ANS : 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.
ANS : 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.
ANS : 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 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.
ANS : 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.
At places where water is hard and have larger chlorine content, if FPC based system is being installed, it must be with heat exchanger as it will avoid scale deposition in copper tubes of solar collectors which can block the flow of water as well reduce its thermal performance. ETC based systems will not block the flow of water but its performance may go down due to deposition of salt contents on inner surface of glass tubes, which could be cleaned easily once in a year or so.
ANS : Cost of solar water heater depends on size and type of system installed.
Smallest size of a system is 100 liter per day, which means that it can
deliver 100 litres of hot water in a day at 60 C. 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 & N-E
region, the cost may be 15 to 20% more.
The system cost does not include the cost of cold water tank, & 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.
ANS : No. The subsidy scheme has been discontinued w.e.f 12.08.2014 onwards.
ANS : A 100 litre per day capacity system suitable for 3-4 people can save up to
1500 units of electricity in a year depending on t h e a m ou n t o f hot
water used. It can also save around 140 litres of diesel in an
establishment using oil fired boiler besides reducing greenhouse gas
emissions in the atmosphere. Higher capacity systems will save higher
amount of electricity/fuel oil besides reducing higher amount of GHG
Electricity is expensive and is not available due to power cuts in many areas when required for heating water. Solar Water Heater, since it stores hot water in an insulated tank, provides water all the time when required. Fuel oil is also expensive and creates pollution. Storing the fuel oil for long term use in commercial establishments is another problem.
The table below gives approximate likely electricity and money savings for a typical 100 liters per day system located in different parts of the country.
|Northern Region||Eastern Region||Southern Region*||Western Region*|
|Expected no. of days of use of hot water per year||200 days||200 days||300 days||250 days|
|Expected yearly electricity saving on full use of solar hot water (units of electricity)||1000||1000||1500||1250|
* The use pattern and savings for southern region pertains to the typical climate of Bangalore, while those for western region relate typically to Pune climate.
ANS : 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.
ANS : 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:
|Application||Typical Requirement of Hot Water at 60OC.|
|Household bathing using buckets||10-20 liters per person per bath.|
|Household bathing using shower with a mixing tap||20-30 liters for 10-15 minute bath|
|Shaving, while a tap runs||7-10 liters|
|Household bathing in bathtub (one filling)||50-75 liters|
|Wash basin with a mixing tap (hand wash, brushing of teeth, etc.)||3-5 liters per person per day.|
|Kitchen washing||2-3 liters per person per day|
|Dishwasher||40-50 liters per wash cycle|
|Clothes washing machine||40-50 liters per cycle|
ANS : Ministry has laid 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, he may be blacklisted if informed to the Ministry.
ANS : Domestic solar water heating system do not need significant maintenance requirements. Occasional leakages in the plumbing could be easily repaired by common plumbers. In case quality of water is hard, scale deposition in the collectors may result over the years. This may require de-scaling with acids for which it is best to contact the suppliers. Broken glass may also have to be replaced by the suppliers. If outside exposed surfaces are painted, the paint may have to be redone every 2-3 years to prevent corrosion of the surfaces.
ANS : Some of the troubleshooting steps are mentioned below:
|Problem faced||Probable cause and remedies|
|No water in tap||
|Water not heated at all, although cold water flow is normal||
|Water not hot enough or sufficient quantity of hot wter is not available||
|Little quantity of boiling hot water is received||