Empirical estimates of the radiative impact of an unusually extreme dust and wildfire episode on the performance of a photovoltaic plant in Western Mediterranean

Abstract We have estimated the radiative impact produced by an unusually extreme dust and wildfire episode on the performance of a photovoltaic (PV) plant. The dust and wildfire events were mostly active on 26–28 and 29–30 June 2012, respectively. We took advantage of the consecutiveness of both events to separate and derive empirically the radiative effect of dust and smoke aerosols. With this purpose, we employed measurements of aerosol load, radiation and PV power output from a collocated atmospheric station and PV plant located at Burjassot (Valencia, Spain). The empirical estimates were obtained by direct comparison with a summer background day, happened right before the two consecutive case studies. The whole episode is characterized by high aerosol optical depth (AOD) at 500 nm, reaching values up to 1 and 6 for dust and smoke, respectively. Our analysis shows an average daily energy loss of −132 kWh, that represents a fraction of 20% of the energy generated by the PV plant on the reference summer background day. A significant fraction of the energy lost was due to smoke, with a daily maximum of 43% and a daily average of 34%. In case of dust, the energy reduction was moderated, with a daily average of 6%. In terms of instantaneous power reduction, we have obtained peaks of 8 and 51% for dust and smoke, respectively. The energy reduction due to aerosols is strongly dependent on AOD. Further, we have found that the power loss per unit of AOD at 870 nm is useful to separate the radiative impact of different aerosol types. Essentially, the efficiency of smoke to reduce the energy generated by the PV plant is much greater than that of dust. This effect is mainly due to the different optical properties in the near infrared that result in a daily Power Aerosol Forcing Efficiency at 870 nm of −5.7 and −19.1 kW, for dust and smoke, respectively. Our results indicate that both the AOD and aerosol type drive the radiative impact of aerosols on the PV output, confirming that extreme aerosol events may drastically reduce the power generated by operative PV plants. This reduction may be as large as that reported for particle soiling. Therefore, considering both amount and type of aerosols in the PV power analyses is mandatory in order to obtain accurate forecast scenarios and improve the grid integration, especially during extreme episodes.