Solar water heaters -Principle and applications:
Solar energy has several advantages over the other energy sources. It is inexhaustible, it is free from any pollution and unlike fossil fuels, transformation of solar energy does not produce any toxic by-products. No nation can put an embargo on its supply. So, if a means could be found to make efficient use of solar energy, it would mean a continuing free supply of energy which would not degrade our environment and also reduce our dependence on non-renewable sources of energy. The estimated solar energy potential in the country is 200 MW/sq.km and can be utilized both for thermal and electrical applications. The solar thermal applications include hot water systems for industrial, commercial and domestic use besides solar cookers, solar dryers, solar stills and solar photovoltaic cell operated applications aimed at producing power
Solar water heater
The solar water heating systems come with a solar collector of 25 sq. m area for solar tank of 100 litre capacity. It occupies an area of 35 sq. ft on the roof top. The water is loaded in the daytime and is stored in the storage tank for a period of 48 hours. This system can be connected to bathrooms and kitchen. Generally, the life of the system is about 15 years and it requires no maintenance.
Flat Plate Collectors (FPC) based Solar Water Heaters
The solar radiation is absorbed by Flat Plate Collectors which consist of an insulated outer metallic box covered on the top with glass sheet. Inside there are blackened metallic absorber (selectively coated) sheets with built in channels or riser tubes to carry water. The absorber absorbs the solar radiation and transfers the heat to the flowing water.
Capacity (in LPD) for 600C SWHS |
Recommended Collector Area (in Sq.m) |
100 |
2 |
200 |
4 |
300 |
6 |
500 |
8 |
1000 |
16 |
Evacuated Tube Collectors (ETC) based Solar Water Heaters
Evacuated Tube Collector is made of double layer borosilicate glass tubes evacuated for providing insulation. The outer wall of the inner tube is coated with selective absorbing material. This helps absorption of solar radiation and transfers the heat to the water which flows through the inner tube.
Capacity (LPD) |
Tube size |
Collector Area (Sq.m) |
||
|
Dia:47mm Length:1500mm |
Dia:47mm Length:1800mm |
Dia:58mm Length:1800mm |
|
100 |
14nos |
12 |
10 |
1.5 |
125 |
18 |
15 |
13 |
1.93 |
150 |
21 |
18 |
15 |
2.25 |
200 |
28 |
23 |
19 |
3.0 |
250 |
34 |
28 |
23 |
3.75 |
300 |
40 |
33 |
27 |
4.5 |
400 |
52 |
43 |
35 |
6 |
Type of Solar Water Heater:
Domestic water heater |
Industrial water heater  |
 |