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

Abstract

Ionic polymer-metal composite (IPMC) is an electro-active polymers which exhibits the property of ion migration under the application of external electric field. This property of IPMC along with the ability to operate in aqueous environment is useful in dissociating chemical bond in water (H2O), and produce hydrogen (H-2) and oxygen (O-2) gases. In this paper, a control-oriented model of IPMC as an electrolyzer is presented. By equating the thermodynamic and electrochemical equations of the system, a linear relationship between flow rate of hydrogen generation and the source current is derived. A nonlinear state-space model is then used to capture the source current related to the voltage input. The model has been verified with the experimental data. Temperature-dependent effect and energy-conversion efficiency have been investigated, which shows the need of state feedback control for achieving high energy conversion efficiency. Based on a linearized model, a linear quadratic regulator (LQR) is designed to optimize the control performance. Experimental results have shown that the output performance of LQR is better than that of PID. It has also been validated that the control-oriented model is useful in optimal control of IPMC electrolyzer.