June 15, 2007
Dealing With Wastewater
Recovering heat from sewage, new in Canada
Most wastewater leaving homes and businesses is warmer than the surrounding environment, a fact on which countries outside of Canada are already capitalizing.
Projects in Sweden, Germany, Finland and Japan show waste energy from sewers can be efficiently transferred to clean water used to heat homes or provide residential hot water, said Ken Church, community planning, sustainable buildings and communities’ manager with Natural Resources Canada.
“I would say that the technology is not yet popular in Canada because we’ve never had to do it before,” he said.
“Low temperature heat recovery requires particularly bulky equipment that puts some people off. And why buy a heat exchanger for $20,000 when a boiler costs only a few thousand? Canada is not the centre of the universe when it comes to sustainable thinking,” Church said.
A 2005 study by Vancouver’s Compass Resource Management, Sustainable Energy Technology and Resource Assessment for Greater Vancouver, indicates the most cost-effective applications for sewer heat recovery are new sewer lines or lines that need to be replaced, because the cost of retrofitting existing lines is prohibitive.
But while capital costs for new applications are high, operating costs are low, said Robert Hicks, an engineer with the policy and planning department in the Greater Vancouver Regional District.
“It’s essentially the same technology that’s used in extracting geo-thermal heat with heat pumps,” Hicks said.
The technology has already proven effective for industries using large volumes of hot water — commercial food processing plants and laundry facilities, for example.
“Typically we can recapture up to 90 per cent of the energy from warm wastewater,” says Carroll Gorrell, president of Kemco, a U.S. company that manufactures heat recovery equipment.
Heat recovery from cooler sewage is less efficient, but still economically viable. Swiss technicians have developed a general formula for sewer heat recovery, Hicks said.
“Two-thirds of the upstream heat from sewer water can be recaptured to heat the lower third. Using current heat exchange technology, you can heat water to a maximum of 50 degrees Celsius. That water temperature can then be boosted to 54 degrees for home heating.”
New Westminster, B.C. has identified a sewer heat exchange system as a preferred heat source for its new Poplar Landing housing development.
The City of Vancouver will be incorporating the technology in a new neighbourhood development on the southeast corner of False Creek, an urban development on former industrial lands.
Since the heat can’t be stored for very long, having a residential “load” is essential to the efficiency of a sewer heat recovery system, Hicks said.
“Turning these old industrial lands into residential and commercial neighbourhoods provides a wonderfully feasible demonstration of the technology. And there’s never a problem finding enough sewage.”
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