In recent months you have probably heard a lot of talk about renewable energy, air source and ground source heat pumps. But what actually are ground source heat pumps, how do they work, and how much do they cost?
In this article, we will run through the ins and out’s of ground source heat pumps (GSHP), including how they work from a technical standpoint and how much you can expect to pay.
Ground source heat pumps are renewable energy systems that heat homes and water through geothermal energy. Depending on a few factors, you can choose a horizontal or vertical GSHP.
Heat from the ground is absorbed by piping buried in your garden. This heat is then passed into your home through an exchanger and is circulated to your radiators, underfloor heating and water systems.
As well as being a source of heat, ground source heat pumps also work as cooling systems during the warmer months. The system works similarly to heating your home, just in reverse!
The system absorbs the warmer air that circulates your home. As the ground temperature is lower, the warm air is transferred into the ground.
GSHPs are among the most efficient renewable heating systems on the market today. Investing in ground source heat pumps could save you hundreds on your energy bills every year.
How does a ground source heat pump work?
Now into the technical bit. Essentially the ground source heat pump system works like a refrigerator but in reverse.
The second law of thermodynamics states that heat will naturally flow to something that is a lower temperature. Hence, if you left an ice cube on the side, it would eventually melt, not get colder.
Step 1: An antifreeze liquid, often referred to as glycol or brine, runs through the collector pipes that are buried underground. As this liquid is at a lower temperature than the soil, heat is absorbed by the fluid.
Step 2: This is then fed into a heat exchanger called an evaporator, which houses a refrigerant. Mixing with a refrigerant (not directly), the warmed liquid is boiled and turned into a gas.
Step 3: A compressor then compresses the gas to increase the temperature further.
Step 4: This gas then flows into an almost identical system called a condenser, pushing the heat to your radiators, underfloor heating and water.
Once all the heat has been unloaded, the now liquid is passed to an expansion valve which further reduces the pressure and temperature. The process is then repeated all over again.
How much space is required?
The type of ground source heat pump installed depends on the size of your garden.
Usually, a horizontal system requires around 700 meters squared so that the piping can be looped in shallow trenches underground.
Vertical systems using boreholes need only about 0.25m in width but up to 100m in depth.
As heat pumps aren’t an extension to a building, you won’t need planning permission. However, if you overlook a listed building or are located in a conservation area, you should double-check with the appropriate authorities.
How much are ground source heat pumps?
The cost depends on which heat pump works for you. As there is more manual labour involved with vertical heat pumps, due to the drilling of the borehole, on average, you’re looking at around £49,000.
Horizontal ground source heat pumps come in a bit cheaper at around £24,000.
It’s important to note that although the upfront cost can be expensive, heat pumps will save you hundreds of pounds every year!
In April, the government launched the new Boiler Upgrade scheme to replace the Renewable Heating Incentive. This government grant could save you up to £5000 on the initial cost of certain renewable heating systems, with ground source heat pumps included.
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