Geothermal Heat Pumps
In the UK the ground has a high thermal mass, at a depth of between 1.5-2 meters a temperature of between 7-10°C is available. If we run plastic pipe in the ground and circulate a water and glycol mix we can capture that heat. You can think of a heat pump as a fridge working in reverse.
The heat pump consists of four main elements, an evaperator, a compressor, a condensor and an expansion valve. The working fluid in the system is converted to gas by evaporation, and at the end of the cycle back to a liquid by condensation. The temperature difference at the end of this cycle can be as much as 3.5 - 4 times the input.
This means that a ground temperature of 7-8°C can result in a temperature of 35-45°C being available to the underfloor heating circuit. This is ideal for underfloor heating in a solid floor construction. We can see then that for every Kw of electricity put in to the system we can get 3.5-4 Kw out.
As technology has moved on we can now offer a heat pump that will provide your home with domestic hot water to a temperature of 60°C. Please advise us if this is the model you would like us to quote for.
Basic principal
The ground collector normally takes two basic forms:
- A trenched system
- A vertical borehole
In the trenched system the pipe is buried in a series of trenches, the length of which is carefully calculated to match the heat load. The pipes are brought together at a collector manifold which can be sited below ground in an inspection chamber close to the heat pump location, or by the heat pump itself. A typical trench is shown bellow. We normaly use a 50mtr trench with two 100mtr loops in it.
