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

In recent years the energy shortage and environmental impact from consuming fossil fuels have led to the development of renewable energy source systems. Since these sources are not reliable and are usually time dependent, an energy storing system like hydrogen production is required. In this regard, a PEM electrolyzer can be efficiently used to decompose liquid water into hydrogen and oxygen. Because of the dynamic nature of renewable sources, a dynamic model of a PEM electrolyzer is a necessity for investigating its performance. In this paper, a new one-dimensional dynamic modelPEM electrolyzer which solves electrochemical and two phase fluid flow equations at each time step is proposed. The finite volume method with an upwind scheme is used to solve a set of nonlinear partial differential equations of fluid flowfor 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 thecapability of system level simulation. Storing gas produced by the 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 was raised by increasing vessel pressure, the hydrogen concentration was essentially constant along the electrolyzer on the cathode side. It was also observed that increasing vessel pressure results in high power consumption. However, when the pressure on the anode side reaches the moderate level the water mass flow rate can be reduced, which causes a reduction in pump energy consumption.

Keywords:

PEM , Dynamic modeling , Finite Volume , Hydrogen production