• Energy Research
• DE close
• EU close
• CH close
• Fraunhofer Society close

Abstract Waste disposal is a core issue worldwide. Different researches are being carried out in order to handle waste materials, generated in industrial production and application processes, e.g. paint residue from metal coating in the automobile industry. Often waste is disposed in landfills at substantial economic and environmental cost. Combustion is another way to get rid of possibly hazardous waste. Pulverized fuel combustion is one of the latest combustion technologies. However, pulverized fuel combustion faces severe problems if the waste (fuel) contains components with low melting point. Having a low melting point, it gets difficult to manage and convey the pulverized material to the hot combustion chamber. The melting of fuel causes clogging in the fuel transport nozzle used to convey the material into the combustion chamber. In this work, a new technology for combustion of materials with low melting points is proposed, focusing on apparatus and nozzle design to prevent clogging. For this purpose, different nozzle designs were evaluated by multi-phase CFD simulations. Two sets of nozzle air flow rates were used in four nozzles. Effect of different flow rates and fuel particle size on combustion temperatures are also discussed. It was noted that nozzle air flow rate has a strong influence on the temperature distributions. Small fuel particle sizes result in wider combustion zones while larger particles give longer combustion zones. The results come up with optimized nozzle design and nozzle air flow for transportation of pulverized material with low melting point.

The variability of large scale wind power generation at high penetration levels has a significant impact on the secure and economic operation of onshore power systems. Grid bottlenecks, high gradients and wasting of wind energy can be avoided using local Energy Storage Systems (ESS) with dedicated power and capacity. The storage type considered in this study is an adiabatic compressed air energy storage (ACAES). This paper presents a comparison of different ESS applications aiming both to increase the profit of the power plant operator in selling the electricity into the electricity market and to support the intermittent electricity production of the wind park. This contribution presents the investigation methodology and discusses computation results for a region in Germany.

The unpredictable nature of renewable energies is drawing attention to lithium-ion batteries. In order to make full utilization of these batteries, some research works are focused on the management of existing systems, while others propose sizing techniques based on business models. However, in order to optimise the global system, a comprehensive methodology that considers both battery sizing and management at the same time is needed. This paper proposes a new optimisation algorithm based on a combination of dynamic programming and a region elimination technique that makes it possible to address both problems at the same time. This is of great interest, since the optimal size of the storage system depends on the management strategy and, in turn, the design of this strategy needs to take account of the battery size. The method is applied to a real installation consisting of a 100 kWp rooftop photovoltaic plant and a Li-ion battery system connected to a grid with variable electricity price. Results show that, unlike conventional optimisation methods, the proposed algorithm reaches an optimised energy dispatch plan that leads to a higher net present value. Finally, the tool is used to provide a sensitivity analysis that identifies key informative variables for decision makers The authors would like to acknowledge the support of the Spanish State Research Agency and FEDER-UE under grants DPI2016-80641-R and DPI2016-80642-R; of Government of Navarra through research project PI038 INTEGRA-RENOVABLES; and the FPU Program of the Spanish Ministry of Education, Culture and Sport (FPU13/00542).

A novel free-standing and flexible counter electrode for dye solar cells has been developed by conveniently transferring a vertically aligned carbon nanotube forest onto an oxygen-plasma-treated flexible, free-standing and conductive nanocomposite foil. Vertically aligned carbon nanotubes were first grown onto an aluminium foil by chemical vapour deposition and then transferred to the nanocomposite surface by hot pressing. The most meaningful electrochemical parameters have been quantitatively analyzed by means of electrochemical impedance spectroscopy and cyclic voltammetry in order to elucidate how the implementation of the anisotropic carbon nanotube top layer impacts the ultimate catalytic performances of the plate. Such an engineered counter electrode is able to guarantee a fast and effective reduction of the iodide-based electrolyte as well as to provide a solar conversion efficiency that is comparable with a typical Pt/TCO-coated rigid counter electrode. A photocurrent density higher than 13.36 mA cm−2 along with a solar conversion efficiency of 7.26% have been reported for the dye solar cell mounting a counter-electrode based on vertically aligned carbon nanotubes implanted onto a conductive nanocomposite plate.

