How summer heat was meant to last until winter
Heat gathered from garage-roof collectors in summer was to be held in 144 boreholes and drawn on in winter, a method already proven in Europe when the project launched in spring 2005.
Event date: 2005-04-04
The obvious question
The first thing people asked in 2005 was how heat collected in July could still be useful in December. The answer was that the idea was not new. European projects had shown that it worked and could be affordable.
Water heated by collectors on the garage roofs would be sent into 144 boreholes beside the homes. The ground around them acts as the store. On sunny winter days there would be no need to touch the stored heat at all, because the collectors could feed the homes directly.
Keeping the heat in
Losing heat was the main worry, so the design leaned on insulation. The top of the borehole field was covered and insulated, and the layout was optimised to keep losses low. From above, the field would look like an ordinary park with grass and trees.
Only about ten per cent of the heating was expected to come from natural gas. The remaining share, for both water and air heating, was to be solar.
Why Okotoks, and what it would cost
Several reasons were given for the site. The area gets as much sun as parts of Italy and Greece by one comparison, the building industry south of Calgary was active, and an energy company was willing to operate the system over the long term. The homes were to meet the R-2000 standard, which means a tight, well-insulated shell. See the homes page for the finished houses.
On price, the solar heat then cost about as much as electric heating. Later projects were expected to come cheaper, and federal and Alberta support meant the 52 homes would not cost buyers more than comparable neighbours.
What became of the plan
The 90 per cent figure was a target at that stage. Monitoring later recorded 97 per cent by 2012 and 100 per cent in the 2015-16 heating season. The system began to deteriorate from about 2020, decommissioning started in 2024, and most homes switched to gas furnaces. Anyone who needs the present status of the site should ask the Town of Okotoks or ATCO. The full explanation of the system is on the how it works page.
Quick answers
How could July heat be used in December?
Collector heat was pumped into 144 boreholes, where the surrounding ground held it for months until the district heating loop needed it.
How much natural gas was the system expected to need?
About ten per cent of the heating load at design stage, with solar covering the other 90 per cent.