U.S. Army Strategy for Utilizing Fuel Cells as Auxiliary Power Units

Fuel Cell APU for Silent Watch and Mild Electrification of a Medium Tactical Truck

“…Electrification of accessories and use of an Auxiliary Power Unit is seen as being particularly effective in reducing parasitics and fuel consumption associated with hotel loads. While fuel cells are considered not to be ready for heavy propulsion, the technology has already been demonstrated on a smaller scale suitable for APU [1,6].…”

“…Examples of these advanced technology devices in military trucks include advanced radio communication equipment, navigation systems, GPS, movement tracking systems, night vision systems, cabin ventilation, Air Conditioning (A/C) and Nuclear Biological and Chemical (NBC) protection systems, computers, and displays. The US Army projects the need for up to 10 kW of electric power for various battlefield equipment per Dobbs et al [1], while maintaining minimal thermal and acoustic signature. Power for these devices needs to be available during driving as well as when the vehicle is parked, i.e.…”

“…The projections for future military trucks are based on the plans for army transformation and battlefield digitization. Equipment necessary for digitization of the tactical vehicle includes digital radio systems, navigation systems (GPS, 3D mapping), encryption systems, computer and displays, movement tracking system (MTS), identification friend-or-foe, and driver vision enhancement (DVE) [1]. In addition, Nuclear, Biological and Chemical (NBC) protection requires high-capacity ventilation system for over pressurizing the cabin combined with air/conditioning.…”

“…The main determining factors are the state-of-charge lower limit that guarantees safe restarting of the engine, and the effect of the depth of recycling on battery life. Dobbs [1] estimates the practical stand-by operation, using only electronics (no A/C), to be up to 30 minutes with two military batteries. This would increase to one hour on the FMTV equipped with four batteries -still far less than the expected length of the silent watch of 4 -10 hours.…”

Design Under Uncertainty and Assessment of Performance Reliability of a Dual-Use Medium Truck with Hydraulic-Hybrid Powertrain and Fuel Cell Auxiliary Power Unit

“…Nevertheless, there is an increasing need for on-board electric energy in both commercial and military trucks in order to supply the required power for electric accessories used during the so-called "silent-watch". To eliminate the need for excessive near-idle engine operation and overcome the energy density and capacity disadvantages of batteries, while fully exploiting the benefits of the hybrid-hydraulic configurations, fuel cells (FC) are considered as auxiliary power units (APUs) enabling electrification of powertrain components [3][4][5][6][7]. A recent simulation-based analysis demonstrated that using a fuel cell APU can improve fuel economy up to 10% while driving and almost six times while at standstill, during the silent watch (relative to using a diesel engine only) [8].…”