Deep water cooling improves building efficiency

Andrew Wilcox, Vice-President, Project Development & Sales, Enwave
Monday, August 12, 2013

Deep water cooling systems are touted as being environmentally-friendly and efficient tools in commercial, residential and institutional buildings.

Here, Andrew Wilcox of Enwave explains how Toronto’s deep lake water cooling system works and how the district energy system can benefit property owners and developers.

What is deep lake water cooling?

Deep lake water cooling uses cold water pumped from the bottom of a lake as a heat sink for climate control systems.

In Toronto, this renewable source of energy (operated by Enwave) is used to air condition buildings in the city’s downtown core. From a technical standpoint, Toronto’s deep lake water cooling system is the world’s largest geothermal cooling system; but instead of using energy stored in the ground, it uses the natural coldness of Lake Ontario.

The heat that is generated in customer buildings does not make its way back to the lake but, instead, is passed into Enwave’s system and then transferred into the city’s drinking water supply before making its way to taps and showers in homes and offices. Simple heat exchangers at Enwave’s deep lake water cooling facilities and customer sites move heat from inside buildings out into the environment in a low impact, sustainable way.

What are the benefits of deep lake water cooling over other cooling methods?

Unlike traditional chillers or air conditioners that use a great deal of electricity to create cool air, Toronto’s deep lake water cooling system uses relatively little electricity to power pumps that circulate cold water from plants out to customer buildings through a network of underground pipes. Because heat is only moved or pumped from one location to another, deep lake water cooling can save some buildings up to 90 per cent of the electricity used for air conditioning, as well as thousands of gallons of clean potable water each year that would otherwise be used to transfer heat out to the atmosphere in traditional chiller plants.

These energy savings translate into removing significant electrical demand from Toronto’s power grid, especially when the electrical system is at its maximum capacity during the hottest summer days. Deep lake water cooling also reduces carbon dioxide emissions and removes tens of thousands of pounds of harmful refrigerants from customer buildings.

Are there any incentives for property owners and developers to use deep lake water cooling?

With 60 to 90 per cent of energy savings realized by using deep lake water cooling instead of traditional chillers, a building is eligible for up to 10 LEED (Leadership in Energy and Environmental Design) points in a number of categories if it uses the service. Building owners can also convert large mechanical spaces originally designed to house mechanical cooling equipment in a building into revenue generating storage, parking or leasable commercial space, making more efficient use of the floor area.

Because Enwave’s deep lake water cooling system uses very little electricity internally, it decouples the service rates from volatile utility markets, offering predictable Consumer Price Index (CPI) related rate escalations each year. This means a property owner is able to predict their costs of cooling for decades to come, instead of constantly adjusting rental rates based on rising power prices. The cost model also provides cooling to buildings at equal, if not lower, operating costs.

What are the limitations to deep lake water cooling?

Because of the very high capital costs associated with the distribution system, deep lake water cooling in Toronto is geographically limited to the city’s downtown core. Expanding the system’s reach to connect smaller buildings outside the financial district is not feasible.

However, as far as a property owner is concerned, there are no limitations inside their building. Deep lake water cooling provides at least the same service as traditional chillers, and often provides more flexibility to building operators to improve conditions in tenant spaces by finely adjusting the amount of cooling that is provided.

Is deep water cooling used in other Canadian cities besides Toronto?

In Canada, buildings in Vancouver and Halifax use ocean water for some small cooling applications. There are many similar systems installed throughout Europe, Asia and, more recently, in Hawaii. Deep lake water cooling is by far the largest lake or seawater-based cooling system in the world.

The deep lake water cooling concept is not unique from an engineering standpoint but is notable in Toronto due to the scale of construction. Enwave has built a tremendous amount of infrastructure for this system, most of which resides underground and is not visible to the public.

Andrew Wilcox is vice-president of project development and sales at Enwave.

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