| Work Detail |
A British-Saudi research group has investigated the impact of non-uniform fouling on photovoltaic modules and found that it can lead to greater performance losses due to different operational effects at the intracellular level. Academics carried out a series of experiments on a residential rooftop in Muscat, Oman throughout 2021.
A team of scientists from Imperial College London (United Kingdom) and Imam Abdulrahman Bin Faisal University (Saudi Arabia) has investigated for the first time the effect of non-uniform distributions of intracellular dirt on the surfaces of photovoltaic modules.
“To the best of the authors knowledge, no work of this type has been published,” the researchers explain. “The novelty of this work is that it provides a comprehensive evaluation of the effect of non-uniform dirt characteristics on a photovoltaic module.”
In the article “ Experimental investigation of nonuniform PV soiling ,” published in Solar Energy , the research team explains that they conducted their tests with 50 mm × 50 south-facing mini monocrystalline PERC solar modules. mm × 4 mm and with tilt angles of 0 degrees, 23 degrees, 45 degrees and 90 degrees. The panels had a power of 92 mW, a maximum voltage of 2.2 V and a maximum current of 42.4 mA,
“Consideration of the vertically inclined surface has been incorporated into this study, not only for its immediate implications, but also for its prospective relevance for building integrated photovoltaics (BIPV),” the group specified, adding that each module could be built with up to four solar cells connected in series. He also used a liquid UV adhesive to stick the cells onto a clean glass sample.
The academics collected soil samples from a residential roof in Muscat, Oman, while replacing the front glass every month during 2021. They used a Shimadzu UV-2600 spectrophotometer to measure the optical properties of the dirty surface of the module and chose clean glass with low iron content as a reference for testing.
They also used a Quantal FEG 650 scanning electron microscope (SEM) and an energy dispersive x-ray spectrometer (EDXS) to analyze the composition of the dirty material. “Prior to SEM/EDXS imaging, a carbon coater was used to improve the accuracy of surface analysis by enhancing the electron signal required for the imaging process, while preventing damage.” thermals,” they added.
For electrical characterization, the group used an indoor solar simulator capable of reproducing standard lighting conditions. He also applied thermocouples to the back of each solar cell to measure the temperature. “Beyond the average power loss, we are interested in the power variations in the spatial regions tested and the correlations between energy generation and the degree of dirt,” the researchers explain.
Tests showed that non-uniform soiling on minimodules can cause an average temperature increase of 2°C and an average transmittance decrease of 13% compared to the reference glass.
“Transmittance losses are closely related to power generation, with an average power deterioration of between 6 and 7% for every 5% drop in transmittance,” the scientists say. “Specifically, a power generation loss of 30%, 31%, 27% and 32% was measured in relation to a clean sample in the four spatial regions/zones. Finally, a large solid formation was identified in the horizontal tilt sample, which resulted in a localized hot spot.”
Looking ahead, the researchers noted that more “regional” researchers are needed to define standardized parameters to assess soil non-uniformity. “Our results highlight the importance of addressing PV dirt for optimal PV performance and taking into account the spatial non-uniformity of dirt,” they conclude. |
