Guide to renewable energy sources: types, uses, details

In these months of inevitable discussion on nuclear energy, we propose a study on the open question of clean and renewable energies. We also recommend you take a look at the site

What is renewable energy? Are considered renewable forms of energy generated from sources which by their intrinsic nature regenerate or are not "finite" in the scale of "human" time and, by extension, the use of which does not affect the natural resources for future generations. While from a purely scientific point this definition is not rigorous, since according to the postulates necessary to define the first law of thermodynamics (for which nothing is created or destroyed), all forms of renewable energy would have to be considered, from a point the social, political, and therefore, it creates the distinction between in use today considered renewable energy sources (sun, wind, etc ...), whose current use does not affect the availability in the future, and non-renewable resources, the which is to have long periods of training are far superior to those of current consumption (particularly fossil fuels such as oil, coal, natural gas), and to be present in reserves not inexhaustible on the human time scale (in particular the isotope 235 uranium, the element most commonly used to produce nuclear energy), are limited in futuro.La classification of the different sources is therefore subject to many factors, not necessarily scientific, effectively creating situations of non-uniformity of opinion among the various stakeholders .

Classification of renewable sources

As already stated, there is no single definition of all the renewable energy sources, existing in different areas different opinions on the inclusion or not of one or more sources in the group of "renewable". According to the reference standard Italian, are considered "renewable": "... the sun, the wind, water, geothermal resources, tides, waves and converting it into electricity plant products or organic and inorganic waste . »

Fall in this field thus:

• Hydropower

or tidal (or tidal)

or wave energy

or energy talassotermica

• Geothermal energy

• Solar energy

or solar thermal and thermodynamic

Solar or photovoltaic

• Wind Energy

• Energy from biomass

or biofuels, gasification

or vegetable oils

or Chips

• Waste to energy

or refuse derived fuel (or "CDR")

or molecular dissociation

A distinction is often made in this context is that between renewable sources "classical" (mainly hydroelectric and geothermal) and renewable sources "new" (also called "NFER"), among which are generally including solar energy, wind power and biomass.

In the production of electricity renewable sources are also classified into "programmable sources" and "non-programmable sources', depending on which can be programmed according to the energy demand or not. According to the definition of the Electricity Services Operator (ESO, also known as ISO) in the first group includes "hydroelectric plants in the tank and basin, municipal solid waste, biomass, plant treated using fossil fuels, fuels or process residues", while in the second group (non-programmable) are "fluent hydroelectric power plants, wind, geothermal, solar, biogas"

Sometimes, in some areas, including energy saving and energy efficiency are considered-by extension - "renewable sources", although strictly speaking these issues are part of the rational use of energy, and not of their production. Some, again, consider these two aspects, related to the use rather than production, within the category of sustainable energy.

The case of incineration

About the incineration of waste, it is noteworthy that only in Italy (in violation of European directives) is considered totally renewable energy produced by incineration (ie incineration) where the EU considers "renewable" only the organic waste (ie waste biodegradable).

Renewable source, for the EU, it means so reproducible from the Sun through photosynthesis and the food chain.

This position is shared by most of the environmental movement, for which it must be discarded from the calculation of the energy produced from municipal solid waste, as these are also produced with fossil raw materials or synthetic products are not biodegradable. The only organic waste would then be considered truly "renewable".

The case of the nuclear

Although "non-fossil", nuclear energy is not traditionally considered renewable because, at least with regard to the nuclear fission energy and the reaction cycle that is based on uranium-235 as fuel (ie, in practice, the cycle almost exclusively used at present), its use is however dependent on limited reserves of materials. Uranium-235 is in fact only 0.7% of the total uranium present in nature, and based on the uranium reserves proven to date it is expected that the current consumption does not remain that for 200 years, according to the ' hypothesis more reductive.

However, have been demonstrated as actually exploitable other cycles of nuclear fission reaction of the type called breeder realized in suitable reactors of the type called fast breeder reactor. In these reaction cycles, the fuel is made from fissile elements not present in nature and therefore artificially synthesized inside the reactor itself from a fertile material whose abundance in nature allows a period of exploitation beyond the time scale human. For example, one of these cycles involves the use of plutonium-239 as a fuel, a fissile element not present in nature and artificially synthesized so far only for the production of nuclear weapons. Plutonium is synthesized inside nuclear reactors starting with the most abundant in nature uranium-238 (which is therefore the fertile material) for absorption of a neutron. In this type of breeder reactors, therefore, is the same reactor that autoproduce its fuel, and for this reason this type of energy would correspond to the definition of renewable energy. However, within the environmental movement there is a strong reluctance to consider the nuclear fission breeder as a renewable energy.

