More and more of the vehicles seen on airfields including baggage towing tractors and other ground support equipment are electrically powered, by fuel cell systems as well as rechargeable batteries. Bosch Engineering GmbH is offering control units for zero-emission off-highway applications such as these, and the wholly-owned Bosch subsidiary will be presenting its new fuel cell control unit (FCCU) for the first time at the MobiliTec specialist trade show at the 2014 Hannover trade fair.
Bosch Engineering's FCCU will first be applied in the "Innovative On-Board Energiewandler" (InnoROBE) project, which is funded by the German Federal Ministry of Education and Research. The company is providing the project with the central control unit for a fuel cell system that will serve as an energy source for an electrically powered baggage towing truck to increase its zero-emission range.
Designed as a universal controller, the FCCU can be used in various ways in fuel cell applications with polymer membranes. The Fuel Cell Control Unit controls the tank shut-off valve, the pressure regulator and the purge valve in the hydrogen pathway. Hydrogen recirculation can be carried out both passively and actively. If required, the FCCU can also communicate with a refueling facility. The FCCU meets the international functional safety standard ISO 26262. Safety-relevant functions are monitored via redundant software levels. Diagnostics and maintenance can be carried out remotely via the wireless interfaces.
In the air pathway, the FCCU adjusts the air mass flow rate using an electric compressor. A throttle valve is used to adapt the back-pressure. The Fuel Cell Control Unit adjusts the optimal operating humidity for the membrane using a humidifier bypass. The regulated cooling system ensures that the system operates efficiently. The Fuel Cell Control Unit controls the flow rate of the coolant, allowing the entry temperature and the temperature difference to be selected freely.
As part of its control unit functionality, the FCCU records the process variables of pressure, temperature, air mass flow, hydrogen concentration and coolant conductivity, all based on Bosch sensor technology for even greater added value. The Fuel Cell Control Unit provides a variety of operating strategies that can be freely adapted. In addition to airport ground support vehicles, the FCCU is expected to find use in industrial trucks, municipal vehicles, range extenders with fuel cells, stationary power generators, and test bench operation.
The FCCU is based on tried-and-tested Bosch automotive large-scale series production hardware. Together with newly developed software for controlling fuel cell systems, it has the flexibility to be used in various mobile and stationary applications and supports a wide variety of system configurations. The software features integrated hydrogen, air, and coolant control, so it can run a large number of operating strategies to further increase energy efficiency and keep consumption to a minimum.
Electrification of off-highway applications among them airport ground support vehicles, municipal vehicles, and industrial trucks is being driven by the tightening of emissions legislation for internal-combustion engines with over 56kW of output (EU Stage IV and U.S. Tier 4 Final). This is one of the reasons why fuel cell systems are already widespread in these sectors and why hydrogen filling stations are already in place for many airports and vehicle fleets. Fuel cells generate electricity from the chemical reaction between hydrogen and oxygen, which emits nothing but pure water vapor. This makes them ideal for off-highway applications such as forklift trucks and mobile lift platforms, which must operate with zero emissions inside buildings and facilities. What's more, vehicles with a fuel-cell powertrain are quieter and experience a much lower level of vibrations.