Advancing alkaline water electrolysis (AWE) toward high-pressure operation is highly required for reducing the Levelized Cost of Hydrogen (LCOH) in integrated systems by eliminating mechanical compression stages. As part of the EU-funded Project PEACE ¹.

a novel two-stage pressurization concept is being developed to operate at pressures up to 90 bar. While high-pressure operation stabilizes gas volumes during load fluctuations, it simultaneously exacerbates gas solubility and crossover, making precise transient modelling a prerequisite for safe system design.

This work focuses on the experimental validation of the Transient Electrochemical Model for Process and Energy Systems (TEMPEST) ² simulation framework, which has been specifically expanded to characterize the electrochemical and thermal dynamics of the PEACE high-pressure system.

Experiments were conducted at the PEACE system varying current density, electrolyte flow rate and pressure. Outlet temperature and gas purity were measured.

While the PEACE system provides essential data for the behaviour at different pressure levels, its coupled electrolyte circuit limits the direct observation of the individual crossover components of mixing and diffusion. To resolve this, fundamental assumptions regarding gas crossover were cross-validated using a secondary atmospheric test bench capable of operating in separated electrolyte mode.

Furthermore, because the model is primarily founded on fundamental physical equations rather than empirical curve-fitting, it enables reliable simulations of operating conditions that extend beyond the current experimental scope. This provides a robust predictive tool for de-risking high-pressure operation and guiding the transition from experimental prototypes to industrial-scale hydrogen production.

[1] https://www.h2peace.eu/

[2] M.Tomberg et al., Transient Modelling of Solid Oxide Cell Modules and 50 kW Experimental Validation. Stuttgart (2019), ECS Trans. 91