Why geothermal energy isn’t viable for the Isle of Man

With renewable energy generation being a key topic of conversation since the announcement of plans to meet the 30MW through locally generated wind and solar, the question of why the Isle of Man is not exploring geothermal is often asked.

Many countries use geothermal energy. In Iceland, abundant sources of hot, easily accessible underground water make it possible for most people to rely on geothermal as a safe, dependable, and inexpensive source of energy. Iceland now has a 99.96% renewable energy supply (1).

Geothermal energy is the heat that comes from the Earth’s interior. As a renewable resource, it is attractive because it provides constant power, unlike wind and solar energies that vary with weather and light levels.

However, opinions from several geologists have determined geothermal energy generation is unlikely to be viable on the Isle of Man due to the lack of appropriate rocks that are both sufficiently hot and that easily allow water to circulate through them (2).

“Sadly, the short answer is that geothermal energy is very unlikely to work on the Isle of Man. Essentially the geology rules it out.”
Dave Quirk, Consultant Geoscientist from the Manx Geological Survey

Current UK geothermal projects (which have access to large volumes of hot granite rock) are currently struggling to produce sufficient steam quality for power generation. These factors meant it did not feature in the Island’s Future Energy Scenarios by consultancy firm Ove Arup.

Why it’s working for Cornwall and other countries

Geothermal for energy generation works in Cornwall due to its unique geological characteristics and environmental benefits. Cornwall, located in the south western part of the United Kingdom, has granite formations close to the Earth's surface.

“Cornwall’s geothermal gradient is twice that of other parts of the UK” (4).

This images provides a good visualisation of why Cornwall is well placed for geothermal.

As you can see, temperatures in the Isle of Man are much lower, making it more difficult to use geothermal power.

“We do not have radioactive decaying granite rocks that they have down in Cornwall”
Clive Callister, Climate Change Board Advisor on Energy and Electricity

Elsewhere, in volcanically active areas like Iceland and southern Italy, the ground is so hot that water can be circulated through shallow boreholes to form steam which drives turbines for electricity.

In Denmark and Germany, there are porous and permeable rocks (“aquifers”) around 3km depth, contain hot water. This hot water can flow by itself into the boreholes and is brought to the surface where it is distributed to nearby communities via insulated pipes (“as district heating”) (2).

A small-scale scheme has been in operation in Southampton since 1986 where there is an excellent aquifer. No such aquifers exist in the Isle of Man (2).

High cost and feasibility assessment

According to local expert Dave Quirk, Consultant Geoscientist from the Manx Geological Survey, a borehole would take around a year to drill and would cost tens of millions of pounds. At least two boreholes would be needed but then there would not be enough natural water flow – the Manx slate and granite rocks found at these depths are impermeable – meaning you would have to form artificial fractures (“fracking”). This is expensive and time consuming (2).

The Climate Change Transformation Team have discussed the possibility of geothermal in the Isle of Man with Dave and other expert geologists, who all agree that the Island’s geology is not suitable. Further to this, Ove Arup estimated a cost of £2 million to undertake a geothermal feasibility study, therefore currently there is no further investigation into geothermal.

Viable options for the Isle of Man

Recently, advisor to the Climate Change Board, Clive Callister spoke on Manx Radio to discuss renewable energy in the Isle of Man. During this hour-long interview that can be found here, he discussed the feasibility of wave, tidal, on and offshore wind and geothermal.

While the geology of the Isle of Man suggests that geothermal power production is not possible here, the Island is well suited to other forms of proven renewable energy. It is cheaper to generate power from wind and solar energies than by burning fossil fuels. The transition to a secure supply for the Island will make us less reliant on volatile fossil fuel markets, therefore our energy security will be boosted by the net-zero transition and the use of home-grown renewables.

Ove Arup determined the most cost-effective energy mix for the Island, which features interconnectors, biomass generation and varying amounts of small-scale solar and wind generators. (3)

The Island’s new energy strategy, published this year, will be updated on an annual basis to reflect our evolving policy stance, noting that the energy landscape and technology involved is constantly changing.

References:

Topics

Geothermal Energy
Renewable Energy
Green Energy
Future