AN ambitious £3.5m plan to use geothermal energy to heat a North-East heritage site has been unveiled.

The Auckland Castle Trust, led by Jonathan Ruffer, is exploring the possibility of using the renewable energy source for Auckland Castle, in Bishop Auckland.

The town has been identified as a prime site for this project and if successful it could also be used for the trust’s new offices, a Spanish art gallery, welcome tower, hotel and walled garden, and potentially benefit nearby businesses and homes.

A planning application to drill two exploratory boreholes up to 1.8km down on the North Bondgate car park will be submitted to Durham County Council shortly.

If approved, and the investigatory work proves successful, further proposals will be drawn-up to create a network of pipes to take the heat to the Grade I listed castle – making it the first historic building of its kind in the UK to use this environmentally friendly energy.

David Ronn, chief executive of the Auckland Castle Trust, said: “This is an extremely exciting and innovative scheme that has the potential to provide not only long-term benefits for Auckland Castle but the town of Bishop Auckland too.

“It would help the sustainability of Auckland Castle as a visitor attraction with the added bonus that competitively priced heat could be offered to other businesses in the north of the town if the drilling is successful.”

The project will be funded by the trust with the initial stage expected to cost £2.5m and a further £1m will be spent if the scheme is given the go-ahead.

A feasibility study by Cluff Geothermal has indicated there is likely to be an underground reservoir of water at 70c – hot enough to be used for heating but not for electricity.

A drilling rig 30m high will operate 24 hours-a-day for about three months during the initial test stage.

If all goes to plan a geothermal pumping station the size of five car parking spaces would be built.

Mr Ronn added: “This is a rare and sustainable resource we sit on in Bishop Auckland. We are working closely with Durham County Council and we will be doing the same with local people in order to listen to their views.”

The Auckland Castle Trust scheme will use water naturally heated by energy from deep in the Earth’s crust. The water will be pumped to the surface where it will pass through a heat exchanger before being sent back underground to be re-heated.

Mr Ronn said: “In the simplest of terms, all we will be doing is redirecting an underground stream, but one that is as warm as a hot bath.”