When we think about getting hear from the ground we probably imagine geothermal energy; large magma chambers miles underground powering geysers and hot springs, or being tapped to generate electricity through steam turbines. But living next to a volcano can be a risky proposition and might be seen as an extreme way to get cheap heat. The good news is you don’t have to move to an area with an active (and unpredictable) volcano to benefit from the heat beneath your feet; ground source heating technologies make use of stored heat and can be used pretty much anywhere.
The ground stores heat from the sun and does a pretty good job of maintaining an even, stable temperature throughout the year, whatever the weather. You can tap into this heat and grab some of it for yourself by using a ground source heat pump. There are a few variations on the design but all use the same basic principle to get the heat.
The pump uses the principle of heat exchange. Pipes are laid in the ground and a liquid, usually antifreeze, is pumped though the pipes. The antifreeze is warmed by the ground’s heat; it’s pumped back to the surface where the heat is concentrated in a compressor. The now-hot liquid is then circulated around the domestic hot water cylinder, transferring its heat to the water in the cylinder and thereby providing hot water for use in your home. The cooled liquid is then pumped back down into the ground where the process begins all over again. This principle of heat exchange is used in domestic refrigerators, except in reverse.
There are two types of underground heating design – a horizontal pipe which is laid (either coiled or flat) about 6 – 8 feet deep in the garden. If you don’t have a garden, you’ll have to go down; a shaft around 300ft is drilled, and the heating pipe is dropped into this. If this sounds expensive you’re right – it is. Installation is likely to run into the tens of thousands of dollars so the payback period will be long.
The heat generated by ground source heating is fairly low so they tend to operate continually; it doesn’t supply hot water on demand. It’s mostly used for underfloor heating. If you do want it to heat radiators go for big ones as the water temperature is lower than from a gas or electric boiler.
Ground source heating does have benefits. It doesn’t produce any harmful by products, it can lower your heating bill and has very low maintenance and running costs. The pump does use some electricity, but this is minimal.