Power management unit with maximum-efficiency-point-tracking to enhance the efficiency of micro DMFC stack

The micro direct methanol fuel cell (μDMFC) stack shows very different mass transfer and electrochemical kinetics from the battery and the proton exchange membrane fuel cell type of hydrogen-oxygen. Therefore, the current control strategy contianing large-scale auxiliary equipment cannot adopt to the micro-scale μDMFC stack, thus leading to descending energy conversion efficieny during practical application. In order to reduce the energy loss, this study introduces a power management unit (PMU) employing a novel maximum-efficiency-point-tracking (MEPT) strategy to control the μDMFC stack operating with high efficiency. The presented MEPT strategy novelly combines the P&O algorithm and the polarization theory of the μDMFC stack to calculate the operating parameters for the maximum efficiency operation. During start-up at different load, the PMU fast stabilizes the voltage at 5 V within 1 s and the experimental results correlate well with the simulated results. Moreover, the PMU can regulate the output voltage experimentally during dynamic operation process. Although the changing load influences the operation of the PMU, the output voltage remains over 4.85 V with the stabilizing voltage of 5V. The μDMFC power system with the proposed PMU improves the energy conversion efficiency by at least 10 % compared with the one without the PMU. The total energy conversion efficiency exceeds 17 %. The μDMFC power system with the proposed PMU shows significant superiorities in energy conversion efficiency, size, and none auxiliary equipment. The PMU makes it possible to power modern microelectronic portable systems efficiently and stably.