Philipp Dietrich

Performance and Operational Characteristics of a Hybrid Vehicle Powered by Fuel Cells and Supercapacitors

The paper presents experimental results of a fuel cell powered electric vehicle equipped with supercapacitors. This hybrid vehicle is part of an ongoing collaboration between the Paul Scherrer Institute (PSI, Switzerland), the Swiss Federal Institute of Technology (ETHZ), and several industrial partners. It is equipped with a fuel cell system with a nominal power of 48 kW and with supercapacitors that have a storage capacity of 360 Wh. Extensive tests have been performed on a dynamometer and on the road to investigate the operating ability. The highlights of these tests were the successful trial runs across the Simplon Pass in the Swiss Alps in January 2002. The fuel cell system consists of an array of six stacks with 125 cells each and an active area of 200 cm 2 . The stacks are electrically connected as two parallel strings of three stacks each in series in order to match the voltage requirement of the powertrain. The reactant gases and the cooling liquid are fed in parallel through a manifold. The supercapacitors are sized for peak power levelling to assist the fuel cell during hard acceleration. Moreover, the supercapacitors are used to store the energy obtained from regenerative braking and serve to optimize the vehicle efficiency. Polarization curves, efficiency data of the fuel cell system and fuel consumption data from the New European Driving Cycle are presented. The transient behavior of the fuel cell system and its influence on the performance of the vehicle are analyzed.

Towards re-electrification of hydrogen obtained from the power-to-gas process by highly efficient H2/O2 polymer electrolyte fuel cells

In the power-to-gas process, hydrogen, produced by water electrolysis, is used as storage for excess, fluctuating renewable electric power. Reconversion of hydrogen back to electricity with the maximum possible efficiency is one pre-requisite to render hydrogen storage technically and economically viable. Pure oxygen is a byproduct in the electrolysis of water. The use of pure oxygen as the oxidant in a polymer electrolyte fuel cell (PEFC) is a possible way of increasing the conversion efficiency of hydrogen to power, by reducing the fuel cells cathodic kinetic overvoltage, which is the most important energy loss process in low temperature PEFCs. As we demonstrate in this work, when using pure oxygen, either high efficiencies at current densities around 1 A cm−2 are obtained or a very high power density operation (up to 1.6 W cm−2 at cell voltages above 0.62 V) can be reached, giving the technology a broad window of operation and application. The fuel cell stack durability is assessed in accelerated long-term tests of up to 2700 h. The potential of the technology is demonstrated with the realization of a complete 25 kW prototype system delivering a peak efficiency of 69% LHV (57% HHV).

PEFC: Stacks, Systems, and Applications

This article gives an overview on the research and development activities pursued in the area of polymer electrolyte fuel cell stacks and systems in Switzerland in 2004. Work is pursued on several different levels for stacks and systems from portable to automotive applications, in the academic as well as in the industrial area. Todays work focuses on the improvement of specific power and cost efficiency of stacks and systems by development and optimization of new concepts for water management and cooling. This is achieved through function integration i.e. of the gas humidification into the stack and adaptation of the cooling concepts for the specific application.

Technical propulsion strategies for more sustainable mobility

Over the past twenty years, impressive progress has been made with regard to the emissions behaviour of both spark-ignition and diesel engines for automotive purposes, not least as a result of stricter emissions legislation particularly in the USA. Hybrid propulsion systems have made a considerable step towards the realisation of zero-emission drive systems. This article by the Paul Scherrer Institute and the ETH Zurich in Switzerland examines the state of the art and the potential of the fuel cell, the IC engine and the hybrid system as a vehicle propulsion system.

Antriebsstrategien für eine umweltfreundliche Mobilität

In den letzten 20 Jahren wurden sowohl bei Otto- als auch bei Dieselmotoren im Fahrzeugbereich hinsichtlich des Emissionsverhaltens beeindruckende Fortschritte erzielt, nicht zuletzt wegen strenger Emissionsvorschriften vor allem in den USA. Auch Hybridantriebe haben auf dem Weg zum Zero-Emission-Antrieb eine bemerkenswerte Bedeutung erlangt. In diesem Beitrag des Paul Scherrer Instituts und der ETH Zurich, Schweiz, werden der Stand der Technik und das Zukunftspotenzial des Verbrennungsmotors, des Hybridantriebs und der Brennstoffzelle als Fahrzeugantrieb diskutiert.

Optimierte Fahrstrategien eines Hybridfahrzeugs mit schwerer Schwungmasse - der Taktbetrieb als Beispiel

Dieser Beitrag befaßt sich mit den Fahrstrategien för ein neues Hybridfahrzeugkonzept und deren Optimierung. Nach der Beschreibung des ETH Hybrid IH-Konzepts wird gezeigt, wie die verschiedenen Antriebskomponenten unterschiedlich kombiniert werden können, um den Gesamtantriebswirkungsgrad zu optimieren. Dann werden die gewählten Fahrstrategien, deren Umsetzung in ein Steuerungssystem und dessen Struktur präsentiert. Die Verifizierung der Fahrstrategien mittels Simulation wird an Hand eines Beispiels vorgestellt. Schließlich wird das Vorgehen bei der Optimierung an einem Beispiel gezeigt.