Mine water geothermal energy

abandoned mines as a green energy source

Abstract

Abandoned mines offer an opportunity to provide renewable energy. Due to almost constant temperatures all year round and the large rock surfacing as heat-transferring surfaces, mine water is ideal for heating and cooling. At sites where water still has to be pumped upwards after mining has ended this water can still be used for heating or cooling supply of industry or districts e.g. in the German Ruhr area. This offers a positive additional effect of the eternal task for old mining areas. In North America and Europe in particular, a number of pilot plants have already been commissioned. These existing and planned mine water geothermal plants worldwide were studied as part of a literature search. The five largest ones have a maximum heating load of about 0.9 to 11 MW. The construction of further plants often stumbles due to the fact that mine water competes with fossil fuels e.g. natural gas or fuel oil. This is compared under economic and ecological criteria within this paper. As a result, mine water geothermal energy is cheaper to operate than fossil fuels such as oil or gas and labour costs below 6ct/kWh are possible. From an ecological point of view, CO2 emissions are reduced by at least 56 % compared to fossil fuels. One important technical risk for mine water plants is the fouling which must be taken into account: impurities in the mine water can reduce the heat transfer in the heat exchanger, which reduces the efficiency of the plant.