5 KEY CONSIDERATIONS IN SELECTING PV MODULE SUPPLIER
There are many PV module suppliers in the market, and if we assess the different characteristics of the PV module, it becomes challenging to compare the different suppliers and do the apple to apple comparison. Obviously, there are technical as well as commercial considerations while selecting the solar PV modules, however in this article we would like discuss some of the technical considerations which should be kept in your mind while choosing your PV module suppliers.
1. Electro Luminescence (EL) Testing: EL testing is performed by most of the companies however, some of the module manufacturers are doing on random sampling basis, and some reputed suppliers conduct this test on 100% of the PV modules passing through this testing procedure. EL imaging techniques are well established and can identify the defective modules or under performing modules and park them separately in a different lot. EL testing is performed just before the packing of the PV modules in the whole process.
2. Anti-reflective Coating (ARC): Use of ARC coating on the PV module glass reduces light reflectance thus maximizing the light coupling to the solar cells. Typically, about 4% of the incident solar radiation are reflected through a normal glass and use of ARC coating on the PV module glass increases its generation by up to 4%.
3. Bus-bar design: Typically, the electricity from the solar cells is taken by the busbar made of silver foil. A busbar on the module surface area reduces its exposed area to the light, hence some of the PV module suppliers have back contact material and conduct the electricity generated through cells through back contact and makes the cells 100% exposure to the solar radiations. Also, most of the PV module suppliers have typically two bus bars, and some of the suppliers use the three-busbar design which increases the conductive area and increases the cell resistive power losses. The 3-busbar design also reduces the chances of generated current getting lost because of the finger interruptions or breaks.
4. Module Tolerance: It is advisable to select the PV modules with a positive tolerance. Many PV module suppliers provides modules with positive as well as negative tolerance of the range of -5%+5% tolerance (10% range) or a -3%+3% (6%range) tolerance which is difficult to handle and will increase the module mismatch losses.
5. PID Free PV Modules: Potential Induced Degradation is a new problem being observed in the Indian PV modules installations due to high temperature and high humidity operating conditions. It is advised to select a PID free module which has been tested for the PID test of typically a temperature of 85 degrees Celsius, 85% relative humidity, 1000V DC and a time period of about 96 hours. Under these conditions if the module has passed the PID test, then it can be acceptable to work satisfactory in the Indian conditions.
We have just highlighted some five critical factors for module selection, however there are other considerations as well such as Aluminum framing, junction boxes, back side material, 25 year guarantees and warranties, Bank ability of technology suppliers, etc.