FAQs related to Solar Water Heater System in India

Here is the list of some of the frequently asked questions related to Solar Water Heater.

1. What is a solar water heater?

Available with different names in the market viz. Solar Water Heater, Solar water heating systems, Domestic solar water heaters, Solar Gyser, etc., it is the most effective way to generate hot water with the minimum impact on the environment. By collecting solar energy, solar water heater gives hot water as output. Utilization of freely available sunshine makes it cost-effective, pollutionless, eco-friendly and sustainable.

2. What are the major components of the solar water heater?

Basically, Solar Water Heater System consists of three major components: Heat Collector, Storage tank and connecting Pipes. Earlier models couldn’t work at freezing temperature, very hot climate or cloudy day but nowadays, technology up-gradation has made it possible to work effectively even at unfavorable climatic conditions.

3. What are the types of solar heat collectors used in a solar water heater?

As the name suggests, heat collectors are the component that collects heat from the sunshine. These are a vital component in any solar heating system. Basically, there is three types of solar collectors that are predominantly used for residential purposes.

Flate Plate Collector

Evacuated tube Collector

Integral Collector-Storage System

4. What are Flat Plate, Solar heat collectors?

These are the most fundamental type of solar collector that has been used since the beginning. The basic principle of this collectors is: the sun heats a dark flat surface which collects the maximum possible heat and then transfers it to the water. The main components of Flat plat collector are as follow:

Black surface - It absorbs the heat from incident solar radiation.

Glazing cover – It is a transparent layer that transmits radiation to the absorber, and also protects the heat loss by radiation or convection.

Circulating Tubes: These tubes contain the heating fluid to transfer heat from the collector for meeting the end purpose.

Support Structure

Insulation cover

Advantage:

Flat Plate collectors are simple and cheap.

Easy to manufacture, install and operate.

Less maintenance

Permanently fixed.

5. What is the integral collector-storage system?

In this collector and storage are encased in a single unit. It contains single or multiple black painted tanks or collectors. Coldwater flows through the preheated collector tubes or tanks and gets heated. This is more utilizable in mid-freeze climatic regions. Mostly used for household applications.

6. What are evacuated tube collectors?

It contains parallel rows of transparent glass tubes. Each tube has an outer glass tube to receive maximum solar radiation and an inner metal tube which acts as a heat absorber attached to the fin. The fin is duly coated to restrict the heat loss and transfer maximum possible heat to the running fluid or water. These types of collectors are most frequently used across the globe. Also, it is the most used solar water heater in India both for residential and commercial purposes.

7. What are the things to remember while deciding the type of solar water heater to use?

Going solar is now a trend in India. If you are looking for purchasing a solar water heater, don’t follow the crowd. Instead you should focus on your own homework. Before selecting a solar water heater for your home or commercial purpose, you should consider the following things:

1. Determine the correct cost and energy efficiency of the solar water heating system.

2. Work on evaluating the solar heating potential of your site.

3. Find out the correct system size

4. Consider the rebates, discounts or available subsidy.

8. How to determine the efficiency of the solar water heating system?

For determining the efficiency of the solar water heater, there are two indices used worldwide, also relevant in India:

• Solar Energy Factor
• Solar Fraction
• Solar Energy Factor: Solar Energy Factor is a mathematic formula to determine the efficiency of the system. It is the result of the division of energy obtained from the solar water heater system by the energy obtained by the electrical, gas or other conventional water heater. The higher the number, the more will be the efficiency of the system. Normally, it ranges from 1 to 11. If it is 1, it means your solar water heater is performing equivalent to your previously used conventional one while 11 means your solar water heater is 11 times more efficient than the conventional one.
• Solar Fraction: If you are using a conventional water heater as a backup, solar fraction gives up the value of the solar water heater in your overall obtained heat from the combined system. It ranges from 0 to 1. Normally, it is around 0.5 to 0.8. e.g. 0.5 SF means 50% of your heating demand is fulfilled by the sun.

While selecting a solar water heater, one must choose a higher efficient one. If you are choosing a combined assembly, put the SF above than 50%.

Also, the sole consideration of efficiency is not advisable. You must consider the overall cost of the system as well.

