Rapid development of photovoltaics and increase in manufacturing capacity, mainly in China, led to a sufficient drop in the cost of solar panels, making them quite affordable even for simple homeowners. However, some low prices offered mainly by Chinese manufacturers (at the time of this writing $ 0.27-0.30 per watt) seems attractive, but in other hand, they lead to serious reflections. You have to be very careful. Let’s see what can be hidden behind these low prices? How real are they ?
The design of the solar panel is shown in the figure below.
Let’s look at the material specification (BoM) for a standard 60-cell polycrystalline panel. The main contribution to the cost of the panel is made up of solar cells.In addition to the components shown in the figure, some kind of other materials, listed bellow in the table are needed to produce the solar panel. Ribbon and Busbar – thin wires for solar cell connection, waterproof sealant for frame, adhesive tape for fixing the cells, special dielectric sealant with high thermal conductivity for potting the junction box (unfortunately the last component is not used by every manufacturers) and flux for the soldering machine-stringer.
The current prices for all the main materials for production are fairly transparent and can be viewed at http://www.pvinsights.com. Bill of materials (BoM) for the standard 60-cell panel is shown in the table below.
You can simply make several requests to suppliers of materials and components and make sure that the real cost of the panel in China shouldn’t be lower than $ 0.31-0.32 per watt. Note that the manufacturer buying the cell pays for the cell’s watts, but the resulting panel performance is lower than the total capacity of 60 cells and in the case of polycrystalline panels, the loss could be 2-3% (this is the loss due to the electrical resistance of all wires, the loss from the glass and EVA-films, etc.). At the same time, we did not take into bill the cost of salaries, electricity and water costs, as well as the cost of the premises etc.
So if you are offered cheap panels, try to find out for yourself how it turned out so low price.
Here are the possible options (most likely you will have their combination)
1) the real power of the panel does not correspond to the datasheet on the label
2) used cells are B- or C- grade (I’ll write about this next time)
3) has been used low-quality other raw materials.
In first case, you actually pay more than you think, and if the panel is produced qualitatively then it will work properly for many years, but in the last two cases this will affect the lifetime of the panel. For example, even low-quality backsheet will quickly becomes yellow in the sun, which will necessarily affect its reflective qualities and panel performance, bad conductors will lead to the formation of “rust” and loss of power, the aluminum frame can be of secondary aluminum with large amount of mixes and in addition have a low density, which will affect on panel’s rigidity, etc.
Author: Vahe Sharafian