Analysis of cell to module losses and UV radiation hardness for passivated emitter and rear cells and modules

This work presents an experimental analysis and analytical modeling of cell to module losses for passivated emitter and rear cells (PERC), which enables to build a PERC solar module with a record efficiency of 20.2%. Further, it examines the ultraviolet radiation hardness of solar modules employing crystalline silicon (c-Si) solar cells featuring dielectric passivation layers. Passivated emitter and rear cells are on the transition to mass production and expected to become the dominating c-Si solar cell technology in terms of market share in the next few years. Thus, it is of major importance to implement these high efficiency PERC into high efficiency solar modules. When transferring solar cells into a solar module additional recombination, optical, and resistive losses reduce the power of the solar module compared to the power of the solar cell, termed cell to module losses. In this work we study the individual recombination, optical, and resistive characteristics of various cell and module test samples. Based on our experimental results we develop an analytical model that allows to simulate the cell to module losses and reproduces the measurement results of test modules within the measurement uncertainty. We show that a reduction of the cell to module losses requires an adaptation of both, the solar cell as well as the solar module components. We employ the analytical model to improve the cell's front metalization, cell interconnection, light harvesting and cell spacing to reduce the cell to module losses for passivated emitter and rear cells and build an industrial like 60-cell sized solar module with a record power conversion efficiency of 20.2%. Besides the efficiency, the long-term reliability of solar modules is crucial and a performance degradation of new promising technologies can impair their importance for the industry. The application of new metalization pastes that enable to contact lowly doped emitters, increases the spectral response of a PERC in the UV wavelength range. This requires the application of new encapsulation materials with enhanced UV transmittance for PERC solar modules. We report on the UV radiation hardness of solar modules featuring PERC with various silicone nitride passivation layers and employing different encapsulation polymers. Our results reveal that employing polymers with increased UV transparency results in a solar module power loss of 14%. We show that the degradation in module power is due to a reduction of the module's open circuit voltage. This loss is related to an increased charge carrier recombination in the cell, which we ascribe to a degradation of the amorphous silicon nitride (SiN) surface passivation. We develop a novel analytical model to describe the effect of high energetic photons on the solar module performance with a critical energy to deteriorate the surface passivation

PV module current gains due to structured backsheets

We evaluate the optical performance of PV modules with respect to an increase in short circuit current density. Our evaluation is based on the combination of ray tracing simulations and measurements on test modules with four types of backsheets: Two of them are structured, the third is white and diffusively reflecting and the fourth reflects no light. Under normal incidence, structured backsheets reflect incoming light at an angle that causes total internal reflection at the glass/air interface, which guides the light to the solar cell surface. Three different irradiance conditions are studied: a) standard testing conditions (STC) with light incident perpendicular to the module surface, b) variation in the angle of incidence and c) light source with mean annual distribution of angles of incidence. Using the measured refractive index data in ray tracing simulations we find a short circuit current density (Jsc) gain of up to 0.9 mA/cm2 (2.3%) for monofacial cells and a structured backsheet, when compared to a white backsheet with diffuse reflection. For bifacial cells we calculate an even larger Jsc increase of 1.4 mA/cm2 (3.6%). The Jsc increase is larger for bifacial cells, since some light is transmitted through the cells and thus more light interacts with the backsheet. Our optical loss analysis reveals the best performance in STC for edge-aligned Ag grooves. This structure reduces absorption losses from 1.8 mA/cm2 to 0.3 mA/cm and reflection losses from 0.7 mA/cm to 0 mA/cm. This trend also holds under various angles of incidence as confirmed consistently by Jsc measurements and ray racing simulations. Simulations using an annual light source emitting a mean annual distribution of angles of incidence reveal grooves in both orientations edge alignment and east-west alignment achieve similar current gains of up to 1.5% for mono- and of 2.5% for bifacial cells compared to modules with white back sheets. This indicates that for modules with light guiding structures such as these backsheets optimization for STC differs from optimization for annul yield

Antifibrotische Effekte von Regorafenib, Trametinib und Dactolisib auf kultivierte pankreatische Sternzellen der Ratte

Bei der chronischen Pankreatitis und dem Pankreaskarzinom kommt es durch pankreatische Sternzellen (PSZ) zu einem bindegewebigen Umbau des Pankreas (Fibrose). Ziel dieser Arbeit war es, klinisch relevante Kinaseinhibitoren in einem In-vitro-Modell an PSZ der Ratte auf ihre antifibrotische Wirkung zu untersuchen. Sowohl Trametinib als auch Dactolisib wirkten antiproliferativ, ihre Kombination hatte einen synergistischen Effekt. Regorafenib hemmte zwar nicht direkt das Zellwachstum, führte aber zu einer Reduktion proinflammatorischer und zellzyklusregulierender Mediatoren

