Differential algebraic modeling of an alkaline electrolyzer plant

TL;DR

The paper develops a dynamic, first-principles model for an alkaline electrolyzer plant by formulating a differential-algebraic system that couples mass and energy balances across the stack, separators, compressor, storage, heat exchangers, and mixer. A thermodynamic library is integrated to compute properties and reaction energetics, enhancing accuracy over constant-heat-capacity assumptions. Simulation with a step-change in input power demonstrates nontrivial, tightly coupled dynamics and confirms the model's suitability for controller design and optimization. The approach enables rigorous, physics-based evaluation of hydrogen production under varying operating conditions and supports development of advanced control strategies for flexible, grid-responsive operation.

Abstract

We develop a mathematical model for dynamic simulation of an alkaline electrolyzer plant. The plant includes the stack, a water recirculation system and hydrogen storage with compressor. We model each component of the system with mass and energy balances. Our modeling strategy consists of a rigorous and systematic formulation using differential algebraic equations (DAE), along with a thermodynamic library that evaluates thermophysical properties. We perform a simulation with step power input. Dynamic modeling enables simulation and model-based optimization and control for optimal hydrogen production under varying operating conditions.

Figures (4)

• Figure 1: On the left: process sketch of the electrolyzer plant. On the right: working principle of an alkaline electrolytic cell. The reduction reaction happens at the cathode, where hydrogen is produced. The oxidation reaction happens at the anode, where oxygen is produced.
• Figure 2: Gas-liquid separator for the hydrogen stream out of the electrolyzer.
• Figure 3: Multi-stage compressor with heat exchangers.
• Figure 4: Dynamic simulation of the electrolyzer plant using step power input.