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• Field test of cleaning robot's moving shadow on operating PV string. • Much larger power drop for landscape modules than portrait. • Larger power drop for full-cell modules than half-cut. • No cell hotspots created. • Bypass diode heated when module stopped, but not while moving. PV cleaning robots cast a shadow on the PV modules which they are cleaning, if used in daylight. The shadow affects the electrical characteristics (current and voltage) of the module string, and could potentially also create hot spots in modules' cells or bypass diodes. The severity of these effects depends on the layout of cells and bypass diodes and the module's orientation, among other factors. In this study we tested a commercial cleaning robot on strings of two kinds of PV modules with different cell formats, connected to a grid-tied inverter. It was found that the string power was greatly reduced when modules were in landscape orientation, but barely affected in portrait orientation. The robot shadow caused slightly greater power reduction for full-cell than half-cut modules. While the robot was in motion, no heating of cells or bypass diodes was observed, although diode heating did occur if the robot stopped on a module. For the worst case of full-cell landscape modules, a simplified estimate of the energy loss due to one robot pass was roughly equivalent to 0.16% of the string's daily energy production. The results suggest that if PV cleaning robots are used in daylight, the power loss from their shadow could be almost eliminated by installing modules in portrait orientation. [ABSTRACT FROM AUTHOR]

• Vibration of 6 kinds of PV module under robot cleaning were measured. • A module's size was the dominant factor in how much it vibrated. • A module's frame and glass thickness had little influence on its vibration. • Overall the amount of vibration by robot cleaning was small – less than 1 mm. • Strong wind caused more severe module vibrations than the cleaning robot. • Large-format modules and robots that run on the modules may present greater vibration risk. Automatic PV cleaning machines ("robots") are becoming widely used in desert regions. The motion of the robot and its brushing action can vibrate the PV modules being cleaned. This study measured the vibration of six different kinds of PV module, excited by a single kind of commercial cleaning robot. The robot's brushes were straight, rather than helical, which imparted a periodic excitation to the modules at approximately 7 Hz. For comparison, module vibration by strong wind was also measured. It was found that (i) among similar-sized PV modules, the amount of vibration was largely independent of the module construction (glass thickness and frame), (ii) modules tended to vibrate at their natural frequency rather than the brush (excitation) frequency, and (iii) the module deflection range by robot cleaning was approximately 0 mm upward to 1 mm downward, while in strong wind it was approximately 2 mm upward to 1 mm downward. In this study, which used modules up to 2 × 1 m, the particular cleaning robot did not cause significant vibration, however as commercial modules become larger they may also become more flexible and prone to larger deflections. [ABSTRACT FROM AUTHOR]

Arid areas account for more than 20% of Earth's surface. Many of these arid areas suffer from harsh climates where energy consumption is high and production coexists with high hydrological stresses. In such areas, the production of water is directly linked to the production of electricity, bringing the Energy–Water nexus to a higher level [Heggy et al., Sustainable Energy-Water-Environment Nexus in Deserts (Springer, 2022)]. Under the current energy transition from a fossil-based economy to a renewable energy-based system, arid areas are seen as potential reservoirs for electricity production due to their high solar potential, thereby helping to achieve global decarbonation targets. This energy production transition will strongly affect the Energy–Water nexus as it will contribute to the decoupling of electricity from water production. The International Conference on Sustainable Energy–Water–Environment Nexus 2019 (ICSEWEN19) conference was the first to address the Sustainable Energy–Water Nexus in Deserts, bridging the gap between research and industry and highlighting the research capabilities relevant to Qatar, the region, and internationally. The Invited Papers from the International Conference on Sustainability, Energy, Water, and Environment Nexus in Desert Climates Special Collection in Journal of Renewable and Sustainable Energy presents articles covering the main elements of the conference with respect to solar photovoltaic implementation in desert environments as a key element to succeed in this global energy transition. [ABSTRACT FROM AUTHOR]

