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  Power Sources, Physics tutorial

Power Sources-Sources of Electrical Energy:

Electrical energy takes place naturally, but rarely in forms which can be used. For example, though energy dissipated as lightning exceeds world's demand for electricity by large factor, lightning has not been put to practical use because of unpredictability and other problems. Usually, practical electric-power-generating systems convert mechanical energy of moving parts in electrical energy (e.g. generator). While systems which operate without mechanical step do exist, they are at present either extremely inefficient or expensive due to a dependence on elaborate technology. While some electric plants derive mechanical energy from moving water (hydroelectric power), vast majority derive it from heat engines in which working substance is steam. Steam is produced with heat from combustion of fossil fuels or from nuclear fission. These energy resources fall in two main categories, frequently known as renewable and non- renewable energy resources. Each of the resources can be utilized as a source to generate electricity that is a very helpful way of transferring energy from one place to another for example to home or to industry.

Steams as Energy Source:

The conversion of mechanical energy to electrical energy can be accomplished with the efficiency of about 80%. In hydroelectric plant, losses occur in turbines, bearings, penstocks, and generators. Basic limitations of thermodynamics fix maximum efficiency obtainable in converting heat to electrical energy. Necessity of limiting temperature to safe levels also helps to keep efficiency down to approx 41% for fossil-fuel plant. Most nuclear plants use low- pressure, low-temperature steam operation, and have even lower efficiency of approx 30%. Nuclear plants have been able to attain efficiency up to 40% with liquid-metal cooling. It is thought that by using magneto hydrodynamic topping generators in conjunction with normal steam turbines, efficiency of conventional plants can be increased to close to 50%. These devices remove the restrictions imposed by blade structure of turbines by using steam or gasses generated by combustion as working fluid.

Environmental Concerns:

The heat generated by the electric-power plant which is not eventually converted in electrical energy is known as waste heat. Environmental impact of this waste is potentially catastrophic, particularly when, as is frequently case, the heat is absorbed by streams or other bodies of water. Cooling towers assist to dispose waste heat in atmosphere. Associated with nuclear plants, additionally to problem of waste heat, are difficulties attending disposal and confinement of reaction products which remain dangerously radioactive for numerous thousands of years and adjustment of such plants to variable demands for power.

Fossil Fuels and Nuclear Fuel:

Fuel cells produce electricity by direct conversion of hydrogen, hydrocarbons, alcohol, or other fuels, with the efficiency of 50% to 60%. Though they have been utilized to create electric power in space vehicles and some terrestrial locations, many problems have kept them from being extensively utilized. Most important, catalyst, that is significant component of fuel cell, particularly one that is operating at around room temperature, is very costly. Controlled nuclear fusion could give virtually unlimited source of heat energy to make steam in generating plants; though, several problems surround its development, and no substantial contribution is expected from this source in near future.

Fossil Fuels:

Sources of electricity comprise fossil fuels are found within rocks of Earth's surface. They are known as fossil fuels as they are thought to have been formed several millions of years ago by geological procedures acting on dead animals and plants, just like fossils. Coal, oil and natural gas are fossil fuels. As they took millions of years to form, once they are utilized up they can't be replaced.

Oil and Natural Gas:

Sources of electricity comprise oil and gases are chemicals made from molecules containing just carbon and hydrogen. All living things are composed of complex molecules of long strings of carbon atoms. Connected to the carbon atoms are others like hydrogen and oxygen. A simple molecule, known as methane (CH4), is main component of natural gas. Crude oil (oil got from ground) is sticky, gooey black stuff. It has several different molecules, but all are composed of carbon and hydrogen atoms.

Advantages:

These sources of energy are comparatively cheap and most are easy to get and can be utilized to produce electricity.

Disadvantages:

When the fuels are burned they produce gas carbon dioxide that is a greenhouse gas and is major contributor to global warming. Transporting oil around world can create oil slicks, pollute beaches and harm wildlife.

Coal:

Sources of electricity can comprise coal that mostly comprises of carbon atoms which come from plant material from ancient swamp forests. It is black solid which is reasonably soft. You can scratch it with fingernail. It is not as soft as charcoal, though, and is fairly strong. It can be carved in shapes. There are different kinds of coal. Few contain impurities like sulphur which pollute atmosphere further when they burn, contributing to acid rain.

Advantages:

Coal is comparatively cheap, with large deposits left which are reasonably simple to get, some coal being close to surface. It is comparatively easy to transport as it is solid.

Disadvantages:

Some sources of coal are deep below ground, as in UK. They can be hard costly and dangerous to mine.

Burning coal without first purifying it contributes to global warming, as well as to production of smog (smoke and fog), that is harmful to health. It is finite resource and will ultimately run out.

Solar Energy:

Solar energy has been identified as feasible alternative. It has been recommended that proficient collection of solar energy incident on 14% of western desert areas of United States would give enough electricity to satisfy current demands. Two main solar procedures could be utilized. Photovoltaic cells (see solar cell) convert sunlight directly in electrical energy. Another method would utilize special coatings which absorb sunlight readily and emit infrared radiation slowly, making it possible to heat fluids to 1,000°F (540°C) by solar radiation. Heat in turn can be converted to electricity. Few of this heat would be stored to permit operation at night and during periods of heavy cloud cover. Projected efficiency of such a plant would be approx 30%, but this fairly low efficiency should be balanced against facts that energy from sun costs nothing and that waste heat from such a plant places virtually no additional burden on environment. Principal problem with this and other exotic systems for generating electricity is that time required for their implementation may be substantial.

Windmills:

Windmills, once extensively utilized for pumping water, have become feasible for electric-power generation due to advances in their design and development of increasingly proficient generators. Windmill farms, at which rows of windmills are joined together as source of electrical energy, act as important, though minor, source of electrical energy in coastal and plains areas. Though, vagaries of wind make this a hard solution to implement on the large scale.

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