Things to remember while selecting a solar water heater

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:

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

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

C. Find out the correct system size

D. Consider the rebates, discounts or available subsidy.

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

The one-time installation cost of any kind of solar water heater is more than the conventional electric geyser, gas or fuel-based boilers. However, in the long run, you can save a huge amount. So, don’t look at the onetime cost, else analyze the overall cost applicable for the entire operational period.

The amount of your savings depends on various factors. Let’s have a look at some of them:

1. Your hot water requirements and the amount you use.
2. The performance of the system.
3. The geographical location of the installed site, solar resources, and availability of obstructions
4. Government incentives, subsidies, and financing model.
5. Cost of the conventional methods and fuel you use before installing a solar water heater.
6. Cost of backup arrangements.
7. Required maintenance.
8. The operational and handling pattern.

In brief, if you are choosing to install a solar water heater, you can save 50% to 80% of your monthly water heating bill which means you have to pay lesser per month that adds up to your cumulative saving and you can achieve the breakdown cost faster. Also, as the sun is free, now and ever so you are well protected from any price hike in electricity or other fuels. Thus, a solar water heater is a smarter choice.

1. Determining the efficiency of Solar Water Heater in India:

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

a. Solar Energy Factor

b. Solar Fraction

a. 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 heaters. 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.

b. 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 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.

2. 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.

a. 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)

b. 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 liters/day as the water requirement.

3. 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

(Source: https://www.energy.gov/energysaver/ )

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

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

Before you buy and install a solar water heater, you must evaluate the potential of the site where you are looking for installing the system. As everything depends on the sun’s radiation that falls on collectors, site location plays an important role in heating the water. Along with evaluating solar heating potential and resources at your site, a solar technician is required to determine the correct orientation and tilt angle for the collectors to harness the maximum possible solar energy from the freely available sunlight.

Sun rays contain a wide spectrum of visible, diffused, infrared, UV and other radiations and the solar water heater works with both diffused and visible radiations. Don’t worry, if you are not located in a colder location. Even on a cloudy day in a cold climate, sun rays have adequate diffused radiations that are enough for heating your water.

So before finalizing, ask the energy auditor or site analyzer to analyze the solar potential of your site, required orientation and tilt. It will also help in estimating the correct size of the system.

Don’t install your system in a shaded area or where any obstructions are present that can restrict the incident sun rays.

Click here to check the solar potential of your site.

Collector Orientation and Tilt:

Only after the site analysis, you can decide the orientation of collectors. Solar collectors are oriented in such a way that maximum energy can be harnessed. Other factors are also considered location orientation, landscape, local weather data, wind velocity, etc.

Normally, nowadays, heating collectors are mounted flat on the roof of the building, but it totally depends on the location’s latitude. The optimal tilt of the solar collector is somewhat equivalent to the latitude of the location.

C. Find out the correct system size

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 systems. Follow the steps for sizing the system:

a. Calculate the overall hot water demand.

b. Select the type of system.

c. 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:

1. Sizing the tankless or direct system:

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

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

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

b. 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.

2. Sizing the 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:

a. Collector Area:

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

b. Storage Volume:

A storage volume of 150litre is recommended for a small family. It increases with an increase in number of members of the family. A medium storage tank of 250 liters is enough for 5 to 7 members.

3. 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.

4. Peak Demand of the day:

Mostly, hot water is more required during morning hours, followed by the evening. Find out the duration when you need most of the water and from that duration, find out the peak demand for hot water.

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

D. Consider the rebates, discounts or available subsidy:

In India, both the state and central governments have focussed on the enhancement of the use of solar energy. For enhancing solar energy applications, they have announced various subsidies for reducing the one-time installment cost. Also, we have announced the tax benefits for one who chooses the solar water heater.

If you are in the general category states, you can avail subsidy up to 30% at the cost of the 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.

Nowadays, due to the presence of various competitors in the market, various easy financing models are available in the market. Opt for no interest EMI model for easing the need for capital investment. Also, various financial institutions are providing loans for the installation of the solar water heater.

Choose the most relevant financial model.

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,