What is a geothermal borehole?

In the modern energy climate, there’s a lot of talk surrounding alternative ways of tapping into natural energy. Over the past decade or so, geothermal boreholes have been popping up with increasing frequency in the news, but what are these boreholes for, and how do they function in practice?

Below, we provide a brief overview of how geothermal boreholes are typically integrated into ground source heat pumps, to help you understand whether it could be a potential solution for your heating needs.

An energy solution

Geothermal boreholes are primarily used as an energy solution. By tapping into the thermal energy stored in the ground beneath us, they allow property managers – whether that’s a home or business premises – to heat those properties at a much lower financial and environmental cost than a lot of the common alternatives. 

Ground source heat pumps tend to be around 4x more energy efficient at heating properties compared to natural gas solutions, such as combi boilers. That being said, while they are generally cheaper to run than boilers, they’re not 4x more affordable, due to the fact that they’re powered by electricity – a comparatively expensive energy source. 

Components of a geothermal borehole

There are several different components to a geothermal borehole, which, when integrated, allow for the ‘capture’ of energy in the ground.

The borehole

The most structurally significant component in these systems is the borehole itself. It will be drilled to a depth of between roughly 50 and 200 metres, depending on the heating requirements of the property in question. 

The loop

Once the borehole has been drilled, a long pipe with a U-bend at the bottom will be installed. This pipe allows for a liquid to be circulated, collecting heat from below and then transporting it back up to the surface above. 

Grout

Once the pipe is in the hole, a thermal grout can be poured around the pipe. This grout ensures that there is a solid thermal bridge between the surrounding ground and the pipe itself, meaning that heat can be transferred as easily as possible without any air gaps or unnecessary inefficiencies. 

Heat pump

The borehole and pipe can then be attached to a ground source heat pump. Using a complex heat exchange system, the heat pump is able to ‘concentrate’ the energy that is extracted from the ground below, using that energy to then heat up water. 

That water can then be used to run a central heating system, or to provide hot water from the taps in the building. Unlike some myths suggest, these systems don’t only work when it’s warm outside – they remain effective right down to temperatures as low as -25C. 

With the right team and equipment, geothermal boreholes are relatively easy to install, and if designed properly, can easily last for 50 years or even longer. It’s important that you find the right drilling provider for your needs, ideally one that can take care of the rest of the project as well, from initial geological surveys to the installation of the heat pump itself.