Violin graphs to supervise the energy performance of PV arrays

To monitor the energy performance of a PhotoVoltaic (PV) plant, solar radiation and air temperature are needed. Nevertheless, small PV plants are frequently not equipped with a meteorological station; therefore, environmental data are not available and only strong failures such as short- or open-circuit are detected. Low intensity anomalies, as premature ageing, cannot be detected until they produce failures. Meanwhile, a drastic reduction of the produced energy occurs. The paper proposes a methodology, based on a statistical tool known as violin plot, to monitor the energy performance of multi-arrays PV plants, in absence of environmental data, if the energy data of the single arrays are available. This is possible for small PV plants, because the same environmental conditions affect all the arrays, whatever the solar radiation and cell temperature. The methodology is applied to the data of a real plant.