Heating your home using outdoor, underground heat pumps can improve the efficiency of your indoor heating system, reduce the associated running costs and free up extra space inside the home that would otherwise be used for boilers and stoves. Ground source heat pumps absorb renewable energy from beneath the surface of the earth. That energy can be carried back up to the surface via a channel of moving water or air.
Wear protective clothing. Dig a set of trenches in the ground using a mechanical digger. Neaten the trenches manually using a spade. Dig to below the frost line, which is the point beneath which ground frost does not affect the flow of hot water. Aim to reach to a depth of five feet for horizontal pipe work or up to 330 feet for vertical pipes if you have a small yard.
Create a ground loop of the required length from 2-inch polypropylene pipes. Choose the size of system you require based on the size of home you need to heat and the size of outdoor space you have available to you. Aim for the longest length possible that fits the space but remains affordable. Bury the ground loop in the hole in a repeating S-shape or coil pattern, so you cover as much ground as possible and extract the maximum amount of heat from the surrounding earth.
Pour sand over and around the pipe work inside the trenches to protect the pipes from being punctured by stones in the backfill. Perform backfilling by tightly refilling the trench with the earth dug out earlier, as this improves the thermal conductivity between the ground and the ground loop. Ensure high quality installation and backfilling by employing a professional for this stage.
Attach a heat pump containing a heat exchanger (or "evaporator") and compressor to the ground loop to push the water through the pipe work. Put the heat pump in a locked box on the side of your property at the source of the main water pipes. Run a cold water pipe into the ground loop and a hot water pipe up from the ground loop, through the heat pump and on to a hot water cylinder inside the home, where it can be stored and distributed to the radiators and under-floor heating systems.
Connect the ground loop to a "slinky," or ground collector, another specialized component that enables the heat pump to draw the heated water into the home. Add approved antifreeze to the water inside the system to prevent it from freezing up as it travels through the shallower stretches of pipe work and into the home. Ethylene or propylene glycol are suitable.