Bath is the UK’s only true ‘hot spring’, but several areas across the UK have good potential for deep geothermal exploitation.
Cornwall has long been seen as the best candidate for power generation, though other areas may also have good potential for geothermal energy, particularly heat, such as the Wessex Basin and the North East, as well as granite batholiths in Scotland and in Northern Ireland.
In 1977 the then Department of Energy (in reaction to the recent oil shock) embarked on a large scale - £50 million - deep geothermal research project which ran until 1991. This included a 2.8 km borehole at Rosemanowes Quarry in Cornwall, alongside several others.
The project made several technical advances but found that the technology was unable to compete with (by then) relatively cheap fossil fuels.
One 1.8 km deep test borehole, at Southampton, later became a key heat input for that city’s heat network.
It has been estimated that geothermal power from the south west of England alone could meet 2% of the UK’s annual electricity demand.
DECC’s 2050 pathways report estimated that at an extreme (‘level 4’) level of effort geothermal could deliver 5 GW of electrical generation capacity in 2030. Levels 2 and 3 would deliver 1 GW by 2035 and 3 by 2030 respectively.
The industry’s estimates of the UK potential for deep geothermal energy are higher, but not enormously so. This is due to the high cost of exploiting the heat that is present at depth - which is agreed to be enormous. In other words, the technical potential of deep geothermal energy is vastly greater than the economic potential.
Estimates of the potential for deep geothermal heat generation are even more unclear, though we know that this is an easier, cheaper and less risky form of the technology. Roll out is of course dependent on adjacent heat demands.