Modeling And Analysis Of Micro Direct Methanol Fuel Cell Stack

With the rapid development of the microelectronic technology, the area of chips forportable electronic device has become smaller and smaller. Meanwhile, since wirelessnetworks become popular in daily life, which leads to the increasing powerconsumption of electronic devices, so the research on micro energy for portable storagedevice attracts more and more attention. Among all kinds of energy supply devices, thedirect methanol fuel cell (DMFC) has the characteristics of simple structure forintegration, extensive source of fuel, high speed to start, etc. DMFC has become one ofthe most promising removable energy sources for possible commercialization.To meet the power demand for electronic device, DMFC stack is always usedthrough the cascade of single DMFCs. It can be further understand the reaction andchanges inside the DMFC stack by doing the modeling work. Modeling can not onlysave the time and cost of structure optimization, but also select more effective workingenvironment through the analysis of operating parameters. Therefore, modeling of thestack is of great significance in the study of micro DMFC.Deep research on structure and working principle of the DMFC are conducted inthis paper: physical and chemical formulas are used to describe the material transport,energy transfer and electrochemical reaction inside the DMFC stack; formulas arederivate and calculated of to set up an equivalent circuit model of the DMFC stack,which have been modified and validated by both the theoretical model and experimentaldata; the equivalent circuit model are used to analyze the influence of the operationparameters, such as reactants (methanol and oxygen) concentration and operatingtemperature on the performance of a DMFC stack. The results show that: increasing theconcentration of reactants can significantly improve the output performance, butincreasing the concentration of methanol will also increase the amount of crossovermethanol, resulting in a loss of fuel; improving working temperature can not onlyenhance the performance of the stack, but also change the flow of methanol on catalystlayer, and the efficiency is improved accordingly; with the lack of fuel concentration,the "polarity reversion" phenomenon is easy to appear in the stack, and the irreversible failure of a single cell can decrease the stack output performance significantly; assemblypressure determines the contact resistance of a stack which has an influence on stackoutput performance, so the assembly pressure should be increased during theassembling progress of a DMFC stack.