Ground Source Heat Pumps
Ground source heat pumps are another alternative type of renewable energy, drawing heat from the ground that can be used to heat the home and provide hot water. Ground source heat pumps claim to be a heating system that requires no regular maintenance and is completely safe with no local greenhouse emissions.
Ground source heat pumps use pipes which are buried in the garden to extract heat from the ground. This heat can then be used to heat radiators, under-floor or warm air heating systems and hot water in your home.
A ground source heat pump circulates a mixture of water and antifreeze around a loop of pipe - called a ground loop - which is buried in the garden. Heat from the ground is then absorbed into the fluid which passes through a heat exchanger into the heat pump. The cooled fluid then gets pumped back into the ground where it absorbs further energy from the ground in a continuous process, for as long as heating is required.
The ground stays at a fairly constant temperature under the surface, so the heat pump can be used throughout the year - even in the middle of winter!
The length of the ground loop depends on the size of your home and the amount of heat you need. Longer loops can draw more heat from the ground, but need more space to be buried in. If space is limited, a vertical borehole can be drilled instead.
Benefits of ground source heat pumps can include:
- Lower fuel bills, if you replace an Electric, LPG or Oil heating system
- Installation grants: Renewable Heat Premium Payment
- Generate income through the government's Renewable Heat Incentive
- Lower your carbon emissions
- Little maintenance needed - they're often called 'fit and forget' technology
Heat pump costs and payback
The estimated cost of installation of a heat pump system is expensive and can vary between £9,000 and £17,000, depending on the size of your home.
The payback period (the time it takes for that initial cost of the system to be recouped in energy savings) will depend on how efficiently your system works, the type of system you're replacing and how you'll be using the heat generated from the pump.
Here are some general rules of thumb to bear in mind:
- Heat pumps can save you more on your heating bills and the system will pay for itself much more quickly if it's replacing an electricity or coal heating system. Heat pumps may not be the best option for homes using mains gas.
- Ground source heat pumps are generally better suited to new-build properties than retrofit - this is because costs could be reduced if the heat pump is included as part of the building specification, rather than having to retrofit the heating system later.
- A well-insulated house is essential to best optimise the heat generated by your ground source heat pump.
- The heat produced by a ground source heat pump comes at a lower temperature than other forms of heating, making it best suited to under-floor heating, which requires lower temperatures, rather than radiators (or, if radiators are used, they should be properly-sized).
- Running costs can be higher if you're also using the system for your hot water supply, and you may require a supplementary electric immersion heater to keep up with your heating needs.
Unlike gas and oil boilers, heat pumps deliver heat at lower temperatures over much longer periods. During the winter they may need to be on constantly to heat your home efficiently. You will also notice that radiators won't feel as hot to the touch as they might do when you are using a gas or oil boiler.
Air source heat pumps are usually easier to install than ground source as they don't need any trenches or drilling, but they are often less efficient than Ground Source. Water Source heat pumps can also be used to provide heating in homes near to rivers, streams and lakes.
All heat pumps do have an impact on the environment as they need electricity to run, but the heat they extract from the ground, the air, or water is constantly being renewed naturally.