The CEI EN IEC 61853 and CEI EN IEC 62670 standards establish the requirements to evaluate the performance of photovoltaic (PV) modules and concentrated photovoltaic (CPV) modules respectively, but they barely apply to hybrid CPV/PV modules, in particular to those integrating a solar tracker. In fact, the performances of the CPV-PV hybrid modules with integrated solar tracker are highly discontinuous over time, both due to the variation in optical efficiency as a function of the angle of incidence (AOI), and to the travel limits of the internal solar tracker.
The discontinuity in the power curve of the hybrid module thus hinders the measurement of its nominal power: if this value were measured according to the above standards (which provide for a measurement of power only at normal incidence), it might not be representative of its actual energy producibility. For this reason RSE has started a study for the purpose of developing a new methodology to measure the power performance of hybrid modules, and also coordinated a working group within the International Electrotechnical Commission (IEC) aimed at drafting a new norm/standard (IEC 63387). The preliminary version of the new methodology was used to measure the performance of a hybrid module functional unit (FU) developed by RSE, which integrates a solar tracking system based on shape memory actuators (SMAs). The outdoor characterization of the functional unit demonstrated the perfect functioning of the solar tracking system based on SMAs, and allowed for the measurement of an efficiency value under STC conditions of the CPV part of the FU (as defined by the IEC 63670-3 standard) close to 29%. This value is in line with the performance of other commercial CPV modules, which, however, require an external solar tracker that is expensive, bulky and subject to reliability problems. Furthermore, the outdoor energy characterization activity of four commercial CPV modules was completed: the resulting Performance Ratio (PR) values (ratio between the actual energy production and the theoretically possible energy production according to the nominal power) are similar to those measured during the energy characterization already carried out in LA1.10. Finally, from the final indoor tests no degradation problems of the CPV cells emerged during the outdoor tests, which confirms their good reliability.