Solar Water Heating System

Solar Water Heating System (S.W.H) is the conversion of sunlight into heat, for water heating, using a solar thermal collector. A variety of configurations are available at varying cost to provide solutions in different climates and altitudes. S.W.H's are widely used for residential and some industrial applications. An estimated one million residential and 200,000 commercial solar water-heating systems have been installed in India.



How SWH 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 Heating Systems

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 ETC’s are made of glass which are of fragile 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.

 

Which type of Solar Water Heater is suitable for different places/category of users?

ETC based systems are cheaper than FPC based system. They perform better in colder regions and avoid freezing problem during sub-zero temperature. FPC based systems also perform well with anti-freeze solution at subzero temperature but their cost increases. In other regions, both perform equally well.

Systems working on thermosyphon principle are simple and relatively inexpensive. They are suitable for domestic and small institutional applications, provided water quality is good and it doesn’t have large chlorine contents. Forced circulation systems are generally preferred in industries or large establishments.

  

What is the approximate cost of solar water heater?

Cost of solar water heater depends on size and type of system installed. Smallest size of a system is 100 liters per day,which means that it can deliver 100 liters of hot water in a day at 60 degree centigrade. A 100 lpd capacity system is sufficient for a family of 3-4 members and it may cost Rs. 15,000 to Rs.22,000 in plains depending on the type of system. In hilly and North Eastern region, the cost may be 15 to 20% more.

The system cost does not include the cost of cold water tank, and its stand which is required if overhead tank is not installed in a house/ building. Cost of hot water insulated pipe line also, may be extra if number of bathrooms is more than one. Additional cost towards all these components may increase by 5 to 10%.

The cost, however does not increase linearly with increase in capacity, rather it comes down proportionately as we go for higher capacity system.

Is there any subsidy available from Government? 



No.The subsidy scheme has been discontinued w.e.f 12.08.1014 on wards.

What happens on cloudy/rainy day? Do I still get hot water?

On cloudy days, 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 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 hot enough to bath. With that you will get hot water all the time even on overcast days.
It is suggested to install one instant geyser. If water is not hot enough to take bath during overcast days, you can take advantage of that. As water from SWH is warm, you don’t need much power to heat.

How do I assure that a good quality system is installed at my house?

Government has penned down some minimum technical requirements for installation of solar water heating systems in the field. These have been made mandatory for manufacturers and suppliers and are available on MNRE website: www.mnre.gov.in. These requirements are have been prepared in such a way that even a lay man can also check them and ensure that those are being adhered to by the manufacturers/suppliers. In case any manufacturer/supplier is found not sticking to these requirements, they may be blacklisted if informed to the Govt..

Trouble Shooting Guide for solar water heating systems

Some of the troubleshooting steps are mentioned below:

Problem Faced	Cause and Remedies
No water in tap	-No cold water supply -Wall at the outlet of system closed -Air lock in the pipes
Water not heated at all, although cold water flow is normal	-Consumption of hot water may be too high; Check use points and use pattern -Collector may be shaded -No flow of water through the collector as it might be choked due to scaling; Get it checked from the manufacturer.
Water not hot enough or sufficient quantity of hot water is not available.	-Cloudy weather -Consumption too high -Frequent on-off of hot water tap -Collector dirty -Vapour lock in the collector which can be removed by allowing it to cool and draining the system. -Partial choking of the collector