Since 2015 the SinoGerman research project SIGN supports water quality improvement in the Taihu region, China

The Taihu (Tai lake) region is one of the most economically prospering areas of China. Due to its location within this district of high anthropogenic activities, Taihu represents a drastic example of water pollution with nutrients (nitrogen, phosphate), organic contaminants and heavy metals. High nutrient levels combined with very shallow water create large eutrophication problems, threatening the drinking water supply of the surrounding cities. Within the international research project SIGN (SinoGerman Water Supply Network, www.water-sign.de), funded by the German Federal Ministry of Education and Research (BMBF), a powerful consortium of fifteen German partners is working on the overall aim of assuring good water quality from the source to the tap by taking the whole water cycle into account: The diverse research topics range from future proof strategies for urban catchment, innovative monitoring and early warning approaches for lake and drinking water, control and use of biological degradation processes, efficient water treatment technologies, adapted water distribution up to promoting sector policy by good governance. The implementation in China is warranted, since the leading Chinese research institutes as well as the most important local stakeholders, e.g. water suppliers, are involved

Visualisierung und Optimierung von Wassertransportpfaden in Gasdiffusionslagen einer PEM-Brennstoffzelle

The efficiency of polymer electrolyte membrane fuel cells (PEMFC) operated in the low temperature range is still affected by water blockage in the porous layers. Emerging water at the catalyst layer is transported through the micro porous layer (MPL) and the gas diffusion layer (GDL) to be discharged in the channel. The porous layers fill up with water, so that the gas transport to the catalyst layer and hence the performance of the fuel cell are reduced. In this work synchrotron radiography and tomography are applied to analyze the water transport and the water distribution in the porous layers. With synchrotron tomography of the GDL and MPL material and with the water transport analysis during fuel cell operation, cracks in the MPL are identified as origin of water transport pathways. However, a low crack size and crack density result only in a minor enhancement of the water transport. Thus, artificial perforations are added to the porous layers by mechanical or laser treatment to enhance this water transport effect. The radiographic analysis reveals for the laser perforated GDL and MPL an improved water transport which is affirmed by a higher performance at the fuel cell test. To find the optimum in perforation size the diameter is varied between 30 mym and 400 mym. By electron microscopy analysis it is revealed that a lower laser power leads to smaller perforation sizes and a hydrophilic surrounding, whereas a higher power leads to larger perforations but causes the removal of the MPL in the surrounding. However, with synchrotron radiography a higher water transport is measured, if the perforation diameter is increased. Nevertheless an optimum in performance is achieved for a diameter of 60 mym which is caused by the water channeling effect of the hydrophilic surrounding. Under these conditions a maximum gain in performance of 23 % is achieved

Development of self-supporting MPLs for investigations of water transport in PEM fuel cells

The performance of a polymer electrolyte membrane (PEM) fuel cell has a strong dependence of its water management. The membrane needs humidity to have sufficient ion conductivity. But at high humidity, especially at high current densities, flooding of the electrodes can occur and consequently the available active area begins to decrease. The primary purpose of a micro porous layer (MPL) on a gas diffusion layer (GDL) is the effective wicking of liquid water from the catalyst layer into the diffusion media as well as reducing electrical contact resistance with the adjacent layers. In synchrotron radiography studies the importance of liquid water pathways through the porous structure for the water management is proven. These pathways can be formed by natural cracks in the MPL and the texture of the carbon fibre substrate or by artificial pore paths through the GDL. With artificial paths in a carbon fibre GDL produced by laser perforation an overall performance gain has been obtained. To get additional information about the function of the MPL as an interconnection between the reaction layer and the macro porous carbon fibre substrate a self-supporting MPL was developed. This allows the manufacturing and the following treatments of the MPL independent from the GDL substrate. This MPL consists of a thin nonwoven of synthetics coated on one side with a mixture of carbon and PTFE produced by the dry spraying technology. It is possible to perforate this layer alone and press it with the non-coated side on a commercial GDL without MPL (Sigracet® GDL25BA from SGL). Thus it was feasible to perform experiments for investigation of the influence of artificial pores in the MPL on the water management. As a consequence, the liquid water transport of non-perforated GDL/MPLs is compared to the perforation of both layers as well as to the exclusive perforation of MPL and the GDL, by means of in-situ synchrotron imaging. Further measurements, in particular Ucell(i)-curves up to limiting current densities and electrochemical impedance spectra were done in a 5 cm² fuel cell setup, to obtain a correlation of the global intrinsic properties of the MPL, like through-plane permeability, electrical conductivity or hydrophobicity, with fuel cell performance

