Model-based analysis of water management at anode of alkaline direct methanol fuel cells

Abstract

Alkaline direct methanol fuel cells (ADMFCs) produce water at the aqueous fed anode. This complicates water management at anode which is analysed in this study by modelling three extreme case scenarios assuming different conditions for water transport or removal. All scenarios include recycling of methanol solution at anode outlet to achieve high methanol efficiencies. One scenario reveals that high operation times and high methanol efficiencies necessitate active stabilisation of anodic water level since both water accumulation and depletion can take place depending on operation conditions. Another scenario shows that water level can be stabilised by adjusting cathodic evaporation and the corresponding water removal from the system. The results indicate that feeding cathode with water-saturated gas is detrimental for stabilising water level. The last scenario suggests the addition of a gas flow to anodic outlet to remove excess water for water level stabilisation. Minimization of additional methanol loss requires to reach high humidities by evaporation. The present paper reveals the impact of processes occurring in ADMFCs on anodic water management and indicates the necessity to quantify water transport through membrane. Knowledge of the influence of operation conditions on water level in the anodic loop are beneficial for design of ADMFC systems.