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A fuel cell system consists of a stack, a hydrogen fuel supply and an air supply system. This provides the required air flow and pressure which allows the stack to properly react on the cathode side to recombine Oxygen with the Hydrogen's protons and electrons resulting in water and heat. In addition the air flow and pressure are supporting directly or indirectly the water management. In this paper different air supply systems for automotive application developed by NuCellSys are compared: screw compressor and electrical turbo charger. Different technologies and control strategies allow the fuel cell system integrator to find the optimum between performances, weight, volume and cost. The authors describe the challenges and the new frontier of air supply systems for automotive fuel cell system application.

Since the last decade, alternative powertrains are playing an important role in the strategy of car manufacturers. One important goal is the introduction of zero emission powertrains. These powertrain systems raise increasing political and public interest with the hydrogen fuel cell engine being the most competitive powertrain technology. During the development of this new technology, all the functional aspects including the automotive vehicle safety need to be considered. Hydrogen sensors are installed in the system to optimize the performance of a hydrogen fuel cell system and to enhance the safety concept. New results of sensor optimization and innovative test and development methods based on real vehicle data are described in this paper.

Fuel Cell Auxiliary Power Units (APU) are more and more considered as having the potential to improve fuel economy, to be environmental friendly and to add new functions and features to vehicles. There are several APU system architectures combined with different fuels and power levels applied to various vehicles A liquid fuelled APU with a power of 5 kW can address a significant market potential in the field of transportation systems. The future higher voltage architecture and the increasing electrical power demand on board of vehicles are two of several drivers that make the APU solution interesting for many applications. XCELLSIS, The Fuel Cell Engine Company, is developing and manufacturing APUs for automotive application. In this paper, the potential of APUs, their market, and their application, are presented.

Fuel cells convert a fuel together with oxygen in a highly efficient electrochemical reaction to electricity and water. Automotive fuel cell systems mainly use compressed onboard stored hydrogen as fuel. Oxygen from ambient air is fed to the cathode of the fuel cell stack by an air supply subsystem. For its current and next generation air supply subsystem NuCellSys has employed screw type compressor technology, which in the automotive area initially was developed for supercharged internal combustion (IC) engines. As NVH expectations to fuel cell vehicles differ very much from IC-engine driven vehicles, specific efforts have to be taken to address the intense noise and vibration profile of the screw compressor. This paper describes different counter measures which have been implemented into the NuCellSys next generation air supply subsystem.

A liquid fuelled, fuel cell auxiliary power unit (APU) can provide efficient, quiet and low pollution power for a variety of applications including commercial and military vehicles. Truck idling regulation, customer comfort or military “stealth” operation by using electrical power, require a device disconnected from the main diesel engine. The power can be utilized for air conditioning as well as other auxiliary systems found on board commercial trucks for driver comfort. In a military vehicle, this regulated power could be supplied to telecommunication and other computer equipment required for military operations. A system designed to be an add-on or retrofit solution using alternative fuel can have the potential to meet these requirements on the hundreds of thousands of existing vehicles currently in service or as optional equipment on a newly procured vehicle.

Fuel cell Auxiliary Power Units (APUs) can use a variety of fuels as a hydrogen carrier. Projects showing the use of hydrogen as a fuel for an APU have been completed and the prospects of using methanol as an alternative fuel has been discussed before. Despite the success of the previous fuel cell APU demonstrations, potential military and commercial customers desire a single on-board fuel for the main propulsion engine and for the APU. Such an application would require a fuel processor that can produce sufficiently pure hydrogen for utilization in a fuel cell from prevailing hydrocarbon fuels. The position of the U.S. Army's National Automotive Center (NAC) is to address this challenge by first using a synthetic diesel fuel as part of a phased fuel reformation program. This paper presents an analysis of the use of a synthetic fuel as a hydrogen carrier.

The main issues related to the vibration response and acoustic noise emission of a new liquid fuelled fuel cell APU (auxiliary power unit) system are discussed and analyzed. These problems are being addressed in an on-going research project. The APU is comprised of several critical subsystems including the fuel processing system, fuel stack, heat exchanger, compressor, as well as high-pressure and low-pressure components. The vibration concern deals with the design of a two-stage isolation mount system to shield these critical parts from the shock and steady-state dynamics coming through the truck frame during on-road traveling conditions. A lumped parameter dynamic model is formulated for use in optimizing the mount stiffnesses and locations. Acoustic concerns are primarily related to exterior noise levels when the truck is at a rest stop. To address those issues, experimental studies are conducted to quantify the main sources and paths for noise.