Harnessing hot rocks

Newcastle University engineers are planning to develop a power plant on former cement works in County Durham that will harness heat from deep underground.

The twin-borehole geothermal system will allow water to be continually cycled through a maze of granite fractures as deep as 1km, where it will be heated up to temperatures of 30°C or more, then brought up to the surface and passed through heat exchangers before being returned underground to be re-heated.

According to project leader Prof Paul Younger of Newcastle University, the system will provide renewable energy for homes and businesses in the planned Eastgate eco-village in Weardale, County Durham, complementing four other forms of renewable energy - solar, wind, biomass and hydro - that are also harnessed there.

Aside from heating homes and businesses, some of the natural hot water will also be used in a spa - the first such development in the UK since the Romans tapped the hot springs at Bath. It will also be used to provide an environment for farming Tilapia fish, an alternative to cod that thrives in warm water.