What is it?

Ground sourced heat technology – This is designed to harness energy from the top layers of the earth’s surface.  These top layers are heated up by the sun and maintain a relatively constant temperature which tends to be warmer than the surface in the winter and colder in the summer.  This generates a constant energy source that can be used to both heat and cool our homes depending on the time of year.  This technology has been growing across the UK, and it is now commonplace for ground source heat pumps to be installed in new property developments.

Geothermal power - As you move closer to the earth’s core, the surrounding rock increases in temperature, this phenomenon is described as the geothermal gradient.  Deep Geothermal utilises the gradient at depths >500 meters to heat a solution and convert it into steam, this is then captured and used to drive turbines, like those seen in the biomass powerplants.

How does it work?

Ground sourced heat technology – This is usually harnessed via an electrical device called a heat pump, which extracts heat from one place and transfers it to another.  These devices are attached to a fluid circulation system, which pumps a solution underground, and uses the ambient temperature of the earth to either heat or cool the solution.  It is then pumped back up to ground level for use in domestic appliances such as heaters and air-conditioning units.

Geothermal power – This is a growing technology in the UK which utilises temperatures >160 degrees to generate steam and drive a turbine.  To reach these temperatures, there needs to be a geological anomaly, such as a radiologic granite intrusion.  These can be found in the UK in areas such as Cornwall, Northern England and Scotland and tend to be 5000m below the earth’s surface. Two deep boreholes are drilled - one shallower than the other – and water is pushed into the rock through the shallower borehole, it is heated and turned into steam, which is then captured by the deeper one, creating an engineered geothermal system.  The captured steam is then used to turn a turbine at the earth’s surface and generate electricity.

What are the advantages of these technologies?

Ground source heat technology

• Accessibility – This technology can be employed either in a large-scale project or by individual homeowners. 

• Efficiency – Ground source heat pumps are three times more efficient than modern gas-powered boilers. Fitting a heat pump could drastically reduce a household’s energy bill.

• Reliability – The heat source is not greatly affected by seasonal fluctuations in temperature, this, therefore, means you have a reliable and consistent means of heating that can be accessed at any point throughout the year.

Geothermal power

• Reliability – In areas where deep geothermal power can be harnessed, the temperatures are constant and are heated by an ‘infinite’ source.  It, therefore, has the potential to generate a constant supply of electricity.

• Fuel dependency – There is no fuel required, which removes the dependency on another resource.  This also removes the need for mining or other fuel extraction methods.

 What are the disadvantages of these technologies?

Ground source heat technology

• Installation – Despite its accessibility to the consumer market, the installation costs remain high.  Cost is offset by the energy savings made over the lifetime of the technology but remains a major barrier to its wide-scale adoption in the UK.  Furthermore, there are restrictions on the type of buildings, local geology, and space which can prevent a heat pump from being fitted to a property.

• Carbon neutrality – Heat pumps rely on electricity to run, so their carbon neutrality depends on the source of that electrical energy.

Geothermal power

• Location restricted – There are only certain areas in the UK that can generate the temperatures required within reachable depths.  This limits the scale that geothermal power can be employed across the country.

• Initial Costs – The initial cost for installing the technology required for a geothermal power plant is significantly higher than other renewable and fossil fuel-driven power sources.  However, like ground source heat technology, this can be offset over the life of the project.

• Gases released during drilling – Many greenhouse gases are stored below the surface that can be released during the drilling phases of installation.  While these gases are also released into the atmosphere naturally, the rate increases near geothermal power plants.  However, these gas emissions are far lower than those associated with fossil fuels.

Current energy production?

Despite their advantages, in 2019 only 2% of households had been fitted with ground source heat technology.  Geothermal power does not currently produce any energy in the UK; however, four major projects are under development.

Location of geothermal potential

Ground source heat technology that is driven by the sun can be accessed across the entirety of the UK, this is one of the key advantages of this technology.  However, deep geothermal power production is only available in a thew location in the UK.  The illustration shows areas in which geothermal power could be harnessed, for heat, or heat and electricity.

Deep geothermal potential (Credit: Eden Geothermal)

Key projects in the industry

• United Downs Geothermal Project - https://geothermalengineering.co.uk/united-downs/

• Eden Geothermal - https://www.edengeothermal.com/

Future projects and development of ground-sourced heat and geothermal

Ground sourced heat continues to grow as a realistic and affordable energy source.  The UK Government has outlined plans to instal up to 600,000 heat pumps by the year 2028.  The Climate Change Committee (CCC) has suggested that 3.3 million heat pumps need to be installed in existing homes by 2030, rising to eight million by 2035.  The scaling up of ground-sourced heat technology is going to be essential to reaching the 2050 net zero target, and this provides an excellent opportunity for service leavers, veterans and spouses/partners.

Geothermal power is still in its infancy in the UK.  The key projects in the industry outlined above are pioneering the race for harnessing deep geothermal energy and they are expecting to produce electrical and heat energy by 2030.  This area remains highly specialist, however, it has great potential, and it is important for service leavers to understand that with limitless power, there could be a significant investment and job creation.