There's a heat wave gripping Central Canada -- and with it the inevitable smog -- prompting people to crank up their air conditioners or head for the cool, clean-air comfort of public buildings amid health cautions from local authorities.
This summer, many buildings from Ontario to the Maritimes are staying cool using nature's own gift -- frigid lake and ocean waters -- and through a process that doesn't add to the bad air.
A number of downtown Toronto office buildings are being cooled by an innovative, energy-saving system that produces no pollutants, such as carbon dioxide or CFCs, needs no upfront capital investment, and costs building owners between 10 and 15 per cent less than conventional air conditioning in annual operating expenses.
On the East Coast, Halifax's Purdy's Wharf complex continues to stay cool, courtesy of the ocean, whose deep water has been harnessed for 21 years to provide air conditioning.
In Toronto, Enwave Energy Corp., which has provided heating for downtown office buildings since 1982, launched its deep lake water cooling system in 2004.
There are financial as well as environmental benefits here, says Dennis Fotinos, president and chief executive officer of Enwave, which is jointly owned by the City of Toronto and the Ontario Municipal Employees Retirement Board.
"In older buildings, we can reduce electricity consumption due to air conditioning by as much as 90 per cent, and in newer, more efficient buildings, by about 75 per cent," Mr. Fotinos says.
He adds that the system's near-100-per-cent reliability is often a critical factor. "Some companies can't afford to be without cooling if there is a blackout, like the one in 2003, because their computers will have runaway heat gain and crash after 15 minutes of air conditioning failure."
Building owners are increasingly concerned about rising electricity costs, he says. "We charge our customers an annual fixed rate that escalates with the inflation rate, which gives them certainty over the course of the 20-year contract."
And for the foreseeable future, there is a certainty of supply of the cooling water. Enwave's system draws icy cold (4 C) water from 83 metres below the surface of Lake Ontario. The water travels five kilometres through three polyethylene pipes to be treated at the Toronto Island Filtration Plant before it is sent to an energy transfer station in downtown Toronto, in the vicinity of the Rogers Centre.
There, the lake water flows through one side of a plate frame heat exchanger where its cold temperature chills the water that is circulating through Enwave's underground pipe system that serves its downtown office customers.
The lake water on the other side of the heat exchanger, having been warmed somewhat during the heat exchange process, moves on to Toronto's potable water system.
John O'Toole, executive vice-president of CB Richard Ellis Ltd. In Toronto, says many of the city's downtown towers are 30 or 40 years old and their air conditioners are nearing the end of the life cycle. "Purchasing new conventional chillers could cost tens of millions of dollars, but by adopting this system they can save that expense."
One of Enwave's newest customers is the $500-million, 750,000-square-foot Trump International Hotel and Tower, which is scheduled to hold its long-awaited ground-breaking in Toronto's financial district later this year.
"We examined a number of options," says Barry Landsberg, Toronto director of marketing for Trump International, a joint venture between Donald Trump and Talon International Development Inc. "In the end, we chose lake water cooling, because it eliminated the need to install chilling units and also eliminated the noise and pollution that they cause."
But Enwave's lake water cooling system will likely remain limited to about 15 square kilometres of downtown Toronto, Mr. Fotinos says. "It's too bad that the costs of digging under the city streets is so high -- at $1,800 a foot -- that it becomes cost prohibitive to do much more."
There are currently 14 towers in downtown Toronto using deep lake water cooling and 32 more are scheduled to be connected early next year, but in many other cities, the system isn't practical, he says.
"You need a dense, urban centre, located close to a body of deep cold water. In Chicago, for example, you need to go out 15 kilometres to get water as cold as we get at five kilometres out and the cost of a pipe that long would be very high. We are the main city on the Great Lakes that can make it work."
He adds that within two years, as more buildings are connected, Enwave expects to free up more than 61 megawatts of power from the Ontario electricity grid, enough to power about 7,000 homes and to reduce about 79,000 tons of carbon dioxide from the air, which is equal to taking 8,000 vehicles off the downtown streets.
In Halifax, meanwhile, the Purdy's Wharf complex accomplishes the same but by using sea water. It began this type of air conditioning in 1985 and was the first major commercial building in North America to do so, says Bill Macneil, manager of technical services at GWL Realty Advisors, the building's manager. The complex towers over Halifax Harbour and includes two office buildings of 18 and 22 storeys, and a four-storey commercial building, in all totalling more than 65,000 square metres.
Sea water at 8 C or less is piped from about 23 metres down in the harbour and 140 metres offshore, to the Wharf's basement, where it is circulated through a titanium heat exchanger.
Mr. Macneil says the system works smoothly for about 10½ months of the year; when the sea water temperature rises above 8 C in the summer, conventional chillers are used to cool the buildings.
Purdy's Wharf and the nearby waterfront Casino Nova Scotia are the only two buildings in Halifax to use sea water cooling, probably because their close proximity to the harbour makes the system cost effective, Mr. Macneil says. He adds that the system saves the Wharf $250,000 in operating costs, prevents annual emissions of about 2,000 tonnes of carbon dioxide and 272 tonnes of sulphur dioxide, as well as saving 2,700 megawatt-hours of electricity a year.
Toronto's deep lake water cooling system
Island filtration plant
Three intake pipes draw 4oC water from Lake Ontario from a depth of 83 metres. The water is then filtered and treated for Toronto's potable water supply.
Energy Transfer Station
At the Energy Transfer Station, the icy cold water is used to cool Enwave's closed chilled water supply loop through pairs of heat exchangers.
Enwave cooling plant
Chilled water can bypass the cooling plant and continue to the customer building. If necessary, water can be further chilled by two 4,700 ton steam-driven centrifugal chillers.
Customer site
Heat exchangers at the customer building cool the internal building loop, providing chilled water for its cooling system.
SOURCE: ENWAVE