A Detection Method for Methanol Concentration in Direct Methanol Fuel Cells Based on Thermal Parameters and Application

A methanol concentration detection method for direct methanol fuel cells (DMFC) based on thermal parameters was proposed. By analyzing the laws of heat generation, conduction, and dissipation in the electrochemical reactions of DMFC, a thermal mathematical model integrating the entropy change of methanol oxidation and mass transfer characteristics was constructed, a quantitative correlation between methanol concentration, temperature, and current density was established, and online detection of methanol fuel concentration was ultimately achieved through thermal parameter measurement. Experimental and simulation verifications showed that the relative error of this method for detecting methanol solutions with concentrations ranging from 0.5 to 1 mol/L was ≤2.3%, and its anti-interference ability against carbon dioxide (CO2) bubbles was improved by more than 40% compared with traditional sensors. The methanol concentration control strategy designed based on this detection method, when applied to small embedded DMFC systems, could stably control the methanol concentration within the ideal range of 0.5‒1.0 mol/L: for the 25 W system, the concentration fluctuation during 12-h operation was ≤±0.02 mol/L, and for the 50 W system, the fluctuation was ≤±0.04 mol/L. This method required no additional sensors, and its computational complexity was only 1/50 of that of traditional neural network models, providing a low-cost, low-power consumption, reliable online detection and control scheme for the engineering application of DMFC in micro-scenarios.