The companies of the photovoltaic industry have experienced considerable growth in recent years. And further growth is forecasted for the coming years. By now, nearly two million single photovoltaic (PV) installations generate electricity from sunlight around the world. Thereby, the wafer-based PV products have a market share of about 80-85%. The interim shortage of silicon and the increasing cost pressure in the market give rise to ever thinner and larger wafers. Thus, the "PV Roadmap for Crystalline Silicon" of the German cell producers expects an average wafer thickness of 100 µm until 2020 and the next generation of wafer thickness in 2015. This trend brings about new challenges for the PV industry: due to the manual and automated handling in the manufacturing the silicon-based wafers are exposed to mechanical stress. If the wafers, however, become ever thinner they lose their mechanical stability and might form cracks when exposed to huge forces during the handling.These cracks, however, cause a higher breakage rate and are one of the main reasons for breakdowns of the finished modules. The damage-free handling of the very fragile silicon wafers will gain in importance due to the expected increase in the throughput. Therefore, the handling systems and components must not only handle the sensitive substrates as gently as possible but also with high speed and precision in the µm range. For this purpose, new adjusted handling components are required. This thesis aims at making a contribution to the optimal selection of handling components for the photovoltaic industry. The primary target is the development of an objective and vendor-independent evaluation procedure for grippers especially used in the cell and module manufacturing. The procedure to be developed should be suitable for cell, equipment and machine manufacturers as well as for component suppliers. Furthermore, the procedure should be applicable to identical and variable grippingprinciples. The result of the method should be the optimal decision guidance for the user and should enable an adequate and neutral classification of the tested gripper. Der enorme Ausbau der Produktionskapazitäten der Photovoltaik-Industrie in den vergangenen Jahren hat auch die Anforderungen an den Maschinen- und Anlagenbau erhöht. Die Automatisierung in der Fertigung von Solarzellen spielt dabei zur Sicherung von Qualität und Ausbeute und somit auch für die Kostenreduktion eine entscheidende Rolle. Die sich erhöhenden Materialtransportintensitäten zwischen den einzelnen Prozessschritten stellen dabei eine nicht zu vernachlässigende Herausforderung dar: Die zunehmend dünneren und fragilen Substrate bei verkürzten Zykluszeiten bringen insbesondere die Handhabung an deren physikalische Grenzen. Vor diesem Hintergrund gewinnt eine Bewertung der Leistungsfähigkeit von Handhabungskomponenten verstärkt an Bedeutung. Die Ausgangssituation zeigt, dass in der Zellfertigung aktueller Fertigungslinien insbesondere die greiferbasierte Handhabung mit Pick-and-Place-Charakter bereits parallel eingesetzt wird, um den hohen Durchsätzen gerecht zuwerden. Hierbei muss der Aufnahme- und Ablagevorgang so schnell und schädigungsarm durchgeführt werden, dass sowohl der geforderte Durchsatz, wie auch die erforderliche Qualität erreicht werden können. Durch diese Randbedingungen sind neue und erhöhte Anforderungen an die Greiferauswahl und die optimale Parametereinstellung des eingesetzten Greifers zu stellen. Die vorliegende Arbeit beschreibt ein neues, angepassten Verfahren für die Leistungsbewertung von Greifern für Silizium-Wafer. Im Vordergrund steht die Entwicklung eines objektiven und herstellerunabhängigen Bewertungsverfahrens für Greifer, die insbesonders in der Zell- und Modulfertigung eingesetzt werden. Das zu entwickelnde Verfahren kann sowohl von Zellherstellern, Anlagen- und Maschinenbauern, aber auch von Komponentenlieferanten eingesetzt werden. Das daraus resultierende Ergebnis soll eine optimale Entscheidungshilfe für den Anwender darstellen aber auch eine adäquate, neutrale Klassifizierung der getestetenGreifer ermöglichen.

This article investigates the impact of the back-surface-field (BSF) thickness variation within a local aluminum contact on the performance of passivated emitter and rear contact solar cells. A significant difference of BSF thickness between contact endings and the center of dash-shaped contacts is verified experimentally by a comprehensive statistical analysis using scanning electron microscopy. The impact of local BSF thickness differences on the cell performance is studied with 3-D technology computer-aided design (TCAD) device simulations. Several device parameters such as BSF thicknesses, the doping concentration in the BSF profile at rear contacts, or the metallized area fraction at the cell rear side are varied. Our simulation study shows that the open-circuit voltage is mainly affected by locally reduced BSF thicknesses, resulting in an efficiency loss up to 0.14%abs or 0.84%abs, respectively, if an area fraction of 1% or 20% within a local contact has reduced BSF thicknesses. This effect can be minimized either by reducing the metallized area fraction at the cell rear side or by increasing the doping concentration in the BSF profile at aluminum rear contacts. In addition, we demonstrate that the 3-D simulations can be approximated with 2-D simulations by applying a single doping profile with an average BSF thickness, calculated with the harmonic mean.

The investigation of degradation of seven distinct sets (with a number of individual cells of n $ 12) of state of the art organic photovoltaic devices prepared by leading research laboratories with a combination of imaging methods is reported. All devices have been shipped to and degraded at Risø DTU up to 1830 hours in accordance with established ISOS-3 protocols under defined illumination conditions. Imaging of device function at different stages of degradation was performed by laser-beam induced current (LBIC) scanning; luminescence imaging, specifically photoluminescence (PLI) and electroluminescence (ELI); as well as by lock-in thermography (LIT). Each of the imaging techniques exhibits its specific advantages with respect to sensing certain degradation features, which will be compared and discussed here in detail. As a consequence, a combination of several imaging techniques yields very conclusive information about the degradation processes controlling device function. The large variety of device architectures in turn enables valuable progress in the proper interpretation of imaging results—hence revealing the benefits of this large scale cooperation in making a step forward in the understanding of organic solar cell aging and its interpretation by state-of-the-art imaging methods.

Abstract The market diffusion of plug-in electric vehicles (PEVs) is a research topic which is often addressed, yet PEV market diffusion models differ in their approaches, the factors they include and results. Here, 40 market diffusion models for PEVs are compared in their scope, approach and findings to point out similarities or differences and make recommendations for future improvements in modeling in this field. Important input factors for the US are the purchase price and operating costs, while for Germany energy prices and the charging infrastructure are mentioned more often. Furthermore, larger sales shares of plug-in hybrid electric vehicles than battery electric vehicles are often found in the short term results (until 2030) while the picture is not so clear for the medium- to long-term. Future market penetration models should include specific PEV features like the limited range of battery electric vehicles or access to charging infrastructure, which are currently not covered by many models. Also, the integration of current policy regulations and, if possible, indirect policy incentives would enhance research in this field.