The surface of the earth receives from sun about kW of solar energy. The amount of solar energy reaching the earth is not easily convertible. There are two obvious obstacles in harnessing solar energy. First it is not constantly available on earth and secondly the energy is diffused. Therefor it requires a large capital investment for conversion apparatus.
Flat Plate Solar Collector
Fig. 1 shows a flat plate collector which consists of following components.
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| Fig. 1 Flat plate solar collector |
i) An absorber plate : It intercepts and absorbs solar radiations.
ii) Transparent covers : These are one or more sheets of solar radiation transmitting materials and are placed above the absorber plate. They allow solar energy to reach absorber plate while reducing convection, conduction and re-radiation heat losses.
iii) Insulation : Is is placed beneath absorber plate. It minimizes and protects absorbing surface from heat losses.
Solar Power Plant
Fig. 2 represents a schematic diagram of solar power plant.
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| Fig.. 2 solar power plant |
The basic components of solar power plant are also exactly identical to thermal power plant except boiler is replaced by a flat plate solar collector.
The energy from solar radiation is collected and utilized to generate a steam to run steam turbines. For obtaining reasonably high efficiency, concentration type of collectors are used when steam is used as working fluid. The cost of concentrating collector is more than flat plate collector. Therefor, new working fluid whose saturation temperature is lower than that of water at considerably high pressures are normally used in this type of power plant. But the thermal efficiency of the plant will be low due to low temperature range.
This is more suitable in rural areas for house lighting and water pumping for irrigation purpose.
1.1 Advantages
Solar energy has following advantages.
1) Solar radiation does not disturb ecological balance.
2) It is available freely in nature.
3) It is non-depleting source.
4) It is easily available all over the wind.
1.2 Disadvantages
Following are disadvantages of solar energy.
1) Collections and conversion of solar energy into useful forms must be carried out over a large area which requires a large capital investment for comversion.
2) Such power plants require direct light and are not operative when the sun is even partly covered with clouds.
3) Reflecting surface undergo deterioration with passage of time.
4) These power plants are uneconomical.
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