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Research

Exploring geothermal energy potential

(4 July 2017)

Representation of a geothermal heat extraction system. Credit: Charlotte Adams

Researchers at the University’s Durham Energy Institute (DEI) are exploring the Earth’s geothermal energy potential

Led by the Centre for Research into Earth Energy Systems (CeREES), researchers are investigating how this potential can be harnessed to provide a low carbon, clean, non-intermittent energy source.

A potential source of heat and warmth for homes could come from the flood water found in abandoned coal mines.

Here, Dr Charlotte Adams, DEI member/Assistant Professor in the Department of Geography and Research Manager for the BritGeothermal Consortium, explains more about how research could help tap into this valuable resource.

Q: What is geothermal energy and what are its benefits?

A: Geothermal energy is created by heat that is produced at the centre of the Earth radiating outwards towards the Earth’s crust. With every km depth there is an average increase in temperature of 35°C. This energy is derived from several different geological settings including volcanic regions, deeply buried granites and sedimentary basins, ageing or abandoned hydrocarbon wells and abandoned mines, the latter being the focus of this article.

Depending upon the source temperature, geothermal offers a low carbon option for heat and in some cases electricity production. One third of UK energy demand is used to produce heat. Gas is the most common fuel used for this but the UK has been a net importer of this since 2004. In addition to offering a low carbon continuous energy supply that could meet baseload heat demand, geothermal energy offers energy security by using an indigenous resource.

Q: What is the global potential of geothermal energy?

A: Because of the diverse range of geothermal sources, most regions of the globe have access to geothermal energy. As energy prices rise, concerns over fuel security increase and technology development improves prospecting, drilling and energy conversion techniques. The world energy council predicts that over eight per cent of global electricity demand could be produced from geothermal sources and this could supply around 17 per cent of the global population. China is currently the largest producer of geothermal heat and the USA is the largest producer of geothermal electricity. In response to the oil crisis, the UK assessed its geothermal potential during the 1980s. This concluded that there is enough heat in place to meet UK heat demands for over a century. Research carried out at Durham continues to extend this estimate by assessing additional sources of geothermal heat such as abandoned hydrocarbon wells and abandoned mines.

Q: Tell us about your project exploring the geothermal potential of former coal mines in County Durham, North East England.

A: Many towns and cities in the UK grew on the strength of their coal reserves and Spennymoor, in County Durham, is one example of this. The town has had a mining history spanning over 150 years and consequently there are considerable areas of abandoned mine workings beneath the town and areas planned for new housing developments. This research will estimate the volume of water in the workings and subsequently the amount of heat that can be extracted. This figure will be used to calculate the number of homes that could be heated and different scenarios will be investigated to optimise system configuration. This project also involves community consultation to find out what local people think about the scheme.

Q: Are there already examples of successful geothermal energy projects and how long might it be before geothermal becomes a common part of the energy mix?

A: With respect to mine water systems, there are a couple of smaller schemes in the UK that are used to heat small blocks of flats and individual buildings. There is good overlap between areas of mining and areas of heat demand in many UK towns and cities. Beyond the UK, there is a large municipal scheme at Heerlen in the Netherlands and a long-running scheme at an industrial site in Nova Scotia in Canada. There is potential all over the world for example, Australia, America, Spain, France, Germany and Poland all have flooded abandoned mines that could be used as a source of energy.

Q: What is the next step in your research?

A: Societal and technical aspects need to be addressed. Societal aspects include raising awareness which is crucial. Lack of awareness and risk averse attitudes to novel technologies present a key challenge especially when considering low carbon sources of heat. In addition to scoping the potential resource, the present study includes undertaking surveys with local people to gauge levels of interest and understanding; these qualitative data will form part of future research.

With respect to the more technical research, this continues at Durham University within Durham Energy Institute to improve power and heat conversion systems. The intention would be to undertake test drilling to prove the potential. Ultimately a mine water heat system may require higher upfront capital, but offers long-term savings in addition to reduced carbon emissions and improved energy security.

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