An Investigation into the Potential for Enhanced Geothermal Systems (EGS) Electricity Generation in the UK
|In recent years, UK National energy policy has focused on increasing supply from indigenous renewable resources. Detailed policy objectives set out in the Climate Change Bill aim to achieve a 60% reduction in carbon emissions by 2050 (White Paper, 2008a), and reduce reliance on foreign energy (DTI, 2006). To achieve these goals in the most cost efficient manner possible requires a diverse portfolio of electricity generation technologies and strategies that are detailed in the 2020 marginal abatement cost curve for carbon (White Paper, 2008b). One technology that has been overlooked on the marginal abatement curve, and would align closely with UK energy policy, is Enhanced Geothermal Systems (EGS) electricity generation. This paper investigated the potential for EGS geothermal in the UK context.
Firstly, the thermal energy resource base available for EGS geothermal technology in the UK was quantified. The study boundary defined candidate hot dry rock for EGS development as between 3 km to 10 km below the surface and greater than 1500C. Due to limited field data, temperature depth profiles and thermal energy content was quantified theoretically according to local heat flow and thermal conductivity parameters. Areas of high heat flow granite in Cornwall were identified as the most suitable resources for development with calculated temperature gradients that exceeded 340C.
The performance of thermal energy extraction and conversion technologies according to calculated resources were reviewed. Results showed it was technically feasible to install 9,399 GWe of renewable base-load generation capacity if the entire thermal energy accessible resource base between 9 km to 10 km was developed, and 1,056 GWe if only granite resources were developed.
The final part considered the economics of EGS in the current UK generation market. Itemised levelised cost calculations were carried out to determine possible economic barriers. The economic installed capacity of EGS was estimated at 255 GWe for granite resources with an average levelised cost of 5.88 p/kWh before subsidies. The practical installed capacity is an area identified for further research, although conservative assumptions were made to place EGS geothermal on the marginal abatement cost curve.
As EGS geothermal is an emerging technology, the nature of research was fundamentally theoretical. To ensure accuracy and conservatism, results were validated and cross-checked through literature survey, case studies, conference proceedings and industry interviews.