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Renewable Sources of Energy-I: Energy Sources and Solar Energy

Energy Sources

We can broadly categorise the source of energy according to periods of usage as follows:

  • Conventional source of energy, which are easily available and have been in usage for long time.
  • Non-conventional source of energy, that are other than the usual or that are different from those in common practice.
Conventional and Non-Conventional
ConventionalNon-conventional
Conventional non- renewable energyConventional renewable energy1. Solar energy
Mostly fossil fuels found under the ground.Mostly non-fossil fuels seen above the ground.2. Hydro power
Coal, oil, natural gas etc. are the examples.Firewood, cattle dung from vegetable wastes, wood charcoal etc. are the examples.3. Wind energy
4. Nuclear energy
5. Hydrogen energy
6. Geothermal energy
7. Biogas
8. Tidal energy
9. Bio-fuel
  • Most of the renewable resources of energy are directly or indirectly related to sun or solar energy.
  • Renewable sources of energy or non-conventional energy sources include sunlight, wind, water and biomass (firewood, animal dung, crop residue, agricultural wastes, biodegradable waste from cities and towns) .
  • Energy received from sun is known as solar energy, energy generated by water is hydel energy and energy obtained from underground hot dry rocks, magma, hot water springs or natural geysers etc is called geothermal energy. Tidal energy is derived from waves and tidal waves of oceans and seas.

2 Renewable or Non-Conventional Sources of Energy

  • Inexhaustible energy resources as ‘those resources which can be harnessed without depletion’ . Most of these resources are free from pollution and some of them can be used at all places.
  • These renewable energy resources are also known as non-conventional or inexhaustible or alternate energy sources. These energy sources are solar, flowing water, wind, hydrogen and geothermal. We get renewable solar energy directly from the sun and indirectly from moving water, wind and biomass.

Solar Energy

  • Sun is an abundant source of energy and it is inexhaustible. In the broadest sense, solar energy supports all life on earth and is the basis for almost every form of energy we use.
  • The sun makes plants grow, which are burned as fuel or rot in swamps and are compressed underground for millions of years to become coal and oil. Heat from the sun causes temperature differences between areas, causing the wind to blow.
  • Water evaporates because of the sun, water vapours are carried to high elevations, and when the water vapours condense and precipitate as rainfall. The water rushes down towards the sea through rivers, spin turbines is too made for generating electricity.
  • It thus becomes clear that hydroelectricity is an indirect form of solar energy. However direct solar energy can be used as heat, light, and electricity through the use of solar cells.

Direct Solar Energy

Solar energy is abundant, everlasting and available free of cost. Direct use of solar energy can be used through various devices broadly directed into three types of systems:

  • Passive
  • Active
  • Photovoltaic

Passive Solar Energy

As you know some of the earliest uses of solar energy were passive in nature such as to evaporate sea water for producing salt and to dry food and clothes. In fact, solar energy is still being used for these purposes. The more recent passive uses of solar energy is for cooking, heating, cooling and for the daylighting of homes and buildings. The effectiveness of passive solar energy depends on good building design; no mechanical means are employed in passive use of solar energy.

Passive Use of Solar Energy for Cooking

  • The energy from the sun can be harnessed, to cook food without any large, complex systems of lenses or mirrors.
  • when sunshine falls on a dark surface, it is absorbed and transformed into heat energy.
  • Glass is bad conductor of heat but if a shallow glass covered chamber painted black inside and insulated all around is exposed to sun for some time the inside temperature would soon exceeds up to 100oC which is sufficient to cook food.
Illustration: Passive Use of Solar Energy for Cooking