Control-oriented modeling of ionic polymer-metal composite enabled hydrogen gas production

Abstract

Hydrogen gas has been pointed out as a promising fuel with green and minimum emission for energy storage applications. Standard resources to extract hydrogen gas such as gasoline, propane and diesel are vulnerable to depletion. Whereas, resources such as methanol and ethanol, require complex synthesis to produce the hydrogen gas. Among all of the technologies available today for extraction of hydrogen, electrolysis is the easiest and the cleanest method. However, commercial hydrogen production constitutes 3-4% from electrolysis processes. Proton exchange membrane (PEM) and Ionic polymer metal-composite (IPMC) has been identified as the new technologies to extract hydrogen using electrolysis. Significant research has been carried out on the PEM's as future mechanism to perform electrolysis; however, the performance of IPMC for similar application has remained less explored. Owing to its advantages such as high mechanical durability and low ohmic losses, IPMC can also be considered as an agreeable future for hydrogen gas generation using electrolysis. In this paper we present the performance of IPMC as an electrolyzer. By equating the thermodynamic and electrochemical equations of the system we provide a linear relationship between flow rate of hydrogen generation and the source current. Linear and nonlinear parameters of the model are realized by incorporating nonlinear capacitance, pseudo-capacitance and a nonlinear resistance. A state space equation is obtained to simulate the proposed circuit model for electrolysis. System output in terms of the flow rate of hydrogen gas is controlled by designing a LQR controller. Experiments are carried out and are compared with the generated results. The results show convergence of proposed model with prediction error less than 5%.