The Fraunhofer Institute for Manufacturing Technology and Advanced Materials (IFAM) has further developed a diagnostic method for electrolyzers and fuel cells that enables condition analysis during operation. The so-called dynamic impedance spectroscopy is intended to detect overloads in real-time and uncover weaknesses early. According to the institute, this can increase the lifespan and efficiency of the systems and reduce operating costs.
Electrolyzers and fuel cells are subject to varying loads during operation, such as those caused by the fluctuating input of renewable energies. These can lead to material aging, performance decline, and shortened lifespans. The previously common classical impedance spectroscopy requires an interruption of operation to reach a stationary state. It is time-consuming and hardly reflects the real operating condition.
Multifrequency signal superimposed on operating current
In the new method, researchers superimpose a small multifrequency signal on the normal operating current. It measures how current and voltage change. From the ratio of these quantities, the system calculates the complex impedance, which can be understood as a frequency-dependent electrical resistance.
“It is precisely this frequency-dependent character that makes impedance so valuable for the mentioned applications and interesting for us. Unlike a simple resistance value, it provides a comprehensive picture of the processes inside an electrochemical system,” explains Hermann Pleteit, project manager at Fraunhofer IFAM. Various physical and chemical processes—such as reactions at the electrodes, ion transport through the membrane, electrical contact resistances, or the supply of involved substances—affect different frequencies. This allows them to be distinguished and individually evaluated.
From the temporal course of the spectra, the system draws conclusions about the condition and aging. An increase in certain resistance components can indicate deteriorated electrode reactions, corrosion, or declining electrical contacts. Shifts in phase behavior indicate membrane wear, water management issues, or restricted substance transport.
Leap from laboratory to industrial dimensions
According to the institute, the progress lies in transferring the method from the laboratory scale to real application dimensions. Operating currents up to 30 amperes can now be superimposed with the measurement signal. An integrated online data processing calculates the temporal development of the impedance and displays it directly.
“With our new dynamic measurement method, we obtain meaningful data directly from the real ongoing process with significantly higher current strengths than in the previous laboratory setup,” says Pleteit. In combination with AI-based models, the results can be transferred to changed environmental conditions such as pressure and temperature fluctuations as well as to new material compositions.
Integration into plant control
According to Fraunhofer IFAM, the extended system can be directly integrated into plant control, such as the Energy Management System. Operators of PEM fuel cells and alkaline electrolyzers continuously receive condition data that reflect the state of health of the plant. Based on this, processes such as catalyst degradation can be detected early, maintenance intervals planned, and operating strategies adjusted.
“Instead of reacting only when the plant is already down, we can accurately predict maintenance work and avoid costly downtime,” says Pleteit, adding: “This significantly reduces lifecycle costs and ensures the economic viability of green hydrogen projects.”
