Wales has a long history of coal mining and the country was key in firing up the industrial revolution. Once abandoned, it left Wales with one of the longest legacy carbon footprints of any country in the world.
A new project aims to pay back some of this ‘carbon debt’. Many of the mines have long since filled with water after the pumps were turned off, and this now offers an energy resource that the Welsh Government hopes to tap.
This mine water is warmed by the Earth’s core. Depending on depth, temperatures typically range from 12.5C at 100 metres to almost 30C at 800 metres. In the former coalfields of Flintshire and Wrexham, this offers an opportunity.
“With heating accounting for 50% of energy use in the Wales, mine water heat could improve the sustainability of the places where we live and work,” said Ken Skates, cabinet secretary for the economy, transport and North Wales. Cardiff has now released a scoping report into possible sites where this energy can be harnessed.
Drawn up by the Coal Authority, it assessed potential sites in 11 local authorities and categorised them into “good”, “possible” and “challenging”. Below are the evaluations for Wrexham and Flintshire, the others being in South Wales.
Wrexham
Coal mining has taken place in the Wrexham Council area since at least the 16th century. The last mine to close was Bersham in 1986. The presence of numerous gravity-fed surface discharges’ suggests most mines are now flooded.
Up to 12 individual coal seams were worked in the area. In the 1970s and 1980s, collieries were often linked together underground to form “complexes” – this improved efficiency by making use of common surface facilities. These underground connections make Wrexham a good case for mine water extraction. Sign up now for the latest news on the North Wales Live Whatsapp community
Good extraction opportunities
Generally, the area to the west of Wrexham City is the most favourable. Here, mine workings are mostly in multiple seams by the B5102 and B5097 roads to the west of the A483. As these lie at depths of less than 300m, they will be cheaper to drill.
Wrexham Maelor Hospital lies near this area, offering a potential recipient of warm mine water. Main settlement areas also align well with this corridor, including Brymbo, Brynteg, Bersham, Rhosrhedyn, Pentre Bach and Stansty. “Further opportunities are also likely at Rhosllannerchrugog, Plas Madoc and Rhosymedre,” added the Coal Authority.
Possible schemes
Opportunities lie to the south west of Wrexham county following the route of the A483, specifically where it intersects with the B5426. However, as this is a mainly rural area the development potential is limited, as having large customer numbers close to boreholes make schemes more viable. Future housing schemes and other developments may change this perspective.
Challenging sites
The area northeast of Wrexham, including Llay, Pandy, Gresford, Little Acton Borras and Rhosnesni, offers significant potential for mine water heat. However, the mines are more than 500 m deep – the deepest workings around Llay approach depths of almost 1,000 metres.
Another problem is that these mines are single-seam workings. “While mine water heat schemes may be technically possible here, they are unlikely to be commercially viable due to high drilling costs,” said the Coal Authority.
Flintshire
Half a millennia of coal mining in Flintshire came to an end with the closure of the Point of Ayr in 1996. The colliery’s workings were flooded from the sea and the Coal Authority said the status of this sea connection is unknown.
Large areas of Flintshire contain coal mines but many were relatively shallow and occurred in small localised areas. As seams were often closer to the surface and easier to extract, coal has been mined in the county since at least the 16th century and probably much longer.
Up to 21 individual coal seams were worked to varying extents in the county. Some were connected, mainly in north Flintshire, where the deepest workings occurred, going down to 500 metres. Some of the county’s mines were worked at depths of less than 30 metres below the surface. It’s thought some mines have not yet been topped up with water through reflooding.
Good extraction opportunities
Although several good areas have been identified across much of Flintshire, their viability is questionable. The age, nature and location of the workings will make integration into a potential heat network difficult.
“Good coastal opportunities include Talacre, Mostyn and Bagillt,” said the Coal Authority. “But these residential areas are likely to be too small to generate the number of users required for a district scheme.” However the report added there may be sufficient industrial demand in Mostyn to make a scheme viable.
This leaves built-up areas around Buckley, Little Mountain, Burntwood Pentre and Mold as the best candidate sites. Another is the area between Ewloe Green and Ewloe. There is also a good opportunity west of Flint centred around the Red Wood area.
Possible schemes
Two reasonable areas lie south of Northop Hall but these are unlikely to ever be developed as they run beneath the A55 or A494. The same applies to an area beneath the A548 north east of Flint.
Possible areas include those around Buckley Mountain and Burntwood Pentre. There is an isolated area south east of Nercwys centred on The Poultry Court, a business that may be able to use mine water to decarbonise and save energy costs.
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The Coal Authority added: “The area to the north west of Greenfield represents an area of good-to-possible opportunity. But this is a combination of coastal and rural, which will make and future development challenging.
“Other good areas exist but are either situated in rural areas or areas near the coast without any potential heat off-takers. These include rural areas to west of Pontblyddyn centred on Leeswood Green Farm.”
Challenging sites
Small isolated areas around Shotton are unlikely to be viable options. The same applies south of Mold and Padeswood, a rural area where demand is likely to be too low to justify the costs. Sign up for the North Wales Live newsletter sent twice daily to your inbox
The 14 best mine water sites in northeast Wales
These are the most likely places to potentially deploy mine water heat schemes. The Coal Authority suggests they warrant further investigation. All but Hawarden, a surface discharge site, would be borehole schemes if progressed
Wrexham
- Brymbo
- Brynteg
- Rhosllannerchrugog
- Pentre Bach
- Stansty
- Rhosymedre
- Plas Madoc
- Rhosrhedyn
- Bersham
Flintshire
- Hawarden
- Buntwood Pentre
- Buckley
- Ewole Green/Ewole
- Mostyn