BLOG:: SELECTING THE RIGHT SOLAR PANEL: THE RECIPE AND COOK EQUALLY MATTERBy Ayoola Brimmo
Published on 7 July 2014
Today, it's easy to find a plethora of solar (PV) panel manufacturers offering a 25 years warranty period. A warranty period that lengthy most often seems like an awesome deal - after all you would be presented a warranty certificate with a striking resemblance to that of a degree certificate.
In the PV industry, one cannot solely rely on this 'ostentatious sheet of paper' as you would find that majority of these companies are still very young. One might think; how could they possibly offer such when they have not been in operation long enough to test their products for the 25 years offered. So with little or no experience in the PV industry, how does one choose the right product?
It might help to think of PV panel (or module) as jollof rice (also known as jollof). Almost every restaurant in West Africa makes this dish in the same way: rice, tomato paste, spices, maybe a veggie or two- but at a glance it is very easy to tell if the dish is made from basmati or long grained rice. And even within Ghana −where jollof is predominantly made from basmati rice- the taste of this dish varies.
Solar panels are generally not as tasty as jollof − with my atrocious attempt at preparing this dish being an exception- however; you would find that the 'recipe' and 'chef' are equally as important in this industry. Most top-tier, large-scale solar panel manufacturers have very similar components: solar cell, aluminum frame, glass cover, encapsulations, back sheet, junction box and perhaps some anti-reflection coatings. Among these, the single most important is the solar cell- just as the rice is to jollof. A simple test can easily differentiate between a good quality and a 'not so good' quality solar cell- just as your taste bud would to jollof. Fortunately, solar cell manufacturers are obliged to include the result of this test in their catalogue hence you would always have access to it. As it is impossible to justify an exegesis on the catalog's electrical engineering jargon whilst sticking to the jollof rice analogy, I would go straight to the pith: the most important quality indicators are the Fill Factor (FF) and cell efficiency which typically range between 0.5-0.82 and 10-19% respectively, for most commercially available cells. So, for the best quality cells, you should be looking at an FF close to 0.8 and a cell efficiency close to 19%. Except you are building a space shuttle where you would probably want to go for multi-junction solar cells which can have efficiencies as high as 44%.
Sadly, just knowing how to pick a good solar cell doesn't guarantee you a high quality panel as the PV cell is only an 'ingredient' and the quality of the final product − solar panel − is also a responsibility of the 'chef'. Information on top selling solar modules is just a Google search away and hence, the route most PV consumers thread. However, one must be careful before getting on this bandwagon as it is most often driven by the erroneous use of the 'low price' and 'high quality cell' keywords as the search criteria for 'high quality module'. This is a risky endeavor as most companies who make claims of offering 'high quality' and 'low cost' modules eventually end up defunct in a few years. The easiest to grasp, 'TTT' criterion for selecting a high quality solar panel is the manufacturer's 'kitchen age' as majority of the old timers- at least 25 years old- do tremendously well. However, like you would find some highly talented young jollof chefs, you can also find some fledgling manufacturers with exceptional ratings. In a situation where you are not convinced by the “kitchen age” criterion, a comparison between the cell and module efficiencies is advised. As this difference is an indication of the losses accrued while assembling the solar cells to form a module, this gives an idea of how good the company is in this process. While adapting this method, bear in mind that material imperfections make it impossible to find a module with an overall efficiency equal to that of its cell. Hence, the cell to module efficiency loss is in the 11 − 17% range for most manufacturers. Oddly, this is way less complicated to decode than reports on the percentage of rice nutrient loss when jollof rice is prepared
So there you go − the recipe and chef make a difference in the quality of jollof rice AND solar panels. Now that we have an idea of how to select a good quality solar panel, who's ready for some jollof?