Design of a Battery System for a Fuel Cell Powered UPS Applica- tion With Extreme Temperature Conditions. Markus Lelie 1,3 , Susanne Rothgang 1,3 , Manop Masomtob 1,3 , Martin Rosekeit 1,3 , Rik W. De Doncker 1,2,3 , Dirk Uwe Sauer 1,2,3 1) Institute for Power Electronics and Electrical Drives (ISEA), RWTH Aachen University, Germany 2) Institute for Power Generation and Storage Systems (PGS), E.ON ERC, RWTH Aachen University, Germany 3) Jülich Aachen Research Alliance, JARA-Energy, Germany Abstract In a currently running research project, a UPS system for peripheral components in rural applications in Siberia is being developed. As main components, the UPS contains a battery system, a high temperature proton exchange membrane fuel cell (HT-PEM FC) with an auto thermal reformer (ATR), as well as two DC/DC converters to adapt the voltage levels between the individual components and the load. This work describes design aspects of the battery system, which is needed for a successful operation of the complete system. In case of a power failure, the fuel cell is not able to deliver power immediately, as it has to be heated up first. In addition, the ATR, which converts natural gas to a gas with a larger share of hydrogen, also needs about 20 to 30 minutes to heat up. Thus, for about 30 minutes the load and the heating process itself have to be supplied completely from the battery. In order to operate the fuel cell at an efficient and sustaining operating point, the battery is still needed after the heat up phase and is recharged by the fuel cell. The needed energy content as well as the peak and mean power have been calculated by a full system simulation. Implemented in Matlab Simulink, this simulation models the behavior of each system component during system operation. The main challenge for all components is the extreme temperature range in Siberia. For the desired location of the UPS built in the project described here, an environmental temperature range of -40 ◦ C up to +50 ◦ C is specified. From the battery point of view this means, that both, heating and cooling could be necessary. Thermal simulations were carried out in COMSOL Multiphysics, using the preliminary battery case design, to confirm these necessities. For the simulations worst case scenarios for winter and summer temperature profiles were used. The summertime simulations included influence from the resistive battery losses, as well as heat input from fuel cell and reformer as an addition to the environmental heat. In order to meet the performance requirements at -40 ◦ C, all battery types in question for this application have to be heated. In this regard different heating methods are considered. Apart from traditional electrical heating (e.g. using resistors), approaches for heating the battery with a superposed AC current are examined. Furthermore the battery cell selection, cell tests, passive components selection, the Battery Management System (BMS) and thermally optimized operation of the battery module are addressed in this work. 1 Introduction The main aim of the research project EURHOPE is the development of an uninterruptible power supply system (UPS), which has to be able to work at Siberian environ- ment temperatures. The system should be able to supply a load of 1 kW for a theoretically unlimited amount of time by using natural gas as energy source. This should be achieved by using an auto thermal reformer (ATR) to reform natural gas in order to be able to feed it to a high temperature proton exchange membrane fuel cell (HT-PEM FC). The Institute for Power Electronics and Electrical Drives (ISEA) of RWTH Aachen University is responsible for two parts of the UPS: a battery system to bridge the first min- utes after a power failure, as well as the power electronic components to connect the individual elements of the sys- tem. Fuel cell system and ATR are developed by project partners. Main focus of this document are the battery system and the design challenges resulting from the given environmental conditions. 1.1 Environmental conditions Based on the available information on the climate con- ditions at the designated location in Siberia, where the system should be operated later, the specifications for the whole system were defined. Thus the system’s determined operating temperature ranges from -40 ◦ C to +50 ◦ C, which means that it has to be designed in order to be able to work in a wide temperature range and especially at ex- INTELEC(r) 2013 · 13. - 17. October 2013, Hamburg - © VDE VERLAG GMBH · Berlin · Offenbach ISBN 978-3-8007-3500-6 190