ground source heat pumps

Ground Source Heat Pumps

Inherent energy are experienced at installing a wide range of heat pumps from top quality manufacturers including Kensa, IVT and Dimplex.

Ground source heat pumps offer an ideal solutuion when combined with underfloor heating. The pump is very efficient at raising water upto a temperature of around 35 C after this the performance starts to come down. At this point the system can be connected to a buffer tank which means the boiler only has to increase the water temperature from 35 C to 60 C suitable for domestic hot water use.  The heat pump can also work in reverse allowing therefore cooling a building in the summer.

Systems are usually laid in trenches as seen in the photos below and large systems over 50kW will usually be layed in bore holes. Boreholes are more expensive than trenches, by the time to are upto 50kW systems we have usually run out of space for trenches.

How they work

Heat pumps extract solar energy stored in the ground, water courses and in the air and convert this to a higher temperature to use in a building’s heating distribution system. They work in a similar manner to a fridge in reverse, where the inside of the fridge is the heat source and the grill at the back of the fridge is the heating system.

A ground source heat pump (GSHP) extracts heat from the ground by circulating a cold solution of water and antifreeze (brine) around pipes buried in the ground. As these pipes are buried below 1m in depth, where the temperature of the ground remains pretty constant (8 to 10°C), heat is absorbed from the ground into the fluid (approximately 5°C). This brine is then passed through one side of a heat exchanger (called the evaporator) and a refrigerant through the other. The refrigerant has a very low boiling point and by absorbing the energy in the brine this causes the refrigerant to evaporate.

The refrigerant gas is then passed through a compressor where its pressure is increased which in turn increases its temperature. This high pressure hot gas then flows around a second heat exchanger (called a condenser) with the heating distribution fluid passing through the other side of the heat exchanger. Energy is then transferred from the refrigerant into the heating distribution system; this in turn causes the refrigerant to condense.

This high pressure cold refrigerant is then passed through an expansion valve (or throttle) and the pressure is reduced. The whole cycle is then repeated.

GSHPs are an extremely energy efficient technology, with every unit of electricity used (to drive the pumps and compressor) producing between 3 and 4 units of heat.                                                                                   GSHP Slinky in trench

 

 Kensa Heat Pump             GSHP Slinky                 GSHP coiled slinky