Solar Water Heaters are becoming quite popular these days. Through a lot of government support, marketing and subsidies these products have come a long way in India. They have become quite affordable now and many people have started adopting solar water heaters for their water heating needs. Many big brands have now started making (& selling) solar water heaters in India. And some of them are also available online on e-commerce platforms. In India, heated water is generally required from 200-300 days and investment in this area is a financially viable project. If you are someone who is looking to buy a solar water heater then this post will help you out in understanding the technology and buying one.
What is a Solar Water Heater?
A solar water heater is a system that utilizes solar energy (or the energy from sunlight) to heat water. It has a system that is installed on a terrace or open space where it can get sunlight and the energy from the sun is then used to heat water and store it in an insulated tank. The system is not connected to electricity supply and thus does not have an on-off switch, but it uses the sunlight throughout the day to heat the water and store it in the storage tank. Most of the solar water heater on a sunny day can provide heater water at about 68° ±5° C temperature. Water from the storage tank can then be used for any application as desired.
One can feed this heated water to the electric geyser so that when sunlight is not enough, it uses electric energy to heat the water to the desired set temperature. This is also called Hybrid Water Heater but no one is marketing it and it has to be designed for your requirement by the solar water installer by laying a separate pipe to your geyser.
In hilly areas, where the temperature during the day time is very low and one is using an electric heater for room heating can make use of heated water for heating the room. For this also, there is no standard product available in the market and one has to design this as per the requirement with the help of an installer.
Top Brands Selling Solar Water Heater in India
Several of the known water heater brands in India have started selling solar water heaters in India. Some of them include (click the link to get more information):
- Havells: Product catalogue says ETC system and price including Taxes is 300l-Rs. 46,500; 200l-Rs. 36,500; 150l-Rs. 29,500 and 100l-RS 23,500.
- Racold: Manufactures mainly ETC type
- AO Smith: Catalogue, manufacturers large capacity with integrated gas heating for a large requirement.
- Venus: Manufacturers mainly ETC type
- V Guard
Not all make is available on e-commerce site. Few of the makes as available on amazon e-commerce platform are as under:
Using a solar water heater has a life of 15-20 years is economically viable for the consumer and is a win-win situation for consumers, utilities and the environment. Renewable energy is future and embracing the same makes a lot of economic and environmental sense.
Solar Water Heater – types and benefits
There are 2 types of solar water heaters that are available in the Indian market:
1) FPC (Flat Plate Collectors) system: Flat Plate Collector Systems are metallic systems. They contain an insulated metallic box covered with a toughened glass. The metallic box has a layer of a copper sheet which is good for absorbing heat. The copper sheet is further coated with a black coating which improves heat absorption. The metallic box contains copper tubes arranged vertically and connected at the top and bottom by two horizontal copper pipes called headers. The cold water enters the collector (the metallic box) from the bottom pipe and rises up into the vertical pipes. It gets heated up in the vertical pipes. As it gets heated the water becomes lighter (hot water is lighter than cold water) and it rises up and gets collected in the storage tank via the top horizontal pipe (or header). This water now gets available for use.
These are metallic type systems and have a longer life.
2) ETC (Evacuated Tube Collectors) system: Evacuated Tube Collector systems are made of Glass. It has vertical tubes that are made out of two co-axial glass tubes. The air between the two coaxial tubes is removed to create a vacuum which improves insulation. Additionally, the surface of the inner tube is coated to provide better heat absorption and insulation. Coldwater is filled up in these glass tubes and it gets heated up due to the sunlight. Hot water is lighter than cold water, and so it rises up and gets collected in the storage tank from where it is available for use.
These systems are made up of glass and are fragile.
Both these type of water heaters come with or without a pump. The pump is used to move water from collectors to the storage tank. Those without pump use the thermosiphon principle to move water from collectors to storage tank automatically.
How to decide on which type to buy
ETC systems are fragile but are cheaper. They are also very good for colder regions where the temperature is sub-zero. In a place where the water is salty, these systems require regular cleaning due to deposition of salt on the inner surface of glass tubes.
FPC systems are long-lasting, as they are metallic. But they are expensive than ETC systems. They can work in colder regions with sub-zero temperature but will need an antifreeze solution making the system expensive. In places, with salty water, a heat exchanger is required with the FPC system to avoid scale deposition that can impact the heating capability of the system.
A system without a pump is ideal for domestic and small application users (as it is cheaper) provided water does not have high chlorine content. Those with pumps are good for industries.
The approximate rate for 100 lpd solar heater of FPC is between 30-35 thousands and that of ETC is around 20-25 thousand based on the UP govt website.
How does the system perform on rainy/overcast days
Many people have concerns that solar systems will not work on overcast days. A solar water heating system can still work if the overcast is not long (less than a day or two) as the system works on diffused radiation in the atmosphere. A solar system can also be integrated with an existing electric system that can act as a backup during the days when the overcast is long. The electric system can switch on if the water temperature from the solar water heater goes down below 40oC. Electric backup is not required in a solar system if you have an existing electric water heater. In case you do not have an existing water heater, you can install an electric backup. You can also keep the two systems separate and use the electric system only when needed.
Maintenance requirements of solar water heater
- If you have ETC system then glass can break, as it is fragile. So the glass may need occasional replacement.
- Scaling happens on solar water heaters regularly especially if the water is hard. So the collectors need regular cleaning using acid.
- If the outside surface of the water heater is painted, then it may need a repaint every 2-3 years to prevent corrosion.
- Occasional leakages could happen in the system and local plumbers can repair those.
Sizes of solar water heaters are available in the market
Solar water heaters available in the market start from size of 100 ltr per day. The other sizes that are available are 200, 250, 300 and 500 lts per day. The maximum area required for the collectors to be installed on a terrace/open area is:
|Capacity (litres per day)||The area in sq. m. for ETC system||The area in sq. m. for FPC system|
The litre per day mentioned above is litres of hot water at (60-70oC). A 100 litres size is suitable for a family of 4. You can check more on the sizing of water heaters in our article: Choose the right sized water heater/geyser for electricity saving.
Savings that can be achieved using a solar water heater
A 100-litre per day water heater can save yearly electricity units in various parts of India as per the table mentioned below:
|Expected no. of days of use of hot water per year|
|Expected yearly electricity saving on full use of solar hot water (units of electricity)|
The units used for water heating depend on the amount of water that is heated, so the number of unit increases proportionately as the size increases. You can use our calculator to find out how much do you pay per unit of electricity to evaluate savings: Online Electricity Bill Calculator – For all states in India.
Is there any subsidy on Solar Water Heater
There is a provision of subsidy for installation of a solar water heater and the amount and procedure of subsidy varies from state to state. Himachal Pradesh Govt. provide a subsidy of 30% up to 200 lpd capacity. Uttarakhand Govt provides a subsidy of Rs. 100/month in the energy bill. There is no subsidy in UP from 2014. Most of the time, the installation of a solar water heater is quite economical without subsidy. In view of this, one should check the subsidy rule for his state and visit the website of his state as given in the table below.
|Sl. No.||States||Renewable Energy Development Authority Website|
About the Author:
Abhishek Jain is an Alumnus of IIT Bombay with almost 10 years of experience in corporate before starting Bijli Bachao in 2012. His passion for solving problems moved him towards Energy Sector and he is keen to learn about customer behavior towards Energy and find ways to influence the same towards Sustainability. More from this author.