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This article discusses two case studies presented at the TCI EXPO in 2023, where The Davey Tree Expert Company and Petzl collaborated to find safe and compliant work-positioning solutions for crews on nontraditional job sites. The article focuses on working on green roofs and confined-space entry for plant-health-care tank cleaning and maintenance. It emphasizes the need for new solutions for fall protection and rescue on these types of job sites. The authors highlight the importance of compliance with proper standards and training before performing any work. [Extracted from the article]

Bifacial solar cells can be encapsulated in modules with either a glass/glass or a glass/backsheet structure. A glass/backsheet structure provides additional module current under standard test conditions (STC), due to the backsheet scattering effects, whereas a glass/glass structure has the potential to generate additional energy under outdoor conditions. In this study, we quantify the current contributions due to various mechanisms in both module structures under STC. The current contributions due to different mechanisms are calculated by measuring the reflectance and transmittance of mini-modules with both structures, together with a MATLAB-based simulation. Our results show that under STC, glass/backsheet modules provide approximately 2.2% more power, as compared with glass/glass modules using the same bifacial solar cells with a standard cell gap of 2.0 mm. Using module optimization, we demonstrate that the maximum possible cost reduction benefit in $/WP of glass/backsheet modules over glass/glass modules under STC is limited to 3.3%. Due to the potential outdoor energy yield advantages of glass/glass modules reported in the literature, we recommend a glass/glass module structure for bifacial solar cells. Furthermore, in order to compensate for the lower performance of glass/glass modules under STC, we propose a methodology to measure and fairly rate bifacial glass/glass photovoltaic (PV) modules.

The performance of ten photovoltaic (PV) modules with nine different solar cell technologies (and one different module construction) is monitored in the tropical climate of Singapore. The types of modules included in this study are monocrystalline Si (glass-backsheet with frame and glass-glass without frame), heterojunction crystalline Si, monocrystalline Si back-contact, multicrystalline Si, double-junction “micromorph” Si, single-junction/double-junction amorphous Si, CdTe, and CIGS. Three years of outdoor monitoring data are used to extract degradation trends of the performance of the various modules. Statistical decomposition methods are used to extract trends for performance ratio (PR), short-circuit current (ISC), open-circuit voltage (VOC), and fill factor (FF). The degradation rates of the monocrystalline Si modules are found to be equal to or less than -0.8% per year, mainly contributed by the decrease in ISC. The multicrystalline Si module shows a slightly higher degradation rate of -1.0% per year. The amorphous Si, micromorph Si, and CdTe modules show degradation rates of around -2% per year. The CIGS module showed an exceptionally high degradation rate of -6% per year. The decrease in FF and VOC is found to be significant for all the thin-film modules but not for the crystalline silicon modules.

The spectral influence on the performance of four different thin-film photovoltaic (PV) modules (single-junction amorphous Si, CdTe, CIGS, and double-junction “micromorph” Si) is studied. Two methods are used to quantify the effective irradiance intensity for the investigated four modules. The first is based on spectral mismatch factors calculated from the measured outdoor spectrum and the spectral responses of the PV modules. The second is based on the measured short-circuit currents of the modules. The effective irradiance ratio (EIR) of a PV module technology, for a given time period, is defined as the ratio between the cumulative effective irradiance intensity received by the module and the cumulative irradiance intensity measured by a c-Si reference cell. We find that the average photon energy of the spectrum in Singapore is higher than that of the AM1.5G reference spectrum, indicating that the spectrum is “blue-rich.” Compared with the AM1.5G spectrum, this blue-rich spectral irradiance results in an annual EIR of 1.07 and 1.03 for the single-junction a-Si module and the CdTe module, respectively. An EIR larger than 1 indicates energetic irradiance gain. CIGS is not significantly affected by the blue-rich spectrum, while micromorph Si shows an annual EIR of less than 1.

Photovoltaic (PV) modules are rated under standard test conditions with normally incident light, whereas under outdoor conditions photons arrive on a PV module surface at all angles. In this study, the angular losses of PV modules with a planar and textured front glass are investigated for the tropical conditions of Singapore. Angular reflectance for both modules is first measured using a goniophotometer. From the measurements, the angular loss factors due to the different radiation components are calculated. Then, the angular losses under Singapore outdoor conditions are determined using three transposition models: Liu and Jordan, Hay and Davies, and Perez et al. Two 60-cell PV modules with a planar and textured glass are fabricated and measured outdoors for validation of the modeling results. Outdoor measurement results show that the PV module with textured glass captures 1.4% extra light compared with the PV module with planar glass for the 6-mo period studied. Next, the annual angular loss, monthly angular loss, and typical meteorological day angular loss for both module structures are studied. For all cases studied, the PV module with textured glass has consistently lower angular losses compared with the PV module with a planar glass.

The tropical regions will see an increasing share of solar photovoltaic (PV) applications. This paper therefore analyses the irradiance distribution in tropical Singapore and then experimentally determines the dependence of the PV efficiency on irradiance level, for nine different commercially available PV module technologies. For several of the PV module technologies, we also determine the dependence of the temperature coefficient of the modules' maximum power on the irradiance level. A full year of outdoor module testing data in Singapore show that the irradiance distribution has two energy peaks, one at around 400 W$\cdot$m-2and the second at around 850 W$\cdot$m-2. Most PV technologies cannot fully convert the second peak due to the fact that, in Singapore, high light intensities are always associated with higher module temperatures, which in turn reduces the module efficiencies.