Ground Source Heat Pumps

Very early on in our project we decided to use a ground source heat pump to heat the house. These are clever devices that use a heat pump (reverse of a fridge) to raise the temperature of a coolant (in this case a water glycol mix) and have been used for many years in Scandinavian countries. As our house is part of a farm there is no shortage of space to dig a 1 metre deep trench about 150 metres long into which we put the ground collector (posh name for some 38mm plastic pipe). You can have a straight out and back loop, or a coiled loop (slinky) if space is at a premium, or even panels of piping (like a radiator in the ground) or even bore down vertically into the ground. Oddly, going deeper than 1 metre does not give you higher temperatures but does cost more to do so loops are the most cost effective route to go if you can.

greenline-csml.jpgThe ground loop brings water/glycol mix into the house at about 12 degrees centigrade and the heat pump uses electricity to raise this to about 50-60 degrees centigrade.

While this output is slightly lower than ideal for a radiator system, it is ideal for an underfloor heating system.

greenline-c-internalsmall.jpg We will also use the ground loop to cool the house in the summer using a heat recovery unit which should acheive a 7 degree reduction over ambient.

Our heat pump suppliers had 8 employees when we met them in 2006 but so great has been the growth of demand they now have 80 staff just 2 years later!

If you would like advice on installing a heat pump and have any particular questions about the many claims of heat pump suppliers and the costs, send your question via a comment on an appropriate blog entry.