Concept development of innovative and space-optimized lightweight tanks

At Leibniz-Institut für Verbundwerkstoffe GmbH, the "LH2-Flatlight" project addresses current challenges in the storage of hydrogen as an energy carrier in emission-free mobility. These include the relatively low volumetric energy density of hydrogen compared to fossil liquid fuels such as gasoline or diesel. Figure 1 shows that approx. four times of the volume is required for the same amount of energy in pure gasoline when hydrogen in liquid form is stored at 2 bar. This characteristic leads to unsuitable size ratios for current hydrogen pressure vessels for the use in motor vehicles and future aircraft.

Typically, a pressure tank has a cylindrical shape, as, in addition to the spherical shape, a particularly small surface area is required in relation to the stored volume. In addition, both geometries have an extremely favorable effect on the internal stresses. These advantages are offset by the fact that most installation spaces have rectangular cross sections. This reduces the packing density and the number of tanks, see. Figure 2. This is because each individual pressure accumulator usually has to be equipped with connecting elements such as hoses, sensors, pressure reducers and valves. These framework conditions mean that flat tank concepts for liquid hydrogen are particularly promising.

The "LH2-Flatlight" project focuses on the development of several concepts for flat, lightweight tanks that can be used to store liquid hydrogen. The primary objective is to realize the possibility of flexible tank geometries for use in mobile applications. The project aims to go beyond the state of the art in order to achieve the following project goals in the context of liquid hydrogen storage:

• Selection and evaluation of suitable materials
• Development of innovative construction methods
• Development of efficient manufacturing processes
• Implementation of monitoring technologies

The development at IVW offers numerous advantages thanks to a holistic approach that is pursued by various specialist departments. It is possible to measure material characteristics and to access a wide range of plant technologies in the field of process and processing technology. These resources are supplemented by numerical simulation methods. As part of the project, new plant technologies will be acquired that enable the permeability properties of various materials to be investigated in relation to hydrogen diffusion. In addition, a cryogenic test infrastructure will be set up to measure mechanical parameters in a low temperature range. For example, the diffusion properties of joined components can be quantified in the joining zone, which exhibit different properties compared to the core material due to changes in fiber orientation or microstructure, see Figure 3. This aspect is relevant e.g. for the induction welding of assemblies  because it leads to different hydrogen diffusion rates in addition to the choice of material and strength properties.

The LH2-FlatLight project is funded by the state of Rhineland-Palatinate via the Ministry of Science and Health (Funding Code 724-0027#2023/0003-1501 15404).

Sources: