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What is Solar Water Heater? It is simple device which utilizes solar radiation and provides hot water at a temperature of 60-80oC for application such as bathing, cloth washing, dish washing, etc. How does it work? The Sun’s rays fall on the collector panel (a component of solar water heating system). A black absorbing surface (absorber) inside the collectors absorbs solar radiation and transfers the heat energy to water flowing through it. Heated water is collected in a tank which is insulated to prevent heat loss. Circulation of water from the tank through the collectors and back to the tank continues automatically due to thermo siphon system. What types of systems are available in the market? Generally two types of solar water heater are available in the market: 1. Flat Plate solar water heater (Figure 1): Solar radiation is absorbed by flat plate collectors which consist of an insulated outer metallic box covered on the top with glass sheet. 2. Evacuated Tube Collector (Figure 2): The Collector is made of double layer borosilicate glass tubes evacuated for providing insulation. |
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What are the site requirements for installation? The basic requirement for SWH is the availability south facing shadow free area. For domestic purpose, it could be the roof of the house. As a thumb rule, the requirement of shadow free area is around 3 sq. m for each 1 x 2 m collector used. As far as possible, the area should be flat, away from rain water drains and as far as possible, close to the bathrooms where hot water is to be supplied. Cold water should be available at the height of around 2.5 m from the base of the system. What about the multistory building, can SWH be installed there? Yes. In multistoried buildings even if the space for installation can be made available on the roof, and the systems are installed there, the piping from the system to the use point will become long leading to extra cost as well as to extra heat losses. A better option in such cases could be installation of the systems on the wall mounted brackets, close to the bathrooms. Will they work on cloudy days? For totally cloudy days the output of SWH system would be ZERO. On partially cloudy days some output can be expected. But, the system can be designed with a suitable heating back up heater to take care of hot water demand on cloudy days. Will I get hot water in the morning when sun is not there? Hot water produced by the solar system during the day is stored in an insulated storage tank & water remains hot without significant drop in temperature for around 24 hrs. Thus water heated during the previous day should be available for use in the next morning. What are the maintenance requirements? Domestic solar water heating systems do not need significant maintenance requirements. Occasional leakages in the plumbing could be easily repaired by common plumbers. In case quality of water is hard, scale deposition in the collectors may result over the years. This may require descaling with acids for which it is best to contact the suppliers. Broken glass may also have to be replaced by the suppliers. If outside exposed surfaces are painted, the paint may have to be redone every 2-3 years to prevent corrosion of the surfaces. What should I check while buying a SWH system? Bureau of Indian standards has laid down specifications of flat plate collectors for use in solar water heating systems and thus the IS mark is an assurance on use of proper materials. There are many BIS approved suppliers of solar water heating systems in the country. |
