Repowering for decades of long-lasting operation

 Solar PV is one of the most promising energy sources among the renewable energies, due to its low cost and simplicity. Here in Japan, thanks to the governmental 20 years of FIT program, we could increase the capacity of PV significantly. However, some people complain about minor drawbacks, as if it was a fatal issue based on misunderstanding. For example, many people misunderstand the durability of PV modules and they believe the lifetime of the PV modules are very short such as 20 years or so and it stop their power generation immediately after the "lifetime", because it is written 25 years as a guarantee period. On this basis, many people, including governmental official worries about the disposal of old PV modules. Such people believe we will have a huge amount of waste of PV modules simultaneously at the end of FIT period or the end of the lifetime of PV modules. Of course we know it will not happen, because the expected lifetime of PV modules is much longer and the end of the all the life will not come at the same time coincidentally. Just imagine our lifetime if it is a kind of exact number and everybody has exactly the same number or not. 

On the other side of the truth, PV modules degraded  slowly as a probability issue, some degraded relatively slow and the others quickly. It will cause the mismatch of the maximum power point in its strings and the group of strings handled in the same MPPT group. To avoid such mismatch, we need to replace the degraded PV module, but due to the progress of PV module technology, it is not easy to find the same module to align the string condition several years after installation. To avoid this issue, we have to align the string voltage inside the MPPT group, to do it, we need to replace much more modules than the number of damaged modules. It is not efficient at all. 

Although some people believe we need to dismantle PV plants after FIT period, due to the expanding demands of renewable energies, it is better to keep our PV plants far more than 20 years. Then we need to think about how to replace PV modules in an efficient manner. As far as I know at this moment, I can introduce a good idea to make future module replacement easy is to use use optimizer. With optimizer, we can make string voltage aligned even with inhomogeneous string configuration. To do that, we need to replace the inverters to the one with optimizers such as SolarEdge system, we call this inverter replacement attempt as "repowering". With repowering, we can increase the power generation to make ROI better while reducing various risks of PV plats such as system fault and unnecessary replacement of components as I have mentioned about the merit of repowering in another article in this blog. Now we have found another good reason to recommend repowering your PV plants for decades of long-lasting operation.