Given the scale of fuel poverty, the time is ripe to reap the benefits of geothermal heat generated by old coal mines. It’s ironic and perhaps paradoxical to suggest that a solution to the fuel poverty crisis could come from the most polluting, black and dirty fossil fuel which we, as a nation, have worked so hard to remove from our energy mix. This effort has been so effective that the UK power generation had its first coal-free day last April. To date, the focus on geothermal energy in the UK has concentrated on areas like the granites of the Cairngorms and Cornwall because they have a higher geo-thermal gradient. While it’s evident these areas can provide heat locally, industrial-scale supply to the people that need it most is impractical because of the difficulty of storage and transportation to centres of population. But a different kind of geothermal heat source could provide an answer: renewable energy from the most unlikely of sources. A major benefit of coalfields is that most are close to and often directly beneath large conurbations. Although they are not going to be as productive as areas marked by volcanic activity, like Iceland or Hawaii, they could provide enough heat to serve the needs of the stressed communities where fuel poverty hits hardest. Coal mine geology is also highly favourable and, unlike solid rocks where natural porosity, permeability or fracture patterns dictates flow, water can pass through a pit’s trellised network of shafts more easily since they are akin to fluid ‘su per highways’. The process by which heat can be extracted is similar to that used by a fridge. The warm water from the mine is moved into a store in which a refrigerant can extract the heat and convert it to a gas. The gas passes through a compressor which heats it to around 50C to warm the water in a tank. This then supplies warmth to the property. The compressor does use up some electricity but is hugely efficient, giving back around four times more energy than is needed to power it. The cooled water extracted from the mine, the gas needed to heat the water tank and the hot water used to heat the house can all be used again in the same process. Importantly, the system can be reversed and a building may be cooled during summer months. Small pilot schemes are already working to supply heat from coal mining areas to a housing estate in Rutherglen and a swimming pool in Stanley, County Durham. The Scottish Government’s Geothermal Energy Challenge Fund is supportin g studies at Fortissat, North Lanarkshire, Polkemmet in West Lothian and Grangemouth in Stirlingshire. In addition, a sedimentary aquifer project is being investigated at the site of an old paper mill at Guardbridge near St Andrews and a large-scale district heating network is serving a low-carbon development in Kilmarnock. While the Rutherglen housing scheme demonstrates that old mine workings can supply heat locally, the question remains – can heat supply be replicated on a scale with a positive impact on social well-being? A large research site is being developed in the Clyde Gateway, an area of urban regeneration in the east end of Glasgow. Funded through the Department of Business, Energy & Industrial Strategy (BEIS), commissioned by the Natural Environment Research Council (NERC) and delivered by the British Geological Survey (BGS), the UK Geoenergy Observatories project will assess the feasibility of heat sources from abandoned mine workings. The Clyde Gatew ay lies above former coal mines in which the main seams occur at depths of up to 300m below the surface and at an ambient temperature of around 15C.
Scotsman 16th Oct 2018 read more »