Book/Dissertation / PhD Thesis

FZJ-2025-01945

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Dynamischer Betrieb von Polymer-Elektrolyt-Membran Wasserelektrolyseuren

Rauls, E. (Corresponding author)FZJ*

2025
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich
ISBN: 978-3-95806-811-7

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Please use a persistent id in citations: urn:nbn:de:0001-2504140913116.459385823088  doi:10.34734/FZJ-2025-01945

Abstract: Dynamically operated water electrolyzers can provide security of supply and power system stability in energy systems with a high proportion of fluctuating renewable energy sources such as wind power or photovoltaics. Polymer Electrolyte Membrane (PEM) electrolyzers are particularly suitable for these operating scenarios due to their ability to handle highly dynamic load changes. This work addresses the impact of dynamic operation of PEM electrolyzers on efficiency and potential operating scenarios in future energy systems. For this purpose, a dynamic simulation model for PEM electrolyzers is developed, parameterized, and validated on a 100 kWel electrolyzer. This model is scaled up to the megawatt range and dynamic aspects are investigated on different scales. The heat-up process of electrolyzers has the highest average efficiency of 74.1 %LHV when part-load operation is directly entered at moderate cell voltages around 1.80 V. Heat-up with auxiliary electric heaters has a maximum efficiency of 60.0 %LHV and is therefore less efficient than heatup under partial load but it qualifies electrolyzers as flexible power sinks. Standby modes allow reduced start-up times of nominal power but require electrical power to maintain operating conditions. Electrolyzers of 400 kWel and larger require about 2 % of their rated power in warm standby mode and between 7 and 9 % of their rated power under minimum load. For a 1 MWel electrolyzer, it can be energetically beneficia to stay in warm standby mode for more than 24 hours, which shortens the return to the nominal operating point from 37 minutes to a few seconds. During dynamic operation, short-term fluctuations in operating temperature of less than 5 K around the set point are observed, affecting system efficiency by less than ± 0.5 %LHV. With 50 μm membranes, average cell efficiencies of more than 73 %LHV and system efficiencies of more than 67 %LHV are possible, regardless of the nominal system power. Oversizing the auxiliary heating from 2.5 to 10 % of the nominal electrolyzer power of a 1 MWel electrolyzer does not improve the cell efficiency but worsens the average system efficiency from 59.7 %LHV to 53.5 %LHV. Completely eliminating auxiliary electrical heating improves the efficiency and part-load capability of electrolyzers. For example, for a 400 kWel electrolyzer coupled to a photovoltaic system, simulations demonstrated that the average system efficiency over one day in increases from 68.7 %LHV when using auxiliary heating to 70.2 %LHV in autothermal operation. The results of the present work can be used for the development and optimized operation of electrolysis systems. For energy system analyses, the consideration of the transient operating conditions of electrolyzers offers a complementary contribution towards a better understanding of the effects of fluctuating energy sources on grid stability provision services.

Note: Dissertation, RWTH Aachen University, 2024

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Contributing Institute(s):

1. Elektrochemische Verfahrenstechnik (IET-4)

Research Program(s):

1. 1231 - Electrochemistry for Hydrogen (POF4-123) (POF4-123)

Appears in the scientific report 2025

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