Avoid fuel cell oxygen starvation with air flow controllers . By

uel cell systems offer clean and efficient energy production and are currently under intensive development by several manufacturers for both stationary and mobile applications. The fuel cell (FC) concept dates back to the early 1800s. The idea was first published in [1], and its invention has largely been attributed to W.R. Grove [2]. Although the availability and abundance of fossil fuel has limited interest in FCs as a power source [3], recent advances in membrane and electrode material, reduced usage of noble metal catalysts, efficient power electronics, and electric motors have sparked interest in direct electricity generation using FCs. In particular, proton exchange membrane FCs (PEM-FCs), also known as polymer electrolyte membrane FCs, are considered to be more developed than other FC technologies. These FCs have high power density, solid electrolyte, long cell and stack life, and low corrosion. Moreover, these FCs operate at low temperatures (50–100 ◦C), which enables fast start-up. PEM-FCs consist of a proton-conducting membrane sandwiched between two platinum-impregnated porous electrodes (membrane electrode assembly, MEA), as shown in Figure 1. Hydrogen molecules are split into protons and free electrons at the anode catalyst. The protons diffuse through the membrane to the cathode and react with the supplied oxygen and the returning electrons to produce water. During this process, the electrons pass through an external load circuit and provide useful electric energy. A typical PEM-FC provides up to 0.6 W/cm2 depending on the catalyst loading, the membrane and electrode material, and the reactant (oxygen O2 and hydrogen H2) concentration in the anode and cathode. To satisfy different power requirements, many FCs are connected electrically in series to form an FC stack (FCS). Compared to batteries, FCs provide higher energy density. For example, a methanol FC powertrain has an energy density of about 1,900 Wh/kg, whereas a lead acid battery provides 40 Wh/kg [4]. Moreover, battery recharging is more time consuming than refueling FC vehicles with hydrogen or liquid fuel. FCs have higher efficiencies compared to heat engines, and their use for modular electricity generation and electric vehicles propulsion is promising [5]. FC efficiency is high at partial loads, which occur in the majority of urban and highway driving scenarios [6]. At the nominal driving speed of 30 mph, the efficiency of an FC electric Avoid fuel cell oxygen starvation with air flow controllers. By Jay T. Pukrushpan, Anna G. Stefanopoulou, and Huei Peng