Finally, the nuclear fusion of deuterium and tritium in the cycle, is produced from elements practically inexhaustible in nature, extractable from seawater, and therefore also to be considered renewable energy as defined above. In this case, however, as proof of the high yield of the reaction is given by the practical realization of Nuclear Weapons (the H-bomb]), to date it is technically impossible to build reactors that are able to confine the reaction for exploitation purposes peaceful. And this will remain still for at least 50 years, according to the most optimistic estimates. Therefore appears sterile try to classify this form of energy is not currently available.

According to some studies finally, even geothermal energy would be considered "totally renewable."

Details on renewable sources

Renewables classic

Renewable sources generally called "classical" are those that are exploited for the production of electrical energy from the beginning of the industrial age. Their future use depends on the exploration of potential resources available, particularly in developing countries and demands in relation to the environment and social acceptance.

Among the oldest are certainly hydropower plants, which have the advantage of having long-term (in fact, many of the existing plants have been operating for over 100 years). In addition to hydroelectric plants are clean and have fewer emissions. However it has been found that the emissions are appreciable only if they are associated with shallow basins in hot locations (tropical). In general, many hydroelectric plants produce fewer emissions in their "life cycle" than other types of power generation. Other criticisms directed at large hydroelectric power stations in the basin include the displacement of the inhabitants of the areas where you decide to make the reservoirs required for the collection of water and the release of large amounts of carbon dioxide during construction and flooding of the reserve.

The energy produced, which played a key role during the growth of power grids in the nineteenth and twentieth centuries, is experiencing a resurgence of research in the twenty-first century. The areas with the highest growth in hydroelectric Asian economies are growing rapidly, with China leading the way, but also many other Asian nations are installing hydropower. This growth is driven by rising energy costs - especially for imported energy - and the widespread desire for power generation "at home", clean, renewable and cost effective.

Geothermal plants can operate 24 hours a day, providing an energy base and the world production capacity estimated potential for geothermal power generation is 85 GW for the next 30 years. However, geothermal energy is available only in limited areas of the world, including the United States, Central America, Indonesia, East Africa, the Philippines and Italy. The cost of geothermal energy has dropped dramatically compared to the systems built in the 70s. The generation of heat for the geothermal heating can be competitive in many countries able to produce it, but also in other regions where the resource is at a lower temperature.

New sources of renewable energy

The market for the technologies of the NFER is strong and growing mainly in countries such as Germany, Spain, the United States and Japan. The challenge is to broaden the basis of the market for continued growth in the world. The strategic dissemination in a country not only reduces the cost of technology for local users, but also for those in other countries, contributing to an overall reduction in costs and improved performance.

The solar heating systems are second generation technologies well known and generally consist of solar thermal collectors, a fluid system for transferring heat from the collector to the point of use and a tank or a tank for the storage of heat for later use. Such systems may be used to heat the domestic water, one of the pools or to heat environments. The heat can also be used for industrial applications or as an energy source for other uses, such as cooling devices. In many climate zones a solar heating system can provide a very high percentage (from 50 to 75%) of the energy needed to heat the domestic water.

In the 80s and early 90s, the majority of photovoltaic modules supplied electricity for remote areas only (can not be reached from the mains), but since 1995 about industry efforts have focused significantly on the development of photovoltaic panels integrated into buildings and power plants connected to the grid. Currently the largest photovoltaic power plant in North America is the one at Nellis Air Force Base (central 15 MW). There are proposals to build a solar power station in Victoria in Australia, which would become the largest in the world with a production capacity of 154 MW. Other large photovoltaic power plants, planned or under construction include the powerhouse "Girrasol" (62 MW), and the "Solar Park Waldpolenz" in Germany (40 MW).

Some of the second-generation renewable, such as wind, have a lot of potential and have already reached the low costs of production, comparable with those of other energy sources. At the end of 2006, the worldwide production capacity by wind turbines was 74.223 megawatts and despite currently produces less than 1% of the world, produces about 20% of electricity in Denmark, 9% in Spain and 7% in Germany. [15] [16] However, there is some resistance to the positioning of the turbines in some areas for aesthetic reasons or landscapes. Furthermore, in some cases it may be difficult to integrate wind generation in electricity networks because of '"randomness" of supply provided.

Brazil has one of the largest renewable energy programs in the world, involving production of ethanol from sugar cane, and ethanol now provides 18% of automobile fuel. As a result, together with the exploitation of local deep oil reserves, Brazil, which previously had to import a large amount of oil needed for domestic consumption, recently reached complete self-sufficiency in oil.

Most of the cars used in the U.S. today can use blends of up to 10% ethanol, and engine manufacturers already produce vehicles designed to use mixtures with higher percentages. Ford, Daimler AG and General Motors are among the companies producing cars, trucks and vans "flexible-fuel" (literally "flexible fuel") using mixtures of gasoline and ethanol from pure gasoline up to 85% of ethanol (E85). Since mid-2006 were sold about six million E85-compatible vehicles in the United States.

