Electricity is produced by geothermal in 24 countries, five of which obtain 15-22% of their national electricity production from geothermal energy. Direct application of geothermal energy (for heating, bathing etc.) has been reported by 72 countries. By the end of 2004, the worldwide use of geothermal energy was 57 TWh/yr of electricity and 76 TWh/yr for direct use. Ten developing countries are among the top fifteen countries in geothermal electricity production. Six developing countries are among the top fifteen countries reporting direct use. China is at the top of the latter list. Geothermal energy is available day and night every day of the year and can thus serve as a supplement to energy sources which are only available intermittently. Scenarios for future development show only a moderate increase in traditional direct use applications of geothermal resources, but an exponential increase is foreseen in the heat pump sector, as geothermal heat pumps can be used for heating and/or cooling in most parts of the world. It is considered possible to increase the world installed capacity for direct use of geothermal resources from about 60 GWth in 2010 to about 800 GWth in 2050 (thereof 90% with heat pumps). The mitigation potential would be of the order of 300 million tonnes CO2/yr in 2050. The mitigation potential would, however, be much higher if the electricity for the heat pumps would be produced by renewable energy sources. The CO2 emission from lowtemperature geothermal water is negligible or in the order of 0-1 g CO2/kWh depending on the carbonate content of the water. According to the scenarios, it is considered possible to increase the installed world geothermal electricity capacity from the current 10 GWe to 70 GWe with present technology, and to 140 GWe with enhanced technology. Enhanced Geothermal Systems, which are still at the experimental level, have an enormous potential for primary energy recovery using new heat-exploitation technology to extract and utilise the Earth's stored thermal energy. An installed capacity of 140 GWe and a production of 1,100 TWh/yr by geothermal in 2050 would mitigate about 500 million tonnes CO2/year if substituting natural gas and about 1,000 million tonnes CO2/yr if substituting coal.
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