Description
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".
Advantages
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
Disadvantages
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
