Heat Pumps

Ground source heat pumps.

Ground source heat pumps use the principle that the ground remains at a higher temperature than the outside air and comprise a system by which heat extracted from water in a ground loop, is concentrated by a heat pump and distributed through the property. The air source heat pump works in the same way as ground source by taking heat from the air.

Heat Pumps - Specifications
Types of System Ground loops can be vertical boreholes (more expensive but need less space) and horizontal trenches. Need 14-18m of vertical loop per kW of heat pump. 20-25m if horizontal trench. Design system to meet 50-80% of peak load and supplement with conventional system to meet demand and raise DHW temp to >60°C. GSHP CoP approx. 3.5 - 4 ASHP CoP approx. 2.5 - 3
System Costs Typical 8kW system, £1,400 per kW for horizontal system (typically £11,000), and £1,700 per kW for vertical system (typically £14,000). The air source heat pump costs approx £8-10,000 for the 8kW unit. Ensure the energy efficiency levels of the building are as high as possible before sizing the heat pump. A rule of thumb for heat loss of the building is 50-60 watts/m².
Running Costs Cost of electricity to run the heat pump and water circulation pump, typically = to GCH running cost. Consider running the heat pump on a special electricity tariff offered by some suppliers. Scottish Hydro E10.
More information GIR 72 - Heat pumps in the UK: A monitoring report. GPG 339 - Domestic ground source heat pumps - design and installation of closed loop systems
Websites GSHP Association: www.gshp.org.uk

Heat Pumps - Specifications

Types of System

Ground loops can be vertical boreholes (more expensive but need less space) and horizontal trenches.
Need 14-18m of vertical loop per kW of heat pump. 20-25m if horizontal trench.
Design system to meet 50-80% of peak load and supplement with conventional system to meet demand and raise DHW temp to >60°C.
GSHP CoP approx. 3.5 - 4
ASHP CoP approx. 2.5 - 3

System Costs

Typical 8kW system, £1,400 per kW for horizontal system (typically £11,000), and £1,700 per kW for vertical system (typically £14,000).

The air source heat pump costs approx £8-10,000 for the 8kW unit.

Ensure the energy efficiency levels of the building are as high as possible before sizing the heat pump.

A rule of thumb for heat loss of the building is 50-60 watts/m².

Running Costs

Cost of electricity to run the heat pump and water circulation pump, typically = to GCH running cost. Consider running the heat pump on a special electricity tariff offered by some suppliers. Scottish Hydro E10.