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What is a 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 daytime which is stored in an insulated storage tank for use when required including mornings.

How does Solar Water Heater Works?

A Solar Water Heater comprises of array of solar collector/s 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.

What are Different types of Solar Water Heaters?

A variety of systems are available in the market but mostly can be characterised in the following categories:

1. Based on collector type: ETC/FPC
2. Based on pipe and system pressure: Pressurised/Non pressurised
3. Based on system construction material: SS/GI

Evacuated tube collector (ETC) based systems are most common these days and are based on advanced vacuum tube technology. Stainless steel (SS) systems look better and last longer compared to galvanised iron (GI) based systems, however demand 10-15% premium. In dwellings with pressure pumps, pressurised systems need to be installed

Are the tubes made of glass? How sensitive are they ? Can monkeys break them?

The tubes are made of a material called Borosilicate that is also used in laboratories. They can withstand hailstorm with hails up to 30 mm. Monkeys could break them only if they get notorious whereas mere climbing or sliding on the tubes should not particularly damage the system.

Why Should I go for Solar Water Heater ? What do I save from it?

A big cost of multiple electric geysers can be replaced by a low costing central solar water heating system.
-It significantly reduces the electricity bill. -80% accelerated depreciation for commercial users. -Rebate on monthly electricity bills from Discom (UPCL) for domestic users as per UK state government rules.

What is the maximum possible temperature it could attain?

About 60 to 80º C. The rise in temperature depends on: Solar radiation, weather conditions & number of solar collectors

Do I need to install the SWH at my Rooftop?

It is preferable to install the system at your roof top where the solar radiations are freely available. However, it could be installed in the Balcony, Terrace and open ground. Smaller systems may also be installed at the window by providing a suitable structure to support the system.

How much time does it take for the system to heat water?

5 to 6 hrs of normal sunlight is required to heat the whole capacity of the tank.

How long will the water remain hot in the tank?

Hot water produced by the solar system during the day is stored in an insulated storage tank. The insulation of the tank is such that water remains hot without significant drop in temperature for upto 24-48 hrs. Thus water heated during the previous day should be available for use in the next morning.

How does use of solar water heater help the environment?

A 100 litre system for the average size of a household of 2-3 members can prevent emissions of 1.5 tonnes of carbon dioxide per annum. The reduction in emissions of carbon dioxide (one of the major green house gases) can positively help in slowing down the pace of global warming. And it will also help Central govt. to achieve SDG-7 Targets.

How is the Solar Water Heater System Specified and what is LPD?

The capacity of a solar hot water system is specified is LPD. It is a short form for Litres Per Day. The intensity of Solar radiation varies throughout the day, hence capacity cannot be specified in terms of hourly output.

How much Area is required to install solar water heater for my residential use?

A 100 LPD system requires open surface of 2M X 2M.

What are the site requirements for installation of a solar water heating system?

The basic requirement for functioning of a solar system is availability of unobstructed sunlight for the whole day.

1. Typically, domestic solar water heating systems are installed on the roof of the house.
2. The collectors of the system have to face the sun and hence should be oriented due south for maximum interception of sunlight. Thus there should be no obstruction to sunlight in the south, west and east directions in that order of preference (an arc of about 120 °, 60° both sides of the southern direction should ideally be shadow free).
3. As a thumb rule, the requirement of shadow free area is around 3 sq. m for each 1 x 2 m collector used.
4. It is best is the area is flat, away from rain water drains and as far as possible, close to the bathrooms where hot water is to be supplied.
5. Cold water should be available at the height of around 2.5 m from the base of the system.

Is any electricity required for operation of the solar water heater?

No electricity is required for any operation in solar water heating systems. However, in case a back up heater is provided to take care of hot water requirement during cloudy days, electricity will be required.

What are the operational requirements?

Domestic solar systems do not require any special operational skills. However, if following are observed, the efficiency of the systems will be maintained at a high level:

1. Try to consume most of the heated water at one time - either in the morning or in the evening. Frequent on and off of the hot water tap would lead to reduced electricity savings.
2. If an electrical back up is provided in the tank, set the thermostat at the lowest acceptable temperature.
3. In the north Indian climate, hot water may not be used for bathing in summers. If the system is to be put totally out of use, it should be drained of water and the collector should be covered.
4. Alternatively, if the hot water requirement remains in summers also, though at a reduced level, cover the collector partially.
5. Dust deposition on the collector would reduce its efficiency. Try to clean it at least once in a week.

What are the maintenance requirements?

1. Domestic solar water heating system does not need significant maintenance requirements. Occasional leakages in the plumbing could be easily repaired by common plumbers.
2. In case quality of water is hard, scale deposition in the collectors may result over the years. This may require descaling with acids for which it is best to contact the suppliers.
3. Broken glass may also have to be replaced by the suppliers.
4. If outside exposed surfaces are painted, the paint may have to be redone every 2-3 years to prevent corrosion of the surfaces.

What are the desirable characteristics of hot water storage tank?

1. The hot water storage tank in domestic solar water heating systems is typically a double walled tank.
2. The space between the inner and the outer tanks is filled with insulation to prevent heat losses.
3. The inner tank is generally made of copper or stainless steel to ensure long life.
4. The outer tank could be made of stainless steel sheet, painted steel sheet or aluminum.
5. Electrical heating elements controlled by thermostats can be provided as an option in the tank itself to take care of those days when sun is not there or demand of water has gone up.
6. The capacity of the tank should be in proportion to the collector area used in the system. A commonly used thumb rule is to provide 50 liters of storage for every sq. m of collector area. Too large or too small tanks reduce the efficiency.

