The Potential for the Exploitation of Geothermal Energy in the United Kingdom
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The Southampton City Geothermal and CHP scheme provides a useful case study within the UK of a small-scale geothermal scheme that actually works. So why are geothermal aquifers not being exploited much more widely? The problem is not just one of marginal economics and geological uncertainty, but is to do with the mismatch between resource availability and heat load, itself a function of population density. Over half the resources are located in east Yorkshire and Lincolnshire, essentially rural areas lacking concentrated populations. The other UK areas are little better, though several large conurbations in the midlands and North West could benefit form geothermal schemes such as that in Southampton. For example, there has been discussion about reopening and exploiting the Cleethorpes well if high flow rates could be maintained at around 50°C (see Boyle, G10 p388). Should fossil fuel prices ever escalate again, no doubt geothermal aquifers in the UK will receive much more attention than at present.
Hot Dry Rock Technology (HDR)
When asked whether there is potential in the UK for geothermal electricity production Dr Robin Curtis of GeoScience Limited stated 'there is no potential for electricity power generation in the UK other than by Hot Dry Rock Technology which is still being developed in a few other countries but is currently on hold in the UK'.
Hot Dry Rock technology is often referred to as 'heat mining' and aims to exploit volumes of hot rock that contain neither enough permeability nor enough 'in situ' fluid in their natural state for commercial exploitation. The permeability is created by stimulation techniques and the fluid is placed and circulated artificially (see Ledingham, P1 p4).
Research on hot dry rock technology began in the 1970's to develop reservoir creation and exploitation techniques that would allow access to an almost limitless resource base virtually independent of location. The original dream behind HDR concept was that if a method could be found to induce permeability into basement rocks that would not otherwise support significant flows of water, then this would give access to the huge amount of thermal energy stored within the accessible layers of the Earth's crust.
Such a resource would be available virtually everywhere, would reduce dependence on imported fuels, provide temperatures adequate for electricity generation even in tectonically stable regions, and would discharge very little waste and almost no greenhouse gases (see Ledingham, P11 p296).
Of the three principal granite zones in the Eastern Highlands, Northern England and Southwest England, the latter is characterised by the highest heat flow, as shown in (Appendix 5a). However, large areas of the more northerly granite masses are covered by low thermal conductivity sedimentary rocks and so, from The Heat Conduction Equation, temperatures will be higher at depth than if the granite bodies came to the surface.
By the mid-1980s, detailed evaluation of the radio-thermal and heat conduction properties of al ...
