PNNL

Abstract

A 15-We portable power system is being developed for the US Army, comprised of a hydrogen-generating fuel reformer coupled to a hydrogen-converting fuel cell. As a first phase of this project, a methanol steam reformer system was developed and demonstrated. The reformer system included a combustor, two vaporizers, and a steam-reforming reactor. The device was demonstrated as a thermally independent unit over the range of 14 to 80 Wt output. Assuming a 14-day mission life and an ultimate 1-kg fuel processor/fuel cell assembly, a base case was chosen to illustrate the expected system performance. Operating at 13 We, the system yielded a fuel processor efficiency of 45% (LHV of H2 out/LHV of fuel in) and an estimated net efficiency of 22% (assuming a fuel cell efficiency of 48%). The resulting energy density of 720 W-hr/kg is several times the energy density of the best lithium-ion batteries. Some immediate areas of improvement in thermal management also have been identified and an integrated fuel processor is under development. The final system will be a hybrid, containing a fuel reformer, fuel cell, and rechargeable battery. The battery will provide power for startup and added capacity for times of peak power demand.