As PV cleaning machines become widely adopted in desert regions, there is concern that frequent dry-brushing might abrade modules' anti-reflective coating (ARC). It is common to study ARC abrasion via accelerated lab tests, which typically differ from real-world PV cleaning regarding sample format, test conditions and characterization tools. This paper reviews research on PV ARC cleaning abrasion, focusing on differences in experimental techniques between the lab and field. The main conclusions are: (1) coupon tests should be verified with full-size modules due to dependence of coating properties on sample size, (2) lab tests should be verified outdoors with non-accelerated cleaning schedules because abrasion is largely caused by the soiling layer itself when brushing, (3) reflectivity is well suited to measuring ARC abrasion because it can be performed in the field and is reasonably consistent with module optical performance, (4) different ARCs exhibit a wide range of abrasion susceptibility whereas bare glass is essentially immune to dry brushing. [ABSTRACT FROM AUTHOR]

Japan intends to increase the share of photovoltaic (PV) energy in its mix of electricity production from 4.5% today to 12% by 2030. However, as a result of Feed-in-Tariff (FIT) reductions and limited grid access for new projects, Japan's PV demand shrank by 23% year-over-year in 2016 and another 10% in 2017. Even so, in terms of the cost and pace of deployment, solar PV has grown much more quickly than expected in Japan, similar to what has occurred in other markets in the past (for example, the Spanish market between 2000 and 2008). Due to this fast growth, the generation cost of solar PV appears high in Japan compared with international benchmarks, something that can damage future market development. [ABSTRACT FROM AUTHOR]

The author reflects on the significance of the International Photovoltaic (PV) Module Quality Assurance Task Force (IPQAT), which aims to develop standards for PV product assessment. She notes the objective of IPQAT to establish a rating system addressing the needs of customers and countries to come up with a single test protocol. She provides the benefits of the system including module design durability, interest rate reduction and module design optimization.

Presents a study which shows that modest alternating-current electric fields can be used to monitor and influence the relative motion within certain rotaxanes, molecules comprised of a ring that rotates around a linear thread. Observation of birefringence at frequencies which correspond to the molecule's motion; Experimental confirmation that mechanical motion within the rotaxanes can be addressed and to some extent controlled by oscillating electric fields.

An introduction is presented in which the editor discusses various reports within the issue on topics including a cell concept based on silicon heterojunctions, a solution for high efficiency modules, and the use of microwave photoconductivity in metal thin films.

The article presents the author's opinion on five selected technical reports which were discussed at the Photovoltaic Technical Conference held in Provence, France in 2011. These papers reportedly tackles low cost photovoltaic solutions to address the grid parity objectives crucial for competitive electricity produced by renewable energy sources. She comments that the solutions presented are key factors in the success of future photovoltaic technologies for consumer production of electricity.

This special issue gathers a selection of papers in Advanced Materials and Nanotechnology for Photovoltaics (PV) that were presented at the 2nd EU PV Clusters Workshop and General Assembly “Progress in Photovoltaics and Nanotechnology: from FP7 to Horizon 2020”, held at the University of Barcelona (Spain) in November 2013 (cf. the Preface on pp. 10–12). A relevant contribution from the European Project SCALENANO is the development of new Cu(In,Ga)Se2 solar cell architectures incorporating ZnO nanorod arrays that are reviewed by Ohm et al. (pp. 76–87), following the processes schematically shown in the cover image. This paper describes new technological insights that are given for the synthesis of devices using electrodeposited ZnO nanorods as either front or back nanostructured contacts, exploring new promising concepts to maximize photonconversion by optical and electrical enhancement. These device architectures are compatible with the use of vacuum‐free processes with a high potential for reduction of production costs, as spray pyrolysis based processes that are described in the paper by Espíndola‐Rodríguez et al. (pp. 126–134). In the field of Si based technologies, the application of doped colloidal silicon nanocrystals sandwiched between hydrogenated amorphous silicon layers as emitters in silicon heterojunction solar cells may turn out to be an interesting system to exploit quantum confinement effects in solar cells or for the processing of low‐cost and potentially printable emitter layers, as described in the Feature Article by Leendertz et al. (pp. 156–161) from the European project nanoPV. The cross‐sectional TEM micrograph on the cover shows a crystalline silicon wafer covered with an amorphous layer and n‐type Si‐nanocrystals. Areas with regular lattice structure provide proof for the existence of nanocrystals inside the amorphous layer. In this paper, the authors discuss the technological challenges of such an approach and present first solar cells that reach conversion efficiencies of 13.7%. [ABSTRACT FROM AUTHOR]

An introduction to the journal is presented in which the author discusses various reports within the issue on topics including low-cost photovoltaic solutions, enhancing photovoltaic efficiency, and critical grid parity needed for competitive electricity.

