Geothermal energy comes from the heat inside the Earth. Geysers and steam vents (called fumaroles) occur when ground water seeps through cracks and comes in contact with volcanically heated rocks. By taking advantage of these naturally occurring geysers, hot springs, and fumaroles, hot water, and steam can be gathered for heating purposes. Geothermal heat has been used by humans since the Palaeolithic Era for bathing, but was not used to heat homes and businesses on a commercial scale until the 1920s.

Geothermal diagram
Geothermal diagram

Geothermal energy may also be used for electricity generation. Water is pumped deep into the Earth where the naturally high temperature causes it to turn into steam, which then rises back to the surface where it is used to spin a turbine. The steam is then condensed back into water, and re-circulated. This technology works best in areas with a large geothermal gradient (the rate at which the temperature increases with depth). Currently, Canada does not have any installed geothermal power capacity, however a survey done in 2012 by the Geological Survey of Canada (53 MB PDF) concluded “Canada’s in-place geothermal power exceeds one million times Canada’s current electrical consumption, although only a fraction of this can likely be produced”.

The locations with the highest potential for successful geothermal power generation are in British Columbia, Alberta, North West Territories, and the Yukon — though that doesn’t mean that New Brunswick can’t also make use of geothermal energy.

Ground source heat pumps

The temperature of the soil below about 2 m (7′) remains constant regardless of the weather or season. In most places throughout southern Canada, soil temperatures at this depth hover between 5 and 10 °C (41–50 °F). The difference between air and deep soil temperatures can be used for heating and cooling in a very efficient manner, with a ground-source heat pump (also called a geothermal heat pump).

A ground-source heat pump works the same way a refrigerator does. Like a fridge, a heat pump uses a compressor, lengths of sealed tubing for gathering and dispersing heat (heat exchangers), and a fluid with good heat-transfer characteristics (called the refrigerant). An essential part of the heat pump is the network of tubes buried deep in the soil near the home. The compressor motor, located inside the house, circulates the refrigerant around this network. Heat from the surrounding soil warms the liquid refrigerant in the buried tubes, changing it to a gas. The refrigerant gas enters the compressor, which squeezes it, raising its pressure and temperature. The hot refrigerant circulates through radiators inside the house, releasing the heat collected from the soil to the inside of the house. This process changes the refrigerant back into a liquid and the process starts again.

By reversing the flow of the refrigerant, the heat pump system can cool the house in summertime. Heat collected from inside the house can be released back into the cool soil, resulting in a highly efficient air conditioning system for the home. A ground source heat pump requires some electricity to run the compressor. In an efficient, well-insulated home, this electricity could be easily supplied by a rooftop solar panel.

For more information on geothermal heat, see: