(36e) Test and Evaluation of the Smart Fuel Cell C20-Mp Direct Methanol Hybrid Fuel Cell System as a Soldier Power Source

Recent advances in fully integrated, portable fuel cell system development have highlighted the potential benefits they might offer to military users in the near term. Soldier power (1 watt ? 100 watts direct current) fuel cell applications have seen significant attention of late due to challenges in ongoing operations to meet power demands for the Warfighter's equipment. This challenge has resulted in the use of secondary (rechargeable) batteries in the field, something that was only done in training exercises prior to recent operations. Consequently, the logistics burden for dismounted Soldiers on missions longer than 24 hours has become quite arduous. As such, the growing need for lightweight, rugged, and environmentally benign soldier power systems has been targeted as an excellent entry market for portable fuel cell systems. The U.S. Army Communications-Electronics Research, Development, and Engineering Center (CERDEC) Fuel Cell Technology Team located at Fort Belvoir, VA has been developing soldier power sources to meet such a need. In March 2005, one of the most advanced, fully integrated direct methanol fuel cell (DMFC) systems developed to date was received by CERDEC and a test and evaluation program was initiated. The Smart Fuel Cell (SFC) C20-MP is a portable DMFC hybrid power system rated for 20-watt continuous operation and was developed by Smart Fuel Cell AG of Brunnthal-Nord, Germany. Weighing approximately two (2) kilograms and fueled by hot-swappable, 500-milliliter methanol fuel cartridges, the system is fitted with an exchangeable 1.5-ampere-hour lithium polymer rechargeable battery. Two (2) SFC C20-MP systems were delivered: one was designed for moderate ambient temperature operation (1 ? 35 degrees Celsius demonstrated) and operated with ?neat? (high purity) methanol fuel (dubbed the Normal unit); the other was designed for high ambient temperature operation (1 - 50 degrees Celsius demonstrated) and operated on a dilute methanol-water fuel mixture (dubbed the Desert unit). CERDEC testing indicated that the Normal unit had a peak fuel efficiency of 19.1% at 19.6 watts average power output, whereas the Desert unit had a peak fuel efficiency of 19.7% at 20 watts average power output. Both systems showed improved reliability and electrical characteristics when compared with previous DMFC systems tested by CERDEC, but further developmental work is still needed in order to reach compliance with MIL-STD-705C for generator sets (U.S. Dept. of Defense 1989). During the system level test program with the SFC C20-MP, several factors were evaluated. One goal of the program was to demonstrate a technology readiness level (TRL) five (5) to six (6). Military significance was evaluated by comparing the increased or new capabilities of the SFC C20-MP with fielded power supplies of similar size. One performance factor that indicates military significance for portable power systems is mission specific energy density, which was calculated at 400 watt-hours per kilogram for the SFC C20-MP Normal system for a 20-watt continuous, 72-hour mission. Finally, technical deficiencies that remained with the SFC C20-MP systems and with DMFC technology in general were identified primarily as ?growing pains? typical of any technology in development. Although DMFC technology is largely believed to be very suitable for portable systems in the 20-watt range, some limitations remain. For example, extreme environmental conditions (especially those below freezing and above 40 degrees Celsius) can cause problems for many DMFC systems during startup and continuous operation. Other technologies such as reformed methanol fuel cells are potential competitors with DMFC technology in the portable market, due primarily to high system efficiencies and their inherent advantage of a wide range of environmental operation. Consequently, CERDEC continues to monitor the activities of the commercial sector with hopes that multiple fuel cell technologies will be successful in the portable market. CERDEC also continues its mission to develop and demonstrate a rugged 20-watt portable hybrid fuel cell system that weighs ¾ kilogram, uses packaged (safe and transportable) fuel, and is capable of 700 watt-hours per kilogram for a 72-hour, 20-watt continuous mission by 2008. If such a goal can be realized, the Warfighter will ultimately be able to perform longer (3-day) missions without the need to replace or recharge heavy batteries currently required.