How does geothermal energy work?

Pretty much every week, we’re met with more evidence of the urgent need to rethink our energy systems. Whether that’s price hikes brought about via war and supply chain disruption, or the devastating impacts of global warming, there’s no shortage of arguments that we need alternative solutions. 

Part of the problem lies in the fact that most of us haven’t been taught about how these alternative energy systems work, and as a result, they might not even be on our radar of potential options. 

Below, we explore a specific and increasingly popular solution, geothermal energy, looking at how it works and some of the main practical applications. 

Trapped heat

In short, geothermal energy systems work by tapping into the heat trapped in the Earth’s crust. Wells are drilled into the ground, to a depth of around 50-200m in smaller-scale domestic projects, but up to over 5km in depth in national electricity production projects.

Once a borehole has been drilled, a loop is installed. That loop is then filled with a water-antifreeze mix, which can be cycled through the loop. The water that comes up will be warmer than the water that went down, and that heat energy can then be used for a range of purposes. 

Harnessing geothermal energy

There are two main ways that geothermal energy can be harnessed.

Heating 

The most common use of geothermal energy is to use it directly for heating. After the heated water/antifreeze mix comes up from below, it is placed through a complex heat exchange and compression process, which elevates the temperature of the water substantially. 

That water can then be used to either heat a property through a central heating system, or to provide hot water for washing purposes. These kinds of projects can be done at a small scale, and are increasingly popular for domestic usage. 

The set-up cost is significant, but there are a range of government grants available that can substantially reduce the cost-related barriers for a lot of people.

Electricity generation

While less common, geothermal boreholes can also be used to generate electricity. To generate electricity, the heat trapped in the Earth’s crust can essentially be magnified until it’s hot enough to heat water into steam. 

That steam can then be used to spin a turbine, which runs a generator to produce electricity. Due to the infrastructure complexity, these kinds of projects tend to only be viable on much larger scales compared to geothermal heating systems. As a result, you’ll rarely see them operating on a domestic scale, or even on the scale of smaller businesses or commercial operations.

Geothermal energy systems are likely going to play an increasingly important role in contributing to our energy needs. On both a domestic and national scale, these systems can play a critical role in our heat and electricity requirements, with the added benefit that they are not as dependent on the weather as either solar or wind energy sources.

It’s worth keeping an eye on how these technologies continue to advance, whether you’re personally interested in investing in a solution or just wish to remain informed.