What is closed loop geothermal drilling?

As you start to research geothermal energy and heating solutions, one of the concepts you’ll come across is closed-loop geothermal drilling. 

Groundsource energy systems, including heat pumps, rely on transferring heat up from the ground below through closed-loop pipe systems, and this is generally why geothermal drilling projects are carried out. 

Below, we go into a little more detail, from how the systems work to the importance of geological surveys. 

How closed-loop geothermal systems work

Closed-loop geothermal energy solutions are installed by placing a closed loop made from plastic pipes underground. This is why boreholes need to be drilled, so that the pipes can then be installed in those holes. 

An antifreeze fluid mix is then circulated through the system, absorbing heat from the ground as it travels through the pipes. When this fluid comes back up to the surface, it runs through the heat pump to transfer the heat to a separate refrigerant, where a complex combination of compression and condensation extracts the heat from the refrigerant and uses it to heat water or a property. 

In summer, this process can be reversed, with heat from the property being released into the comparatively cooler ground beneath, and colder fluid being brought up to the surface. 

The two types of systems

There are two common types of closed-loop configurations: vertical and horizontal. 

Vertical systems

For properties that don’t have an abundance of space around them, vertical closed-loop systems tend to be the most common options. Geothermal boreholes will be drilled to a depth of between 50 and 200 m, in pairs. 

Pipes can then be installed with a U-connector at the bottom, so that fluid can be pumped down one side and then back up the other. The gaps between the pipe and the sides of the borehole will be sealed with a thermally conductive grout, so that heat can transfer as efficiently as possible. 

Horizontal systems

If there’s a lot of spare land to dig hundreds of metres of trenches, then horizontal systems might be appropriate. Here, the same principles apply, but instead of drilling directly down, the loop is placed in trenches that are just a few metres deep. 

Geological surveys

There are a whole host of factors that can have an impact on how the hole is dug, how deep it needs to be, and what safety precautions need to be taken to mitigate potential risks. 

The sooner you have a geological survey carried out, the better you’ll be able to make a clear plan based on the results of that survey. Whether that proves that investing in a geothermal heating solution is an excellent idea, or shows that you should probably try an alternative solution, it’s a necessary step that allows you to move forward. 

Closed-loop geothermal drilling projects are becoming increasingly common, and this trend is likely only set to continue. If you’re looking for an efficient heating solution that pays for itself relatively quickly, geothermal energy solutions are definitely worth keeping in mind.