Environmental Science & Engineering - www.esemag.com - September 2003
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Deep lake water cooling - a matter of degrees

By Tom Davey, Environmental
Science & Engineering

While Torontonians sweated out electrical blackouts and loss of air conditioning, a press tour took place on a pleasure craft sailing from the Toronto waterfront. The boat trip gave a unique view of an impressive engineering scheme which will, ultimately, use extremely cold Lake Ontario water to cool buildings in the huge office blocks in downtown Toronto and bring water to Toronto’s Island Filtration Plant for treatment to potable standards. As our boat tour got underway, the airwaves were full of horror stories from Ontarians complaining about the loss of air conditioning - this in stark contrast to the cooling breezes on our boat trip.

The final sections of pipes for Toronto’s Deep Lake Water Cooling (DLWC) began to be placed deep into the chilly waters of Lake Ontario in August, 2003. The final pipe is one of three high density polyethylene pipes that will extend five kilometres out into the lake and reach a depth of 83 metres below the lake surface.

By using the naturally occurring cold water from Lake Ontario, Enwave’s Deep Lake Water Cooling project will provide an alternative source of air conditioning for downtown office buildings in Toronto. In exchange for providing new raw water intake pipes to Toronto’s Island Filtration Plant, Enwave will be permitted to transfer the cold temperature from the City water to its chilled water system. This process will not have any negative impact on the potable water quality because there will always be physical separation between the City’s potable water and Enwave’s cooling loop. The Deep Lake Water Cooling project will produce enough cooling to service over 1,800,000 square metres of office space or approximately 100 Toronto office towers.

“This will be the largest lake water cooling service in the world, and the first of its kind in Canada,” said Dennis Fotinos, Enwave President and CEO.

One source of water...two uses
•	4ºC water is drawn through three new intake pipes, treated at the Island Filtration Plant and directed through an existing cross-harbour tunnel to the John Street Pumping Station (JSPS).
•	Prior to entering the drinking water supply, the water is sent through heat exchangers and energy is transferred between the City and Enwave systems.
•	Water enters the City side of the heat exchangers at 4.4ºC and leaves at 12.5ºC, with 8.1ºC transferred to the water on Enwave’s side of the heat exchanger.
•	Physical separation between Enwave’s system and the City’s system is maintained via heat exchangers that are designed to facilitate the transfer of energy, not water.
•	One source of water provides coldness for Enwave’s system and drinking water for the City.

There are two stages to the Deep Lake Water Cooling project. The first stage, called the marine component, was expected to be completed by the end of August 2003 with the installation of the remaining pipes. The land construction stage will continue until the spring of 2004. When complete, Enwave will activate Deep Lake Water Cooling. The DLWC project is an excellent example of public private partnership with the City of Toronto’s Water and Wastewater Services division and Enwave. At the time of writing, it had not received funding either from the Province of Ontario or the Federal government.

Established over 20 years ago, Enwave is one of North America’s largest district energy systems. Anchored by three modernized steam plants, a 20 kilometre distribution network supplies over 130 buildings in the downtown Toronto core with reliable, cost-effective heating.

In 1997, with the opening of its Simcoe Street Cooling Plant at the Metro Toronto Convention Centre, Enwave introduced district cooling to Toronto.

Originally established as Toronto District Heating Corporation (TDHC) in 1982, Enwave underwent a legislative restructuring in 1999 and is deemed to be incorporated under the Ontario Business Corporation’s Act. Enwave’s shareholders are BPC Penco Corporation, a wholly owned subsidiary of the Ontario Municipal Employees Retirement System and the City of Toronto.

Two of the three HDPE 1,500 mm pipe intakes will ultimately total 15,592 metres comprising 897 fused joints. Concrete anchor blocks will total 2,837 comprising 7,271 m³ of concrete.

Deep Lake Water Cooling is an environmentally-friendly, reliable, cost-effective, long-term method of replacing CFC-based chillers.

Significant statistics include:

DLWC uses 90% less electricity than conventional air conditioning and 75% less energy overall.
It reduces carbon dioxide, nitrogen oxide, sulphur dioxide, smog, acid rain, greenhouse gases and ozone-depleting chlorofluorocarbons (CFCs).
DLWC cuts the greenhouse gas carbon dioxide emissions by 40,000 tons per year - the equivalent of taking 5,000 cars off the road.
Sulphur dioxide emissions will be reduced by 176 tons each year. Sulphur dioxide combines in the atmosphere to make sulphuric acid, which kills aquatic life in Lake Ontario.

The ecology of the lake will not be affected, as the DLWC system will be used for the City’s potable water supply and will make its way to consumers for cleaner drinking water.

The system will save 75-90% of electricity that would have been generated by a coal-fired power station.

Contact: Enwave District Energy, Tel: (416) 392-6838, Fax: (416) 363-6052.

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