Ground Source Heat Pump

The basis of heat pump technology is something that we are all familiar with as it is the same as that used in refrigerators or air conditioning units. The core function of these units is to take heat from the ground and transfer it to a building for the purpose of heating water. This heated water is commonly used for space heating but can additionally be used as the basis for all hot water provision in the building given an additional boost from a complementary boiler system.

Heat pumps consume energy in the form of the electricity used to power the pump; this is a relatively efficient use of energy producing between two and four units of heat for each unit of electricity consumed. The system is at it most efficient when used to run an underfloor heating system.

Heat is gathered from a ground loop; this is constructed from lengths of pipe in a closed loop and filled with a blend of water and antifreeze. This liquid is pumped through the pipework loop and absorbs heat from the surrounding ground. The ground loop is either buried in trenches to the depth of around a meter or sunk into a borehole. The borehole option requires less ground area, but is more expensive to excavate and install than a trench.

The pumped liquid bears its absorbed heat to the heat pump where the evaporator takes the heat from the liquid and the compressor circulates the gaseous refrigerant and compresses it to the desired temperature. The condenser then transfers the heat to a hot water tank from which the heat distribution system is fed. In turn, the heat distribution system heats space through under-floor piping or wall mounted radiators.

At the time of writing; from a cost perspective this method of heating is cheaper than all options except mains gas. The high cost of electricity from solar photovoltaic (PV) cells means that supplying the electricy needs of the system from that source is not currently cost effective and off-peak electricity provisioning should be considered.

For the coldest times of the year it is appropriate to consider an additional secondary source of heating such as a multi-fuel or wood burner that should be fuelled from sustainable sources.

A heating system based around this technology is a cornerstone of a healthy house design, providing a lower air temperature, surface heating, healthy heating solution.