22 cell and the electric motor, as well as putting them individually through bench testing. Also, in 2023, we integrated the electric propulsion system into the snow groomer and tested it, although not yet with the fuel cell at that time. “Today, we’re in the final stages of development as we’ve assembled our electric powertrain, including the hydrogen system, integrated it in the snow groomer and completed our first rounds of tests of the complete FCEV system on Groupe GCK’s test circuit near Clermont-Ferrand, with the next round of testing set to take place in the Alps, starting in April 2024.” Retrofitting the 600 The H2D2 snow groomer is a retrofitted and electrified PistenBully 600, which defines several of the physical dimensions described earlier, and the consortium has aimed to keep the size, weight and power the same as on the original to prevent operators or fleet managers needing to get to grips with dramatically different vehicle dimensions or dynamics. The vehicle is a very popular model in the ski resort industry, making it a logical proving ground for the viability of commercially electrifying such vehicles. In the rear, where there would normally be a six-cylinder diesel engine, there now sits an electric motor, both to ensure the availability of shaft horsepower to drive the transmission systems for the ground tracks and the snow blade or tiller equipment, and to maintain the system’s weight distribution and low centre of gravity (CoG). The battery pack is located under the driver’s cabin, thereby contributing to the CoG and weight distribution. Meanwhile, the fuel cell and tanks are installed in a chassis behind the cabin. Naturally, the inverter is mounted adjacent to the motor, as is a DC/DC converter for stepping up the fuel cell’s low voltage to one high enough for recharging the battery efficiently. Throughout the cabin and powertrain, cabling and connectors have been judiciously selected to maximise the lifespan of the powertrain against repeated thermal expansions and contractions (as well as weathering caused by moisture freezing, expanding, and melting in the nooks and crannies of part enclosures). Aussibal explains that thermal management of the various powertrain systems poses the biggest overall challenge, and to that end the battery and the electric motor have been designed with novel cooling systems. Centralised control architecture Engineering the communications and information transmissions throughout the control network was a considerable challenge, as the team needed to achieve comms performance between each system (and driving response) on a par with the original snow groomer. This meant, for instance, that the acceleration pedal had to achieve the same throttle response from the electric motor as with the diesel engine previously installed. The vehicle’s data and signal network run on a centralised control architecture, centred around a commercial off-theshelf (COTS) vehicle control unit (VCU). “All systems communicate with this VCU. The operator can monitor motor speed, temperature and torque, as well as the battery voltage, current and so on,” Aussibal says. “The VCU will communicate and transmit output signals to the motor for speed, power and torque, based on driver inputs.” While the VCU hardware is a largely unaltered COTS system, the software is continuously adapted for smooth and error-free communication with the electric powertrain systems, cabin systems and grooming equipment. Much of the original cabin systems have been kept as they were on the original PistenBully 600. Key changes include the integration of a dedicated tablet system, through which the driver can selectively monitor health and performance parameters across the battery, fuel cell, motor and inverter. The GCK-FEV fuel cell The fuel cell located behind the cabin has been co-developed between GCK and Aachen-based FEV Group (GCK working in parallel with the latter on high-performance fuel cells for the Dakar Rally through its motorsport arm). The system is a proton-exchange membrane (PEM) fuel cell. For those unfamiliar with such systems, they consist broadly of a tightly sealed Dossier | H2D2 snow groomer May/June 2024 | E-Mobility Engineering The proton-exchange membrane fuel cell weighs about 400 kg and gives 175 kW net power (Image courtesy of Groupe GCK)
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