Calculation of annual operational cost:

Before making the final decision on the type of solar water heating system, you must consider the annual operational cost of the available options and compare them to have a detailed overview. It will help you in the evaluation of annual savings and also determine the payback period. While considering the efficiency, always opt for a lower operational period to minimize the payback period.

For calculating the annual operational cost, follow these steps:

Step 1: Find out your requirements and size of the system.

Step 2: The Solar Energy Factor of the System

Step 3: Cost of the conventional system (Gas or electric)

Step 4: Perform the respective calculations for cost-saving.

1. If the conventional system is Gas based: Determine the unit fuel cost and put them in the formula:

365 × 0.4105 ÷ SEF × Fuel Cost (therm) = estimated annual operating cost saving

Unit fuel cost in therm. ( 1 therm = 1,00,000 BTU), (BTU = British Thermal Unit)

2. If the conventional system is electric geyser: Use this formula:

365 × 12.03 kWh/day ÷ SEF × Electricity Cost (kWh)= estimated annual operating cost saving

This formula is based on taking 250 liter/day as the water requirement.

Cost comparison and payback period:

After calculating the overall operational cost of the available options, compare the cost with the conventional water heater or geyser and determine the overall payback period. You can use the following table for easier comparison.

Model

Installation Cost

SEF

Annual Operational Cost

Model A

Model B (more efficient)

Additional Cost of Model B

=Price of B- Price of A

Additional Annual Cost Saving (Model B)

=Operational Cost B- Operational cost A

Payback Period (Model B)

=Additional Cost of B/Cost B’s Saving per year

Also, consider the maintenance cost for a more detailed approach. Contact us for more detailed analyses.

9. How to improve the efficiency of the solar water heater?

There are various energy saving and efficiency improvement tips to enhance the performance of your installed and duly maintained solar water heater system. Browse for the latest energy-saving strategies and devices which are more cost-effective to install with the heater.

Always monitor the working efficiency of the system. Make a record of it and analyze it in your free time. If it is not working satisfactorily, call your contractor and ask for any maintenance or repair, if required.

Solar technology is not new but evolving. Every day, new innovations are entering in the market. Stay updated for any new add-ons for improving the energy efficiency of your system.

10. What are the sizes of the solar water heater available in the market?

Presently, there are many brands and solar contractor in the Indian market that provides various size of the solar water heater. The size of the solar water heater depends on the hot water requirement and other factors that we have discussed previously. The size of the solar water heater available in market starts from 100 litre per day.

Available sizes for ETC solar water heater (Domestic or residential purpose)

Capacity in Litres per day

Utility Points (max.)

Applicable Number of Persons using hot water

Total Number of Evacuated Glass Tubes

Size of inlet/Outlet pipe of the storage tank

Evacuate tubes(size)

100 LPD

2

2 to 3

10

1.9 cm (3/4")

58 x 1800 mm

125 LPD

2

3 to 4

13

• p>

58 x 1800 mm

150 LPD

3

4 to 5

15

• p>

58 x 1800 mm

200 LPD

4

5 to 6

20

• p>

58 x 1800 mm

250 LPD

5

6 to 7

25

• p>

58 x 1800 mm

300 LPD

5

8 to 9

29

2.54 cm (1")

58 x 1800 mm

Commercial(Capacity above 300 LPD)

Capacity in Litres per day

Utility Points (max.)

Applicable Number of Persons using hot water

Total Number of Evacuated Glass Tubes

Size of inlet/Outlet pipe of the storage tank

Evacuate tubes(size)

500 LDP - PR

8

14 to 15

44

2.54 cm (1")

58 x 1800 mm

1000 LPD - PR

14

29 to 30

87

• p>

58 x 1800 mm

Apart from this, there are various other sizes with a different types of solar water heaters.

Also, check this table which includes also the sizing of the system.

Capacity (liters per day)

Area in sq. m. for ETC system

Area in sq. m. for FPC system

100

1.5

2

200

3

4

250

3.75

5

300

4.5

6

350

7.5

10

Here, ETC means an evacuated tube collector system and FPC is Flate plate collector system.

