In addition to the life span of a module, the expected yield over this period is the second factor that is indispensable for every calculation. Most module manufacturers, however, do not provide any information on the expected yield: The data sheet shows the rated power in watts, according to which the sales price is also set. However, the yields from a 300-watt module made by manufacturer A can differ significantly from those of a 300-watt module made by manufacturer B – this leads to lower or higher electricity generation costs in system operation. A higher yield would justify a higher price per watt.
Together with the information obtained from the endurance test, the gold standard among the PHOTON module tests therefore includes a statement about the expected yield of a module over a certain period of time.
Measuring the yield from solar modules was the first test PHOTON developed. The PHOTON laboratory started these measurements in 2004, and they quickly became the world's largest test series of their kind to date. PHOTON has developed a measuring device for this purpose which records the current-voltage characteristic curve of a module every second. The measurement is carried out directly on each individual module, eliminating falsification caused by cable routes or even an intermediate inverter. This allows the power produced, i.e. the module yield, to be recorded very precisely. Since the incident solar irradiation and temperature are also continuously measured, further statements can be made about the behavior of the test candidates.
In the meantime, results are available for around 200 different module types for the period up to June 2015. The measurements were suspended in 2016 and 2017, but will be resumed in 2018.
Moreover, the PHOTON laboratory has meanwhile developed a new generation of measuring instruments that operate with an accuracy of plus minus 0.5 percent and are even more precise than the first generation instruments. The new measuring devices are also suitable for high-capacity high-performance modules: in the case of modules with back-contact cells, it is important not to perform the measurement too quickly, as otherwise charge carriers will accumulate in the cell and falsify the result. The first generation of measuring instruments sometimes had difficulties coping with this effect. For more detailed information please have a look at the data sheet.
Furthermore, PHOTON's module measuring instruments are also offered to third parties, allowing module manufacturers and solar park operators to carry out their own measurements.
We will be happy to answer any questions you may have regarding PHOTON module tests.
Julio Magdalena de la Fuente