Frequently Asked Questions 

What is Geothermal Energy ?

Geothermal comes from the words ‘Geo’ (Earth) and ‘Thermal’ (Heat). There are many different sources of geothermal energy, including near-surface (ground-source heat pumps), mine water, abandoned oil & gas wells, volcanic fluids or deep hot fluid reservoirs. These hot fluids can be used directly for heating and cooling or to generate electricity.

Geothermal power production and heating is not new. The UK is a long way behind many other countries around the world such as Iceland, New Zealand, Indonesia and the Netherlands who are using different types of geothermal energy to help combat the serious issue of climate change.  

Why Should We Use Geothermal Energy?

UK heating and hot water currently make up around 40% of the country’s energy consumption, and almost a third of greenhouse gas emissions, so new sources of clean, renewable baseload power and heat are desperately needed to help us meet our climate targets. 

Geothermal energy provides a source of low-carbon, baseload electricity and heat. This means it is generating 24/7, almost all year round no matter what the weather is like or the time of day. It also requires a much smaller land area per unit of power than almost any other type of energy generation. 

In addition, adding a brand-new source of green, baseload electricity to the UK national grid will also increase the country’s energy security. 

How do you select a geothermal development site?

There are a huge number of criteria considered when looking for a suitable geothermal development site. 

Three of the major considerations are:

1) Suitable geology 

2) Access from a main road to allow transport of equipment 

3) Proximity to local power infrastructure. 

However, ideally, we also require a site to have a good-sized level working area, low ecological and environmental sensitivity, and potential for renewable heat users. 

Is Geothermal the same as ‘Fracking’?

No, Fracking is where a large volume of fluid with a complex chemical composition is injected at extremely high pressures to create new fractures in intact rock, to drain the oil or gas from the reservoir. 

Geothermal power projects simply circulate fresh water in pre-existing fractures and, once the heat has been used at the surface, the fluid is reinjected into the same formation to re-heat. 

What is the difference between deep geothermal wells and domestic water boreholes?

There are many differences between deep geothermal wells and domestic water boreholes. Deep geothermal wells are cased in steel and cement from the surface for approximately ¾ of their depth and bring geothermal fluid contained in fractures at 4,000-5,000m depth to the surface. 

After the hot fluid has been used to produce renewable electricity, the water is reinjected underground to approximately 2,500m depth. In comparison, domestic water boreholes are rarely more than 200m deep and are cased with either steel or plastic with either an open hole section or perforated cased section in the part of the rock which contains the fresh water. 

The water from domestic boreholes is not deposited back underground, therefore the water extracted from a borehole is not replenished by the borehole user

What effect will geothermal drilling have on groundwater?

NONE - Geothermal developments must follow regulations and guidance from the Northern Ireland Environment Agency (NIEA) to ensure that groundwater is not impacted by drilling or operations. 

At first, a pilot hole is drilled approximately 30” wide and 11m deep and cased with a steel cylinder, to stabilise the top of the well. Air is used to extract the debris, so no fluid is injected or extracted. 

The next section of the well is then drilled to approximately 900m. In this section, clean water is used to lubricate the drill bit and No water is extracted from the ground at these depths; therefore, borehole water supply is never depleted. 

As drilling continues, the well is cased with more steel and cement to around 3,000m, effectively sealing of the entire well from ground water and preventing any possible interaction of well fluid with groundwater. 

Where Can I Find Out More ?

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