You can save money, electricity and get piping hot water for your home with a solar water heater. In 2006, New Delhi made it mandatory for homes, institutions and offices to install solar water heaters, replacing water geysers that run on electricity. Almost all big cities of Maharashtra had, by 2002, amended their building bylaws to promote solar heaters and in some cases provide rebates such as concessions in price, cuts in monthly electricity tariffs or a reduction in property tax. Similar rules are in place in 14 other states.
But why then do we not install a solar water heater?
We don't understand the technology
It is a simple device, which absorbs solar radiation and heats cold water. The solar water heater works on the principles of blackbody radiation and greenhouse effect it absorbs solar radiation efficiently, but does not allow it to reflect easily. At the heart of the system is a collector which absorbs the solar radiation.The system also includes hot water storage tanks, circulation systems and controls.
Two types of solar water heaters are sold in the Indian market. The flat plate collector, which has been promoted by government and industry for the past 25 odd years, and the newer evacuated tube collector. There are 60-odd manufacturers of flat plate heaters in the country, certified by the Bureau of Indian Standards. These heaters have copper tubes, making them less prone to breakage. They have a life of 15-20 years. But these heaters are also less efficient in trapping energy, require more collector area and their tubes are susceptible to blockage as a result of salt deposition, particularly if water is hard. A flat plate heater that can heat up to 100 litres a day costs around Rs 16,000-24,000.
The evacuated tube collector is entering the Indian market from China. It's compact design means it requires less area. The heater is also more efficient and, most importantly, is significantly cheaper than flat plate collectors. A Chinese system of 100 litres costs between Rs 12,000 and Rs 19,000. But with glass tubes, these heaters are more prone to breakage. There are also fears that the vacuum in the glass tubes--to eliminate heat losses--could be prone to leakages.
What about installation?
You will need 3-4 sq m space on the rooftop to place the collectors and the storage tank. You
will have to connect the heater to your bathroom or kitchen. It can be routed through existing hot water geysers in your house or might require extra piping--the cost quoted by suppliers incudes extra piping costs.
What will I save?
On average, a solar water heater with a100-litre per day capacity (which should meet the needs of four-five people easily) has the potential to save up to 1,500
kwh of electricity a year. At the current electricity rates of Rs 3.50 per unit, the capital cost can be recovered in three or four years.
Do I get any discounts?
If you live in Delhi, in addition to a soft loan (at 2 per cent interest countrywide) you will get a rebate of Rs 6,000 for installing the solar heater. The Haryana government gives monthly rebates on electricity bills, ranging from Rs 100-300, based on the capacity of the solar water heater. In other words, a 100-litre capacity system earns a rebate of Rs 100 per month. Uttarakhand gives a similar monthly rebate of Rs 75 per sq m of collector area--roughly Rs 150 for 100 litre capacity plant. A resident of Bangalore can get a rebate of 50 paise per unit of electricity consumed. In West Bengal, you will get a rebate of 40 paise per unit, to a maximum of Rs 80 per month.
Is it cheaper than electric geysers?
No. The geyser is cheaper to install but you will pay for electricity every month.
If you use your geyser for only 106 days (over winter) and calculating that you need 5 units to heat water everyday, you will spend Rs 1,850 over this season (assuming electricity is Rs 3.50 a unit).
Will the solar heater work in winter?
Yes. Except for the time when the sun is behind clouds, the solar water heater will work. In India, even in the highest ranges of the Himalayas this means that it will work for 320 days at least.
How long will it take to heat water?
It takes 6-7 hours of average solar radiation to heat water up to 60
c. But households do not use water so hot. Also, the system insulates the heated water in the tanks. So before sunrise on a day, you should get heated water from the day before.
will have to connect the heater to your bathroom or kitchen. It can be routed through existing hot water geysers in your house or might require extra piping--the cost quoted by suppliers incudes extra piping costs.