The renewable Energy is energy by-product of the resources that are regenerative or for all practical purposes cannot be exhausted. For this reason, the renewable sources of energy are fundamentally different from the hydrocarbon, and they do not produce as many gases greenhouses and other contaminants like combustion of hydrocarbon. The traditional uses of the humanity of wind, the water, and solar energy are widespread in countries developed and revealing; but the mass production of the electricity that utilizes the renewable sources of energy has come be more common recently, reflecting the greater threats of the change of the climate, the exhaustion of hydrocarbon, and of the social, environmental risks and politicians of hydrocarbon and to be able nuclear. Consistently, many countries promote renewable energies by stimuli of tax and subsidies.

The renewable energy comprises about 14% of the world energy consumption, but the technical potential is sufficiently large to cover many times the current, and the consumption, several times the projected of energy in 2100. The renewable such as geothermal technologies and water power are often economically competitive without subsidies. Other technologies such as solar power is substantially more costly, although the future costs can diminish to a fraction of present levels.

Three energy sources

The renewable flows of the energy imply the natural phenomena such as the sunlight, the wind, the tides and the geothermal heat. Each one of these sources have extraordinary characteristics that influence how and where they are utilized.

The majority of renewable technologies of energy is directly or indirectly driven by the Sun. The Land-Atmosphere system is in equilibrium in that the heat radiation into space is equal to the incoming solar radiation, the resultant level of energy inside the system of Land-Atmosphere can be described approximately as the Earth's climate. The hydrosphere (water) absorbs a greater fraction of the incoming radiation. The majority of the radiation is absorbed in low latitudes around the equator, but this energy is dissipated around the globe in the form of currents of winds and ocean. The movement of the waves can play a role in the mechanical process to transfer energy between the atmosphere and the ocean by wind stress. Solar energy is also responsible for the distribution of precipitation that is utilized for hydroelectric projects, and for the growth of plants to create biological fuels.

Wind

The air currents can be utilized to run wind turbines and some are capable of producing 5 MW of power. The turbines with the production valued at MW 1.5-3 have come to be very common for commercial use. The production of power via a turbine is a function of the cube of the velocity of wind, so as wind velocity increases, it drives the increases of the production dramatically. Areas where winds are stronger and more constant, places close to the coast and of higher altitude are preferred as locations for windfarms.

Wind power is the faster growing of the renewable technologies of energy. In last decade, the maximum global capacity of 2.500 MW in 1992 had grown to more than 40.000 MW by the end of 2003, in an annual growth rate close to 3 30%. Due to intermittency of resources of wind, the majority of the turbines produced an average of 25% of its maximum power valued.

Globally, the long-term technical potential of wind power is believed to be five times the current production of the global consumption of energy or 40 times the current demand for electricity. This would enable large quantities of land to be utilized for wind turbines, especially in areas with higher wind resources . The resources close to the coast experience mean wind velocities of ~90% greater than that of land, so the resources close to the coast would be able to contribute substantially more energy.

Wind forces near the surface of the Earth vary and thus cannot guarantee the continuous power unless combined with other sources of energy and other systems of storage. Some estimates suggest that 1.000 MW of conventional capacity of wind generation can be depended on for just 333 MW of continuous power. While this perhaps will change as the technology evolves, the advocates have suggested using wind power with other sources of power, or with the energy storage techniques use, with this in mind. It is utilized better in the context of a system that has the significant capacity of the reservesuch as hydro, or load of reserve, such as a desalination plant, to mitigate the economic effects of the changeability of the resource.

The wind power is renewable and does not produce greenhouse gases during its operation, such as carbon dioxide and methane. Studies of birds and windfarms close to the coast in Europe have found that there are very few bird collisions. Various places close to the coastal wind sites in Europe have been in areas utilized extensively by sea birds. The improvements in wind turbine design have helped to reduce the mortality of birds in windfarms around the world. Birds are severely effected by the energy of hydrocarbons; the examples include birds that die due to exposure to oil spills, the loss of the habitat due to acid rain and the elimination of mountaintops through the coal mining industry and of mercury poisoning.

Water

The energy in the water (in the form of energy of motion or temperature differences) can be harnessed and can be utilized. Since water is about a thousand times denser than air it can yield the considerable quantities of energy.

There are many water energy forms:

Hydroelectric energy is a term generally reserved for hydroelectric dams.

Wave power utilizes the energy in waves. The waves generally make large pontoons rise and fall in the water, leaving an area with the height reduced of the wave in the "shadow". The power of the wave now has reached commercialization.

The power of the tide captures energy of the tides in a vertical direction. The tides enter, raise water levels in a basin, and the tides recede. Around low tide, the water in the basin is discharged through a turbine.

Tidal stream power captures energy of the flow of tides, generally utilizing underwater plants that resemble a small wind turbine. Tidal stream demonstration projects exist currently, but the large-scale development requires the additional capital.

Solar

A photovoltaic (PV) module that is composed of multiple PV cells. Two or more interconnected PV modules create an array. In this context, "solar energy" refers to energy that is collected from sunlight. Solar energy can be applied in many ways, including to:

Generate electricity using photovoltaic solar cells.
Generate electricity using concentrated solar power.
Generate electricity by heating trapped air which rotates turbines in a Solar updraft tower.
Heat buildings, directly, through passive solar design.
Heat foodstuffs, through solar ovens.
Heat water or air for domestic hot water and space heating needs using solar-thermal panels.
Heat and cool air through use of solar chimneys.

Biofuel

Plants use photosynthesis to grow and produce biomass. Also known as biomatter, biomass can be used directly as fuel or to produce liquid biofuel. Agriculturally produced biomass fuels, such as biodiesel, ethanol and bagasse (often a by-product of sugar cane cultivation) can be burned in internal combustion engines or boilers. Typically biofuel is burned to release its stored chemical energy. Research into more efficient methods of converting biofuels and other fuels into electricity utilizing fuel cells is an area of very active work.

