One-Dimensional Electrolyzer Modeling and System Sizing for Solar Hydrogen Production: an Economic Approach

In this paper, a standalone solar based Hydrogen production in Tehran, the capital of Iran, is simulated and the cost of produced hydrogen is evaluated. Local solar power profile is obtained using TRNSYS software for a typical parking station in Tehran. The generated electricity is used to supply power to a Proton Exchange Membrane (PEM) electrolyzer for Hydrogen production. Dynamic nature of solar power and necessity of reasonable accuracy for estimating the amount of produced Hydrogen, leads to propose a new 1D dynamic fluid flow model for PEM electrolyzer cell simulation. The Hydrogen price in this system is estimated using Equivalent Annual Worth (EAW) analysis. Although it is convenient to select a yearly useful lifetime for electrolyzer as well as solar cells, in this paper, an hourly lifetime which allows finding the Hydrogen cost based on electrolyzer operating time, is considered. Also, electrolyzer sizing is done by selecting various numbers of cells for each stack and alternatives are compared from performance and economic point of view. In this regard, 4 cases consisting of 2, 3, 4, and 5 electrolyzer cells are compared. Hydrogen price at each case is evaluated and sensitivity analysis is performed. Results represent that the larger the electrolyzer sizes, the higher would be the system efficiency and consequently higher Hydrogen production would be obtained. However, the system with higher efficiency is not always an economical choice. As an alternative, turning the electrolyzer off in some conditions is also investigated for possibility of extending lifetime and reducing the Hydrogen price. It shows reduction in the efficiency for all cases though in this situation the efficiency does not necessarily increase with the electrolyzer size. It is also found that turning off the electrolyzer under specified minimum current density (2000 A/m2) in all cases, reduces the final price of the produced Hydrogen.