How does one identify a good solar water heater?

1. First and foremost requirement of a good solar heater is that it should have sufficient collector area for the capacity claimed. Collector area used in the system determines the capacity of water heating. Fox example, in typical north Indian weather conditions, on a sunny winter day, a sq. m. of collector area can be expected to heat around 50 liters of water by a temperature of 30-40° C.
2. Typical flat plate collectors made in the country have an area of around 2 sq. m and are thus capable of heating around 100 liters of water in a day. This proportion serves as a benchmark.
3. Further, the collectors should use good materials and the absorbers should carry a good quality coating (BIS approved collectors are being provided by large number of established manufacturers).
4. The system should be mounted on a rigid structure and should be firmly fixed with the roof to prevent damage in high winds.

How big a system should one purchase?

1. The fundamental rule is that it is better to buy a system smaller than your requirement. When more water is required, other sources of water heating could be used. This will lead to better efficiency and cause lesser operational problems.
2. The best is to make an actual estimate of daily demand of hot water. While estimating, do remember that the solar system is capable of heating only an approximately fixed quantity of water and is designed for typical sunny days. Also remember that the temperature of water in the solar system is determined by the combination of collector area and the tank capacity. Typically it would be 50 - 60°C, which is much hotter than the bathing water temperature (around 40°C).
3. Estimation of your demand can also be made with the help of the table given below. As a typical example on sizing of solar systems, it may be mentioned that a 100 liters system is considered generally optimum for family of 4 adult members.

Do not want to discard my existing electric geyser as it is in good condition but I also want to install solar water heater at my residence I fully understand the savings achieved through it. Is it possible to use both in combination?

There is no need to discard your Geyser. It can be used in combination with your new SWH. The only thing that you need to do is to connect the out let of your SWH to the inlet of your existing geyser. The temperature of the water coming out of SWH can also be elevated through the electric geyser, if needed.

Is it Possible to get Hot water in the Early Morning?

Yes. The cold water is heated during the day & it is stored in an specially insulated storage tank all night, this insulation prevents the water from losing heat, so that you have piping hot water the next morning.

Can we get hot water all 24 Hrs. of the day?

Yes ! The advantage of the solar hot water geyser is that you get hot water any time of the day or night, and irrespective of the fact whether there is electricity or not! This is true, but is limited to system capacity- the maximum quantity of hot water that can be utilised in a day will depend on the system capacity. If you withdraw more water than the rated capacity, then the water might not be hot enough.

Whether my existing piping (GI Pipes) will be suitable to carry the Hot water or separate insulated / special piping would be necessary?

A separate insulated pipe is required from Solar Water Heater Tank to Utility Point. In case of G. I. Pipe the temperature falls due to heat loss during the flow.

What is the Subsidy/benefits available from UK State Govt. for Solar Water Heater(SWH)?

The Uttarakhand State Government provides subsidy for Solar Water Heater i.e. 50% subsidy in the Domestic Sector & 30% subsidy for Commercial Sector on the approximate installation Cost chart given on Office order. The Approx. Benchmark Cost of Installation is as below:

Who is Eligible for the Subsidy on Solar Water Heater (SWH)?

Applicant should be resident of state having UPCL Electricity bill connection should be of Applicant. The applicant should have valid ID proof (Aadhaar Card, Voter id , Valid Driving license etc).

Are old system installed will be eligible for subsidy?

The subsidy will only be given for the systems installed on or after the date of Office order for subsidy disbursal i.e. 17.11.2023.

The subsidy disbursal method?

On First Come First Serve basis.

What is the Slab for Subsidy disbursement?

For the Domestic applicant the maximum subsidy disbursal limit is 500 LPD and for Commercial it is 2000 LPD.

Is there any list of Empanelled vendors for installation of SWH systems?

No, Applicant is free to choose any vendor the only point he needs to keep in mind is the system installed should be as per BIS / MNRE approval. As the applicant is suggested to give the 30% amount of system after subsidy disbursal of the installed system, so that if the system fails in the technical inspection the applicant ask the vendor to rectify the issues highlighted in the inspection report.

Any guideline for applicant asking subsidy for the SWH System?

Yes the system should be newly installed and as per BIS / MNRE guideline and Shall be operated for atleast 5 years from date of installation it should not be transferred from the place of installation after getting the subsidy.

Is there any application fee?

Yes, 100 rupees per 100 LPD is the Fee for application on SWH subsidy scheme.

Is the SWH system installed would be checked by any officer before subsidy disbursal?

Yes, the system installed by the applicant will be inspected by the respective Sr. Project Officer/Project Officer of UREDA and the report will be given as per actual after that only the subsidy will be disbursed according to the recommendations of the said inspection report.

Account details given for subsidy?

The account details submitted on the application form should be on the name of beneficiary and shall be active.

How important are the Technical Specifications of the system?

The subsidy of the system will be processed/disbursed only for those systems, which meet the technical specifications as prescribed by MNRE / BIS and found technically passed and recommended in the inspection report of the district officer, UREDA. Applicants are also advised to go through the technical specifications (refer to the technical specifications available in the portal) & choose a vendor/firm who abides and works as per technical specifications mentioned on website.

Whether the subsidy for Evacuated Tube Collector (ETC) & Flat Plate Collector are same?

The subsidy on ETC based system & FPC based system is the same and shall be disbursed based on the set benchmark cost in the defined slab, as per the category of the applicant.