Closed Loop Heat Extraction from Deep Single Wells

Abstract

Policies within the European Union are encouraging member States to reduce Carbon Dioxide emissions associated with the production of electricity and heat. Overall, in Europe, residential heat demand accounts for approximately 35% of the entire annual energy consumption. There is therefore a focus on promoting renewable heat technologies. Such technologies include Ground Source Heat Pumps, Biomass and Deep Geothermal heat. Deep geothermal heat has not, to date, contributed meaningfully to the overall renewable heat supply in Europe. This has been due to the geographical distribution of suitable geothermal aquifers, the high cost of drilling and, more recently, permitting/ seismicity issues. To enhance the overall development of the deep geothermal resource, Geothermal Engineering Ltd was funded by the Department of Energy and Climate Change in the United Kingdom to design and test new methods of extracting deep geothermal heat from single wells. This paper reports on the modelling and design of deep geothermal heat exchangers to work in varied geological conditions where the temperatures are suitable for direct heat use in buildings. Of particular interest is the possibility of using wells that have already been drilled for other forms of energy (e.g. shale gas and oil wells). A trial system will be installed in an existing two kilometre deep well in the UK in mid-2014, with commercial installations to follow.