[ezcol_1half]Photovoltaic (PV) modules works under different environmental conditions but still, PV modules are expected to perform without failure or significant performance loss for their expected service life, which is generally 25 years (and, sometimes, this might even extend another 15 years beyond the warranty).So before buying PV modules a thorough inspection should be done so that PV module could achieve the expected performance level. So below given are the few key point that should be checked before buying the solar PV module.
1. Testing Standard
All panels look the same to the untrained eye, but in actual fact they are very different. Brand name and price should not be the only deciding factors. Before buying PV module make sure that modules are tested and certified according to an international set of minimal “type qualification” performance and safety standards, such as from the International Electrotechnical Commission (IEC): IEC 61215 – Crystalline Silicon Terrestrial PV Modules, Design Qualification & Type Approval and 61730 – PV Module Safety Qualification.
A module design shall be judged to have passed the qualification test, and therefore to be IEC type approved. Here are some points that will help you recognize and buy a good quality PV system:
a) Ask for international PV panel certifications such as IEC61215 and IEC61730. Good quality PV panels would also carry the IEC61701 certification for resistance to salt mist corrosion. This is vital for PV systems that are installed close to the sea.
b)The degradation of the maximum power output at standard conditions (STC) does not exceed 5% after each test nor 8% after each test sequence;
c)The requirement of insulation and wet leakage test are met;
d)No major visible damage (breakage or cracks in cells or glass, detachment of the embedding mass, etc.)
e) No sample has exhibited any open circuit or ground fault during the tests.
f)For IEC 61646 only (Thin film): the measured maximum output power after final light-soaking shall not be less than 90% of the minimum value specified by the manufacturer.
One of the most important things to look out for is warranty. It is important to understand the difference between the guarantee on the product and parts and the guarantee on the performance of the system. All solar panels should come with 2 types of warranty:
- Performance Warranty
- Product warranty
a ) Performance warranty
This warranty covers the loss of power from the panels. Usually if the power drops to less than 90% of the specification in the first 10-12 years, you can make a claim on the warranty but after you are sure that power output has dropped. In a warranty case manufacturer will either repair the defected PV‐module free of charge or replace the same by a functional PV‐module of the same type, free of charge. In case that the respective PV‐module type is no longer manufactured by the company at the time of the warranty case, company retains the right to supply a functionally identical PV‐module of the same or higher capacity of a different type. The remaining period of the original warranty period applies to newly supplied PV‐modules
The final thing to check out is whether this warranty is “linear” or “stepped”. A linear warranty of 80% (i.e. a 20% power drop) over 20 years would cover you if the output dropped by more than a twentieth of that 20% in the first year (i.e. 1%), then 2% in the second year and so on at that linear rate of 1% per year until the solar panels were 20 years old. The following figure is depicting the Linear and Stepped warranties.
Linear warranties are rare, but some of the more expensive panels do have them. The more common “stepped” warranty means that, for the “80% over 20 years” example, your panels can lose 19% in the first year and you won’t be covered unless they lose another 1% in the remaining 19 years to get under that 80% threshold.
b)Product warranty-Ten Years Repair, Replacement or Refund
A manufacturer warrants for each PV‐module for a period of 10 years as of the respective PRODUCTION DATE to the END‐CUSTOMER that the respective PV‐module is free of material defects.
In a warranty case manufacturer will either repair the defected PV‐module free of charge or replace the same by a functional PV‐module of the same type, free of charge. In case that the respective PV‐module type is no longer manufactured by the company at the time of the warranty case, company retains the right to supply a functionally identical PV‐module of the same or higher capacity of a different type. The remaining period of the original warranty period applies to newly supplied PV‐modules.
[/ezcol_1half] [ezcol_1half_end]3.Solar Panel Efficiency
Generally speaking, the higher the quality silicon used in production of solar panels, the higher the efficiency. The higher the efficiency, the more power per square inch the panel is producing. High efficiency panels are cut from large, expensive, single ingots of silicon, and are referred to as mono-crystalline. Commodity or lower cost photovoltaic panels are often manufacturer from several smaller cheaper ingots, and are known as polycrystalline, to cut down manufacturing costs. This savings is rarely passed on to consumers, and they end up paying the same price as higher efficiency panels. It is also possible to correlate higher negative power loss with less efficient cells, costing you more money at the time of initial investment.
4. Power Tolerance
Power tolerance is a measurement of how close a module’s actual output will be to its rated output under standard test conditions (STC: cell temperature = 77°F and irradiance = 1,000 watts/m2). Power tolerance is normally expressed as +/- percentage on module datasheets, such as + 3% / – 3%. For example, if a 200-watt module has a power tolerance of +/-3%, its actual output (under STC conditions) can vary from 194 W to 206 W.
The best solar panels have a “positive only” power tolerance, which means you are guaranteed to get at least the specified output from the panel and usually more.
Example: A 200W solar panel with a tolerance of +5%/-0% will produce a minimum of 200W and a maximum of 210W.The power tolerance can be found on the nameplate of the module provided on the back-sheet.
Below is shown a sample nameplate of 60 W panel from the First solar with +/-5% tolerance which means that module actual output would vary from 57 W to 63 W.
So be aware of this number, as it will directly affect the amount of power you can get.
5.Backsheet and Framing Quality
Photovoltaic backsheets play an important role in protecting solar modules over their lifetime. Some of their key functions include:
- Physical protection
- Moisture protection
- Electrical insulation
- Color that helps modules blend into their surroundings
- Efficiency to help modules generate more power
All solar panels have a plastic backsheet glued on the back of the panel to protect the solar cells. A flimsy backsheet with any air bubbles or signs of coming unstuck is a sign of a crappy panel. Certain PV modules have begun showing signs of yellowing, a consequence of backsheet deterioration. This phenomenon can impact on power plant performance and safety, and is emerging as a potential problem waiting to happen with low-cost modules.
Figure 3 – Deterioration of PV backsheet
The aluminum frame which goes around the solar panel is a good indicator of the overall quality of the solar panel’s manufacture.
Look at the corners. Is there any tidy joint? Are the joints anodized after the cut, or before? Anodizing after the cut is more time consuming, but means that the 45 degree edge is anodized too, helping protect from corrosion. Are the panels glued (bad), screwed or welded at the corners. If looks are important to you – then you may want to look for a black anodized frame.
Conclusion – So from the above discussion we can say that a Pragmatic approach in selecting the PV module results in better Performance of the PV plant and thus help the investor in getting returns in short span of time. From the above discussion it is clear that only PV module accredited/certified by an international certification organization is used as they have Performance warranty as well as Product warranty.In a nutshell, installing a PV system is an investment, so it needs to give you back the best returns as quickly as possible. It is in your interest to ensure that you purchase not only the best panels for your energy needs but that the rest of the equipment and the installation is the best in terms of quality and safety.