| Work Detail |
Over-irradiance conditions can affect the operating performance of photovoltaic plants, the stability of the electrical grid and the efficiency of inverters. A team of researchers has warned that the solar industry is not taking these effects properly into account.
An international research team has studied how overirradiance (OI) can affect the performance of photovoltaic installations at low and mid-latitudes and has found that various problems can arise when RO conditions last longer than one minute and at ambient temperatures above 30 ºC.
These phenomena can affect the operating performance of photovoltaic plants, the stability of the electrical grid and the efficiency of inverters. These effects are due to the increase and drastic fluctuation of irradiance, which can vary by more than 900 W/m2.
"In our opinion, the photovoltaic industry has neglected over-irradiance in recent decades, possibly due to ignorance or the belief that these phenomena are rare and isolated," Marco Zamalloa, the lead author of the research, told pv magazine . “We ourselves were not aware of these phenomena before seeing them in our irradiance data a few years ago. However, as we are relatively new to this topic, we cannot say with absolute certainty whether these excess irradiance conditions are now considered by some branches of the PV industry and project developers.”
According to Zamalloa, RO conditions are common and occur everywhere with the formation of clouds. “They can be imagined as the wandering focal point of a magnifying glass,” he further explained. “With the movement of the cloud, it wanders over the earths surface. We only notice the increase in irradiance when the focal point passes next to a sensor.”
In the article “ Overirradiance conditions and their impact on the spectral distribution at low and mid-latitude sites ”, published in Solar Energy, Zamalloa and colleagues analyzed the spectral distribution of RO conditions in Lima, Madrid and Berlin using spectroradiometers, inclination and azimuth angles and sampling interval. Specifically, they measured the spectral distribution of solar irradiance in W/m2/nm, in the range 350 to 1050 nm, using two years of measured spectral data.
Through their analysis, they found that RO conditions cause a redshift and cloud a blueshift of the clear-sky spectrum. “The redshift caused by overirradiance conditions gives rise to different spectral distributions, depending on the mean clear-sky photon energy,” they explained, adding that the spectral redshift indicates an increase in direct normal irradiance by clouds. .
“We believe that the PV industry needs a quantitative assessment of the impacts of overirradiance on the operation of PV systems, which is only just beginning to be done,” said co-author Jan Amaru Töfflinger. “The sudden change in irradiance makes it necessary to improve the response time of the inverters and the MPPT algorithm, both to take advantage of the increase in irradiance and to avoid heating cables, fuses and photovoltaic modules due to the high current generated by the events. of overirradiance.”
Töfflinger also stressed that overirradiance conditions are common in Brazil and can have technical and economic effects on photovoltaic plants. “We have been in contact with colleagues in Brazil, where, so far, most of the articles on the impact of overirradiance conditions on photovoltaic plants have been written,” she concluded. “They say that they are quite aware of the potential risks and that they are taking precautions when sizing the inverter and the protection fuses.”
The research group is made up of scientists from the Pontificia Universidad Católica del Perú, the Helmholtz-Zentrum Berlin für Materialien und Energie GmbH in Germany and the University of Jaén in Spain. |
