Laser microspot welding for interconnection of back-contacted silicon solar cells

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Assembly cell for the manufacturing of flexible solar modules in building integrated photovoltaics

The current use of photovoltaics is often limited to the utilization of roof surfaces or ground-mounted systems. In particular, building integrated photovoltaics (BIPV) have enormous potential to make energy production more sustainable, because the energy is generated where it is used. However, most of these modules either do not meet the aesthetic requirements of the architects as well as the building owner or are uneconomical, since visually appealing building-integrated PV modules cost several times more than standard modules. In this article, an approach for a (semi) automated assembly line that allows geometry- and material-flexible manufacturing of PV modules is presented. The challenges in automating the flexible manufacturing processes include mainly the handling of limp components and the complexity of geometry variability. Appropriate gripper systems are required to ensure safe and reliable handling of the components. A gripper developed in this article offers the ability to flexibly deposit solar strings. Preliminary tests show that 66% of all conducted trials meet the accuracy requirements

Understanding issues related to personal data and data protection in open source projects on GitHub

Context: Data protection regulations such as the GDPR and the CCPA affect how software may handle the personal data of its users and how consent for handling of such data may be given. Prior literature focused on how this works in operation, but lacks a perspective of the impact on the software development process. Objective: Within our work, we will address this gap and explore how software development itself is impacted. We want to understand which data protection-related issues are reported, who reports them, and how developers react to such issues. Method: We will conduct an exploratory study based on issues that are reported with respect to data protection in open source software on GitHub. We will determine the roles of the actors involved, the status of such issues, and we use inductive coding to understand the data protection issues. We qualitatively analyze the issues as part of the inductive coding and further explore the reasoning for resolutions. We quantitatively analyze the relation between the roles, resolutions, and data protection issues to understand correlations.Comment: Registered Report with Continuity Acceptance (CA) for submission to Empirical Software Engineering granted by RR-Committee of the MSR'2

Thin crystalline macroporous silicon solar cells with ion implanted emitter

We separate a (34 ± 2) μm-thick macroporous Si layer from an n-type Si wafer by means of electrochemical etching. The porosity is p = (26.2 ± 2.4)%. We use ion implantation to selectively dope the outer surfaces of the macroporous Si layer. No masking of the surface is required. The pores are open during the implantation process. We fabricate a macroporous Si solar cell with an implanted boron emitter at the front side and an implanted phosphorus region at the rear side. The short-circuit current density is 34.8 mA cm-2 and the open-circuit voltage is 562 mV. With a fill factor of 69.1% the cell achieves an energy-conversion efficiency of 13.5%.Federal Ministry for Environment, Nature Conservation, and Nuclear Safety/FKZ 032514

Laser-welded interconnection of screen-printed Si solar cells

We demonstrate the laser welding of Al interconnects to the BSF rear-side of screen-printed two-side-contacted solar cells. The Al paste on the rear side of solar cell is laser-welded to an Al foil. This reduces the silver consumption of the solar cells by making silver pads on the rear side obsolete. Our proof-of-concept modules are free of laser damage. A 3-cell-module from 6" solar cells shows no change in fill factor within the statistical measurement uncertainty after artificial aging in 500 humidityfreeze cycles.German Ministry for the Environment, Nature Conservation, and Reactor Safety/0325192State of Lower Saxon

Simultaneous Contacting and Interconnection of Passivated Emitter and Rear Solar Cells

The back end process of passivated emitter and rear cells (PERC) consists of at least one laser process and three screen-printing steps followed by the stringing and tabbing of the cells. To reduce the number of steps we have developed a process that metallizes the rear side including contact formation and simultaneously interconnects the cells. We attach an Al foil to an encapsulant layer. By laser processing we form 'laser-fired and bonding contacts' (LFBC) on the passivated rear side of the solar cells. The Al foil contacting the rear is laser welded to the Ag screen-printed front side metallization of the next cell and thus forms the cell interconnection. The laser contacts on the rear show a surface recombination velocity Scont for the contact regions of cm/s and a contact resistivity of 3.52 m?cm2. We present a first proof-of concept module combining the in-laminate Ag-Al laser welding and the LFBC reaching an efficiency of 18.4%. In accelerated aging test modules show no degradation (< 1% in efficiency) after 100 humidity-free cycles.Federal Ministry for Environment, Nature Conservation, and Nuclear Safety/FKZ/0325192State of Lower Saxon

