Perovskite Solar Cells go Outdoors Field Testing and Temperature Effects on Energy Yield

Perovskite solar cells PSC have shown that under laboratory conditions they can compete with established photovoltaic technologies. However, controlled laboratory measurements usually performed do not fully resemble operational conditions and field testing outdoors, with day amp; 8208;night cycles, changing irradiance and temperature. In this contribution, the performance of PSCs in the rooftop field test, exposed to real weather conditions is evaluated. The 1 cm2 single amp; 8208;junction devices, with an initial average power conversion efficiency of 18.5 are tracked outdoors in maximum power point over several weeks. In parallel, irradiance and air temperature are recorded, allowing us to correlate outside factors with generated power. To get more insight into outdoor device performance, a comprehensive set of laboratory measurements under different light intensities 10 to 120 of AM1.5 and temperatures is performed. From these results, a low power temperature coefficient of amp; 8722;0.17 K amp; 8722;1 is extracted in the temperature range between 25 and 85 C. By incorporating these temperature amp; 8208; and light amp; 8208;dependent PV parameters into the energy yield model, it is possible to correctly predict the generated energy of the devices, thus validating the energy yield model. In addition, degradation of the tested devices can be tracked precisely from the difference between measured and modelled powe

Photovoltaic module cascaded converters for distributed maximum power point tracking: A review

© The Institution of Engineering and Technology 2020 Operating photovoltaic (PV) systems under partial shading conditions results in significant power losses. To mitigate partial shading effects, distributed maximum power point tracking (DMPPT) architectures have been proposed. An emerging DMPPT technique represented by PV module cascaded converters (MCCs) has been widely reported in the literature. In this architecture, a DC converter is allocated for each PV module to process and maximise its power. In this sense, mismatch effects are mitigated between PV modules. While MCC architecture has prominent advantages and value-added features, its challenges and limitations cannot be ignored. This study presents a comprehensive review of the state of the art of PV MCC architecture to help readers realise the progress of this DMPPT technique. Several points are extensively discussed and analysed including concept realisation and analysis, DC converter topologies and design optimisation, DMPPT performance limitations, DMPPT control, and protection. The main concepts are reemphasised through a set of simulations. Finally, a list of potential research areas in this field is introduced

Coronal Heating as Determined by the Solar Flare Frequency Distribution Obtained by Aggregating Case Studies

Flare frequency distributions represent a key approach to addressing one of the largest problems in solar and stellar physics: determining the mechanism that counter-intuitively heats coronae to temperatures that are orders of magnitude hotter than the corresponding photospheres. It is widely accepted that the magnetic field is responsible for the heating, but there are two competing mechanisms that could explain it: nanoflares or Alfv\'en waves. To date, neither can be directly observed. Nanoflares are, by definition, extremely small, but their aggregate energy release could represent a substantial heating mechanism, presuming they are sufficiently abundant. One way to test this presumption is via the flare frequency distribution, which describes how often flares of various energies occur. If the slope of the power law fitting the flare frequency distribution is above a critical threshold, $\alpha=2$ as established in prior literature, then there should be a sufficient abundance of nanoflares to explain coronal heating. We performed $>$600 case studies of solar flares, made possible by an unprecedented number of data analysts via three semesters of an undergraduate physics laboratory course. This allowed us to include two crucial, but nontrivial, analysis methods: pre-flare baseline subtraction and computation of the flare energy, which requires determining flare start and stop times. We aggregated the results of these analyses into a statistical study to determine that $\alpha = 1.63 \pm 0.03$. This is below the critical threshold, suggesting that Alfv\'en waves are an important driver of coronal heating.Comment: 1,002 authors, 14 pages, 4 figures, 3 tables, published by The Astrophysical Journal on 2023-05-09, volume 948, page 7