Fabrication Spread and Mismatch Losses

So-called mismatch losses arise when cells with different I – V characteristics are interconnected because of the fewer degrees of freedom left to bias the devices, so that the array output is less than the sum of the powers the individual cells could deliver. The differences come from the unavoidable fabrication spread or from nonuniform irradiance or working temperature within the array.

To minimize mismatch losses, finished cells are measured and sorted in the factory. For series connection the important parameter is the current at the maximum power point (mpp). It is common practice to measure the current before encapsulation at a fixed voltage close to the mpp, and to classify the cells accordingly, though other classification criteria are possible [190]. Inside each class all devices present similar currents within the specified tolerance that ensures that, when connected in series to form the module, the mismatch loss will be below the desired limit [191]. Depending on the class being processed, the power rating of the resulting module will vary and this explains why manufacturers offer different module families although they are built in exactly the same way.

Updated: August 23, 2015 — 8:23 pm