Comprehensive energy conversion efficiency analysis of micro direct methanol fuel cell stack based on polarization theory

This paper develops a novel analyzing method in order to describe the energy conversion process (ECP) of the micro direct methanol fuel cell (μDMFC) stack quantitatively. The method employs the Debye-Hückel ionic atmosphere theory to study the generation and loss of the energy during polarization coupling. The polarization and energy conversion efficiency (ECE) analyzing results show that high output power does not also mean high ECE of the μDMFC stack. After exceeding the corresponding output current (OC) of peak output power, the ECE falls significantly. The simulated ECEs of the proposed method are validated experimentally and the experimental results correlate well. Moreover, the presented method achieves the highest ECE of 27.96 % for the μDMFC stack fabricated in this research. The corresponding anodic methanol supply concentration (AMSC) and the OC are 2.7 M and 240 mA respectively. Compared with recent researches, the proposed method achieves an even more significant ECE improvement. The novel method of this research makes it possible to predict the highest ECE and the corresponding operating parameters, thus improving the ECE of the μDMFC stack accordingly. The practical application of μDMFC stack in powering portable devices for marine use will significantly benefit from the presented analyzing method.