Digital Model of PEM electrolysis for hydrogen and waste heat production with heat management

Abstract

Globally, it has been decided to strongly reduce harmful emissions. Hydrogen has a high heating value and works well as an energy carrier. Using hydrogen, e.g., inexpensive but fluctuating wind power generation peaks can be smoothed out by storing surplus peaks in various hydrogen absorptions (ammonia, MH, P2X). When burned, hydrogen produces water as emissions. The hydrogen economy systems can reduce CO2 emissions and replace current fossil economic systems. Electrolysis using green electricity splits water molecules, produces green hydrogen, oxygen, and heat. Total hydrogen production (2024): by electrolysis only 4 %, which is growing, the main hydrogen production method was SMR. The aim of thesis was to develop a Digital PEM Electrolysis Simulator in University of Oulu using the MATLAB® Simulink, which is easily scalable to different powers and concepts, to study: hydrogen production, percentage of excess heat in relation to electrical power, the excess heat (waste heat) management, behavior, control, and utilization. The resulting Digital PEM Electrolysis Simulator (with waste heat production ~20 % of electrical power) was tested for operation under varying electrical current input effects: e.g., hydrogen production, water consumption, hydrogen production price, but especially excess (waste) heat generation, behavior, and controllability, as Simulator was coupled with the Heat Management Model. The thesis investigated how the simulator combination i.e., the PEM Electrolysis System Model, and the Double-tube Heat Exchanger Model with PID Controllers’ cascade-connected to both the secondary circuit cooling water mass flow and its outlet temperature manages to control the system so that avoids the overheating of the equipment and maximizes the excess heat energy utilization. As conclusions of the thesis, it was confirmed that the Digital PEM Electrolysis Simulator is valid for studying the production of hydrogen and the utilizable waste heat, also in different power scales. Using the Digital PEM Electrolysis Simulator, various system concepts can be mapped before designing physical PEM electrolysis systems (Example: For common High-efficiency Hydrogen Production PEM Electrolysis System Concepts built with more expensive precious metals, there may also be another profitable alternative concept. In the Alternative Concept, the PEM Electrolysis System is built with more sustainable and cheaper metals, as a result, the Hydrogen Production Efficiency may remain low, but correspondingly it produces more Excess (waste) heat, and when maximally utilized, it keeps the overall system efficiency at a high level). Using the Digital PEM Electrolysis Simulator, systems and functions in various scenarios can be quickly investigated.