Renewables NB

The Source for small-scale, renewable energy projects in New Brunswick, Canada

Earth

A tremendous amount of free heat is available from the sun and the earth. Few buildings or heating systems take advantage of this.

Geothermal heat has been used to heat homes and businesses on a commercial scale since the 1920s. In most cases, communities take advantage of naturally-occurring geysers, hot springs, and steam vents (called fumaroles) to gather hot water and steam for heating. Geysers and fumaroles occur when ground water seeps through cracks and comes in contact with volcanically heated rocks.

Ground Source Heat Pumps

The temperature of the soil below about 2 meters 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. 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 gas 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 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, visit the website of the Pembina Institute, or the website of the Canadian Geothermal Energy Association.