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
-
58 x 1800 mm
150 LPD
3
4 to 5
15
-
58 x 1800 mm
200 LPD
4
5 to 6
20
-
58 x 1800 mm
250 LPD
5
6 to 7
25
-
58 x 1800 mm