11. How to find out the correct size of the solar water heating system?

The system size solely depends on the type of solar water heater system you have opted and the total requirement of the hot water. Here are the three types of solar water heating system. Follow the steps for sizing the system:

• Calculate the overall hot water demand.
• Select the type of system.
• Find out the cumulative sum of area requirements of all the components.

Let’s have a look at the sizing of the solar water system on the basis of their type:

Sizing the tankless or direct system: Tankless system or direct system means that the hot water is directly transferred to the end-user without hauling at storage tank. For sizing such system, follow the steps:

• Find out the flow rate of the hot water application.

For finding this, determine the flow rate at individual outlet points. For example, required flow rate at the taps, showers or another utility point. Find out their algebraic sum.

• Find out the temperature rise

The temperature rise is the difference of the inlet cold water temperature and required hot water

On the basis of these two factors, the solar water heater provider will suggest a suitable size for you.

Sizing solar water heater system: In this, the overall collector area and storage capacity is calculated to determine the overall size of the system. After calculating the water requirement, follow these steps:

• Collector Area: For the first two family members, normally a collector area of 20 to 25 square feet is suggested. For every additional member, collector area of approximately 8 to 10 square feet is added to the previous one. It again depends on location and its solar resources.
• Storage Volume: A storage volume of 150litre is recommended for a small family. It increases with an increase in number of members of family. A medium storage tank of 250 liters is enough for 5 to 7 members.

Sizing storage or heat pump type solar water heater: If you are thinking of an active solar water heater, calculate the area requirement of heat pumps and other plumbing components.

The type of system, water requirement, storage requirement, and peak demand collectively gives the size of the system you needed.

12. How much does it cost to install a solar water heater?

The cost of the system depends on various factors. Some of the factors are as follow:

• Type of the system
• Size of the system]
• System Brand name
• Associated warranty and guarantee
• Free Maintenance period
• The effective life span of the system
• The efficiency of the system
• Assured performance of the system
• Add-Ons with system
• Monitoring units or other additional equipment with the system.

The approximate cost of the system has been enlisted in the following table. It may vary as per the trend and market demand.

Overall Capacity of the system (liters per day)

Cost of evacuated tube collector system (in Rs)

Cost of Flate Plate Collector system (in Rs)

100

15000

22000

200

28000

42000

250

34000

50000

300

40000

58000

350

62000

85000

The above cost includes the following:

• Cost of collectors
• Insulated hot water storage tank
• Piping and essential plumbing component
• Electrical Backup
• Installation cost.

The additional cost may be of plumbing to the utility point, additional heat exchangers, pumps (If it is active system), etc. If you are located in any isolated locations or hilly terrain, the cost can further increase. Also, the cost varies from manufacturer to manufacturer, contractor to contractor and location to location.

Contact us to know the exact cost at your location.

13. Which solar water heater is best?

All are good, depends what you require and need.

• Evacuated tube collector systems are fragile in nature as they contain glass. Thus require smooth handling and care. These systems work satisfactorily in the colder regions even at sub-zero temperatures. If there is much salt content in the water, it gets deposited inside the tube. Therefore, tubes are required to cleansed properly after specific time period.
• Flate Plate Collector system has a longer effective life as they are metallic, but they are expensive than the evacuated tube collector system. If there is much salt content in water, heat exchanger mechanism is required to avoid salt deposition which further adds to the cost of the system.
• Passive solar water heater systems are preferable for small domestic or residential purposes while for larger commercial practices, an active system i.e. systems with additional pump is required.

14. How effective are solar water heaters?

The effectiveness and efficiency of solar water can be calculated from SEF (Solar Energy Factor) where SEF is Solar Energy Factor is a mathematic formula to determine the efficiency of the system. It is the result of the division of energy obtained from the solar water heater system by the energy obtained by the electrical, gas or other conventional water heater. The higher the number more will be the efficiency of the system. Normally, it ranges from 1 to 11. If it is 1, it means your solar water heater is performing equivalent to your previously used conventional one while 11 means your solar water heater is 11 times more efficient than the conventional one.

On the basis of types of solar water heating system and its operation, you can calculate is effectiveness.

15. Do solar hot water systems save money?

Of course, the solar hot water system saves money.

