Simple and functional direct methanol fuel cell stack designs for application in portable and auxiliary power units

Simple and functional stack designs were developed for direct methanol fuel cells (DMFCs) with the aim of reducing capital costs. A simplified planar and monopolar ministack, with a reduced number of components, was designed for portable applications. This planar design facilitated the manufacturing of a compact passive mode operation ministack. The ministack provided an output power of 1.30 W under air breathing mode operation, at room pressure and temperature without any auxiliary. For application in auxiliary power units (APU), a self-heating and modular bipolar stack, operating up to 90 °C without internal cooling, was designed. Bipolar stacks consisted of 5-10 cells (100 cm2 active area), providing an output power of 90-180 W. The recirculated methanol solution was used as thermostating fluid. The stacks achieved a normalised power density per cell of 180 mW cm−2. Whereas, for the passive mode operation, ministack approached 30 mW cm−2 with 5 M methanol feed. These results favourably compare with the best performance reported in the literature for DMFCs operating under similar conditions.