ABANDONED coal mines could become a source of low carbon energy in the Wee County.

Following extensive work by the British Geological Survey (BGS) across Scotland, Clackmannanshire Council and the Scottish Government are considering utilising untapped natural resources to generate geothermal energy for local homes, schools and businesses.

Public consultation is currently being carried out by Clackmannanshire Council to hear what local residents think. The council is asking people's views on the issue as well as their opinion on climate change, energy sources and efficiency. A report on the findings is expected to come before elected members in the future.

Hugh Barron, business manager and chartered geologist and scientist at BGS Scotland, explained that after mines are abandoned, they fill up with water.

The shafts, where geothermal energy can be harnessed, usually go as deep as at least 400 metres underground, where rocks are naturally warmer than on the surface.

Over time, the water trapped in the mines warms up to the temperature of the rocks, which may only be around 15-18 degrees Celsius, but is enough to be utilised for a low-temperature (50 degrees Celsius) heating systems through a heat exchanger, which extracts heat from the water.

The water used in the process is then returned underground where it can filter through the rocks and heat up again.

Mine workings south and west of Tullibody, south-west of Tillicoultry, south of Dollar and around Clackmannan are deep enough and may be suitable for mine water heating and storage, according to the geologist. There is also potential that geothermal energy could be harnessed all around the central belt of Scotland and some of the mines in Clacks extend beyond the county.

Mr Barron told the Advertiser: “[Geothermal] is well suited to new-built housing with underfloor heating. You can retrofit it if you install larger radiators, because normal gas central heating systems run at 70-80 degrees.”

Deeper mines can provide waters with much hotter temperatures and also have the potential to generate electricity, not just heat.

Mr Barron continued: “There's really only two main coal seams what were mined in Clackmannanshire.

“How you engineer the system depends on the geometry of the workings, the height they are at and the spacial distribution. Each one is an individual project.

“What we do at BGS is we build a 3D model of all these mine workings because we have all the data, then the engineers can work out how best to build [injection and extraction] boreholes.

“At the moment – there's extensive mine workings, but we haven't really worked out what the potential is for extraction. But, we have been working with the council and renewable energy consultants.

“We are just trying to tie up where the mine workings are to where the heat demand is or [where] potential new builds are in Clackmannanshire.”

It is unlikely that geothermal could provide heating for the whole county, but it could be a major contributor in reducing carbon emissions, and it is still early days.

There are, however, some risks involved. Mr Barron explained: “You can do modelling and you can work out potentials about how much heat you might get.

“But until you actually drill the boreholes and run the system you never really know because it's so complex.

“That's one of the reasons why it hasn't taken off. I know exactly what the costs of a biomass boiler or a gas central heating system are, but with mine workings – it could be this, it could be that. There is a risk in it.”

It has not always been a legal requirement for mining companies to have maps of all the workings.

Mr Barron added: “There's large areas in central Scotland where we know there are really shallow old mines, but we don't know exactly where these are located. Quite often people drilling boreholes are drilling into mine workings.

“That is a problem and these shallow mine workings have not so much potential for geothermal energy, they are more of a risk that you have to pass through. It's really the deeper workings and the more recent mine workings that we target [for geothermal energy].”

It is understood that it could take up to around a year to finalise a business plan before a demonstrative project could get underway.