3.1.0 Solar energy conversion modes:
Solar energy is captured by being converted to other forms of energy by (a) chemical reaction (b) thermal excitation (c) photovoltaic effect. Solar energy is chemically converted into energy through photosynthesis. This directly produces food and wood. Simple thermal conversion devices, such as flat plate collectors, are suitable mainly for providing low energy, high entropy heat to systems of the same nature. The flat plate collector can deliver temperature up to approximately 100 C. The direct conversion of sunlight to electricity by means of solar cells is the photovoltaic effect. The solar cell use energetic photons of the incident solar radiation, converting solar energy into electricity.
Some advantages of photovoltaic devices are,
(a) no inherent life time limit, (b) efficiencies are independent of size, (c) modular (d) compatible to all environments, (e) fairly constant voltage independent of sunlight intensity, (f) relatively low maintenance, (g) low operating and maintenance costs, (h) simplicity, (i) no cooling water required.
Potential areas of commercialisation of solar photovoltaics are (a) domestic lighting (b) community lighting (street lighting) (c) health care (d) telecommunication (e) water pumping (f) entertainment gadgets like television, radio etc. Solar photovoltaics alone cannot successfully cater to the energy requirements without a very high efficiency balance of system design. The choice of balance of equipments may be carefully made. Another major requirement is the storage of energy wherein batteries of low maintenance and high recycling capacities are to be used. However, some disadvantages are: (a) Theoretical efficiency of about 25% combined with low energy intensity of sunlight requires a relatively large collector. (b) economically not competitive with other sources and (c) requirement of DC to AC inversion equipment to supply AC loads
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