5 questions you must ask before installing a ground source heat pump
Posted by Sam Tonge on 14 December 2017 at 4:15 pm
Following the recent waves of snow and ice seen across much of the UK, you might consider the ground as a rather cold surface emitting no warmth whatsoever! In contrast, the ground actually provides a naturally-occurring source of heat which can be used to provide central heating and hot water for your property.
Ground source heat pumps (GSHPs) provide a very efficient form of electric heating, ideally suited to new, larger properties and qualify you to receive income through the Renewable Heat Incentive. They extract heat stored in the ground (which is replenished from the sun) and pass it through a heat exchanger to raise the temperature of water high enough to heat a home.
When planning to install a ground source heat pump, it’s important to look at these five considerations:
Do you have access to the ground?
This might seem an obvious point, but you'll need to check that you have a large enough area of land. Most systems installed in the UK use heat collecting pipes (loops) buried in shallow trenches and you need to check you have enough space to install these, especially if you need to heat a sizeable building. Otherwise, it's possible to place the heat collector in a vertical borehole, which only needs a limited surface area for access.
Is your property well-insulated?
As with any new heating system, it's important to take a ‘fabric-first’ approach and make sure that the heat you produce isn’t wasted through poorly insulated walls, ceilings or floors. When planning to install any new heating system, it might be cheaper to add extra insulation first, in order to reduce the capital cost on installation and the running costs of using it.
How big a system do you need?
Once the heat loss through the fabric of your home is known, it's possible to calculate the maximum heat demand under typical winter weather conditions. This calculation will also consider whether domestic hot water (DHW) is to be provided either wholly or partially from the heat pump. This can then be converted to give the optimal size for the heat collector loops (whether in trenches or a borehole). The installer will also be able to advise whether the ground conditions will permit summer heat replenishment around the collector loops that will enable successful heat extraction in colder months for many years.
Can you combine my heat pump with other methods of heating?
Ground source heat pumps tend to work most efficiently when raising water to a temperature around 40°C, and so are best matched to a wet underfloor heating system, although 'oversized' radiators can be used as an alternative. As it's not normally cheap to fit a wet underfloor heating system into an existing property, ground source heat pumps are most commonly installed into new properties. They can be installed in older buildings if attention is given to improving insulation and - if necessary - increasing the size of the heat emitters such as radiators.
How efficiently do heat pumps perform over time?
The source of the heat collected by the ground loops is ultimately the sun's energy that warms the surface of the earth and gets absorbed by the ground. The only conventional energy used in a ground source heat pump system is electricity for the pumps and compressors, which are needed to run the system. Typically, these use only a quarter as much energy as is released into the building in the form of heat so a ground source heat pump can be 300-400% efficient.
The performance of a ground source heat pump depends greatly on the quality of the design and installation. Maximum performance is achieved by matching the specification of the installation to the needs of the building and its use, and ensuring that a balance of heat exchange is maintained within the ground over the year in a sustainable way by utilising solar recharge of the ground.
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About the author: Sam joined YouGen in 2017 as a Project Officer, after having achieved a BSc (Hons) degree in Geography from Royal Holloway, University of London.
He is passionate about renewable energy and sustainability and has undertaken a variety of placements focused in these areas.
Sam coordinates the YouGen blog, newsletter and recommendation service on behalf of installers, as well as driving the platform forward through an active social media presence.
If you have a question about anything in the above blog, please ask it in the comments section below.
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