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How long will the water heated by solar energy remain hot in the tank?

Hot water produced by the solar system during the day is stored in an insulated storage tank. The insulation of the tank is such that water should remain hot without significant drop in temperature for upto 24 hrs. Thus water heated during the previous day should be available for use in the next morning.

Is any electricity required for operation of the solar water heater?

Domestic solar water heaters work on the principle of thermosyphonic action, in which water circulates through the system by virtue of density difference between hot and cold streams. No electricity is required for circulation of water or for any other operation in such systems. However, in case a back up heater is provided to take care of hot water requirement during cloudy days, electricity will be required.

What is the expected life of a solar water heater?

A solar water heater made using materials as per BIS specifications could last for 15 -20 years depending upon the general upkeep, etc.

How much electricity and money can I save through a solar hot water system?

The table below gives approximate electricity and money savings for 100 liters of water per day in different parts of the country.

Will I get hot water on cloudy days?

The heating of water by the solar system will obviously be affected on cloudy days. If it is so cloudy that energy received from the sun is almost zero, the output of solar collectors will also be nil. On partially cloudy days some hot water can be expected. But, the system can be designed with a suitable electrical back up heater to take care of hot water demand on cloudy days.

What would happen if water supply to the solar water heating system is irregular?

A regular cold water supply, at a height of around 2.5 m is necessary for the system to function efficiently. In case cold water is not available continuously, a separate cold water tank of equal capacity may have to be installed. In case cold water supply is interrupted, the heating of water by the solar system may not be affected significantly, although hot water cannot be drawn for use till the water supply is restored.

Can the system be installed in multi-storied buildings?

Yes, solar water heating systems can be installed in multistoried building.

Can the system be installed somewhere other than on the roof?

The system can also be installed on a bracket on a south facing wall, close to the bathrooms. However, the installation is difficult and leads to extra cost. The fixing of the system to the bracket should be proper. Access to the system for repairs should also be ensured. Cost of hot water distribution piping however could be reduced in such installations as the system will be close to the use point.

Can the solar water heating system match with the exteriors of my house?

Though aesthetics are a matter of individual preference, most domestic solar water heating systems can be designed to blend with the exteriors of a building or hidden from view. If a system is well installed and maintained, it can even add to the aesthetics of your house.

What are the site requirements for installing a solar water heater?

For a solar water heater system to function efficiently, it requires unobstructed sunlight the whole day. Collectors must face the sun and should be oriented south for maximum interception of sunlight. As a thumb rule, the requirement of shadow free area is 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 close to the bathrooms as possible.

How much would a solar water heater cost?

The cost of a solar water heating system is dependents on parameters like, capacity, materials used for inner and outer tanks, length of distribution piping required to take hot water to the bathrooms etc. Typically, for an Indian made system with single BIS approved flat plate collector of 2 sq. m area, the costs could range from Rs. 15,000-20,000 , excluding the distribution piping. However this range is indicative, and can vary from place to place.

How do I decide on the size of the solar water heater I need to purchase?

Make an actual estimate of the daily demand for hot water in your family using the table below. A 100 liters system is generally optimum for a family of 4 adults.

How do I identify a good solar water heater?

A good solar water heater should have sufficient collector area. For example, on a sunny winter day in North India, a sq. m. of collector area can heat around 50 liters of water to a temperature of 30-40C. Typical flat plate collectors made in the country have an area of around 2 sq. m and are thus capable of heating 100 liters of water per day. Further, the collectors should use good materials and the absorbers should carry a good quality coating (BIS approved collectors the best).

How does a solar water heater work?

A typical heater consists of a hot water storage tank and one or more flat plate collectors. The collectors are glazed on the sun facing side to allow solar radiation to come in. A black absorbing surface (absorber) inside the flat plate collector absorbs solar radiation and transfers the energy to water flowing through it. Heated water is collected in the tank which is insulated to prevent heat loss. Water circulates from the tank through the collectors and back to the tank continues automatically due to density difference between hot and cold water.

Why should I install a solar water heater?

Solar water heaters save both electricity and money. As electricity is becoming more expensive, a solar water heater is a great way to access 24/7 hot water at far cheaper rates. They are also safer than electric geysers as they are located on the roof and are a super way to display your commitment to the environment.

What is the maintenance required for a solar water heating system?

A domestic solar water heating system does not require major maintenance. Occasional leakages in the plumbing can be fixed by any plumber. In case quality of water is hard, scale deposition in the collectors can result over the years. This requires descaling with acids. This issue do not arise in the case of ETC model.

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