Renewable Energy

　　In the past century,it has been seen that the consumption of non-renewable sources of energy has caused more environmental damage than any other human activity. Electricity generated from fossil fuels such as coal and crude oil has led to high concentrations of harmful gases in the atmosphere.This has in turn led to many problems being faced today such as ozone depletion and global warming. Vehicular pollution has also been a major problem.

　　Therefore,alternative sources of energy have become very important and relevant to today's world.These sources,such as the sun and wind,can never be exhausted and therefore arc called renewable.They cause less emission and are available locally.Their use can. to a large extent,reduce chemical,radioactive, and thermalpollution. They stand out as a viable source of clean and limitless energy.These are also known as non-conventional sources of energy.Most of the renewable sources of energy are fairfy non-polluting and considered clean though biomass,a renewable source,is a major polluter indoors.

　　Solar Energy

　　Solar energy is the most readily available source of energy.It does not belong to anybody and is,therefore,free.It is also the most important of the non-conventional sources of energy because it is non-polluting and,therefore.helps in lessening the greenhouse effect.

　　Solar energy has been used since prehistoric times.but in a most primitive manner.Before 1970,some research and development was carried out in a few countries to exploit solar energy more efficiently,but most of this work remained mainly academic.After the dramatic rise in oil prices in the 1970s,several countries began to formulate extensive research and development programmes to exploit solar energy.

　　When we hang out our clothes to dry in the sun,we use the energy of the sun.In the same way, solar panels absorb the energy of the sun to provide heat for cooking and for heating water.Such systems are available in the market and are being used in homes and factories.

　　Solar energy can also be ursed to meet our electricity requirements.Through Solar Photovoltaic(SPV)cells,solar radiation gets converted into DC electricity directly.This electricity can either be used as it is orcan be stored in the battery.This stored electrical energy then can be used ac night.

　　Hydro Power

　　Hydro power is one of the best,cheapest,and cleanest source of energy,although,with big dams,there are many environmental and social problems.Small dams are,however,free from these problems.This is in fact one ofthe earliest known renewable energy sources.in the country(since the beginning of the 20th century).

　　In fact,for the last few hundred years,people living in the hills of the Himalayas have been using water mills.or chakki,to grind wheat.Besides being free from the problem of pollution.small hydropower plants arealso free from issues and controversies that are associated with the bigger projects.namely affecting the lives of thousands of people living along the banks of the rivers.destruction of large areas under forest.and seismological threats.

　　New environmental laws affected by the danger of global warming have made energy from small hydropower plants more relevant.These small hydropower piants can serve the energy needs of remote rural areas independently.The real challenge in a remote area lies in successful marketing of the energy and recovering the dues.Local industries should be encouraged to use this electricity for sustainable development.

　　It is a technology with enormous potential.which could exploit the water resources to supply energy to remote rural areas with little access to conventional energy sources.It also eliminates most of the negative environmental effects associated with large hydro projects.

　　Energy From the Sea-Ocean Thermal,Tidal and Wave Energy

　　On an averaige,the 60 million square kilometre of the tropical seas absorb solar radiation equivalent to the heat content of 245 billion barrels of oil.Scientists feel that if this energy can be tapped a large source of energy will be available to the tropical countries and to other countries as well.The process of harnessing this energy is called OTEC(ocean thermal energy conversion).It uses the temperature differences between the surface of the ocean and the depths of about lOOOm to operate a heat engine.which produces electric power.

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