Answer: A ground source heat pump needs more space than an air source heat pump. A typical horizontal system requires around 700 square metres. A vertical system needs enough space for the drilling rig to access the site, but boreholes are only around 20 centimetres wide. If multiple boreholes are needed, these are placed 5-6 metres apart.
Ground source heat pumps (GSHPs) extract heat from the ground. This heat is extracted from rock or surface soil, and can also be extracted from underneath lakes and riverbeds. There are a couple of options for ground source heat pumps; you can drill a deep borehole or lay heat collectors in shallow trenches. We will discuss the sizings in more detail in the next section.
A ground source heat pump will circulate a solution of water and antifreeze around collectors called ground loops. This is what is laid in trenches or boreholes. This absorbs the heat underground and puts it through a heat exchanger into the pump. It is an efficient method of heating residential and commercial buildings in the UK, offering heat all year round.
Also read: The benefits of a heat pump
A ground source heat pump requires more outdoor space than an air source heat pump. This one reason is why air source heat pumps are the most common form of heat pump in the UK. Let’s take a look at how much space you need for horizontal and vertical GSHP systems.
Horizontal systems are preferred, mainly due to reduced costs when compared to vertical systems. However, they do require a larger amount of outdoor space.
The details are perfectly summed up on the Source Energy website:
“While there are of course other factors to consider when sizing a system, it’s fair to suggest that as a guide, an 8kW Thermia ground source system would require around three ground loops, each at 200 metres in length. A minimum land area of 700 square metres would be necessary for loops of this size to be laid. In order to visualise how the ground loops are laid within this space, imagine that each loop is laid as a rectangle with 1 metre of separation – the rectangle formed by the loops would be 7 metres in width by 100 metres in length.”
Vertical systems are often more efficient, due to a constant temperature and the lack of impact from the changing seasons. These systems are often chosen due to lack of space for trenches, or in situations where the earth is not suitable for horizontal systems.
In terms of space, the main issue is access for the drilling rig. This can be tricky in confined built-up areas. For the typical UK home, one borehole is enough. This borehole is perhaps 0.25m across, and up to 100m deep. Loops are then placed into the hole, feeding into the system in a nearby plant room. If multiple boreholes are needed for larger properties and/or district heating systems, these are placed around 5-6m apart from one another.
With regards to space needed inside your property, you will require a plant room to host the ground source heat pump system. A plant room usually needs to have a 1 x 3 metre footprint, subject to the system size. This should be considered before the start of the project.
For more information about what type of heat pump you need, and for advice about the process of installation, contact Smart Renewable Heat today. If you’d like to see how much a ground source or air source heat pump can save you, and how much the Renewable Heat Incentive will pay you, try our free online calculator.
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