Dynamics of direct hydrocarbon polymer electrolyte membrane fuel cells

Abstract

Hydrocarbons have 50-100 times higher energy per unit weight compared to commercially available batteries, thus harvesting only 10% of the energy from hydrocarbons could provide a far lighter energy source for portable electronic devices. With this motivation, the feasibility of using polymer electrolyte membrane fuel cells with propane fuel, operating at low temperatures (< 100oC), was explored. It was interesting to note that there was a significant influence of the current history on the fuel cell performance. In particular, at higher current densities (>24 mA/cm2) the power output gradually decreases then rapidly "extinguishes" (i.e., produces no power). However, by employing an unconventional operating mode (load-interrupt) where the current is shut off for a short period of time and then reapplied, the average maximum power density increased to 11.6 mW/cm2. Furthermore, the extinction of the fuel cell can be further improved by seeding a small amount of unsaturated hydrocarbons (∼2000ppm) into the fuel stream and can extend the lifetime of the fuel cell by more than 10 times.