Impact of Ag Pads on the Series Resistance of PERC Solar Cells

Screen-printed passivated emitter and rear cells (PERC) require Ag pads on the rear side to enable solderable connections for module integration. These Ag pads are separated from the silicon by a dielectric layer to avoid recombination of minority charge carriers. The drawback of this configuration is an elongated transport path for the majority charge carriers generated above the pads. This results in an increase in series resistance. The strength of this effect depends on charge carrier generation above the Ag pads that critically depends on shading of the cell's front side. Ag pads are usually wider than the busbars or the interconnector ribbons and thus are only partially shaded. We build PERC test structures with various rear side configurations of Ag and Al screen printing as well as with and without laser contact openings (LCO). Using experiments and finite element simulations we investigate the impact of shading the Ag pads by the busbars and other means. While fully shaded regions do not increase the lumped solar cell's series resistance, unshaded Ag pads lead to an increase of about 37%.German Federal Ministry for Economic Affairs and Energy/032564

NIRS-based detection and removal of pyrrolizidine alkaloid containing weeds in crop plants after harvest – PA-NIRSort

Pyrrolizindinalkaloide (PAs) sind lebertoxisch wirkende, sekundäre Pflanzeninhaltsstoffe, die den Pflanzen zum Schutz vor Fraßfeinden dienen. In den letzten Jahren sind PAs verstärkt in den Fokus gerückt, da sie als ungewollte Beiernte besonders in Bio- und Kindertees zu zum Teil sehr hohen Alkaloid-Belastungen führten. Inzwischen wurden strenge PA-Grenzwerte vom Bundesinstitut für Arzneimittel und Medizinprodukte (BfArM) publiziert, denn Arzneipflanzen können mit PA-haltigen Unkräu­tern wie verschiedenen Kreuzkraut-Arten, Gemei­nem Natternkopf, Ackervergißmeinnicht, Gewöhnlicher Hundszunge, Wasserdost oder Borretsch verunreinigt sein und so über Arznei- oder Aroma-Tees Menschen potenziell gefährden (BfArM, 2016). Durch diese strengen Grenzwerte genügen unter Umständen vier bis fünf PA-bildende Pflanzen des Gemeinen Greiskrauts (Senecio vulgaris) je Hektar Anbaufläche, um die Verkehrsfähigkeit einer Tonne Medizinaldroge zu gefährden. Dies zu verhindern erfordert eine engmaschige regelmäßige Feldkontrolle und mechanisches Unkrautentfernen, das unter ökonomischen Aspekten kaum realisierbar ist. Daher kommt einer, der Ernte nachgelagerten Qualitätskontrolle zum Entfernen potentieller PA-Beikräuter eine besonders wichtige Rolle zu. Ziel des im März 2019 gestarteten, von der Fachagentur für Nachwachsende Rohstoffe (FNR) geförderten Verbundprojekts des Julius Kühn-Instituts Berlin (Institut für Ökologische Chemie, Pflanzenanalytik und Vorratsschutz) und des Fraunhofer-Institut für Optronik, Systemtechnik und Bildauswertung (IOSB) ist die Entwicklung einer leistungsfähigen Detektionsmethode auf Basis von Hyperspektral-Nah-Infrarot-Spektroskopie (hyper­spektral-NIRS) zur Erkennung von Verunreinigungen durch PA-haltige Pflanzen(teile) im Erntegut von Arznei- und Gewürzpflanzen. In Kombination mit einer gekoppelten Sortiereinheit (beispielsweise über Druckluftimpulse) soll so eine Abtrennung unerwünschter und poten­tiell toxischer Beikräuter erzielt werden. Am Ende des Projektes soll ein Prototyp zur echtzeitfähigen Rei­nigung der Erntechargen verschiedener Arznei- und Gewürz­pflanzen vorgestellt werden. Ähnliche Systeme sind bereits in der Kunststoff-Abfallsortierung bzw. der Qualitätskontrolle von Weinbeeren auf Basis des Oechsle-Grades etabliert (Freund et al., 2015). Angestrebt wird ein Durchsatz von bis zu 1,5 t/h. Mit einer solchen automatisierten Sortiertechnik ließen sich die gesundheitlichen Risiken durch PA-verunreinigte Arzneipflanzenprodukte für die Anbauer und Verarbeiter von Arzneipflanzen ökologisch und ökonomisch effizient reduzieren. Dies würde auch eine Sicherung der qualitativ hochwertigen und konkurrenzfähigen Produktion pflanzlicher Arzneimittel in Deutschland bedeuten. Erste Ergebnisse zeigen, dass eine Klassifizierung der Pflanzenarten mittels NIR-Spektroskopie zuverlässig möglich ist. Um solche Bildanalysen auch in Echtzeit durchführen zu können, werden die zu verarbeitenden Datenmengen mittels multifaktorieller Datenanalyse auf entscheidende spektrale Merkmale (Faktoren) reduziert.The general objective of the project is the development of an efficient sorting system based on hyperspectral near-infrared spectroscopy (NIRS) for the detection and separation of impurities by pyrrolizidine alkaloid (PA)-containing plant-derived contaminations in cultural plants, e.g. medicinal and aromatic plants. PAs are liver-toxic secondary metabolites that protect plants from predators and have drawn more attention in recent years after harmful concentrations were found in medicinal teas. By now, the German Federal Institute for Drugs and Medical Devices (BfArM) has published strict PA limit values because medicinal plants can be contaminated with PA-containing weeds such as various types of ragwort, groundsel, common viper's head, field forget-me-not, common dog's tongue, water-east or borage and thus, potentially endanger people with medicinal or aromatic teas (BfArM, 2016). Four to five PA-containing plants e.g of Senecio vulgaris per hectare are sufficient to contaminate one ton of the drug by exceeding the critical value of maximum uptake of 0,007 μg PA/kg body weight per day published by HMPC. The planned process will analyze fresh and dried plant material on a flat-conveyer using hyperspectral NIR spectroscopy to detect impurities in the crop. After identification, contaminants should be removed by a sorting technique, e.g. using compressed air pulses. Similar systems have already been established in plastic waste sorting and quality control, for example for grapes (Freund et al., 2015). The aim is to achieve a high throughput of up to 1.5 t/h with such an automated sorting technology, the health risks posed by PA-contaminated medicinal plant products could be reduced ecologically and economically efficient for cultivation and processing of medicinal plants. This would also mean safeguarding high-quality and competitive plant-derived drug production in Germany. First results show that a classification of target plant species and contaminating groundsel using NIR spectroscopy succeeds for various medicinal plants. To be able to carry out such image analyses in real-time, the amount of data to be processed will be reduced to the decisive factors using multifactorial data analysis

