Abandoned mines provide low carbon heating... by Gareth Farr

New 3D Geological model of the South Wales coalfield (Andy Hulbert)
Gareth Farr from BGS in Wales has been discovering how abandoned mines in South Wales could once again be used to supply energy. Mine waters in flooded workings can be passed through a heat exchanger, producing hot water to heat homes and offices. The technology has been proven at a test site in South Wales and offers a secure, low carbon alternative to traditional fossil fuels....
At the BGS we've been working with Cardiff University and WDS Green Energy Ltd on the ‘Seren’ project supported by the European Regional Development Fund (ERDF).

Seren has been aimed at helping businesses find new opportunities by developing innovative engineering technologies to exploit geo-energy. One of these opportunities that has been investigated by the BGS and Cardiff University is the potential for exploiting geothermal energy from mine-waters in the South Wales Coalfield.
Measuring mine water temperature and chemistry at the inflow to a treatment lagoon with Dr Siva Sadasivam (Cardiff University)

We undertook a program of temperature monitoring temperature and chemistry of mine waters, which has accompanied creation of a new 3D geological model of the coalfield and developing a new coal properties database populated by capturing many thousands of historical coal analysis records. The commercial partners have installed a working GSHP system into abandoned mine workings.

Ground source heating relies on the recovery of low grade heat energy from the earth or from groundwater, with the energy being harvested using a ground source heat pump (GSHP). There is little use for mine waters as they are often below drinking water standards, however the large volumes of water could offer a potential source of low grade heat. In the South Wales area it is estimated that as much as 2000 – 3000 litres per second is still being pumped or drained from old mine workings.

WDS Green Energy Ltd have installed a working GSHP system into abandoned mine workings as part of this project. The system is working well, heating a large property and several outbuildings. This photograph shows some of the above ground workings.
To assess this potential we installed temperature monitors where water flows out of the abandoned mines. The temperature was recorded every 30 minutes and by the end of the project we had collected over 300,000 individual temperature readings. We found that many of the mine waters had temperatures above that of ‘normal’ groundwater (~11°C) and offered an exciting potential for use with GSHPs.

Combining what we had learnt about the temperatures of mine waters with information collected by the Coal Authority on the volumes of water leaving the mines we were able to estimate that there was potential to generate enough energy to heat 20,000 homes. This estimate is based on sites where data has been collected so the real potential is likely to be much greater.

Temperatures of mine water discharges measured every 30 minutes over a one year period
To prove this concept our commercial partners WDS Green Energy Ltd installed a real GSHP system into flooded mine working and have been successfully providing heating energy for a large house and outbuildings in South Wales.

Seren has shown that there is considerable potential to use mine waters as a source of heating, providing energy security, reduction in carbon emissions and reducing reliance on traditional fossil fuels.
by Gareth