Liquid biofuel is usually either a bioalcohol such as ethanol or a bio-oil such as biodiesel and straight vegetable oil. Biodiesel can be used in modern diesel vehicles with little or no modification to the engine and can be made from waste and virgin vegetable and animal oil and fats (lipids). Virgin vegetable oils can be used in modified diesel engines. In fact the Diesel engine was originally designed to run on vegetable oil rather than fossil fuel. A major benefit of biodiesel is lower emissions. The use of biodiesel reduces emission of carbon monoxide and other hydrocarbons by 20 to 40%. In some areas corn, cornstalks, sugarbeets, sugar cane, and switchgrasses are grown specifically to produce ethanol (also known as grain alcohol) a liquid which can be used in internal combustion engines and fuel cells. Ethanol is being phased into the current energy infrastructure. E85 is a fuel composed of 85% ethanol and 15% gasoline that is sold to consumers. Biobutanol is being being developed as an alternative to bioethanol.

In the future, there might be bio-synthetic liquid fuel available. It can be produced by the Fischer-Tropsch process, also called Biomass-To-Liquids (BTL).

Solid biomass

Sugar cane residue can be used as a biofuel. Direct use is usually in the form of combustible solids, either wood, the biogenic portion of municipal solid waste or combustible field crops. Field crops may be grown specifically for combustion or may be used for other purposes, and the processed plant waste then used for combustion. Most sorts of biomatter, including dried manure, can actually be burnt to heat water and to drive turbines.

Sugar cane residue, wheat chaff, corn cobs and other plant matter can be, and is, burnt quite successfully. The net Carbon Dioxide emissions that are added to the atmosphere by this process are only from the fossil fuel that is consumed to plant, fertilize, harvest and transport the biomass. Processes to grow perenials such as switchgrass, miscanthus, and willow, field pelletize and co-fire with coal for electricity generation are being studied and appear to be economically viable.[10] Co-firing this cellulosic biomass with coal to make electricity is more effective for reducing carbon dioxide emissions to the atmosphere than using it to make ethanol.

Solid biomass can also be gasified, and used as described in the next section.

Biogas

Biogas can easily be produced from current waste streams, such as: paper production, sugar production, sewage, animal waste and so forth. These various waste streams have to be slurried together and allowed to naturally ferment, producing methane gas. This can be done by converting current sewage plants into biogas plants. When a biogas plant has extracted all the methane it can, the remains are sometimes better suitable as fertilizer than the original biomass.

Alternatively biogas can be produced via advanced waste processing systems such as mechanical biological treatment. These systems recover the recyclable elements of household waste and process the biodegradable fraction in anaerobic digesters.

Renewable natural gas is a biogas which has been upgraded to a quality similar to natural gas. By upgrading the quality to that of natural gas, it becomes possible to distribute the gas to the mass market via gas grid.

Geothermal

Geothermal energy is energy obtained by tapping the heat of the earth itself, usually from kilometers deep into the Earth's crust. It is expensive to build a power station but operating costs are low resulting in low energy costs for suitable sites. Ultimately, this energy derives from the radioactive decay in the core of the Earth, which heats the Earth from the inside out.

Three types of power plants are used to generate power from geothermal energy: dry steam, flash, and binary. Dry steam plants take steam out of fractures in the ground and use it to directly drive a turbine that spins a generator. Flash plants take hot water, usually at temperatures over 200 °C, out of the ground, and allows it to boil as it rises to the surface then separates the steam phase in steam/water separators and then runs the steam through a turbine. In binary plants, the hot water flows through heat exchangers, boiling an organic fluid that spins the turbine. The condensed steam and remaining geothermal fluid from all three types of plants are injected back into the hot rock to pick up more heat.

Although geothermal sites are capable of providing heat for many decades, eventually they are depleted as the ground cools. The government of Iceland states It should be stressed that the geothermal resource is not strictly renewable in the same sense as the hydro resource. It estimates that Iceland's geothermal energy could provide 1700 MW for over 100 years, compared to the current production of 140 MW.

The geothermal energy from the core of the Earth is closer to the surface in some areas than in others. Where hot underground steam or water can be tapped and brought to the surface it may be used to generate electricity. Such geothermal power sources exist in certain geologically unstable parts of the world such as Iceland, New Zealand, United States, the Philippines and Italy. The two most prominent areas for this in the United States are in the Yellowstone basin and in northern California. Iceland produced 170 MW geothermal power and heated 86% of all houses in the year 2000 through geothermal energy. Some 8000 MW of capacity is operational in total.

There is also the potential to generate geothermal energy from Hot Dry Rocks. Holes at least 3km deep are drilled into the earth. Some of these holes pump water into the earth, while other holes pump hot water out. The heat resource consists of hot underground radiogenic granite rocks, which heat up when there is enough sediment between the rock and the earths surface. Several companies in Australia are exploring this technology.

New generation of solar thermal plants

Solar Two, in California's Mojave desert, a concentrating solar thermal power plant. Construction of the largest solar thermal power plant to be built in 15 years, in Boulder City, Nevada, is nearly complete.

The 64MW Nevada Solar One power plant will generate enough power to meet the electricity needs of about 40,000 households and follows in the steps of the 354MW SEGS solar thermal power plants located in California’s Mojave Desert. While California’s solar plants have generated billions of kilowatt hours of electricity for the past two decades, the Nevada Solar One plant will use new technologies to capture even more energy from the sun.

Offered by Lloyd Goff
Phone: (303) 671-5340
Email: lloydgoff@hotmail.com

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