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 cm². 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.