Geothermal Energy

Expensive to install (roughly $25,000).	Requires large effort; best done when building a new house.	In Alberta, usually requires a fair amount of coal-fired electricity to run its heat distribution pump. Requires renewable electricity to achieve significant GHG reductions.

What is geothermal energy?

Geothermal- also known as ground-source and, increasingly, geoexchange - energy uses the constant temperature of the subsurface earth to heat buildings in winter and help cool them in summer.

How does it work?

In a typical residential installation, four or five backyard boreholes are drilled and loops of pipe inserted into them; it is also possible to lay much shallower horizontal loops, though a broader area must be excavated. In winter, the earth's subsurface heat - in many Alberta locations, about 10 degrees Celsius at a depth of three or four metres - is transferred to water/antifreeze-filled loops and then compressed and distributed, by a heat pump, throughout the house as either forced air or in-floor radiant heating. (This process is similar to how a refrigerator works, drawing heat from the food and expelling it into the surrounding room.) In summer, the process is reversed, with excess building heat pumped into the ground, so the system is now working like an air conditioner.

How efficient is geothermal energy as a space heater?

Quite efficient. About the only energy expended is the electricity needed to condense the earth's heat and distribute it through the house. An ENERGY STAR^® heat pump will have a so-called Coefficient of Performance rating of at least three, which means that for every unit of electricity required, three units of heat are produced. This can also be expressed as an energy efficiency ratio of 300 per cent, compared with 100 per cent for, say, an electric base board heater or a natural gas furnace.

Is geothermal a completely renewable form of energy?

Not in most cases. While the heat from the ground is certainly a renewable resource, the electricity needed to compress and pump it is not, unless it's tied to a renewable source like wind, solar or hydro power. The vast majority of Alberta's electricity is still produced from burning non-renewable coal, which produces twice as much carbon dioxide as does an equivalent amount of natural gas. A typical geothermal system, using 11,000 kilowatt hours a year of coal-fired electricity (see below) will thus produce some 10 tonnes of carbon dioxide per year.

How much electricity does a geothermal system use?

It varies, depending on such things as the size of the system and operating times. According to the Canadian GeoExchange Coalition, an average residential unit will consume 11,000 kilowatt hours of electricity per year. This means that it will be the largest consumer of electricity in a typical Alberta house, costing about $1,100 a year to run (at an effective electricity rate of 10 cents per kilowatt hour).

Does using geothermal energy to also cool an Alberta house in the summer improve the system's economics and environmental impact?

The economics and environmental performance do improve if the homeowner's alternative is to buy an air conditioner, which can consume considerable amounts of electricity, especially if it is in steady use. In Alberta's climate, there may be relatively few summer days when air conditioning is truly needed. Cooling alternatives include improving house insulation, installing energy-efficient windows, installing window coverings, and planting trees that shade the house in summer.

Do geothermal systems work well during Alberta's winters?

Yes. Because the temperature of the earth below the frost line - where geothermal loops are installed - is a fairly constant 10 degrees Celsius in much of Alberta, the system will work well regardless of the air temperature. On particularly cold days, an electric-resistance heating element inside the unit may be needed to boost the house temperatures to comfortable levels.

Where can I find a qualified geothermal installer?

The Canadian GeoExchange Coalition is the national voice of the geothermal industry. You can find local installers by visiting http://www.geo-exchange.ca/.

How large should my geothermal system be?

It depends on such things as how much energy your house requires. While systems can be designed to meet 100 per cent of the building's heat loss, ones sized to 70-75 per cent of the heat loss should meet heating needs on all but the coldest days and thus considerably reduce the installation cost. On the other hand, an undersized system may be forced to work too hard to heat a house. A revised CSA standard for installation (C448) covers proper design of geothermal systems.

A four-ton unit (50,000 BTU of heating capacity) should be sufficient for an average 1,700-2,000-square-foot house. Of course, the required size of the system, and its installation cost, can be considerably reduced if your house is well insulated and you follow good energy conservation practices.

Are there any rebates available if I install a geothermal system?

Yes. Natural Resources Canada (NRCan) is offering grants of up to $3,500 for a residential retrofit installation of a CAN/CSA-C448 compliant ground- or water-source heat pump. The program runs until March 31, 2011. Click here to visit the website for the ecoENERGY Retrofit Program.