If you compare the operational cost of a conventional heater and solar water heater, it is much lesser for solar water heater. Though the one-time investment cost of solar water heater is higher than the conventional heater, you are saving a lot in the longer run. If you break down the cost with respect to the overall operational period, solar water heater is a worthy investment.

Look at the following table to have an approximate idea of overall savings

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

(source: bijlibachao.com)

So, you are saving a lot while opting solar water heater.

16. What size solar hot water do I need?

The size of solar water you will need directly depends on your overall hot water demand. More the consumption of hot water more will be the required size. Also, it depends on the type of solar water you choose like if you are opting for a tankless or direct solar water heater, you will require a smaller size. Also, the size criteria vary for integrated storage collector system, flat plate collector system, evacuated tube collector system, etc.

For a small family of 4-5 members, a small 150 LPD solar water heater is sufficient. A medium storage tank of 250 liters is enough for 5 to 7 members.

For the first two family members, normally a collector area of 20 to 25 square feet is suggested. For every additional member, collector area of approximately 8 to 10 square feet is added to the previous one. It again depends on location and its solar resources.

17. What are the major types of solar hot water systems?

In broad categories, solar water heater or solar hot water systems are of two types:

a. Active solar water heating system- (have a pump)

• Direct Circulation System:
• Indirect Circulation System:

b. Passive solar water heating system (doesn’t have pumps)

• Integral collector storage system:
• Thermosyphon system:

18. Does solar water heater need electricity?

No, if you are using solar water heater solely, it doesn’t require any electricity at all. In case, you are opting for an additional electric geyser as a backup, electricity will be required.

So the case is, it solely depends on you. Solar water heater doesn’t need electricity for running. Electricity is only required if you need backup.

19. Does solar water heater work in winter?

Winter does have sunlight. If there is sunlight, solar water heater works. Don’t consider the warmth of the environment, sun rays consist a wide spectrum of radiations – diffused radiations, visible radiations, infrared, ultraviolet, etc. The system performs well in winters as well. But if the temperature goes below the freezing point for a longer period, you need to install or arrange for additional heating fluid or heating exchangers to avoid freezing of water.

In case, temperature rarely goes below the freezing point, no additional arrangements are required except some additional plumbing fixtures.

20. Are solar water heaters worth the investment?

If you compare the operational cost of a conventional heater and solar water heater, it is much lesser for solar water heater. Though the one-time investment cost of solar water heater is higher than the conventional heater, you are saving a lot in the longer run. If you break down the cost with respect to the overall operational period, solar water heater is a worthy investment.

Look at the following table to have an approximate idea of overall savings

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

(source: bijlibachao.com)

So, you are saving a lot while opting solar water heater.

You are not only saving the electricity cost, but also the carbon footprint, pollution, and your environment.

21. How long do solar water heaters last?

Normally, solar water heaters last for 10 years (Warranty period) without any serious maintenance or repair. If you maintain it wisely, it may last for 25 years with some occasional repair and maintenance. Duly follow the maintenance guidelines for a longer life cycle.

22. Do solar water heaters work on cloudy days?

Yes, If there is sunlight, solar water heater works. Don’t consider the warmth of the environment and the visible spectrum of sunlight. Clouds can only restrict visibility of the sun, not the presence of sunlight. The sun rays consist a wide spectrum of radiations – diffused radiations, visible radiations, infrared, ultraviolet, etc. The system performs well in winters as well.

There are storage tanks as well which are duly insulated to inhibits the heat loss. You can also opt for electric heater or geyser as a backup in case, solar water heater is not working satisfactorily during cloudy or shady days. Normally, it is not required, until or unless you are in amazon rain forest. Oh, a major part of that has burnt off. Now, it works there also.

23. How do I know if my solar hot water is working?

Simple is that, If you are getting hot water, your solar hot water or heater is working. Jokes apart, in most of the sophisticated systems, there are temperature indicators that tell the temperature of the stored and heated water. So, check it. Also you can opt for more advanced monitoring gadgets and devices that will tell you about the complete health of your solar water heater.

In case, your solar water heater is not working, call your contractor or service provider for a health checkup.

