Alkaline electrolysis for green hydrogen production: techno-economic analysis of temperature influence and control

Abstract

To mitigate climate change, a stronger reliance on renewable energy sources is foreseen, and Power-to-Hydrogen systems can be adopted to minimize curtailment losses derived from the intermittent nature of wind and solar power. Among different alternatives, alkaline water electrolysis is the most mature process for hydrogen production using sustainable electricity as its main energy source. The mathematical modelling of the alkaline electrolysis process is a crucial tool to improve green hydrogen production, energy conversion efficiency, sizing (model-based design) and thermal energy management. Although several studies have investigated alkaline electrolysis modelling, these analyses often neglect property variations along the stack area and its economic implications. In this work, the need for increasing the modelling complexity in system models by introducing a one-dimensional model of the alkaline electrolyzer cell/stack is investigated. With this, several operation parameter variations can be modelled, and among these, the internal temperature variation plays a crucial role in both technical and economic aspects. Results show that efficiency could vary between 58-70% while the Levelized cost of hydrogen is within the range of 1.3-1.6 €/kg, when various inlet-outlet temperature differences are considered. Furthermore, from both technical and economic aspects, the optimal temperature control of alkaline electrolysis is to maintain a very low-temperature difference (~1°C), from inlet to outlet, controllable with the alteration of the electrolyte flow rate.