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Renewable energy sources, hydro energy excluded, are giving less than 1% of the globally required energy. In the future this portion should be significantly increased because the number of non-renewable sources is shrinking with time, and their damaging influence has significantly increased in the last couple of decades. Sun delivers 15 thousand times more energy to Earth than humanity really needs in this stage, but despite this some people on Earth are still freezing. This fact shows that we should exploit renewable sources much more and that we do not have to worry about the energy after fossil fuels cease to exist. Development of renewable energy sources (especially from wind, water, sun and biomass) is important because a couple of reasons:
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Renewable energy sources have the major role in decreasing the emission of the carbon dioxide (CO2) into an atmosphere.
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Increased proportion of renewable energy sources enhances energetic viability of the system. It also helps in enhancing energy's delivery security by decreasing dependency of importing energetic raw materials and electrical energy.
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It is expected that renewable energy sources will become economically competitive to conventional energy sources in middle till longer period.
Number of technologies, especially wind energy, small hydroelectric power stations, biomass energy and solar energy are economically competitive. Other technologies are greatly depending on market demands to become economically profitable in relation to the classical energy sources. The main problem concerning new installations is its starting price. This raises the price of gained energy in first couple of years to the level of complete non cost effectiveness in relation to other, commercially more available sources of energy. Large part of energy production from renewable sources is a result of population's ecological consciousness, which despite poor initial economic cost effectiveness installs new installations for "clean" energy production. European Union has strategy that includes doubling the use of renewable energy sources from year 2003 till the year 2010. This means that renewable energy sources maximum quantity would enlarge from at this moment 6% up to a 12% in the year 2010. That plan also includes a series of measures which should encourage private investments in objects that transform renewable energy sources in to a useable energy (mostly electrical energy). Because of the momentary financial crisis which is taking place in largest European countries, it's very likely that this plan won't be fully fulfilled.
Most interesting energy sources ( wind energy, Sun energy, water energy and bio-energy) are separately explained in special chapters, and less interesting renewable sources will be described in following pages. Sun radiation is the major generator to a majority of renewable energy sources, but there's also couple of sources that do not originate from Sun. These are geothermal energy and energy that can be gained from high tide and falling tide.
Geothermal energy
Geothermal energy applies to using the warmth of Earth's inner side. To use that energy, many technologies have been developed, but if we want to keep it a simple as possible, there are two basic ways: direct and indirect. Direct use means using a hot water which bursts (or pumps out) from underground. It can be versatile: from use in baths, for heating the houses or greenhouses, different procedures in industry (milk pasteurization). Indirect use of the geothermal energy means getting the electricity. Here the working method is not that different than the one of classical thermal power plants on coal and crude oil- difference is only the procedure of gaining the water steam. Depending of the water's temperature (or steam) in underground, couples of different technologies were developed. Advantage of this energy source is that is cheap, stable and durable source, there's no need for the fuel, usually has no damaging side effects, beside the water steam, and sometimes some other gases. Weaknesses are coming from the fact that Earth isn't having a large number of areas where hot underground water isn't located to deep, such areas, so called "geothermal zones" are related to the volcanism or lithosphere plate's borders. Since these areas are also often seismic, the installations' building requires increased expenditures. These areas are also often remote to inhabited areas which results in energy transition expenditures, and sometimes are protected by law which prohibits construction works (for instance NP Yellowstone). Leading countries are USA, Philippines, Mexico and Japan.
Tidal Power
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| Most famous tidal power plant is the one on the river Rance delta in France built in 1960 and still functional. |
Tidal power is a consequence of Sun's and Moon's gravity forces. For now, there's no major commercial exploitation of this energy, despite of its big potential. This energy can be gained in places where sea changes are extremely emphasized (for instance some places have difference between high tide and low tide bigger then 10 meters). The principle is quite simple and very similar to the one of the water power plant. On the entrance to some gulf, escarpment is build and when the level of the water rises, water leaks across the turbine in to a gulf. When gulf is filled with the water escarpment is sealed and after the level of the water falls the same principle is being used to direct water out of the gulf. In more simple case water leaks through turbines in only one direction, and in this case turbines are more simplified (unilateral, not bilateral). The biggest problems of this use of energy are vicissitude of tidal power (it is needed to wait the sufficient level of the water to rise enough, or to fall enough) and small number of places suitable for using this energy source. The most famous power plant is the one on the river Rance delta in France (picture) built in 1960 and still functional. Russia has build small power plant near city of Murmansk, Canada in gulf Fundy, China small number of them, but neither one of this countries hasn't made any significant progress. Alternative method of use relates to the location of power plants in sea ravines where due to a canalizing tidal wave, its energy increases, and underwater turbines similar as the ones of the wind power plants would be used as the generator's machinery. Energy of the sea currents is also planned to be used in the same way, but this technology is still in very early phase.
Wave power
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| Principle of using the wave power. You can see from this picture that huge wave's amplitude is needed in order to achieve efficient transformation. |
Wave power is a form of transformed Sun energy which is creating constant winds in some parts of the Earth. These winds are causing constant waving in some areas and in this areas use of its energy is possible. Big problem when using this energy is the fact that power plants should be build on main because waves are too weak near the shore. This significantly increases construction expenditures. Another big problem is also transition of this energy to its users. Current results didn't get far as planed, all is still hanging on the prototypes and demonstration units. This picture shows the principle of transforming wave power in to an electrical energy. According to the picture, wave power first transforms itself in to an air waft, and that wind runs the turbine. Wave’s amplitude must be big in order to make transforming process more efficient.
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