Geothermal energy currently provides a stable and environmentally attractive heat source for approximately 20 district heating (DH) systems in the United States. The use of this resource eliminates nearly 100% of the conventional fuel consumption (and, hence, the emissions) of the loads served by these systems. As a result, geothermal DH systems can rightfully claim the title of the most fuel-efficient DH systems in operation today. The cost of producing heat from a geothermal resource (including capitalisation of the production facility and cost for pumping) amounts to an average of 1 US dollar per million Btu (0.0034 dollar/kWh). Briefly presents the historic development and current status, and design, of geothermal district heating systems (GDH). Presents environmental considerations in GDH design. States that the major challenge for geothermal systems is proper management of the producing aquifer. Many systems are moving toward injection of the geothermal fluids to ensure long-term production.

KEYWORDS: year 1996, geothermal energy, district heating, environment, discharging, waste water, aquifers