Geoexchange in Residential applications
Geoexchange (sometimes referred to as geothermal or ground source) is a heating, cooling, hot water and pool heating solution that can utilises the near consistent temperature of the earth, ground water, lakes, dams or ponds as a heat exchange to provide a very high efficiency comfort solution.
Is geoexchange a new technology?
The answer to this is no. Geoexchange heatpumps were developed around the 1940’s and have been constantly developed ever since. In Australia geoexchange systems have been in use since the early 1990’s with some of the first installations being in South Australia.
What makes geoexchange different?
Conventional heat pumps work on the principle of moving heat from the outside air (when heating) to your home via ducting or through hydronic heating systems and doing the opposite when cooling by rejecting heat from your home to the air outside.
The problem with this is that as the outside air temperature drops it becomes harder for the heat pump to extract the heat required to heat your home. This reduces the system’s efficiency and increases the running cost. The same problem occurs when the air outside is hot and you are trying to cool your home it is hard to reject heat to hot air.
The times you want your conventional system to work is when it is least efficient. This is where geoexchange is different as it is not affected by the fluctuations in outside air temperature.
How does it work?
A few meters beneath the surface, the earth’s temperature remains fairly constant. Geoexchange takes advantage of this constant temperature to provide extremely efficient heating and cooling.
In winter, a water solution circulating through pipes buried in the ground absorbs heat from the earth and carries it into the home. Inside the home a heat pump is utilised to concentrate the earth’s thermal energy and then to transfer it to either water for a hydronic underfloor, a hydronic radiator system or to air circulated through ductwork to heat the home.
In the summer, the process is reversed. The heat inside the home is extracted from the air and transferred through the heat pump to the ground loop piping. The water solution in the ground loop then carries the excess heat back to the earth.
Heat exchange options
Geoexchange is not just restricted to using the ground as a heat exchange. The following options are also available and work well.
Used where adequate land is available, horizontal loops involve one or more trenches that are dug using an excavator. High density polyethylene pipes are inserted, and the trenches are backfilled.
Vertical loops are used when space is limited. Holes are bored using a drill rig, and a pair of pipes with a special u-bend fitting on the end is inserted into the holes. The area around the loop is then grouted with a special concrete mix.
If an adequately sized body of water is close to your home, a pond loop can be installed. A series of coiled, closed loops are sunk into the bottom of the body of water. The body of water will need to be over 1.8 meters deep.
An open loop is used where there is an abundant supply of bore water. The water that is used for the system can be reinjected into the ground, rejected to a dam or body of water or used for irrigation.
Please feel free to view this video that gives you an overview and explanation of geoexchange.