Optimal Control of a Unitized Reversible Fuel Cell System for Hydrogen Production with Renewable Power^*

This paper is concerned with the optimal control of a hydrogen production system that is powered by photovoltaic solar energy and assisted by the grid. To achieve this, a simple dynamic model that accounts for the main components of the system is proposed. The current in a unitized reversible fuel cell is used as the control variable to obtain the control sequence that optimizes the grid energy consumption despite the variability of solar energy. A significant restriction on the obtained solution is the switching behavior of the unitized reversible fuel cell, which can operate as a fuel cell or electrolyzer, which results in a non-smooth and non-continuous problem. The Hermite-Simpson collocation and a nonlinear programming solver are used to solve numerically the optimal control problem, resulting in an open-loop control trajectory. Results from simulations are presented to demonstrate the effectiveness of the proposed control method.