Geothermal In everyday life, people often come to make use of different types of energy sources for their needs. Such traditional energy sources as coal, wood, oil, and gas bring to work fuel burning power plants that produce...
... is characteristic for vapor-dominated systems (1977, p.7-5). Whereas, the main content of water-dominated system is water (Dickson & Fanelli, 1995, p.16). It is again pointed out by The Solar Energy Institute (1981, p. 73), that another high temperature underground structure, carrying almost no water and steam, from which energy can be extracted is called “Hot-Dry Rock”. Utilization of geothermal energy on the power plants is a cheap and environmentally safe way of producing electricity. Generally, power plants use either hot steam or low enthalpy fluids to generate electricity. First of all, a vapor with temperatures higher than 473 oK is used to run turbines producing electricity in Dry Steam and Flash type power plants (Albu et al., 1997, p.41). Both of the two types of plants discussed above use a vapor for their production. According to Nemzer, M. L., Carter and Nemzer, M. P., in a Dry Steam Plant, thermal a vapor, extracted from geothermal well, is used to turn the turbines of generator (2000). Another type, add Nemzer, M. L. et al., where liquid with the help of big pressure drop, is converted to vapor, is called Flash Steam Plant (2000). On the other hand, to produce electricity from geothermal liquids, a binary fluid technology has been worked out which drives hot thermal water through the boiler with another liquid that evaporates, and is directly used for electricity production (Dickson & Fanelli, 1995, p.46; Nemzer, M. L. et al., 2000). Therefore, Dry Steam and Binary liquid are the two technologies commonly used in generation of electricity. Capacity of reservoir and costs of production are important for economical considerations in production of electricity. Firstly, regarding the fact that supply is limited, it should be provided Geothermal 6 that reservoir has sufficient capacity to keep a plant in run economically (Dickson & Fanelli, 1995, p.57; Albu et al. 1997, p.180). Secondly, since there is no need for any additional installations like those on fuel burning plants, and due to the fact that financial expenses correlates only with service of working units it is very economical to run a plant working on geothermal energy (Dickson & Fanelli, 1995, p.16; Bowen & Grouht, 1977, p.7-10). To sum up, geothermal energy is thought to be the cheapest fuel for electricity production. Water disposal and polluting gas releases, performed during the production of electricity, only in minor cases can damage environment. The first one, water pollution, is mainly related with waste release of thermal waters which can be successfully cleaned out by re-injection (Brophy, 1996, p.368). How it is reported by The Solar Energy Institute thermal waters usually bear some chemical compounds that can harm the environment (1981, p. 77).The release of big quantities of wastewater must be solved anyway. Pollution caused by wastewater can be successfully avoided by its re-injection into another well (Brophy, 1996, p.372). Beside this, in addition that no smoke or ash is produced during the utilization of geothermal energy, air pollution caused by power plants is insignificant in comparison with any of plants using fossil fuel (Bowen & Grouht, 1977, p. 7-11). Utilization, economical perspective and environmental problems, are important issues of space heating using geothermal energy. First of all, to use geothermal resources for space heating, transportation and residencial heating system have been developed. Also, it has been revealed that not all of geothermal fluids can be used for space heating. In residential heating systems thermal water of low-to-medium temperatures is used (Nemzer, M. L. et al. , 2000). Applications of geothermal energy for space heating is very popular in some countries. For Geothermal 7 example, Iceland is the biggest consumer of geothermal energy, used for heating of districts and residential areas (Fridleifsson, 2001, p. 305). According to Lund (1996, p.406) in heating systems, thermal water is distributed to heat exchangers heating districts and residential areas. Usually, the extraction site of thermal waters, to be utilized for space heating, are found up to 60 kilometers from the residential area. Considering this, Dickson and Fanelli (1995, pp.85-86) point that a pipeline transportation is required to supply a city with energy for heating. Economical considerations of space heating are mostly related with long-term development and ca...