Sensor based concept for PEM fuel cell development based on the IPEK-X-in-the-Loop approach

The development of PEM fuel cell systems can be further improved, if the interactions between the different development levels are considered. The IPEK X-in-the-loop approach allows connecting the operating conditions measured locally at the fuel cell components, like the bipolar plate with data from the drivetrain and the fuel cell system. Measurement data taken from micro sensors can be transmitted to control the fuel cell system components. The mixed virtual-physical approach allows emulating different types of components instantly and facilitates the optimization of fuel cell components and operating strategies. With this development method the fuel cell and the fuel cell system components as well as the operating controls can be improved with respect to power dynamics, power density and lifetime

Sensor based concept for PEM fuel cell development based on the IPEK-X-in-the-Loop approach

The development of PEM fuel cell systems can be further improved, if the interactions between the different development levels are considered. The IPEK X-in-the-loop approach allows connecting the operating conditions measured locally at the fuel cell components, like the bipolar plate with data from the drivetrain and the fuel cell system. Measurement data taken from micro sensors can be transmitted to control the fuel cell system components. The mixed virtual-physical approach allows emulating different types of components instantly and facilitates the optimization of fuel cell components and operating strategies. With this development method the fuel cell and the fuel cell system components as well as the operating controls can be improved with respect to power dynamics, power density and lifetime

Sensor based concept for PEM fuel cell development based on the IPEK-X-in-the-Loop approach

The development of PEM fuel cell systems can be further improved, if the interactions between the different development levels are considered. The IPEK X-in-the-loop approach allows connecting the operating conditions measured locally at the fuel cell components, like the bipolar plate with data from the drivetrain and the fuel cell system. Measurement data taken from micro sensors can be transmitted to control the fuel cell system components. The mixed virtual-physical approach allows emulating different types of components instantly and facilitates the optimization of fuel cell components and operating strategies. With this development method the fuel cell and the fuel cell system components as well as the operating controls can be improved with respect to power dynamics, power density and lifetime

Influence of the MPL on PEM fuel cell performance

The gas diffusion layer (GDL) plays a crucial role for PEM fuel cell performance. The main requirements of a GDL are the provision of a gas and water transport as well a significant electrical and thermal conductivity. For the development of PEMFC diffusion media the still unknown influence of the micro porous layer (MPL) on fuel cell performance is a major obstacle. Therefore a self-supporting MPL was developed because it allows basically to measure the properties of the MPL separately from the substrate. This MPL consists of a thin nonwoven of synthetics coated on one side with a mixture of carbon and PTFE produced by the dry spraying technology. For in-situ experiments and some ex-situ measurements these layers are pressed with the non coated side on a commercial GDL without MPL (Sigracet® GDL25BA from SGL). To get a correlation of the global intrinsic properties of the MPL, like through-plane permeability, electrical conductivity or hydrophobicity, to fuel cell performance, Ucell(i)-curves up to limiting current densities and electrochemical impedance spectra are measured in a 5 cm² fuel cell setup. Additionally the function of the MPL structure on water distribution is investigated. Synchrotron radiography studies proved the importance of liquid water pathways through the porous structure for the water management. These pathways can be formed by natural cracks in the MPL and the texture of the carbon fibre substrate or by artificial pore paths through the GDL. With artificial paths in a carbon fiber GDL produced by laser perforation an overall performance gain has been obtained. In the presented work, we performed further experiments to investigate the influence of artificial pores in the MPL on the water management. Therefore the liquid water transport of nonperforated GDL/MPLs is compared to the perforation of both layers as well as to the exclusive perforation of MPL and the GDL, by means of in-situ synchrotron imaging

Circuit pour véhicule automobile, en particulier pour véhicule hybride ou électrique