Spironolactone and colitis: Increased mortality in rodents and in humans

Background: Crohn's disease causes intestinal inflammation leading to intestinal fibrosis. Spironolactone is an antifibrotic medication commonly used in heart failure to reduce mortality. We examined whether spironolactone is antifibrotic in the context of intestinal inflammation. Methods: In vitro, spironolactone repressed fibrogenesis in transforming growth factor beta (TGF‐β)‐stimulated human colonic myofibroblasts. However, spironolactone therapy significantly increased mortality in two rodent models of inflammation‐induced intestinal fibrosis, suggesting spironolactone could be harmful during intestinal inflammation. Since inflammatory bowel disease (IBD) patients rarely receive spironolactone therapy, we examined whether spironolactone use was associated with mortality in a common cause of inflammatory colitis, Clostridium difficile infection (CDI). Results: Spironolactone use during CDI infection was associated with increased mortality in a retrospective cohort of 4008 inpatients (15.9% vs. 9.1%, n = 390 deaths, P < 0.0001). In patients without liver disease, the adjusted odds ratio (OR) for inpatient mortality associated with 80 mg spironolactone was 1.99 (95% confidence interval [CI]: 1.51–2.63) In contrast to the main effect of spironolactone mortality, multivariate modeling revealed a protective interaction between liver disease and spironolactone dose. The adjusted OR for mortality after CDI was 1.96 (95% CI: 1.50–2.55) for patients without liver disease on spironolactone vs. 1.28 (95% CI: 0.82–2.00) for patients with liver disease on spironolactone when compared to a reference group without liver disease or spironolactone use. Conclusions: We propose that discontinuation of spironolactone in patients without liver disease during CDI could reduce hospital mortality by 2‐fold, potentially reducing mortality from CDI by 35,000 patients annually across Europe and the U.S. (Inflamm Bowel Dis 2011;)Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/92045/1/21929_ftp.pd

The Role and Potential Dangers of Visualisation when Learning about Sub-Microscopic Explanations in Chemistry Education

The core of theory-driven chemistry education consists of the constant shift between the different representational domains of chemical thinking: the macroscopic, the sub-microscopic, and the symbolic domains. Because the sub-microscopic domain can neither be seen nor directly visualised, it requires specific forms of visualisation, i.e. pictures and animations illustrating the model-based level of discrete particles, atoms, or molecular structures. This paper considers the central role visualisations play when learning about the model-based, sub-microscopic level, but it also reflects the dangers inherent in employing insufficiently examined, poorly considered, or even misleading visualisations. This is outlined using different examples taken from both textbooks for lower secondary chemistry education (for students aged 10 to 15) and from the internet. Implications for structuring and using sub-micro visualisations in chemistry education are also given

The Fine Guidance System of the PLATO Mission

PLATO - PLAnetary Transits and Oscillation of stars - is a medium-class mission in the European Space Agency (ESA) Cosmic Vision programme, whose launch is foreseen by 2026. The objective is the detection and characterization of terrestrial exoplanets up to the habitable zone of solar-type stars by means of their transit signature in front of a very large sample of bright stars. The seismic oscillations of the parent stars orbited by these planets is measured in order to understand the properties of the exoplanatory systems. The PLATO payload consists of an instrument with 26 cameras for star observation; 24 normal cameras grouped in four subsets with six cameras each and two fast cameras. Besides providing scientific data for very bright stars, the fast cameras also serve as two redundant Fine Guidance System (FGS) and will be an integral part of the Attitude and Orbit Control System (AOCS). This ensures a very high pointing precision which is needed to achieve a high photometric precision. Working as a star-tracker, the attitude calculation is based on guide star positions on the focal plane and their reference directions given by a star catalogue. Compared to predecessor missions like CoRoT, Kepler, or TESS, the precision of the fine guidance algorithm needs to be increased significantly. This is especially challenging as the optical design is identical for all cameras and optimized to meet the science objectives rather than to serve as a star-tracker. Therefore, a novel approach based on a Gaussian fit is proposed. The shown algorithm provides a noise optimal estimation of the guide star positions which propagates to an optimal attitude estimation. Although, computational more expensive than conventional methods, its suitability for a real-time on-board application is proven with an implementation on the target hardware. Furthermore, its robustness and precision is assessed theoretically and with simulated star images sequences

Improving Robustness of Satellite Image Processing Using Principal Component Analysis for Explainability

Finding test-cases that cause mission-critical behavior is crucial to increase the robustness of satellite on-board image processing. Using genetic algorithms, we are able to automatically search for test cases that provoke such mission-critical behavior in a large input domain. However, since genetic algorithms generate new test cases using random mutations and crossovers in each generation, they do not provide an explanation why certain test cases are chosen. In this paper, we present an approach to increase the explainability of genetic test generation algorithms using principal component analysis together with visualizations of its results. The analysis gives deep insights into both the system under test and the test generation. With that, the robustness can be significantly increased because we 1) better understand the system under test as well as the selection of certain test cases and 2) can compare the generated explanations with the expectations of domain experts to identify cases with unexpected behavior to identify errors in the implementation. We demonstrate the applicability of our approach with a satellite on-board image processing application

Real-Time Hardware-in-the-Loop Test Configuration: Use Case for the Fine Guidance System of PLATO

The presentation describes a real-time hardware in the loop test configuration with payload hardware units and simulators, used for the verification and validation of the Fine Guidance System of the PLATO mission. The presentation covers the motivation behind a combination of real and emulated hardware, a description of the PLATO mission and its Fine Guidance System, the test configuration, the related timing expected during tests and tools for test automation. Morover, a solution for a data archiving tool is provided