(A) study on the light weight composite PEMFC system

Abstract

The proton exchange membrane fuel cell (PEMFC) is a promising source of alternative energy due to its high efficiency and low emissions. However, the low productivity of the bipolar plates and complex balance of plants (BOPs) of the PEMFC system remain obstacles for mass production. Moreover, PEMFCs have some limitations for portable applications because of the weight of the stack and BOPs. In this study, a light weight PEMFC system was developed using carbon composite bipolar plates and an air-breathing design to solve the weight and productivity problems. A carbon/phenol composite bipolar plate for PEMFC was developed using a continuous hot rolling process to increase the curing rate, which would increase the productivity of PEMFC stacks. An air-breathing PEMFC stack with light weight carbon composite bipolar plate was designed, and its prototype was manufactured without the extra humidification device and cooling systems to reduce the weight and complexity of the system. The composite bipolar plates for PEMFC were developed using carbon fabric and resole-type phenolic resin with an acid catalyst of p-toluene to increase the curing rate. An optimum content of the catalyst was investigated considering the electrical conductivity without much deterioration of the mechanical properties. The continuous hot rolling process for mass production of the carbon/phenol composite bipolar plates was optimized through cure monitoring by the dielectrometry. The optimum operating conditions of the air-breathing PEMFC system were designed by considering the heat generation and water management. To reduce the weight of the PEMFC stack, carbon composite bipolar plates and sandwich end plates were employed. However, the open-cathode design for air-breathing PEMFC caused hydrogen leakage and compressive failure of the bipolar plates. To solve the sealability problem, the anode/GDL/MEA assembly unit was developed using silicone adhesive bonding between the anode bipolar plate and the membrane. The sealability and reliability of the anode/GDL/MEA assembly were investigated. To prevent compressive failure of the open-cathode composite bipolar plates, the stacking sequence and the thickness were optimized by finite element analysis and experimentation. Finally, a prototype of the 400 W light weight air-breathing PEMFC was manufactured using carbon composite, and its performance was tested and verified under real operating conditions without humidity and temperature control.