Page 8 - U4SSC Case study: Energy efficiency in buildings, June 2020

Meanwhile, in the 1990s, the City of Toronto experienced a water quality issue. Zebra mussels infested
the city’s potable water intake pipes from Lake Ontario, fouling the water and causing undesirable
odours. To address the problem, the city considered installing carbon filters, which would have
necessitated a large capital investment. Instead, the city decided to evaluate DLWC. Installing very
deep raw water intake pipes could address the water quality issue caused by zebra mussels and provide
a source of water that remains at a consistent, cold temperature year-round to support DLWC. Once
the design and business case for DLWC was developed, the city established Enwave, the district energy
company that developed and operates DLWC.

DLWC is an example of a circular city strategy that has provided, and continues to create, value for the
City of Toronto and its citizens, and for the natural environment.

Promoting circularity

Vision and content

DLWC was initially set out to transform the way in which buildings are cooled, in order to reduce the
environmental impact while providing value to the city and fostering economic development. Originally
commissioned in 2004, DLWC has accomplished this objective. DLWC now serves over 70 buildings
in downtown Toronto, displacing 1 391 kg of CFCs, 61 MW of peak electricity demand, 75 per cent of
total cooling-related electricity consumption, and related GHG emissions. Looking forward, plans for
DLWC continue to support the city’s long-term goals. Through TransformTO, the city has identified that
to achieve its GHG reduction targets by 2050, 75 per cent of its energy consumption will have to be
derived from renewable or low-carbon sources and 30 per cent of all floor space will be connected to
low-carbon thermal energy networks (Scioli, 2). The next evolution for DLWC will be the backbone for
low-carbon heating, as well as for cooling.

How Deep Lake Water Cooling Works

Three DLWC intake pipes extend along the base of Lake Ontario to a depth of over 80 m below the
surface, where the water remains at a temperature of about 4°C throughout the year. Once the water
has been drawn from the lake and treated to make it potable, it is pumped through heat exchangers to
cool it in Enwave’s district system that supplies cooling to buildings throughout downtown. The potable
water continues through the city’s network to individual buildings where it is used, flushed down the
drain and eventually makes its way back to the lake through the city’s wastewater treatment systems.

2 Case study: Energy efficiency in buildings, June 2020