The durability and the reliability of fuel cells are key points to promote hydrogen. To increase the fuel cell system lifetime, diagnostic, prognostic and smart control approaches are developed by researchers. They allow detecting failures, forecasting the remaining useful lifetime and act on the system through sensors to face degradation. Nevertheless, as the ageing of the FC stack is slow, some long-term tests are needed. The aim is to develop accelerated stress tests to reduce expensive and time-consuming experiments to validate durability approaches. This paper is dedicated to studying three different experimental tests on proton exchange membrane fuel cells (PEMFC) and the degradation impact of two stress factors: the frequency and the magnitude

Proton exchange membrane electrolysers are undoubtedly one of the most promising technologies for coupling with renewable energies. However, significant improvements in lifetime and production costs must be achieved before they can be applied on a large scale. Experimental protocols that allow the diagnosis and assessment of degradation, on timescales considerably shorter than the expected lifetime, are of great interest among industries and the scientific community. This work then proposes an experimental protocol aimed at studying degradation under stress conditions. The protocol was implemented in two different configurations: single cell and short stack, with diagnostic periods including a steady-state polarization curve and impedance spectroscopy, both in galvanostatic mode. With a degradation rate of 36.5 uV/h/cell for the single cell and 18 uV/h/cell for the short stack, the experiments show in both cases that: temperature has a very significant effect on the degradation of the cathode catalyst, very low frequency current cycling regenerates the electrochemical conditions, high current densities are the most punishing, and a large proportion of the losses can be recovered with a suitable rest period. Three peaks have been identified in the DRT analysis: P1, mass transport phenomena and P2+P3 oxygen evolution reaction, charge and proton transport.

This paper is dedicated to the control of hydrogen production with an experimental proton exchange membrane water electrolyzer in the context of renewable energy sources. Two control laws, $i \mathbf{P}$ and PI controllers have been evaluated under several scenarii including renewable energy sources variations. A discussion of the performances of the controllers allows to formulate several open issues for the control of PEMWE in a renewable energy context.

The durability and reliability are two main obstacles for the widespread commercialization deployment of Proton Exchange Membrane Fuel Cell (PEMFC). Prognostic and Health Management (PHM) could supervise the State of Health (SoH) and make the right action at the right time to extend the lifetime of PEMFC. In the Remaining Useful Life (RUL) prediction, the Health Indicators (HIs) are able to reflect the degradation state and an efficient Health Indicator (HI) could make sure the prediction accuracy. In general, the voltage and power are the most commonly used HIs because they are easy to measure or calculate. Besides, the current and voltage sensors are convenient to be installed and the voltage and power are always supervised for the control purpose. Nevertheless, these two HIs are more suitable for static operating conditions and assume that their deviation is only influenced by the ageing phenomenon. In the dynamic or time-varying operating conditions, the voltage and power are synthetically influenced by the operating parameters and deterioration factors. So some novel HIs (e.g., virtual stack voltage, average resistance) should be used for the dynamic working conditions. Moreover, two HIs, i.e., polarization resistance and power loss, are proposed in this paper. Finally, the performances of different HIs are evaluated based on the experimental data.