Development of a Micro‐Structured Methanol Fuel Processor Coupled to a High‐Temperature Proton Exchange Membrane Fuel Cell

Abstract

The aim of the work presented in the current paper was the development of a portable power generation device applying methanol as fuel and fuel cell technology with an electrical net power output of 100 W. At the Institut für Mikrotechnik Mainz (IMM), Germany, an integrated micro-structured methanol fuel processor based on oxidative steam reforming was developed. The fuel processor was tested separately and then coupled to a high-temperature fuel cell that had been developed in parallel by the Zentrum für Brennstoffzellentechnik GmbH (ZBT). ObjectivesPower supply of mobile devices by batteries is time limited, owing to weight restrictions. The increasing energy demand of outdoor applications and wireless industrial tools alone amounts currently to approximately 714 GWh in Europe. Therefore, a potential market exists for alternative solutions such as fuel cell technology. Hydrogen storage by metal hydrides and pressurised hydrogen tanks is not suited as a hydrogen source for portable applications, owing to their weight and market introduction barriers, the latter originating mainly from safety considerations of the end-users. Liquid fuels have a high power density and are easier to handle. Applying fuel processing technology, methanol is converted to a hydrogenrich gas mixture, which is then converted to power in conventional proton exchange membrane (PEM) fuel cells. The main advantage of methanol compared to other liquid energy carriers such as hydrocarbons is the relatively low operating temperature of the reformer reactor. The lower temperature reduces the heat losses, which is crucial in the case of systems operating on a smaller scale.Conventional PEM fuel cells, which are usually operated at about 80°C, show very limited tolerance against carbon monoxide [1]. Even specially developed reformate-tolerant lowtemperature PEM fuel cells are limited to carbon monoxide concentrations of about 100 ppm in continuous operation without rapid degradation effects. Therefore, the high-temperature PEM membrane technology of BASF was chosen, which is capable of tolerating carbon monoxide in the percent range at operating temperatures between 160 and 180°C.The practical demands of an autonomous fuel processor/ fuel cell system of portable scale can be summarised as follows: -Autonomous operation after the system start-up, i.e., the system requires only electrical energy to operate the balance of plant components such as pumps and valves, while the fuel processor is maintained at operating temperature by the combustion of fuel cell anode off-gas or the fuel itself. -Turn-down ratio of about 1:3. -Optimum utilisation of hot process gases at limited system complexity and system costs. -Low time demand for system start-up. -Minimum electrical energy demand for the system start-up. Fundamentals and State-of-the-ArtMethanol is converted at 250-300°C to hydrogen-containing reformate by steam reforming [1]: CH 3 OH + H 2 O → 3 H 2 + CO 2 DH 0 = 59 kJ/mol (1)

Modeling and parametric study of a methanol reformate gas-fueled HT-PEMFC system for portable power generation applications

“…However, PBI membrane in the HT-PEMFCs is doped with phosphoric acid to increase the proton conductivity, and it is not thermally stable at high temperatures. Therefore, the behavior of the acid for higher fuel cell temperatures must be considered [1,24].…”

“…The best thermal efficiency among the three designs was obtained for the reactor with microchannel reformer and also higher methanol conversion in their experimental results. It is noted that many experimental reformers of the smaller scale and reformers for industrial applications use conventional Cu/ZnO catalysts [1]. Kolb et al [1] have developed a system for portable power generation with an electrical net power output of 100 W. The system consists of oxidative (auto-thermal) steam reforming of methanol with a catalyst of higher activity than Cu/ZnO catalysts and a high temperature proton exchange membrane fuel cell (HT-PEMFC).…”

“…It is noted that many experimental reformers of the smaller scale and reformers for industrial applications use conventional Cu/ZnO catalysts [1]. Kolb et al [1] have developed a system for portable power generation with an electrical net power output of 100 W. The system consists of oxidative (auto-thermal) steam reforming of methanol with a catalyst of higher activity than Cu/ZnO catalysts and a high temperature proton exchange membrane fuel cell (HT-PEMFC). The effects of the CuO-ZrO 2 -CeO 2 -Al 2 O 3 catalysts on the methanol conversion were investigated by Baneshi et al [14].…”

“…In addition, the lack of access to electricity is a serious economic and social issue in the world, especially in underdeveloped and some developing countries [2]; drawing more attention to portable applications. Although batteries are a promising technology for small scale power storage for portable systems, their wide-scale application is limited because of weight restrictions [1]. Although a number of developmental challenges remain to be tackled, fuel cells can be considered as an alternative technology for portable power generation applications.…”

“…This requirement is currently approximated at 714 GW h in Europe [1]. In addition, the lack of access to electricity is a serious economic and social issue in the world, especially in underdeveloped and some developing countries [2]; drawing more attention to portable applications.…”