24. Is solar hot water cheaper than gas?

Of course, it is cheaper alternative of gas. Sunshine is free of cost so there are no fuel charges of solar water heaters. Also you are prevented from the price hike or market up-downs. Though the one-time investment cost of solar water heater can be high, the overall operational cost is much cheaper. Approximately, it is 5 times cheaper than gas-based water heater comparing the installation and overall operational period applicable throughout the life cycle of the system.

25. What is LPD in a solar water heater?

The abbreviation LPD means Litres per day. It is used to measure your daily consumption or in other words the daily requirements. It is obtained by dividing the overall water consumption or requirement throughout a certain period by the number of days in that certain period.

26. What are the advantages and disadvantages of solar water heater?

Each type of solar water heater has its own advantages and disadvantages. Here are some:

Advantages of Direct Circulation System

• Simple and Reliable: The direct circulation system is simple and more reliable. The concept is simple, less maintenance, no additional fluid, and lesser energy loss make it more reliable.
• Affordable: It requires lesser plumbing components, moving parts, and labor which makes it less expensive than the indirect one.

Disadvantage of direct circulation system

• Not efficient in very cold weather: In conditions of severe cold, when the temperature goes in negative, plain water gets freeze and can even burst the plumbing components. Thus, this type of system is not applicable at all locations, at all temperatures.
• Not efficient for multiple heating needs: If you are looking for heating your two pools of water from the same system, it is not efficient. Multiple purposes mean multiple heaters.

Advantage of the indirect circulation system

• More efficient in a cold climate: As in this type of system either circulating fluid is used as a solar collector or it is mixed with water which further lowers the freezing point makes this system more efficient for such weather conditions.
• Suitable for multiple purposes: Hear can be exchanged to multiple arrays of water make this system suitable for multiple purposes.

Disadvantages of the indirect circulation system

• Less Efficient: Because of the involvement of the heat exchange phenomenon, a great amount of heat is lost, make this system less efficient than another type.
• Expensive: More plumbing components, additional fluid, and the setup take along additional cost which makes the entire system expensive.

Advantages of the integral collector storage system

• Simple mechanism, easy installation, and operation: Being a passive system, this type of solar heater doesn’t require additional pumps or electronic control. Lesser components make the overall cost cheaper. Moreover, less maintenance is required.
• Cheaper alternative: It is the cheapest among the other types of solar water heater and most preferable for any DIY projects where homeowners can install their own built solar water heater with minimum cost.

Disadvantages of the integral collector storage system

• Low performance and efficiency: performance and efficiency are very low. You can’t simply rely on such kinds of heaters. Additional backup is required.
• More weight: Due to the presence of heavy collector tube, the weight of this type of heater is cumulative sum of water, collector tube, storage tank and some add Ons. So, mostly they are mounted on ground. For roof mounting, additional supporting structure is required.
• Not workable at the freezing point: This type of heaters doesn’t work satisfactorily at freezing point or on a cloudy day. However, recent design innovations have made it possible in new versions of ICS system.
• More Heat loss: The collector also acts as a water storage unit in this type of system. For avoiding more heat loss, double or triple glazing layers have been provided on the tubes which further add ons to the weight of the system. Still, there is considerable energy loss in this system.

Advantage of Thermosyphon system

• Highly reliable: these types of systems are most widely used because of their reliability, good performance, and efficiency.
• Cost-effective: Being a passive system, it requires lesser component than the active one. Thus, it is more cost-effective than active systems.
• Less Maintenance: It involves lesser maintenance and operational cost. Thus, a faster cost breakdown can be achieved.

Disadvantages of Thermosyphon system

• Freezing point operation: Thermosyphon system doesn’t work properly at the freezing point which makes is unapplicable for cold prone regions. For such locations, additional fluid is required to use either to mix with water or as a collector fluid.
• Multipurpose uses: For multipurpose use, separate heaters are required which makes it a costlier alternative for multipurpose applications.

27. What are the maintenance guidelines of a solar water heater?

• Passive systems require lesser maintenance while the active system needs more. If you are opting for the second category, duly discuss the maintenance and operational guidelines with the service provider and ask for the maintenance manual.
• Plumbing and other components require the same maintenance as the conventional system.
• Glazing of the collectors is required to be cleansed in dry climate where rainwater is no option for natural cleansing.
• Regular maintenance is required every 3-5 years by certified service providers. If your system has electric components, typically in 10 years, you will need to replace the parts.

