Low-enthalpy geothermal energy resources from groundwater in fluvioglacial gravels of buried valleys

Low-enthalpy geothermal energy can be generated from groundwater in gravels infilling buried valleys formed during the Pleistocene glaciation, when the sea level was significantly lower than at present. Where buried valleys underlie floodplains of present-day rivers, flowing through major cities, a ‘heat island’ effect can generate slightly enhanced temperatures in shallow groundwater. This groundwater can be utilised for space heating buildings by passing it through a heat pump, and the chilled water then used as a heat exchanger to satisfy cooling requirements of the building. For flow rates of 20 l s−1, and a temperature reduction of 8 °C in the heat pump, a 672 kW heating resource can be generated, sufficient to heat buildings of 11,000 m2 floor area. A cooling resource of 336 kW is also available. Potentially, this geothermal resource could be utilised without the ‘heat island’ effect. Cost of the development is minimal and long-term economic benefits are significant.