3 RD

This Writing Was Written By:Md.Raisul Islam Milu
Date:24-01-2010
Signature:
Safe nuclear power plant
Nuclear power plant is power (generally electrical) produced from controlled nuclear reactions. Commercial plants in use to date use nuclear fission reactions. Electric utility reactors heat water to produce steam, which is then used to generate electricity. In 2007, 14% of the world's electricity came from nuclear power, despite concerns about safety and radioactive waste management. More than 150 naval vessels using nuclear propulsion have been built.
Nuclear fusion reactions are widely believed to be safer than fission and appear potentially viable, though technically quite difficult. Fusion power has been under intense theoretical and experimental investigation for many years.
Both fission and fusion appear promising for some space propulsion applications in the mid- to distant-future, using low thrust for long durations to achieve high mission velocities. Radioactive decay has been used on a relatively small scale, mostly to power space missions and experiments.
As of 2005, nuclear power provided 2.1% of the world's energy and 15% of the world's electricity, with the U.S., France, and Japan together accounting for 56.5% of nuclear generated electricity. In 2007, the IAEA reported there were 439 nuclear power reactors in operation in the world, operating in 31 countries. International research is continuing into safety improvements such as passively safe plants, the use of nuclear fusion, and additional uses of process heat such as hydrogen production (in support of a hydrogen economy), for desalinating sea water, and for use in district heating systems.

This Writing Was Written By:Md.Raisul Islam Milu
Date:24-01-2010
Signature:
Solar energy
Solar energy, radiant light and heat from the sun, has been harnessed by humans since ancient times using a range of ever-evolving technologies. Solar radiation, along with secondary solar-powered resources such as wind and wave power, hydroelectricity and biomass, account for most of the available renewable energy on earth. Only a minuscule fraction of the available solar energy is used.Solar powered electrical generation relies on heat engines and photovoltaics. Solar energy's uses are limited only by human ingenuity. A partial list of solar applications includes space heating and cooling through solar architecture, potable water via distillation and disinfection, daylighting, solar hot water, solar cooking, and high temperature process heat for industrial purposes.To harvest the solar energy, the most common way is to use solar panels.Solar technologies are broadly characterized as either passive solar or active solar depending on the way they capture, convert and distribute solar energy. Active solar techniques include the use of photovoltaic panels and solar thermal collectors to harness the energy. Passive solar techniques include orienting a building to the Sun, selecting materials with favorable thermal mass or light dispersing properties, and designing spaces that naturally circulate air. The Earth receives 174 petawatts of incoming solar radiation at the upper atmosphere. Approximately 30% is reflected back to space while the rest is absorbed by clouds, oceans and land masses. Solar thermal technologies can be used for water heating, space heating, space cooling and process heat generation.

2 ND

This Writing Was Written By:Md.Raisul Islam Milu
Date:24.01.2010
Signature:
Natural gas
Natural gas is a gas consisting primarily of methane. It is found associated with fossil fuels, in coal beds, as methane clathrates, and is created by methanogenic organisms in marshes, bogs, and landfills. It is an important fuel source, a major feedstock for fertilizers, and a potent greenhouse gas.Before natural gas can be used as a fuel, it must undergo extensive processing to remove almost all materials other than methane. The by-products of that processing include ethane, elemental sulfur, carbon dioxide, water vapor and sometimes helium and nitrogen.Natural gas is often informally referred to as simply gas, especially when compared to other energy sources such as oil or coal. Natural gas is a major source of electricity generation through the use of gas turbines and steam turbines. Most grid peaking power plants and some off-grid engine-generators use natural gas. Natural gas is supplied to homes, where it is used for such purposes as cooking in natural gas-powered ranges and/or ovens, natural gas-heated clothes dryers, heating/cooling and central heating. Natural gas is a major feedstock for the production of ammonia, via the Haber process, for use in fertilizer production. Natural gas can be used to produce hydrogen, with one common method being the hydrogen reformer. Hydrogen has various applications: it is a primary feedstock for the chemical industry, a hydrogenating agent, an important commodity for oil refineries, and a fuel source in hydrogen vehicles.

This Writing Was Written By:Md.Raisul Islam Milu
Date:23-01-2010
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Greenhouse effect

The greenhouse effect is the heating of the surface of a planet or moon due to the presence of an atmosphere containing gases that absorb and emit infrared radiation. Thus, greenhouse gases trap heat within the surface-troposphere system. This mechanism is fundamentally different from that of an actual greenhouse, which works by isolating warm air inside the structure so that heat is not lost by convection. The greenhouse effect was discovered by Joseph Fourier in 1824, first reliably experimented on by John Tyndall in 1858, and first reported quantitatively by Santo Arsenics in 1896.
The black body temperature of the Earth is 5.5 °C. Since the Earth's surface reflects about 28% of incoming sunlight, the planet's mean temperature would be far lower - about -18 or -19 °C - in the absence of the effect. Because of the effect, it is instead much higher at about 14 °C.
Global warming, a recent warming of the Earth's surface and lower atmosphere, is believed to be the result of an "enhanced greenhouse effect" mostly due to human-produced increases in atmospheric greenhouse gases. Both the greenhouse effect and the greenhouse limit the rate of thermal energy flowing out of the system. On the other hand in the case of a greenhouse, cutting off convection is the principal limit on the flow of energy. In the case of the greenhouse effect the rate of radiation from the Earth to space is limited by the greenhouse gases.