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Frequently Asked Questions


Solar Water Heater Performance

Is it possible to get hot water early in morning ?
Can we get hot water all 24 hours of the day?
Will the Solar Water heater deliver hot water during monsoon?
Are temperatures similar to electronic geysers possible using Solar Geysers? Can higher temperatures be obtained? And can any extra demand for hot water be met, especially when guests are visiting?

Solar Water Heater Economics

What kind of maintenance is required?
What is the estimated life of a Solar Hot Water System?
Is it possible to integrate the Solar Hot water system into the design of my house?

What is Solar Hot water System ?

Solar Hot Water System utilizes solar energy to heat water to the desired temprature. The heated water may be stored in insulated tanks for use in the morning or used during day time. The complete Solar Hot Water Tank, Circulation pump, Temperature Controller for the pump and instrumentation to measure water flow rates, quantity of water used, temperatures of hot and cold water, electrical energy consumed and cumulative time for which circulation pump runs.

How does the Solar Collector work?

The sun-ray pass through the transparent glass and strike on the black surface of the absorber. The black coating on the absorber convert the radiation energy of sun-rays into heat. This heat is conducted to the tubes by fin which is made of copper or high conductivity material. The tube carry water which receives heat from the tube and becomes hot. To reduce the heat losses and thereby increase the efficiency of the solar collector, thermal insulation is provided at the back of the absorber. The glass covers serves two main purpose. It reduces the effect of wind and heat losses, and protects the black coating on the absorber from the effects of weather, rain etc

Why do the Solar Collectors face the south direction?

India in northern hemisphere, therefore maximum sunshine is captured by a surface facing South direction over the whole year. This is particularly so during winter.

Why is the collector kept in an inclined position ?

For maximum efficiency, the sun-rays should Strike the collector at right angles. For water heating applications, maximum output is required during winter when the sun is at lower altitudes. For maximum output therefore, the collectors should face south direction and be kept at an inclination equal to latitude of the place, which is around +15 to +20 degrees.

How is the Solar Hot Water System specified ? What is LPD ?

The capacity of a solar hot water system is specified is LPD. It is a short form for Liters Per Day. The intensity of Solar radiation varies throughout the day, hence capacity cannot be specified in terms of hourly output.

How is the solar system capacity determined for a given requirement?

To determine the capacity of the solar system required first find out the hot water consumed during the day as well as during night, over 24 hours during winter season the capacity of the solar hot water system in LPD should be equal to or grater than the hot water consumed during the 24 hours.

What is forced flow (FF) System and what is Thermosyphon System (TS)?

The water heated by the solar collector needs to be transferred to the insulated storage tank. When the heated water in transferred by means of a pump ( usually for large capacity systems ) it is called forced flow (FF) system. Most industrial systems are FF systems. When circulation of heated water from collector to the storage tank is by means of the density difference between hot and cold water it is called thermosyphon (TS) system. In this system the storage tank storage tank must be placed above the collector.

What is FTC ?

FTC means Fixed Temperature Control. The operation of the circulation pump of forced flow system needs to be controlled to avoid pumping of cold water into the hot water storage tank. In FTC control, it is achieved by monitoring the temperature at the outlet of the collector. The pump is switched ON only when the outlet temperature is higher than the SET temperature. If the temperature falls below the SET temperature, the pump is automatically switched OFF.

Is it possible to get hot water early in the morning?

Yes. The cold water is heated during the day & it is stored in a specially insulated storage tank all night, this insulation prevents the water from losing heat, so that you have piping hot water the next morning.

Can we get hot water all 24 hours of the day?

Yes! The advantage of the solar hot water geyser is that you get hot water any time of the day or night, and irrespective of the fact whether there is electricity or not! This is true, but is limited to system capacity- the maximum quantity of hot water that can be utilised in a day will depend on the system capacity. If you withdraw more water than the rated capacity, then the water might not be hot enough.

What happens during the monsoon season when it is raining and there is less sunshine?

India receives a clear and good sunshine almost throughout the year as it is close to the tropics. Even during winter the Solar Geyser works extremely well as it has been especially designed for maximum efficiency during the winter season. However during the monsoon season, depending on the hours of sun shine available, you may get varying degrees of warm water. India Solar offers an optional electric heater installed within the solar geyser, to heat water during the rainy season, if you desire hotter water.

Are temperatures similar to electronic geysers possible using Solar Geysers?

Electric geysers are usually set to 60 C, so you need to mix some cold water in geyser outlet water to make it suitable for bathing. It is almost the same with domestic solar water heating systems, the water temperature are generally about 60 C with an variation of about +/- 5 C, depending on season. So the Solar Geyser can adequately replace the electric geyser, plus save money on the electric bill.

Can higher temperatures be obtained?

Yes. Much higher temperatures are possible with the Solar Geyser, though the use is restricted to the industrial sector. India Solar has designed many industrial systems with high temperatures such as 95 C for provided boiler feed water.

What kind of maintenance is required?

Most domestic Solar Geysers don’t require a lot of maintenance, as there are no moving parts in the solar geyser. The only maintenance needed is cleaning of the glass once a month for best results. And if you live in a hard water area, the descaling process once every year is recommended.

For Industrial systems, the pumps need to be inspected at frequent intervals, check for scaling and choking periodically and replacement of some parts of the control panel, as and when required.

What is the estimated life of a Solar Hot Water System?

India Solar uses all Aluminium, Stainless Steel or Copper parts for the Solar Hot water systems manufactured by us, hence they usually last for about 15-20 years. Some maintenance may be required periodically to get maximum efficiency like electric back-up etc. may need replacement. We have some of our very first Solar Geysers (manufactured 15-18 years ago!) still functioning properly to the great satisfaction of our customers.

Is it possible to integrate the Solar Hot water system into the design of my house?

Yes! The system can be designed into your house to fit unobtrusively on to a sloping roof, with a storage tank concealed, etc. This is best done, with the active involvement of your architect with our representative at the design stage itself, any modifications or changes later on are difficult to incorporate.