Renewable energy sources



Renewable energy sources arise directly or indirectly from sunlight and involve five major processes

  • absorption of heat from sunlight to produce hot water (solar water heaters)
  • conversion of sunlight directly into electricity (photo voltaic or solar cells)
  • conversion of air movement (wind) into electricity (wind turbines)
  • conversion of sunlight into food which enables plant materials and trees to grow (biomass)
  • concentration of low-grade heat stored within the thermal mass of the earth (heat pumps)

Renewable energy sources can provide heating, cooling or electricity depending upon the source used. Electricity produced from a renewable source is called "green electricity".


The advantages of renewable energy sources are:

  • they are abundant and wide spread
  • they are non-polluting
  • the fuel source in the form of sunlight or wind is free of all charges and is an inexhaustible resource


The disadvantages are:

  • the diurnal (daily) variations which means that the power output cannot be controlled
  • seasonal variations also prevent control of the power output
  • the diffuse source so that the 'collector' or 'absorber' needs to be reasonably large

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