How does ground source heating work?
Find out how a ground source heat pump works and figure out which heat emitters and collectors will help you get the most out of your system.
How do ground source heat pumps work?
Where typical central heating systems burn fossil fuels in order to generate heat, ground source heat pumps work by using electricity to harvest heat from the ground.
A ground source heat pump does this by using a network of pipes – either ground loops or boreholes – that are buried in the ground. These are filled with a refrigerant that gently extracts the heat, before passing it through a compressor in the ground source heat pump to increase its temperature. This higher grade heat energy is then used for heating and hot water
Ground loops or borehole: which should you choose?
There are two ways to harvest the heat energy from the ground with a GSHP: through ground loops or via a borehole. But which should you choose?
Ground loops
Ground loops, or a horizontal ground source heat pump system as they are sometimes known, are the most popular choice when installing a ground source heat pump.
When installing ground loops, collector pipes are buried at a 1 metre depth within the ground, drawing warmth from it, through to the heat pump. Any energy that is extracted is then continually replenished by the sun.
To install ground loops, you need plenty of available land – at least three times the total floor area of the property, ground and upper floors combined.
Pros of GSHP ground loops
- Cheaper to install than boreholes.
- If landscaping works will be happening anyway, it’s no extra upheaval.
- No specialist contractors required.
- The ground loop trench can be dug at the same time as laying the foundations for a new build by the groundworker.
Cons of GSHP ground loops
- A significant area of land is required, which can rule a GSHP out.
- Landscaping is required.
- You can’t develop the area once the ground loops are installed.
If you haven’t got the space to install ground loops but are set on a ground source heat pump, you might consider a borehole.
Boreholes
Installed by a specialist contractor, a borehole is a vertical ground source heat pump system that is typically drilled between 40-120 metres deep. Once this has been drilled, the ground collector, that extracts the heat energy is dropped into the hole. This is then filled with a grout for added thermal conductivity. The exact number of ground source heat pump boreholes required will depend on the specifics of your project.
Pros of ground source heat pump boreholes:
- Less land space required than with ground loops.
Cons of ground source heat pump boreholes
- Cost. Boreholes can cost as much as double in comparison to ground loops. This is due to the contractors, equipment, drilling and logistics involved.
- No additional payback. The Boiler Upgrade Scheme payment remains the same, £7,500, whether you have installed a borehole or ground loops. This means the overall cost to install a ground source heat pump with a borehole is higher.
- Specialist contractor is required.
If considering a borehole to make a ground source heat pump possible, it’s worth weighing up the cost of installation versus choosing an air source heat pump which would be significantly cheaper, is well suited to properties on smaller plots and still returns an efficiency of around 300%.
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How do ground source heat pumps work in winter?
Ground source heat pumps work in winter because they extract heat from the ground using pipes, typically buried 1m below the surface, where the year-round temperature is fairly stable.
This is why ground source heat pumps are generally more efficient than air source, as air temperature fluctuates far more than ground temperatures.
Should I use underfloor heating or radiators with a ground source heat pump?
Ground source heat pumps can work with both underfloor heating and radiators. However, for optimal efficiency it’s generally agreed that pairing a ground source heat pump with underfloor heating would be the preferred combination.
This is because ground source heat pumps are at their most efficient when producing low temperatures, which underfloor heating systems can utilise across a large surface area to heat your home.
In comparison, radiators have a far smaller surface area, and so require much higher temperatures to heat your home to the same level.
FAQs
Do I need a specialist contractor to install horizontal ground loops?
No, Nu-Heat will supply the ground loops required and installing them can be done using standard equipment.
How much space do I need for ground loops?
This very much depends on the size of the property you’re heating and its heat losses, which we will size this for you. However, a good, rough rule of thumb would be 2 – 2.5 times the floor area of the property.
I don’t have space for ground loops, can I have a GSHP?
If you don’t have space for ground loops, boreholes are a great alternative, but it is worth noting that they are usually more expensiv