Die Erfindung betrifft eine Schaltungsanordnung (10) für ein Kraftfahrzeug, mit einer Hochvolt-Batterie (12) zum Speichern von elektrischer Energie, mit wenigstens einer elektrischen Maschine (14) zum Antreiben des Kraftfahrzeugs, mit einem Stromrichter (16), mittels welchem von der Hochvolt-Batterie (12) bereitstellbare Hochvolt-Gleichspannung in Hochvolt-Wechselspannung zum Betreiben der elektrischen Maschine (14) umwandelbar ist, und mit einem Ladeanschluss (20) zum Bereitstellen von elektrischer Energie zum Laden der Hochvolt-Batterie (12), wobei der Stromrichter (16) als ein Drei-Stufen-Stromrichter ausgebildet ist und wenigstens eine einer Phase (u) der elektrischen Maschine (14) zugeordnete Schaltereinheit (46) aufweist, welche zwei in Reihe geschaltete Schaltergruppen (52, 54) umfasst, die jeweils zwei in Reihe geschaltete IGBTs (T11, T12, T13, T14) aufweisen, wobei zwischen den IGBTs (T11, T12) einer der Schaltergruppen (52, 54) ein Anschluss (64) angeordnet ist, welcher direkt mit einer Leitung (34) des Ladeanschlusses (20) elektrisch verbunden ist.The invention relates to a circuit assembly (10) for a motor vehicle, comprising a high-voltage battery (12) for storing electric energy, at least one electric machine (14) for driving the motor vehicle, a converter (16), by means of which a high-voltage DC current which can be provided by the high-voltage battery (12) can be converted into a high-voltage AC current in order to drive the electric machine (14), and a charging terminal (20) for providing electric energy in order to charge the high-voltage battery (12). The converter (16) is designed as a three-level converter and has at least one switch unit (46) that is assigned one phase (u) of the electric machine (14) and comprises two switch groups (52, 54) which are connected in series and each of which has two IGBTs (T11, T12, T13, T14) connected in series, wherein a terminal (64) is arranged between the IGBTs (T11, T12) of one of the switch groups (52, 54), said terminal being directly electrically connected to a line (34) of the charging connection (20).L'invention concerne un circuit (10) pour un véhicule automobile, pourvu d'une batterie à haute tension (12) pour l'accumulation d'énergie électrique, d'au moins un moteur électrique (14) pour l'entraînement du véhicule automobile, d'un convertisseur de puissance (16), au moyen duquel la tension continue à haute tension pouvant être fournie par la batterie à haute tension (12) peut être convertie en tension alternative à haute tension pour le fonctionnement du moteur électrique (14), et d'un raccordement de charge (20) pour la fourniture d'énergie électrique permettant la charge de la batterie à haute tension (12), le convertisseur de puissance (16) étant réalisé sous la forme d'un convertisseur de puissance à trois étages et présentant au moins une unité de commutation (46) qui est associée à une phase (u) du moteur électrique (14) et qui comprend deux groupes de commutateurs (52, 54) montés en série, qui présentent respectivement deux transistors bipolaires à porte isolée (T11, T12, T13, T14) montés en série, un raccordement (64), lequel est relié électriquement directement à une ligne (34) du raccordement de charge (20), étant disposé entre les transistors bipolaires à porte isolée (T11, T12) d'un des groupes de commutateurs (52, 54)

Circuit Arrangement for a Motor Vehicle, in Particular for a Hybrid or Electric Vehicle (US20220032798A1)

A circuit arrangement of a motor vehicle includes a high-voltage battery for storing electrical energy, an electric machine for driving the motor vehicle, a converter via which high-voltage direct current voltage provided by the high-voltage battery is convertible into high-voltage alternating current voltage for operating the electric machine, and a charging connection for providing electrical energy for charging the high-voltage battery. The converter is a three-stage converter having a first switch unit which is assigned to a first phase of the electric machine. The first switch unit has two switch groups connected in series which each have two insulated-gate bipolar transistors (IGBTs) connected in series, where a connection is disposed between the IGBTs of one of the two switch groups, which connection is electrically connected directly to a line of the charging connection

Resistor Network Modeling of Conductive DomainWalls in Lithium Niobate

Here the concept of a 2D resistor network (2D RN) is applied in order tomodel the electrical conductivity along sheet-like domain walls (DWs) insingle crystalline lithium niobate (sc-LNO). The only input to the RN modeling approach is the DW inclination angle distribution, as measured previously with respect to the polar c-axis. The simulations then show that a 2D network of Ohmic resistors not only adequately accounts for the different boundary conditions envisaged in experiments, but equally well provides a direct link between the local domain wall conductivity (DWC) and the DW inclination angle α. Moreover, the RN simulations can be directly compared to local-scale transport measurements, as obtained by scanning probe techniques. The conceptual simplicity and the low computational effort make the present RN modeling approach a useful tool for both the advanced interpretation and evaluation of potential DWC ferroelectrics