Therefore, alternative, low-carbon sources of energy are urgently needed for the world to be able to reduce CO2 emissions and limit global warming temperature rises as well as to increase energy security and eliminate fuel poverty.
Coalmines are just the place to help with this, despite their ‘dirty’ past. They can provide a low carbon alternative for heat production, and here is how.
Heat beneath our feet
There are vast amounts of energy stored in the Earth beneath our feet, which are ultimately provided from two sources: the earth and the sun. Decay of radioactive elements in the Earth’s core provides a constant supply of heat within the earth that dissipates up to the crust. As a result, the deeper we drill into the earth the warmer it gets, with temperatures rising by about 2.5°C for every 100m of depth.
At the same time, the insulating effect of the shallow subsurface is able to store heat from sunlight as well as that lost to the subsurface from the basements of buildings and from other subsurface infrastructure in cities, such as sewers or tunnels . This heat resource is typically distributed by natural groundwater systems and through man-made structures such as the abandoned coal-mines that underlie many of the UK’s cities and towns.
Abandoned coal mines comprise networks of flooded voids with water flowing at depths of a few tens of metres to several hundred of metres below the surface. Even in the shallower mines, temperatures of mine water are elevated, typically around 12-16°C and often higher, especially where mines are deep.
It is this resource that can be exploited for space heating through use of a simple, but ingenious piece of technology: Ground Source Heat Pump systems. These systems take the energy from the thermally-enhanced mine water and upgrade it to higher temperatures, e.g., around 40-50°C, for use in domestic heating.
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