Mine-water geothermal systems are also being explored, utilising the consistent ambient temperature of the earth to raise the temperature of water for heating by circulating it through unused mine tunes. The water will generally require further heating in order to reach a usable temperature. An example is the Glenalmond Street project in Shettleston, which uses a combination of solar and geothermal energy to heat 16 houses. Water in a coal mine below ground level is heated by geothermal energy and maintained at a temperature of about 12 °C (54 °F) throughout the year. The warmed water is raised and passed through a heat pump, boosting the temperature to 55 °C (131 °F), and is then distributed to the houses providing heating to radiators.