Abandoned UK Coal Mines Could Be Turned Into Geothermal Heating System
The UK has around 23000 abandoned coal mines across it. These coal mines are situated underneath about a quarter of the nation’s built up environment. These currently abandoned mines however could come into use. The former mines have been flooded over the years and are therefore filling with water. This water is slowly being heated by the geothermal energy which is radiated from the core of the Earth. If there was some way that this heated water could be extracted, scientists believe that the water could produce enough geothermal energy to meet the demand for heating in the UK for the next 100 years.
Researchers at Durham University, through the BritGeothermal Research Partnership are the experts who believe this and are now working on a way to extract the potential heat. At this moment in time, most households in the UK are heated by gas. However, when gas is burned it produces carbon which is not good for climate change but also over half the gas used in the UK for heating is imported and therefore is not the most secure resource to be using. The suggested mine energy system would work by using the water that has been warmed from the core of the Earth and extracting it to pass through a heat exchanger system on the surface. The heat exchanger would then be used to exchange the heat from the water under the earth to another fluid, brine for example, to then circulate around households to heat them. Then the water from underground will be sent back down there to be reheated.
An assistant professor at Durham University, Dr Charlotte Adams, has stated that using these proposed mine energy systems has the potential to massively reduce the UK’s total carbon emissions. However, the mine energy system is not carbon neutral. Water in most of the mines is not at a hot enough temperature to use straight away, and therefore a heat pump which is powered by electricity has to be used so that the temperatures are hot enough. Researchers have said that for about every kilowatt of energy used to power the pump about 4 kilowatts of heat would be produced. Dr Adams went on to say that even though these systems would not be carbon zero, they are low carbon. And as the grid gets greener due to more renewable energy sources then the carbon content of using the heating pump will drop with time. It is estimated that swapping a standard domestic household boiler for a heat pump would reduce carbon emissions by around 75%.
This problem can be avoided by drilling deeper into the geothermal wells. The deeper they drill the higher the temperatures would be, however drilling deeper is a lot riskier. It is not known how much water there is at the deeper depths meaning there is the potential for there to not be enough water to use. Using the mine energy system at least the scientists and engineers know that there is an abundance of water to use.
Around the world there are 30 sites which already sue the mine energy system technology, whereas in the UK there is currently just the one commercially sized project. This is located in Gateshead where the geothermal energy heats the warehouse of a wine supplier. For this technology to become more widespread, the infrastructure of the heat network would need to be updated and most homes would have to have their gas boilers replaced with heat pumps and heat exchangers.