How do you know if a photovoltaic module is real?

Article published in the 16th edition of Canal Solar Magazine

News of counterfeit photovoltaic modules has been circulating on the market. Regardless of the veracity of this news, it is a fact that there are modules on the market being sold with lower power than that specified on the label.

In other words, the modules are true, but the labels present false information. Perhaps this is the biggest fake on the market. This is more common than you might think, but only now are consumers and distributors beginning to realize this problem.

In our laboratory at Unicamp we frequently receive photovoltaic modules from distributors interested in confirming the characteristics of their imported products. Fortunately, we often confirm that the products are good.

On the other hand, unfortunately, we have already detected several samples of products with specifications lower than those shown on the labels. To speak in simple language, for example: the product is sold with a 550 W label, but it is actually a 500 W module.

Companies ask us to keep the results confidential and, furthermore, we cannot disclose the results because whenever a manufacturer has its quality challenged, the first thing it does is question the quality of the tests carried out in Brazil, suggesting that our equipment is out of calibration. .

Most consumers will never realize that they have installed “counterfeit” modules on their roof. However, large consumers are already carrying out tests in the field or in the laboratory to be sure of what they are buying.

Builders or owners of distributed or centralized generation plants can carry out testing of photovoltaic modules by sampling, both in the laboratory and in the field.

Field tests

Two tests can be carried out at the installation site, where the modules are unloaded: the IV curve test and the electroluminescence test.

Photovoltaic system integrators generally do not have IV curve tracers, due to the high cost of the equipment. The equipment for electroluminescence testing is even more expensive and this procedure is unfeasible in micro and mini generation systems.

Even when an IV curve tracer is available, IV curve testing is always done on strings and never on individual modules. In other words: it is very difficult, whether due to lack of equipment or operational difficulties, to investigate all the modules of an installation.

Normally, when you want to test modules individually (and not within strings), this type of test is done on a small number of samples from the same batch, which may be enough to detect anomalies.

The IV curve test has better accuracy when carried out in the laboratory, but it is recommended to carry it out in the field whenever possible. This test is performed with a portable tracer, as shown in Figure 1.

Figure 1: Portable IV curve tracer. Source: LESF/UNICAMP

The second test that we can do in the field is electroluminescence (EL). This is more difficult, as it needs to be done at night and requires the photovoltaic module to be energized, which poses a certain technical challenge, as an electrical power generator needs to be available at the test site.

The opinions and information expressed are the sole responsibility of the author and do not necessarily represent the official position of Canal Solar.