The share of renewable energies in the energy mix is gradually increasing. This transition brings many challenges in the management of electricity grids, especially because of the fluctuating and intermittent nature of renewable energies. Therefore, hydrogen represents one of the keystones for the sustainable exploitation of our energy resources. Hydrogen allows storing in the long term not consumed but available electricity, and hydrogen is a 'fuel' for mobile, nomadic and remote site applications. Once produced and awaiting consumption, the hydrogen must be stored in optimal conditions of safety and efficiency with regard to the application and its location. The most mature solution to date is the storage under the compressed form, which consists in keeping the hydrogen gas in a container at increasing pressures in order to increase the energy density; cryogenic storage is now well controlled but generally reserved for very specific applications for reasons inherent to the technology and because of significant costs; and finally the so-called 'solid storage', to which the scientific community has been showing a marked interest for several decades in the hope of identifying a lasting solution likely to replace advantageously other solutions. In this paper, these storage media are introduced by evoking their technological characteristics and their fields of application often justified by inherent limitations of the technology. We will also discuss the challenges still posed by these storage solutions today by linking them with the research work carried out in the Department of Applied Mechanics in FEMTO ST Institute.

Vibration sensitivity is an important specification for oscillators dedicated to space or airborne systems. For some crystallographic material, some physical constant are not yet measured. So, computation of stress coefficients of frequency is not possible. This paper presents a simple experimentation which allows the determination of the six stress coefficients of frequency for each high-overtone bulk acoustic resonators configuration. The first three coefficient are s αmn are -2.9×10 -12 /Pa, 4.3×10 -10 /Pa and 9.4×10 -11 /Pa. The relative standard deviation can be high due to experimental uncertainty.

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