raw water intake pipes to the existing District Energy System through a new tunnel from the Island WTP to the ETS, separate from the City’s water supply.

As with the existing system, the cold water would pass through new raw water heat exchangers at the ETS. The warmed up raw water would then be transferred to Enwave’s existing Simcoe Street Cooling Plant (SSCP) via an existing tunnel. At the SSCP, the water would provide supplemental cooling when needed before being discharged back into Lake Ontario via an existing connection to the City’s stormwater system.

The existing DLWC supply uses a renewable cold water resource as the primary source of cooling for Enwave’s District Energy System, which provides cooling to more than 80 buildings, including critical care facilities, government buildings, data centres, universities, and commercial and residential towers in downtown Toronto.

Enwave says the City would benefit from the expansion of the DLWC supply in a number of ways, including:

  • Reducing energy use, in alignment with the City’s TransformTO Plan to reduce greenhouse gas emissions. The expansion of the DLWC system could reduce demand on the electricity grid by about 18 to 74 million kWh, and reduce water demands by about 0.3 to 1.2 billion litres annually through the increased use of this renewable energy for cooling.
  • Improving reliability, redundancy, and operational flexibility through the construction of new and repurposed unused city infrastructure.
  • Increase city revenues under the ETA and reduce operation and maintenance costs.


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