Investigation of vessels pressure effect on PEM electrolyzer performance by using a new OneDimensional Dynamic Model

In recent years energy shortage and environmental impacts due to consuming fossil fuels have led to developing renewable energy sources systems. Since these sources are not reliable and are usually time dependent, an energy storing system like hydrogen production is required. In this regard, PEM electrolyzer can be efficiently used to decompose liquid water into hydrogen and oxygen. Because of dynamic nature of renewable sources, dynamic model of PEM electrolyzer is a necessity for investigating its performance. In this paper, a new one-dimensional dynamic model of PEM electrolyzer which at each time step solves electrochemical and two phase fluid flow equations is proposed. To solve a set of nonlinear partial differential equations of fluid flow, finite volume method with upwind scheme is used for discretization. The obtained algebraic set of equations is implicitly solved to ensure good stability at large time steps as well as low mesh nodes which provide the capability of system level simulation. Storing produced gas from electrolysis process continuously increases vessels pressure and leads to dynamic behavior of the electrolyzer. This phenomenon is investigated in this research using the proposed model. Results show that although the concentration of produced gas is raised by increasing vessel pressure, hydrogen concentration is essentially constant along the electrolyzer at cathode side. It is also observed that increasing vessel pressure results in high power consumption. However when pressure at anode side gets the moderate level, the water mass flow rate can be reduced, which causes a reduction in pump energy consumption.