Also, check the following:

• For ETC, glass tubes can break. Therefore, you may have to provide occasional replacement
• Remove the scaling or deposits regularly. If there is much hardness in the water, acid can be used to clean the collector.
• If your outer system is painted, you may have to re-paint it every 2-3 years to prevent the system from corrosion.
• Occasional leakages or other issues need to be repaired periodically by local plumber or service providers.

28. How to hire a solar water heater contractor or service provider?

While hiring the contractor, you must screen him properly. Don’t rely on the information provided by him or their company only. Believe, you only save yourself from a bad deal and are solely responsible for any bad experiences. Keep in mind to ask the following questions to the contractor or service provider before hiring.

• How old is your company? Do you have the necessary experience in installing and maintaining solar water heating system?

(Always choose an experienced company with a trustful customer base. Don’t rely only on internet ratings. Ask their previous customers about their experiences and inconvenience, if any. More the experience and operational period, the better it is. Prefer a company with international footprints)

• Is your company have the required license or certificated?

(Government and other regulatory bodies have decided of certain certificated and licenses to the verified companies. Ask the service provider to provide you the soft copy or at least show you the required registration, licenses, and certificates.)

• What is the manufacturer’s warranty and performance warranty?

(Ask for the warranty period of both manufacturers and performance warranty. Warranty and guarantees are assurance of the service provider to you. Any verified supplier will provide you warranty of at least 5 to 10 years. Larger the period, the better it is.)

29. How old is your company? Do you have the necessary experience in installing and maintaining solar water heating system?

Green 4 Life Energy is an Indian venture of Green 4 Life Oz - an Australian company with an experience of more than 15 years in the solar domain.

30. Is your company have a required license or certificated?

Yes, we have all the required licenses and certificated that are required for providing the services and products. You can check it on our website. Also, we can give you a copy on the request.

31. What is the manufacturer’s warranty and performance warranty?

With a solar water heater, we provide a warranty of 10 years. Along with this, we provide performance warranty of 25 years.

32. What are the government subsidies available on a solar water heater?

If you are in the general category states, you can avail subsidy up to 30% at the cost of solar water heater. For the residents of a hilly area, northeastern states and islands India, they can avail subsidy up to 60% on solar water heater with certain benchmark: Rs 3000 per sq.m. for ETC and Rs 3300 per sq.m. for FPC systems.

For more detailed information, contact us now.

33. What are the product features and benefits of solar water heater by Green 4 Life Energy?

Product Features and Benefits

• Effective and cost-effective method of generating Hot water without electricity.
• Insulated storage tank that ensures minimum heat loss.
• Compact size, low height, lightweight, easy installation, and maintenance.
• Huge electricity and fuel charges saving.
• Eco-friendly, sustainable and affordable.
• Absorber Coating- AIN-SS-Cu coating
• Inner Tank Material-Stainless steel 304-L Grade
• Stand Parts Material-Mild Steel with Black Powder Coating
• Type of Thermal Insulation- Polyurethane Foam (PUF)

About the author: Green 4 Life Energy is an Indian venture of Green 4 Life Oz - an Australian company with an experience of more than 15 years in Rooftop solar. With headquarter at Jhansi, in Uttar Pradesh, Green 4 Life Energy Pvt. Ltd. has pioneered the concept of harnessing valuable sunlight for energy production by its innovative, affordable and international standardized solar solutions, specializing in high efficiency PV module and comprehensive EPC solutions. We are at fore-front of developing and deploying technological tools to organize and aggregate the roof-top solar industry. Our partnerships with globally renowned and leading solar equipment manufacturers ensure peerless high-quality products and services. With our international presence and firm customer base, we are active contributor in framing the solar revolution in the largest democracy of the world, India.

About the author: Green 4 Life Energy is an Indian venture of Green 4 Life Oz - an Australian company with an experience of more than 15 years in Rooftop solar. With headquarter at Jhansi, in Uttar Pradesh,