The technologies that are still under development include advanced biomass gasification, biorefinery technologies, solar thermal power plants, geothermal energy from hot dry rocks (Hot-dry-rock) and the exploitation of the oceans (talassotermic energy, tidal and wave energy). These technologies are not yet fully tested or have a limited marketing. Many are on the horizon and may have potential comparable to other renewable forms of energy, but are still dependent on having to attract adequate investment in RD & D (Research, Development and Demonstration).

According to the IEA, the new bioenergy technologies (biofuels) that are being developed today, especially biorefineries for cellulosic ethanol, could allow biofuels to play a much bigger role in the future than previously thought. [ 21] The cellulose ethanol can be obtained from organic matter of plants composed mainly of cellulose fibers inedible which form the stems and branches. The crop residues (such as corn stalks, wheat straw and rice), wood waste and municipal solid waste are potential sources of cellulosic biomass. Crops dedicated to energy production, such as Panicum virgatum, are promising sources of cellulose that can be sustainably produced in many regions of the United States.

The solar thermal power plants have been put into commercially successful in California in the late '80s, including the largest solar power plant of any kind, the power of the Solar Energy Generating Systems 350 MW total. The Nevada Solar One is another center recently opened by 64 MW. Other proposals parabolic solar power plants are the two 50 MW in Spain and a 100 MW power plant in Israel.

In terms of exploitation of the oceans, another third-generation technologies, Portugal was the first commercial power plant waves in the world, Aguçadora Wave Park, under construction since 2007. The plant will initially use three machines Pelmis P-750 capable of generating 2.25 MW and costs are estimated at around 8.5 million Euros. If it proves a success, another 70 million Euros will be invested before 2009 in another 28 machines to generate 525 MW. Were announced in Scotland in February 2007 funding for a central waves scozzeze by the Government, at a cost of over 4 million pounds, as part of an investment package of £ 13 million for ocean energy in Scotland. The plant will be the largest in the world with a capacity of 3 MW generated by four Pelamis machines.

In 2007, the first facility in the world to the modern conception of Tidal Energy is installed in Strangford Lough in Ireland (though in France a central feature of this type, with barrier, was already in operation in the 60s). The 1.2 megawatt generator submarine, part of the scheme for funding for the environment and renewable energy in Northern Ireland, will take advantage of the fast tidal flow (up to 4 meters per second) in the arm of the sea. Although it is expected that the generator produces enough energy to supply a thousand homes, the turbine will have a minimal environmental impact, as it will be almost completely submerged and the movement of the rotors is not a threat to wildlife because running at a relatively low.

The solar panels that use nanotechnology, which can build circuits from individual silicon molecules, may cost half of traditional photovoltaic cells, according to state executives and investors involved in the development of the products. The Nanosolar has secured investment of over $ 100 million to build a factory for thin films for solar panels. The company's central foresees a production capacity of 430 MWp (megawatt peak) of solar cells per year. Commercial production began and the first panels have been ordered by customers at the end of 2007.

Italian Renewable Energy Production

For a long time (up to about the early 60's) Italian energy production has been largely renewable, thanks in particular to hydroelectric power plants in the Alps and, to a lesser extent, of the Apennines (in addition to smaller quotas relating to geothermal energy in Tuscany). Today, however, due to the increased demand for energy, as well as the nearly exhausted the possibility of new large hydroelectric installations, renewables represent only marginal units of production.

In 2006 Italy produced almost 52.2 TWh of electricity from renewable sources, equivalent to 15.4% of total electricity demand, with 12.05% from hydroelectric sources and the remainder of the sum of geothermal , wind and biomass combustion or waste. With these values, about 90% of renewable energy production is produced by plants called "programmable".

With these values, Italy appears to be the fourth largest producer of electricity from renewable sources in the EU-15, although still far from the targets expected EU, which provide for the production of 22% of energy demand from renewable sources by 2010.

It should be noted, however, that in recent years the Italian renewable energy production has grown very little or remained stable, despite strong growth in wind power (albeit with low percentages), due to a stagnation of the predominant hydropower production, in fact almost reached the saturation of the economically exploitable potential. To this we must add that, as mentioned, Italy in contrast to what happens in the rest of the EU, is the only one to consider the energy produced by renewable energy plants as a whole.

In addition, despite the incentives, Italy must also reckon with legislative delays and adequacy of distribution networks.

In Sicily studies have been conducted and applications on the production of energy from biomass made up of food scraps.

Environmental impact of renewable energy sources

Are sources of energy that can allow a sustainable development without damaging nature and for an indefinite period. Some of these types of energy (in particular solar energy) can be microgenerate, ie produced in small household systems that can meet the energy needs of a single home or small group of homes. This saves the energy that is lost during the distribution of electricity, for example on the power lines, although the latter also involves the need to redefine the structure of the national grid.

It must, however, remember that it is still under discussion the fact that it is actually possible to meet all the current energy needs of the planet with just the potential energy from renewable sources.



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