Now you might have decided to buy some Solar panels for home to reduce your electricity bill or still you are planning to buy them? Buying a good solar panel is it tedious process for an ordinary person.
As Indian government is promoting use of renewable sources of energy like solar energy, there are more than hundred companies which are selling solar panels. Lack of proper knowledge about the solar power technology among the consumers and penetration of ‘not so good’ quality products by these companies in the market. Selecting one of them is really a cumbersome task. You might get trapped by investing your money in a wrong product.
The only solution of this problem is that the buyer i.e. you must be aware of some basic fundamentals of solar energy, so that you can take better decision while buying solar panels for your home. Keeping in mind this we prepared following step-by-step guide to explore various concepts about solar power technology and help the consumers make an informed choice of good quality products.
1. How electricity is produced by solar panels?
Solar panel consist of solar cells embedded in a plastic mould which is then covered by a sheet of glass. If you have seen the solar panel,you might have noticed the silver coloured wires embedded in a plastic mould beneath the glass. The silver coloured wires are solar cells. These solar cells or you can say photovoltaic (PV) cells cannot directly provide you household electricity (AC).
The cells produce DC current i.e. the current stored in your lead acid batteries mounted in your vehicle. Most of the household appliances run on AC current i.e. the current present in your electric switch board. So to use DC current produced by solar cells, need to be converted into is the AC current by an inverter.
I guess you are clear with the technology behind solar panels. Now you need to know the types of solar panels available in the market.
2. Types of solar panels available in the market
There are two types of solar panels available in the market:
- Monocrystalline solar panels
- Polycrystalline solar panels
You must be clear with these terms because the price of solar system very much depend upon this technology. Here is side by side difference between these two type of solar panels:
|Sr. no||Property||Mono- Crystalline||Multi/ Poly-crystalline||Thin Film (CdTe, CIGS, Amorphous crystalline etc)|
|3||Area occupied per kW||Lowest||Moderate (apprx 100 sq.ft)||Highest|
|4||High Temperature Performance||Poor||Poor||Better|
|5||Generation in diffused light||Average||Average||Better|
After the reading this table, You know why mono-crystalline solar panels are costlier than multi or poly-crystalline solar panels. Thin-film solar panels are not available in India so we are not considering these in our further discussion.
Now the question arises how to identify mono-crystalline solar panels from poly crystalline solar panels in the market?
2.1 Identifying mono-crystalline solar panels from poly crystalline solar panels
Monocrystalline solar panels are generally darker black in colour than polycrystalline solar panels. Mono are dark black colour, and the corners of cells are usually missing as a result of the production process and the physical nature of mono crystalline silicon.
Poly crystalline solar panels, on the other hand, is identifiable by its signature light or dark blue colour, but not uniformly so, some patches are lighter than others. The differences in appearance come about as a result of the manufacturing process.
After deciding type of solar power plant you must check our guide on:
- What size of Solar Power plant (Solar Panels) you need for your home?
- Solar Panel Price in India
- Subsidy on Solar Panel Systems by various State Governments in India
3. Efficiency of solar panels
Efficiency of solar panel is a deciding factor for cost of the solar panels. This might not be an important factor if installation space is not a limitation. This factor only comes into play when you are mounting solar panels in a congested place. In that case you are suggested to buy high efficient solar panels so that there is saving of space or you can say that you can get more solar power from limited space. Generally, The power conversion efficiency of these panels lies between 11 to 20% or more than this.
To get better understanding of this point, let’s take an example of solar panels of 250 W. This solar panel
@ 12% efficiency will require 21 ft.² of space, but
@ 20% efficiency, it will require only 12.5 ft.² space, slightly greater then half of the above.
If space is not a problem or you can say, abundant space is available to you, then you are recommended to buy lower efficient solar panels to save cost. In other terms, you can get more power by low investment with low efficient solar panels.
4. Temperature Co-efficient of solar system
The practical purpose of knowing temperature coefficient of solar panel is to know the performance of the solar cell under varying temperature of the environment. Generally at high temperature, the efficiency of solar cell is less as compared to low-temperature. You might not get desired power during peak hot summer days, when, generally, there is more power requirement to run ceiling fans, air-coolers etc.
The extent of this increase/decrease takes place is given in terms of temperature co-efficient as percentage change per degree of temperature change (eg. Power change = -0.04%/degree Celsius).
If temperature is say 40 degree Celsius, then rise in temperature from 25 degree Celsius (25°C is Base temperature for determining temperature coefficient) is 15 degree Celsius, then, solar power will decrease by (15*0.04)% i.e. 0.6% from its rated power.
You can ignore temperature coefficient if you are installing just 500 W or 1 kW solar panels for your home.
5. Tolerance, Warranty-Guarantee, Approvals/Certifications for solar panels
You might have noticed a term 100 +/- 5% on solar power system. It represent tolerance of the solar cell. It means that you might get 95% power or 105% power depending upon the prevailing conditions on your roof-top. Getting power less i.e. 95% than standard i.e. 100 W, is never recommended.
You should opt for positive tolerance of the solar panels.
Guarantee/warranty of solar power system is an important factor because you are investing a lot of money in purchasing solar panels. Generally, there is 25 years warranty provided by every solar system manufacturer.
One thing that needs to be noted regarding this warranty is that this is performance warranty of the solar cell. It means that the performance of the solar cell doesn’t fall below a certain percentage of the maximum rated power during the warranty period. There is no warranty provided for any breakage due to mishandling or any other factor.
For an example, some manufacturers provide 80-90% performance warranty for 25 years- means that the performance of these panel doesn’t fall below this level 80-90% at the end of 25th Year.
You can check out performance parameters of the panel with a simple digital Multimeter.
As you are investing a lot of money in buying solar panel for your home, you must check some certifications to assess the quality of these panels. The certification assure you the quality in these panels.
In India, the following certifications is provided by Ministry of New and Renewable Energy (MNRE) to different manufacturers:
- For crystalline silicon terrestrial PV modules: IEC 61215/ IS 14286
- For thin film terrestrial PV modules: IEC 61646
- For requirements for construction: IEC 61730 part I
- For requirements for testing, safety qualification of solar panels: IEC 61730 part II.
Installation of solar panels
Apart from these points, proper installation of solar panels is also very important to get maximum out of these panels. Here is our next guide on installing the solar panels at home: