Closed Loop Heat Extraction from Deep Single Wells

Abstract

Policies within the European Union are driving member States to reduce emissions from both electricity and heat production. 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 direct geothermal heat. Direct 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 cost of drilling doublet systems and, more recently, permitting/ seismicity issues. To enhance the development of the geothermal resource, Geothermal Engineering has been funded by the Department of Energy and Climate Change to design and test new methods of extracting deep geothermal heat. This paper reports on the modelling and design of a novel deep geothermal heat exchanger that has been developed to work in any geology where the temperatures are suitable for direct heat use in buildings. One of the drivers has been to make use of existing wells drilled for other conventional forms of energy. The system will be installed and trialled in an existing 2km well in the UK in April 2014, with commercial installations to follow later in the year.