Geothermal space heating

The use ofgeothermal resources for space heating dominates the direct use industry, with approximately 37% ofall direct use development. Ofthis, 75% is provided by district heating systems. In fact, the earliest known commercial use of geothermal energy was in Chaudes- Aigues Cantal, France, where a district heating system was built in the 14th century. Today, geothermal district space heating projects can be found in 12 countries and provide some 44,772 TJ ofenergy yearly. Although temperatures in excess of50 C are generally required, resources as low as 40 C can be used in certain circumstances, and, ifgeothermal heat pumps are included, space heating can be a viable alternative to other forms of heating at temperatures well below 10 C. # 2003 CNR. Published by Elsevier Ltd. All rights reserved.