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The Southampton Geothermal District Heating Scheme provides the city with a supply of hot water.
In 1981, a single geothermal well was drilled at a city centre site to a depth of just over 1800m. Near the bottom of the well, a layer of 200-million-year-old sandstone was found to be holding water at 70°C. The sandstone was porous and permeable, which meant that it acted like a giant rigid sponge, drawing in water from the surrounding rocks as it was withdrawn by the power station.
The water is full of dissolved salts; because it is under pressure, it rises to within 100m of the surface unaided. A pump is installed at a depth of 650m to bring the water to the surface so its heat energy can be used. On the surface, the hot water passes through a heat exchanger where its heat energy is transferred to clean water, which is then pumped around a network of underground pipes to a number of public buildings within a 2km radius of the well. The output capacity is 2MW of thermal energy.
Southampton Civic Centre uses heat from a geothermal well: Photo by kind permission of Southampton City Council