Deep Near-IR Surface Photometry of 57 Galaxies in the Local Sphere of Influence

We present H-band surface photometry of 57 galaxies drawn from the Local Sphere of Influence (LSI) with distances of less than 10 Mpc from the Milky Way. The images with a typical surface brightness limit 4 mag fainter than 2MASS (24.5 mag arcsec^-2 < sb_lim < 26 mag arcsec ^-2) have been obtained with IRIS2 on the 3.9 m Anglo-Australian Telescope. A total of 22 galaxies that remained previously undetected in the near-IR and potentially could have been genuinely young galaxies were found to have an old stellar population with a star density 1-2 magnitudes below the 2MASS detection threshold. The cleaned near-IR images reveal the morphology and extent of many of the galaxies for the first time. For all program galaxies, we derive radial luminosity profiles, ellipticities, and position angles, together with global parameters such as total magnitude, mean effective surface brightness and half-light radius. Our results show that 2MASS underestimates the total magnitude of galaxies with _eff between 18-21 mag arcsec^-2 by up to 2.5 mag. The Sersic parameters best describing the observed surface brightness profiles are also presented. Adopting accurate galaxy distances and a H-band mass-to-light ratio of Upsilon_H=1.0 +/- 0.4, the LSI galaxies are found to cover a stellar mass range of 5.6 < log_10 (M_stars) < 11.1. The results are discussed along with previously obtained optical data. Our sample of low luminosity galaxies is found to follow closely the optical-infrared B versus H luminosity relation defined by brighter galaxies with a slope of 1.14 +/- 0.02 and scatter of 0.3 magnitudes. Finally we analyse the luminosity - surface brightness relation to determine an empirical mass-to-light ratio of Upsilon_H=0.78 +/- 0.08 for late-type galaxies in the H-band.Comment: Accepted by AJ. High resolution version available at http://www.mso.anu.edu.au/~emma/KirbyHband.pd