How to: tap into the Earth's heat

An environmentally friendly heating and cooling system can save you piles of money.

2006 | 2005

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If you are alarmed by volatile energy prices or exercised by that inconvenient truth called climate change (and you want to save a heap of money over time), then start thinking about the energy under your feet. In a geoexchange home residential system, ground-source heat pumps draw energy from constant temperatures naturally stored in the earth or in pools of water. What geoexchange does is efficiently tap into this renewable energy source — available in most Canadian backyards.

This combustion-free heating and cooling system begins with a drilling rig boring holes into the earth. Drilling accounts for 30% to 50% of the cost of an earth energy system: the goal is to tap into constant earth or water temperatures. Plastic high-density pipes looped through the holes carry stored heat to an indoor heat pump in a water-antifreeze solution. The machine essentially moves heat in a direction it wouldn't naturally go on its own. After extracting and upgrading heat from the fluid, the warmth is distributed around the building via air vents or hot water heaters. Many homes and businesses with geoexchange systems boast comfortable in-floor heating. A geoexchange unit also provides hot water through a simple device called a desuperheater. It employs superheated gases from the heat pump's compressor to heat water for free. In summer, the system works in reverse: Heat moves from the home back into the ground, eliminating the need for air conditioning.

A recent study by the U.S. Environmental Protection Agency found that geoexchange systems were “the most energy efficient, environmentally clean and cost-effective space conditioning systems” on the market. The EPA estimates geothermal systems are almost 50% more efficient than gas-powered furnaces, 75% more efficient than oil-powered ones, and that they typically reduce electrical bills between 25% and 50%. What's more, every 100,000 homes connected to earth power effectively reduces oil consumption by 2.15 million barrels a year.

How it works:

A drilling rig bores holes as deep as 150 metres. This is expensive but a preferred option for homes on small lots. Alternatively, shallow horizontal pipes cost less to install, but require more backyard space. The horizontal version tends to be more popular in rural reas. A home heating system is connected to a system of pipes sunk underground. Heat pumps draw warm air from constant temperatures stored in the earth's crust. The pumps use the earth as both a heat source and a heat sink. In summer, this process is reversed, and the pump sends warm air from the home back underground.

Every 100,000 homes that are connected to earth power reduce oil consumption by 2.15 million barrels a year. Geothermal heat pumps are also incredibly energy-efficient, moving three units of solar energy from the earth for every unit of electricity consumed by the heat pump. The amount of solar energy stored in the earth's crust could power the global economy 500 times over.

More on geo-thermal heat…