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Sustainable Okotoks - Energy

North America's First Solar Powered Subdivision - Drake Landing

"Among the most environmentally friendly housing ever built in Canada."
(Alberta Report, September, 2005)

What if there was a way to stockpile the summer's warmth and reuse it in winter? That's exactly what is being done in the Town of Okotoks.

Okotoks has taking a leadership role in the introduction of solar energy technologies at geographic scale in new neighbourhoods. In a partnership with a land developer (United), a 52 home subdivision in NE Okotoks (Drake Landing) is under construction, incorporating solar seasonal storage technology. The technology is extensively used in Europe but represents the first introduction of the technology in North America.

The Drake Landing Solar Community (DLSC) is the first community in the world that is designed to meet 90% of its space and water heating requirements from solar energy. Solar collectors will collect heat during the spring, summer and fall and store the thermal energy in underground boreholes for extraction during the winter. A district-heating network will distribute the thermal energy. The net performance over the baseline is approximately 2.4 tonnes of greenhouse gas (GHG) emissions reduction per home per year or a 72 per cent reduction for the baseline case. This represents more than double what the Government of Canada is asking of individual Canadians in its One Tonne Challenge - part of the government's commitment to the Kyoto agreement.

Every house at the Drake Landing Solar Community (DLSC) will be built to meet the standards of both the R-2000 program (NRCan's top sustainability guideline) and Built Green Alberta's "gold" certification (the Calgary Region Home Builders Association's highest sustainability standard). This means such ecologically sound construction such as frames made of sustainably-harvested lumber, recycled materials in the drywall, hyper-efficient appliances and plumbing, top-of-the-line insulation throughout, and a solar hot-water heater in every unit (supplemented by a natural-gas auxiliary heater). Moving to the R-2000 standard for home construction will reduce the thermal energy load. Without R-2000, about 45 per cent more thermal energy would be needed to deliver to the homes for space heating compared to the current design load.

Each home is designed to be efficient, and all are equipped with their own solar water heater and low water usage fixtures and appliances. But the heart of this innovative community can be found on the garage roofs, and under a corner of the neighbourhood park.

The solar-thermal system tackles the largest single devourer of energy in a Canadian home: heating. And it works like this: On the roof of every garage in Drake Landing, there will be an array of solar collectors - 800 panels in all throughout the community - and this array will be linked by a network of subterranean pipes to a district energy centre. The solar collectors will soak up as much as 1.5 megawatts of thermal energy on a typical summer day and use it to heat a non-toxic glycol solution in the pipes, which will carry the energy to a heat exchanger at the energy centre. The heat exchanger will transmit the glycol's heat to the water in two large storage tanks; the cooled glycol will then pass back through the pipe network to be warmed anew by the solar collectors.

The DLSC presents a tricky situation for long-term storage. The DLSC will have a borehole thermal-energy storage system - a field 35 metres in diameter, dotted with 144 tube-like boreholes, each 37 metres deep, the whole array encased in sand and clay and heavily insulated and waterproofed. The heated water in the energy centre's water tanks will be transferred to the boreholes, which by the end of the summer will heat the field to about 80 degrees Celsius and sit waiting for the cold prairie winter to descend. When residents start to feel the chill, they'll just crank plain old thermostats, which will result in hot water from the borehole storage facility moving down the network of pipes to "air handler" units (the solar-thermal equivalent of furnaces) in their basements. The hot water moves through a fan coil, heating it, and a fan then blows air across the hot coil and pushes it through the house's ducts. And that - along with a yet-to-be-determined monthly maintenance fee and a natural-gas back-up - will be it for heating from the homeowner's point of view.

In the first full year of operation the sun will provide 60% of the heating requirement. This will rise rapidly as the borehole system is "charged" to higher temperatures, leveling off at about 90% after 5 years. High-efficiency natural gas boilers in the Energy Centre supply the remaining energy, as needed.

The project is a partnership between Natural Resources Canada, the Federation of Canadian Municipalities, the Province of Alberta, Climate Change Central, EnerWorks, the Town of Okotoks, ATCO Gas, United Communities, and Sterling Homes. The project was envisioned for the Toronto region, and was eventually attracted to Okotoks given the community's sustainability track record.

Total project cost - $19 million, with much of the cost recovered once the homes are sold. (Ref: Alberta Venture)

Progress:

  • 90% of home heating energy consumption provided by solar energy.
  • 60% of hot water needs generated by solar domestic hot water heating system.
  • Annual reduction of greenhouse gas emissions of 2.4 tonnes per household (72% over a conventional new home).

Links:
Drake Landing Website
Built Green By Sterling Homes
Annual Solar Radiation Map

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