Geothermal is a Renewable Energy
Naturally replenished energy on a human’s time scale is renewable energy. Waves, tides, wind, rain, geothermal heat and sunlight are sources of renewable energy. Renewable energy as an energy source in the world has replaced conventional fuels in generation of electricity and space or hot water heating. Renewable energy sources currently supply 16% of the word’s energy.Global warming and climatic change concerns together with high prices of oil as well as increase in the governments support are driving up legislations on renewable energy (Florence, 2000).
According to John (1998) thermal energy stored and generated in the earth is called geothermal energy. 20% of the earth’s geothermal energy comes from originally stored energy in the earth during earth formation. 80% of the energy is sourced from minerals break down through radioactive decaying process. Geothermal gradient defined as the temperature difference between the surface and the core helps in upward movement of heat energy to the surface from the core. Geothermal energy is regarded as a renewable source of energy because the heat content that is used in power generation is only a fraction of the total internal heat content of the earth and that geothermal power generation cannot exhaust it.
Origin of Geothermal Heat
Heat within the earth’s interior is as a result of two sources. The first is the residual heat that originated from the earth’s formation, which accounts for 20% of the earth’s heat content. The second source is heat from break down of minerals containing radioactive elements which accounts for 80% of earth’s heat content.Heat from geothermal energy may come from as deep as 6400km. The core’ temperature is as high as 50000 C. Heat is conducted to the surrounding rock from the core. Extremely high heat and pressure makes the surrounding rocks unstable and some melt. Rock melt is called magma and since the melt is lighter it moves upward. Water and other rocks are heated by the melt causing a rise in temperature of up to 3710 C. John (1998) views that hot springs resulting from geothermal energy since Paleolithic period have been in use for bathing and for space heating. Currently heat energy from geothermal energy is an important source of electricity. Geothermal energy comes in two forms; liquid dominated form and vapor dominated forms. Superheated steam is offered by vapor dominated sites whose range of temperature is between 2400 C and 3000C.
History of Geothermal Power
High demand for electricity in the 20th century resulted to focus on alternative sources of power. One of the focuses was directed towards geothermal power as a source of energy. On 4th July 1904, the first geothermal power generator was tested by Prince Piero Ginori Conti. At the same location, extraction of geothermal acid began and four light bulbs were successfully lit. The first commercial plant in the world for generating geothermal power was built there. Tycooly International (2011) indicates that this plant was the only producer of industrial geothermal power in the world until 1958 when another plant was built in New Zealand.
Future of geothermal energy
According to the International Geothermal Association (IGA) 24 nations have 10,715 megawatts of geothermal power online. 67,246 GWh of electricity were expected to be generated by 2010. Since 2005, this was to be a 20% rise in online geothermal power. IGA claims that a growth of up to 18,500 megawatts is expected by 2015. This projection is as a result of the numerous geothermal power projects currently being considered especially in regions that were previously perceived to possess little resources that are exploitable. TycoolyInternational (2011) observes that United States is the world’s leading producer of geothermal electricity. Its 77 power plants generated 3,086 megawatts of power in 2010.
Geothermal Technological Development
Though geothermal power historically has been constrained in regions close to tectonic boundaries, it is reliable, cost effective, environmentally friendly and sustainable. Current advances in technology have resulted in expansion of the size and range of resources that are viable. Florence (2000) argues that home heating is one of the beneficiaries of the expansion. The expansion opened potentials for spread in exploitation. Greenhouse gases held deep in the earth are released by geothermal wells. These emissions in comparison with fossil fuel’s emissions have lower energy units. This makes geothermal power a potential energy source for mitigating global warming in case it is deployed widely as a replacement of fossil fuels.
John (1998) points out that cheap energy from geothermal power can directly assist in reduction of poverty by providing energy required for employment and business creation. Geothermal energy technology can directly contribute to poverty alleviation by providing lighting, cooking and space heating energy. Energy from this source will also enhance education since schools will have power supply.