A growing number of studies suggest that climate may impact the spread of COVID-19. This hypothesis is supported by data from similar viral contagions, such as SARS and the 1918 Flu Pandemic, and corroborated by US influenza data. However, the extent to which climate may affect COVID-19 transmission rates and help modeling COVID-19 risk is still not well understood. This study demonstrates that such an understanding is attainable through the development of regression models that verify how climate contributes to modeling COVID-19 transmission, and the use of feature importance techniques that assess the relative weight of meteorological variables compared to epidemiological, socioeconomic, environmental, and global health factors. The ensuing results show that meteorological factors play a key role in regression models of COVID-19 risk, with ultraviolet radiation (UV) as the main driver. These results are corroborated by statistical correlation analyses and a panel data fixed-effect model confirming that UV radiation coefficients are significantly negatively correlated with COVID-19 transmission rates. [ABSTRACT FROM AUTHOR]

The combination of hybrid perovskite and Cu(In,Ga)Se2 (CIGS) has the potential for realizing high-efficiency thin-film tandem solar cells because of the complementary tunable bandgaps and excellent photovoltaic properties of these materials. In tandem solar device architectures, the interconnecting layer plays a critical role in determining the overall cell performance, requiring both an effective electrical connection and high optical transparency. We used nanoscale interface engineering of the CIGS surface and a heavily doped poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) hole transport layer between the subcells that preserves open-circuit voltage and enhances both the fill factor and short-circuit current. A monolithic perovskite/CIGS tandem solar cell achieved a 22.43% efficiency, and unencapsulated devices under ambient conditions maintained 88% of their initial efficiency after 500 hours of aging under continuous 1-sun illumination. [ABSTRACT FROM AUTHOR]

Solution processing of inorganic thin films has become an important thrust in material research community because it offers low-cost and high-throughput deposition of various functional coatings and devices. Especially inorganic thin film solar cells - macroelectronic devices that rely on consecutive deposition of layers on large-area rigid and flexible substrates - could benefit from solution approaches in order to realize their low-cost nature. This article critically reviews existing deposition approaches of functional layers for chalcogenide solar cells with an extension to other thin film technologies. Only true solutions of readily available metal salts in appropriate solvents are considered without the need of pre-fabricated nanoparticles. By combining three promising approaches, an air-stable Cu(In,Ga)Se2 thin film solar cell with efficiency of 13.8% is demonstrated where all constituent layers (except the metal back contact) are processed from solutions. Notably, water is employed as the solvent in all steps, highlighting the potential for safe manufacturing with high utilization rates. [ABSTRACT FROM AUTHOR]

The integration of photovoltaic (PV) elements in urban environments is gaining visibility due to the current interest in developing energetically self-sustainable buildings. Luminescent solar concentrators (LSCs) may be seen as a solution to convert urban elements, such as façades and windows, into energy-generation units for zero-energy buildings. Moreover, LSCs are able to reduce the mismatch between the AM1.5G spectrum and the PV cells absorption. In this work, we report optically active coatings for LSCs based on lanthanide ions (Ln3+ = Eu3+, Tb3+)-doped surface functionalized ionosilicas (ISs) embedded in poly(methyl methacrylate) (PMMA). These new visible-emitting films exhibit large Stokes-shift, enabling the production of transparent coatings with negligible self-absorption and large molar extinction coefficient and brightness values (~2 × 105 and ~104 M−1∙cm−1, respectively) analogous to that of orange/red-emitting organic dyes. LSCs showed great potential for efficient and environmentally resistant devices, with optical conversion efficiency values of ~0.27% and ~0.34%, respectively. [ABSTRACT FROM AUTHOR]