Wet and affordable hydrogen storage – STHYME

In the case of mass production of hydrogen by electrolysis from renewable energies, a hydrogen storage buffer is often needed. This one requires gas drying beforehand, indeed :
- in the case of metallic tank, drying is required to prevent corrosion,
- when hydrogen is stored as metal hydrides, a very dry hydrogen is required.
However, for PEM fuel cell the use of this drying is not necessary. Furthermore, for the combustion of hydrogen in a gas turbine in order to reduce the NOx emissions, a re-humidification of the hydrogen is commonly performed.
This drying operation is costly in energy and investment. In sizing the drying device at the right level, the project aims to significantly improve the energy efficiency of a hydrogen chain coupled to renewable energies and to reduce its cost.
Considering the different ways of storing hydrogen, such drying simplification is not easy, because:
(a) the materials used for storing and conveying hydrogen are low alloy steels sensitive to aqueous corrosion as well as to hydrogen embrittlement, and the interactions between these two types of damages have to be investigated
(b) if we consider a metal hydride storage system, gas moisture accelerates the aging of these hydrides which are very sensitive to hydrolysis,
(c) tanks with internal polymer liners have been designed for storing dry and high-pressure hydrogen. However in the case of wet hydrogen, the hydrolysis and aging behaviour of these liners are poorly known.

The STHYME project aims to simplify the drying for three ways of storage:
- for a pressure storage in a steel tank, by studying the impact of humidity on the corrosion and hydrogen embrittlement of the steel used, in order to design the drying at the correct level and thus to reduce its investment cost and to improve the global energy efficiency,
- for a storage under MgH2 hydrides, by analyzing the behaviour of the hydride at different level of humidity and by developing drying solutions, well adapted to hydride storage and able to re-wet the gas when desorbed, this without energy consumption.
- a direct and cost-competitive storage of wet hydrogen under medium pressure, possibly the outlet pressure of the electrolyser, thanks to the use of an internal liner polymer,
To carry out this project, we rely on strong partnership skills, in PEM electrolysis and fuel cell systems, in corrosion and hydrogen steel embrittlement, in polymer and in hydride storage system.
This partnership will help to develop an innovative drying system coupled with hydride storage system, to evaluate the influence of moisture on the hydrogen embrittlement and corrosion of steel pipe and to implement low cost storage solution, thanks to the use of an inner polymer liner.
In parallel we will rely on techno-economic analysis to guide choices toward solutions providing economic gain and / or energy saving at the system level.
Once the technologies developed, we will achieve for each storage routes, a small demonstrator coupling a PEM electrolyser with the drying solution well adapted to the storage system. Tests will be performed to evaluate lifetime, aging behaviour in order to better quantify the possible economic gains.