PEM electrolyzers for electrical energy storage as hydrogen

Team organizer: Mohamed Becherif, MCF HDR

Decarbonized production of hydrogen and fuel cells constitute a new convincing energy solution for a wide range of use (including large-scale and long-lasting energy storage), allowing significant ecological gain and energy saving. Thus, the main application of this research area will be the remote electrical power sites supply, from such renewable energy (solar and wind energy in particular). It is a new research team within the Research Federation.

The various component subsystems are nowadays relatively well known and have inspired scientific developments (photovoltaic electrolyzer, wind, hydrogen, energy storage, …). Energy optimization of the whole system electrolyzer / hydrogen storage / fuel cell is still much less.

The objective of our work is double; it is first to define a model of the electrolyzer based on the energy involved and related to some important physical properties. Secondly, it is proposed to optimize the power flow between the electrolyzer, sources (wind, solar, …) and means of storage (battery and / or ultra capacitor or the hydrogen storage) and thus to go to an optimal energy management.

During the last decade, a new modeling framework has emerged, called Hamiltonian structure commissioned by Port (PCH: Port Controlled Hamiltonian), which incorporates the concepts of energy and energy flows and encompasses a broader set of systems than Lagrangian and Hamiltonian models. The PCH structure provides energy information that is of some importance in the development of control and energy management. This data is expressed in terms of information on the interconnections between the states of the system that give an indication of the energy exchange between the variables, and in terms of information on the damping of the system that is associated with the dissipation.

Formalisms in the same spirit as the PCH allow us to obtain representations that facilitate the understanding and learning of the system (especially for the simulations) and the interaction with control the energy management modules. Among these formalisms the Energetic Macroscopic Representation (EMR) or the Bond Graphs may also be found. Thus, REM multiphysics modeling of electrolyzers (Figures 1 and 2) was developed by FCLab researchers. The parameters of this model have been identified experimentally allowing validation of the theoretical model on a real bench.

Figure 1 : modèle de représentation énergétique macroscopique (REM) de l’électrolyseur, développé par les chercheurs de FCLAB

 

 Figure 2 : Interactions multi-physiques au sein de l’électrolyseur

The energy management in a system with an electrolyzer results in control of static or rotary converters. Passivity based control methods or methodologies associated with the modeling approach macroscopic energy representation will be employed. The term « control based on passivity » (PBC, Passivity-Based Control) was introduced to define a methodology for the design of controls that ensure the stability of systems by making them passive. PBC usually means simple and robust control laws towards uncertain parameters, and non-modeled or variable over time. At present, the hydrogen production by electrolysis is characterized by these poorly known parameters, which fully justifies the application of passivity based control. We identify a class of PCH models for which PBC ensures the preservation of the Hamiltonian structure, with storage function the energy balance. A final advantage of this method is that it is systematic and that the controller can be easily synthesized using symbolic computation. Several applications of this method to a wide class of physical systems have emerged

Experimental test bench

An experimental test bench including the electrolyzer, renewable sources and means of storage is considered in the research federation FCLab. This test bench, modular and reconfigurable aims at validating the models developed, controlling various actuators (static and rotary) and testing different strategies for energy management of this set of multi-sources/multi- converters.

The test bench will be of a significant scale to allow easy extrapolation to real systems

Topics for future research

Research activities developed along this area are focused on the following points:

1)  Modeling of all components of the system of decarbonized hydrogen production by analytical approaches (electric equivalent equation of state formalism PCH) or REM.
2)  Modeling of storage means of energy (electrochemical storage)
3)  Methods and means of storing electricity in hydrogen in solid form
4)  Control of static or rotary actuators for hybrid set.
5)  Management of the flow of energy by taking into account the constraints of production (light, wind), operation (minimum and maximum operating) and storage (in relation to the axis 4).

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