Heat Pumps

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There are three different types of heat pump available:

  • Ground Source Heat Pump (GSHP)
  • Air Source Heat Pump (ASHP)
  • Water Source Heat Pump (WSHP)

All heat pumps work on the same principle, by extracting solar energy stored in the ground, air or water. The solar energy is supplemented by electricity to reach required temperatures for domestic hot water and central heating.

Heat pumps are rated by their Coefficient of performance (CoP), where:

Energy In : Energy Out = CoP, usually 2.5 – 5.0

The CoP improves dramatically when the heat source temperature is higher, and also with lower demands on the heat distribution temperature, which is why they are extremely compatible with underfloor heating systems which work efficiently at lower temperatures than radiators.

heat pump bro diags 1

heat pump bro diags 2

Ground Source Heat Pumps

• Horizontal trench requires large(ish) area (20-25m per kW), depth of a borehole depends on geology and heat required
• Pipe is normally laid out in loops 1m apart and 1-2m deep
• Trenches need to be 1m apart
• Ideal for new build as the trench can be dug while heavy plant is on site and piping laid, thus avoiding disturbance and allowing ground time to recover
• Potential for CoP to fall during the winter months due to falls in normal outdoor temperature
• Costs around £300/kW
• Can also be laid out in water, utilising a pond or lake
• likely that planning permission will be required
• CoP reduced in the winter months
• No ground works required apart from getting the pipes back to the house

Air Source Heat Pumps

• Planning permission and building warrants are both normally required
• Significantly cheaper to install than other types of heat pump as no ground works required
• Usually have a CoP of 2.0 – 2.5
• CoP is affected by outside temperature therefore a back up (immersion heater) is necessary
• Ideal for retro-fit
• Limited space requirement

Water Source Heat Pumps

• Extraction license from Environmental Agency is likely required
• Significantly cheaper to install than ground
• Higher CoP compared to ground and air as the average winter temperature is higher in water
•  Can be open or closed loops for variable efficiency
• Submerged coils limit space requirement

• Be aware that if the water source dries up then there is no longer heat.

• Be aware that freezing water can be an issue. Supply should really maintain a minimum of 8 degrees for the systems to work effectively

RHI payments will be made for ground and air source heat pumps, but they must be installed by an MCS approved installer.
Further reading or links-
Heap Pump Association (HPA)
Ground source heat pump data sheet from the HPA
Air source heat pump data sheet from the HPA
Energy Savings Trust buyers guide


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