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 Solar Water Heater Works?
A Solar Water Heater comprises of 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.
Types of Solar Water Heater?
Two types of Solar Water Heaters are available; one based on flat plate collectors and the other based on evacuated tube collectors. Flat plate collector (FPC) based systems are of metallic type and have longer life as compared to Evacuated tube collector (ETC) based system because ETCs are made of glass which are of fragile( can be easily broken or destroyed) in nature. Both these systems are available with and without heat exchanger. They can also work with and without pump. Systems without pump are known as thermosyphon systems and those with pump are known as forced circulation systems.
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.
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.
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 solar water heater 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.
Advantages of Solar Water Heater
- Fuel Savings: A 100 liters capacity solar water heater can replace an electric geyser for residential use and saves 1500 units of electricity annually.
- Environmental benefits: A solar water heater of 100 liters capacity can prevent emission of 1.5 tonnes of carbon- dioxide per year.
- Simple to construct and install.
- No or negligible running cost.
- Almost maintenance free.
- Cost is low and economically competitive with electric water heating system.
- It saves time and high grade form of electric energy.
- Required low temperature up to 100 degree Celsius can be achieved by simple flat plate collector.
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