• Auxiliary power unit for on-board electricity supply without the engine running
• Series launch planned for 2010, first applications from 2008
• Staxera: Joint venture with H. C. Starck will be supplying stacks on the market

Stockdorf/Munich. – After an intensive development period lasting around three years, Webasto now possesses the prototype of an auxiliary power unit that runs stably, operates autonomously and can be switched on or off cyclically. Series production is planned to start in 2010.

Webasto has deliberately applied itself to the auxiliary power unit (APU) in contrast to fuel cell technology for propulsion systems: The objective of the development was to provide a unit that would supplement the on-board electrical power supply of vehicles independently of the drive engine, using the fuel (petrol or diesel) that the engine also uses. The APU will make it possible to avoid future problems in the on-board electricity supply due to the increasing number of electrical loads in the vehicle. In addition, it will be possible to implement new comfort functions such as the auxiliary air-conditioning system. It is important to note that the vehicle’s engine does not have to be running for this purpose.

The APU system has been developed by Webasto with some assistance from experienced technology partners. At its core is a high-temperature fuel cell (solid oxide fuel cell – SOFC) that operates between 750 and 850 °C. The system is rounded off by a catalytic fuel reformer as well as a low-emission wide-band burner including heat exchanger. These are for zero-residue combustion of unused fuel cell exhaust gases and for thermal management. Above all as far as the system components (pumps, blower, fuel evaporators) are concerned, Webasto can largely rely on parts that are already in use in series production auxiliary heaters. The advantages are obvious: The system is made significantly more simple and benefits from a considerable reliability boost right from the word go. In addition, cost aspects were consistently taken into account in the early phase of development so as to guarantee the commercial success of the technology.

Webasto’s APU prototype is designed for a power of 1 kW. It is operated with low-sulphur diesel fuel; no additional service products such as water are required. The start only requires a car battery, there is no need for any electrical heating elements whatsoever. The patented reformer operates according to the principle of catalytic partial oxidation (CPOX) which converts the liquid diesel fuel into synthesis gas and creates the hydrogenic gas required for the fuel cell. The operating temperature of the APU is reached at 850 °C although the fuel cell starts generating electrical current from 700 °C upwards and thereby reduces the load on the starter battery. The results achieved already in the concept stage are excellent – the system attains an electrical efficiency of just under 20 %. At the same time, the prototype achieves extremely low emission values both in the starting phase and during continuous operation.

It will be possible to achieve a power range from 500 W up to 5 kW for future series production applications. Depending on the integration level that is implemented on a case-by-case basis, the APU gas – referred to as reducing gas – can additionally be used for improving the combustion process in the vehicle’s engine and for optimising the exhaust characteristics. The first applications for the Webasto APU are planned for 2008 in trucks and leisure vehicles (caravans and boats). Until then, the 25-strong Webasto development team based in Neubrandenburg, Germany, will be working on tweaking the system to achieve a few more optimisations such as quicker start-up times, improved power-to-weight ratio and cost reductions.

The existing cooperation between H.C. Starck GmbH and Webasto AG  started in 2003 and has now been significantly intensified through the foundation of the joint venture company, Staxera GmbH. The objective of the cooperation is to develop SOFC fuel cell modules (stacks) to series production readiness for use both in automotive and stationary applications. The new company, Staxera, will trade as an independent supplier of stacks and make its prototypes available both to Webasto and other system developers. Ever since 2003, the partners have been working closely with the Fraunhofer Institute for Ceramic Technologies and Sintered Materials (Fraunhofer Institut für keramische Technologien und Sinterwerkstoffe, IKTS) in Dresden on integrating components into stacks. This cooperation with IKTS is to be continued by the joint venture company Staxera GmbH.