| Abstract |
District heating is widely used around the world. District heating systems were built in northern Europe from the beginning of the 20th century. The oil crises in 1970s had huge impact on the growth of district heating systems and the number increased rapidly there after. The production of heat is often based on burning of fossil fuels, such as gas, coal and oil or refuse and wood, solely or in cogeneration. Geothermal energy is a common heat source for district heating in countries where geothermal energy is available and heating of buildings are needed. The energy is often reached by drilling down to the hot area and the water used to carry the heat. The use of geothermal energy for district heating has also long history and its use is increasing. Figure 1 shows the world |