Engineering news
A geothermal project to obtain hot water and electricity from granite rock under County Durham is to restart after several years of delays.
Engineers are to start drilling a second borehole at the Eastgate eco-village at the end of this month after receiving £461,000 of government funding. They hope to build a twin borehole geothermal plant for the first time in the UK. The plant will pump groundwater up from permeable granite rock 1000m deep, pass it through a heat exchanger on the surface, and then reinject it via the second borehole.
The system will run continuously to obtain water 30 degrees C, which will be used in a heating system, in a day spa resort and to breed exotic fish. Ultimately, the team want to drill deep enough to use the hot water to produce electricity.
An initial 995m deep borehole was drilled in 2006 to assess characteristics such as the geology of the site and the salinity of the water, but the project was delayed because of planning permission issues for the rest of the eco-village.
Head of the project from Newcastle University, Professor Paul Younger, said “The pressure is important. If you can’t reinject you get a steady decline in the reservoir pressure.
“By reinjecting water using a second borehole we are able to maintain the natural water pressures in the rocks and allow pumping to continue for many decades to come.”
Southampton is the only other site in the UK to exploit geothermal heat, with a single borehole providing energy to a number of businesses in the city centre. A decline in reservoir pressure there now means the borehole mainly only produces heat energy.
According to geological surveys, there are only a few sites in the UK with rock formations suitable for exploitation in this way. A geothermal project using a similar technique is expected to begin drilling into hot granite rocks near Redruth, Cornwall, this year.
Younger said: “Although there are only a few places in the UK suitable, these few areas are very large. There is a lot of potential to get gigawatts of energy from these sites, and unlike every other renewable this is baseload, continuous energy.”
The exploratory work had allowed the team to devise ways of inspecting and repairing the boreholes to avoid pressure loss, he added.
The second borehole is expected to be completed by the end of March this year.
The scheme is being lead by Newcastle University, and the system will be analysed by a team from Durham University and consultancy Parsons Brinckerhoff.