State of Geothermal power
Though the geothermal energy resources in the earth are enough to satisfy the energy needs of humans, profitably exploitable energy is a small fraction. Drupady, Ira Martina, Sovacool and Benjamin (2012) think that exploration and drilling for deeply seated resources needs a lot of money. Interest rates, energy prices, subsidies and technology are important factors that will determine geothermal power’s future. Basing on EWEB (pilot programs research body), a research on people’s regard to the Green Power Program and indicated that people were ready to part with more money for renewable energy sources like geothermal. In the past twenty years, a 25% reduction in the production of geothermal power has been experienced due to the government’s help in research as well as the geothermal industry’s experience. In 2001 the cost of geothermal energy per kilowatt was between 2 and 10 US cents.
Enhanced Geothermal Systems
In Enhanced Geothermal System (EGS), water is actively injected into wells so that it is heated and later on pumped out. The injected water has high pressure so that it can widen prevailing rock fractures. Expanding the fractures is aimed at enabling free flow of water in and out. Techniques used in gas and oil extraction helped in development of enhanced geothermal systems techniques. In this technique chemicals that are toxic are never used and the deepness of the geological formations minimizes chances of damaging the environment.
Economical Aspect of Geothermal Energy
Drupady, Ira Martina, Sovacool and Benjamin (2012) note that except for pumps, fuel is not a requirement in generation of geothermal power. This makes it immune to fluctuations to fuel costs. But there are significant capital costs in power generation. Drupady, Ira Martina, Sovacool and Benjamin (2012) indicate that more than half of the costs are accounted for in the drilling process and significant risks are encountered when exploring for deep resources.
Drupady, Ira Martina, Sovacool and Benjamin (2012), note that mixtures of gases are carried by fluids flowing to the surface from deep within the earth. These gases include; carbon dioxide, methane, ammonia and hydrogen sulfide. If these gases are released, they cause noxious smell, acid rain and global warming. Current geothermal electricity producing plants produce about 122kgs of carbon dioxide on every megawatt-hour of electric power. This represents a small fraction of what fossil fuel plants emit. Geothermal plants experiencing high levels of volatile chemicals and acids are always equipped with systems that control emissions to minimize the exhaust.
In addition to that, toxic elements like antimony, arsenic, boron and mercury may be in the hot water that is released from geothermal sources. When water cools, the chemicals precipitate and if released can cause environmental damage. Injection of geothermal fluids that have cooled into the earth for replenishment helps in reducing risks of the toxic elements since most of them go back into the earth with the injected water.
At a rate of 44.2 terawatt through conduction, internal thermal energy of the earth flows on to the surface. Apart from the original heat energy stored in the earth during formation, radioactive break down of minerals replenish this energy at a rate of 30TW. Though a higher percentage of this energy cannot be recovered, it is more than twice current human energy consumption. The earth’s input and output of energy is not in equilibrium, leading to a slow reduction in its internal heat content. But human extraction of earth’s heat is a minute fraction and does not accelerate cool down.
Geothermal power is classified as a renewable energy source because the heat extracted is lower than the heat content of the earth. The internal heat content of the earth is about 1031 joules. Apart from being renewable, geothermal power is sustainable because of its capability to sustain the intricate ecosystems of the earth. Use of geothermal energy sources by the current generations does not endanger the future generation’s ability to utilize their own resources to the same level of present generation use. Geothermal energy has low emissions, thus is regarded as a perfect energy source to assist in global warming mitigation.
Despite the fact that geothermal power is a sustainable energy source in the whole world, close monitoring of the extraction is needed to prevent local depletion. Individual wells for several decades have led to reduction of the earth’s heat content and water levels resulting in new equilibrium of natural flows being reached. Gysers,Larderello and Wairakei which are the oldest sites have experienced a drop in their outputs due to local depletion. Replenishment of heat and water was slower than their extraction rates, thus the reduction in output. Reducing production and reinjection of water into wells could reinstate their potential. This mitigation strategy is necessary if energy sources from geothermal power are to be sustained.
Renewable energy is highly recommended for countries that are developing. In remote and rural areas, distribution and transmission of fossil fuel generated energy is expensive and difficult. A viable alternative is to produce renewable energy locally. More investment should be directed into generation of geothermal energy given that it does not cause environmental degradation. In addition to that, heat energy reserves deep within the earth more than double the current human consumption, thus should be exploited.
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