Geothermic and Aerothermic Heating
Commonly known in English as Ground Source and Air Source Heat Pumps (GSHP and ASHP). A heat pump is a devise that converts latent heat (the heat from a source found around underground into a more useful heat source). The most common form is a fridge. The heat pump removes the heat from within the fridge and expels it outside (the warm grid on the back of the fridge). The principal for heating is the same. The heat pump takes heat (or more correctly calories) from the heat source (the ground or the air) and converts them into a usable heating source. This is then used to heat a grid of water filled pipes which are encased in concrete in the floor of the building.
The same principal is used for air conditioning. There are various options including heat pumps that can replace a standard boiler and supply to existing radiators (High Temperature heat pumps) and systems that use trunking and warm air blown around the house.
Geothermic was the starting point for the heating system. It uses a grid buried in the ground as its heat source. The ground has a stable temperature (around 10°C) and is easy to extract heat from. The main problem is that you need a larger clear area in which to site the capture area. There are options for vertical capture and capture from the water table but they can be very costly.
In the past five years or so the numbers of geothermic installations has been steadily falling whereas aerothermic has increased dramatically. This is due to it being easier to install with no groundwork involved. Plus, all of the major manufacturers have invested heavily to produce pumps of equivalent efficiency to that of geothermic. Pumps will now give excellent output even at outside temperatures of minus 15°C!
Generally at these temperatures a certain amount of the heat generated comes from an electric element; however, there are new products coming onto the market which use technology that doesn’t depend upon an extra element, can produce heat at -15°C, and can supply standard iron radiators as well as your hot water.
The cost of installation for geothermic is roughly the same as aerothermic, but you will need to take into account the cost of groundwork involved. Expect to pay between €65 and €100 per sqm to install and €2.3 to €3.7 per sqm a year to run the system.
With thanks to Paul Foulkes of Solec Ecohouse