Geoexchange technology is also known as geothermal, ground-source heating or heat pump. It offers unlimited renewable solar energy stored underground - about 50% of the sun's energy is usually absorbed by the ground. It is a simple concept: during winter, heat energy gets drawn out of the earth through pipes, known as a loop, which contains antifreeze solution to prevent freezing as the ground's heat is transferred to the home "heat pump" (basically a compressor and heat exchanger).

The house's heat pump gathers the ground heat and passes it on to heat the home through a duct or hydronic heating system. The heat pump will also supply heat to the home's thermal water tank for domestic hot water. Geothermal energy can come through closed or open groundwater; lake or well water can be transferred to the heat pump to extract energy directly, with cold water discharged back to the lake or another well. Open loop groundwater systems in "hard" water areas need an annual cleansing of their mineral buildup using coil flushing.

The process is reversed during summer; interior heat is transferred to outside water or earth to cool the home. The US Environmental Protection Agency and Canada's Natural Resources claim that geothermal systems are very energy-efficient as they are cost-effective and friendly to the environment. They function like air conditioning systems. There is no burning of fossil fuels; hence no atmospheric emissions. Thus, if the source of electricity running the geothermal system is hydroelectric, there are no greenhouse gas or other dangerous emissions.

The US boasts about a half million geothermal installations with Canada at around 35,000. The yearly energy savings come to about 4 billion kWh of electricity, eliminating 20 trillion BTUs of fossil-based energy and reducing emissions of greenhouse gas by about 3 million tons.

Air-to-Air Heat Pumps

Another heat pump that operates similarly is the air-to-air pump. The difference is that heat and cooling energy are passed through indoor and outdoor air instead of the earth or a lake/well. This type of unidirectional heat pump for space cooling is the central air conditioning system that is prevalent in most homes today.

Air-to-air heat pumps with big heating loads do not work as efficiently as geothermal systems except in mild weather: less energy is absorbed from the atmosphere with a temperature drop. Freezing temperatures will shut the unit off and the typical resistance-heating component found in electric furnaces and baseboard heaters takes over. It may not be a great alternative, but the overall heating effect of this type of heat pump with a resistance heater is better than using the heating element alone.

Measuring Heat Pump Efficiency And Value

Electricity is used to operate the heat pump's compressor to extract about 2/3 of the groundwater energy required by a home. This free energy encourages the heat pump to work harder, rather than relying on grid energy. The energy efficiency of heat pump exceeds 100%. In fact, one kilowatt-hour of energy to the heat pump returns 2.8-6.7 kWh energy to the home.