FAQ - Solar Water Heater

What is Solar Water Heater?
A Solar Water Heater is a device which provides hot water for bathing, washing, cleaning, etc. using solar energy.  It is generally installed at the terrace or where sunlight is available and heats water during day time which is stored in an insulated storage tank for use  when required including mornings

How does it work?
A Solar Water Heater comprises of a or an array of solar collectors to collect solar energy and an insulated tank to store hot water. Both are connected to each other. During the day time, water in solar collectors gets heated which is either pumped or flown automatically on thermosyphon principle to the storage tank. Hot water then stored in the tank can be used for various applications.

What is the maximum possible temperature it could attain ?
About 60 to 80º C. The rise in temperature depends on: Solar radiation, weather conditions & number of solar collectors

Do I need to install the Solar Water Heater at my roof top?
It is preferable to install the system at your roof top where the solar radiations are freely available. However, it could be installed in the Balcony, Terrace and open ground. Smaller systems may also be installed at the window by providing a suitable structure to support the system.

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 Litres Per Day. The intensity of Solar radiation varies throughout the day, hence capacity cannot be specified in terms of hourly output.

How much area is required to install Solar Water Heater for my residential use?
A 100 LPD system requires open surface of 2M X 2M.

I do not want to discard my existing Electric Geyser as it is in good condition but I also want to install Solar Water Heater at my residence as I fully understand the savings achieved through it. Is it possible to use both in combination?
There is no need to discard your Geyser. It can be used in combination with your new SWH. The only thing that you need to do is to connect the out let of your SWH to the inlet of your existing geyser. The temperature of the water coming out of SWH can also be elevated through the electric geyser, if needed.

Why should I go for a Solar Water Heater?  What do I save from it?
A 100 litre per day capacity system suitable for 3-4 people can save upto 1500 units of electricity in a year, depending on hot water used. It can also save around 140 litres of diesel in an establishment using oil fired boiler besides reducing green house gas emissions in the atmosphere.

What happens on cloudy/rainy day? Do I still get hot water?
On cloudy days also, if it is for a day or two, you still get warm water as water gets heated due to diffused radiation available in the atmosphere.The system, however, is either connected to an electric geyser in the house or an electrical back-up is provided in the storage tank of the system which is switched on when water is not sufficiently hot. So, you get hot water all the time even on rainy days.

Is it possible to get hot water in the early morning ?
Yes. The cold water is heated during the day & it is stored in an 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.

Whether my existing piping (G.I. Pipes) will be suitable to carry the hot water or separate insulated / special piping would be necessary?
A separate insulated pipe is required from Solar Water Heater Tank to Utility Point. In case of G. I. Pipe the temperature falls due to heat loss during the flow.

How do I decide about the size/capacity of the system to be installed?
For a house with one bathroom and 3 to 4 members, 100 liter per day capacity system should be sufficient. For more numbers of bathrooms, the capacity will increase accordingly due to pipe losses & more number of family members. Generally the capacity is decided based on hot water required in mornings for bathing. If the usage is in evening & at other times also, the capacity is decided accordingly. Some useful thumb rules for estimating the hot water requirement are given below: