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The Geothermal Energy Cycle |
Science Institute, University of Iceland, Reykjavík, Iceland stefanar{at}raunvis.hi.is
Presently geothermal energy accounts for 0.25% of the annual world-wide energy consumption. Extraction of heat from geothermal reservoirs involves drillings. Exploitation of geothermal resources is generally far less a cause of pollution than fossifuel combustion, making it preferable as a source for power and heat. Geothermal energy exploitation has locally some adverse environmental effects. Possible effects include scenery spoliation, drying out of hot springs, soil erosion, noise pollution, and chemical pollution of the atmosphere and of surface- and groundwaters. Exploitation may enhance seismic activity and cause land subsidence. The development of geothermal fields must sometimes be evaluated against the value of tourism. Various measures have been successfully employed to reduce the adverse environmental effects of geothermal energy utilization. The most important ones are directional drilling and injection of spent geothermal fluid. Future use of geothermal resources should specifically consider further use of geothermal heat pumps, extraction of chemicals from spent geothermal fluids to yield useful byproducts, integrated multiple use of high-temperature systems, and furthering of technology to develop hot-dry-rock systems including those occurring in the roots of active volcanic geothermal systems.
