How it works
Ground source heat pumps are low-carbon heat generating systems which usually circulate a mixture of water and antifreeze around a loop of pipe buried in the ground, which maintains a temperature of around 15°C, even in winter. In new buildings, this loop can be buried vertically into the ground. When the liquid is pumped around the loop, it absorbs thermal heat from the ground. Mostly, this heat is solar heat stored in the surface of the earth. At depth, is likely to be a mixture of solar and planetary heat. This can be transferred to radiators, underfloor heating systems and can heat water. The length of the loop depends on the size of the home. Normally the loop is laid flat or coiled. True geothermal heat tends to come from much deeper than the depth of heat pumps in the UK (more than 1km) and draws on planetary heat. Outside the UK, geothermal heat often draws on volcanic heat.
Performance issues
Ground source heat pumps cost £7,000-£13,000 to install. Running costs for a year, where 50 percent hot water and all space heating can be provided by the system are likely to be around £540 per year if the system is properly sized and designed, and good levels of insulation are put in place The efficiency of ground source heat pump system is measured by a coefficient of performance (CoP), which is the amount of heat they produce compared to the amount of electricity needed to run them. A typical CoP for a GSHP is around 3.2.
Benefits of ground source heat pumps
- Lower carbon emissions: an average ground source heat pump could save around 1.8 tonnes of carbon emissions every year, when replacing an oil boiler.
- Lower fuel bills: ground source heat pumps run on electricity, so there's no need to pay for gas, oil or solid fuels. Heat pumps depend on good insulation and can be useful in locations not connected to a gas supply.
- Less electricity use: heating homes with a ground source heat pump is much more energy-efficient than using electric radiators.
- As the grid decarbonises, heat pumps become low carbon. Also, if a heat pump is powered by a renewable energy source, it is completely renewable.
Support
Permitted planning for ground source heat pumps was introduced in April 2008. The Low Carbon Buildings Programme currently supports ground source heat pumps. LCBP Phase Two provides grant funding to charitable, community groups and public sector organisation projects. Organisations can apply for 50 percent of the cost for installing approved technologies.
Certificated heat pump installations are listed as eligible for tariffs in the recent consultation on the proposed Renewable Heat Incentive (RHI) from 2011. Decisions on RHI have not yet been taken.