Efficient development of lightweight composite hydrogen storage units

»SIMUTENCE engineering and simulation methods enable for an efficient design of composite pressure vessels (CPV). But what are the major steps to be included in the design process?
We’ll answer this question below.«


The reduction of CO2 emissions is a key driver for innovations in the global aerospace and automotive industry. Therefore, hydrogen fuel cells play a key role in future mobility concepts. In this regard, lightweight concepts are of high interest to optimize the maximum driving or flying range. For both, automotive and aerospace applications, hydrogen storage is a key point within the overall concept.


The manufacturing costs of a hydrogen storage system using fiber-reinforced composites depend strongly on the amount of carbon fiber used. Therefore, high utilization of the used composite material is important for a successful storage system development. This can be achieved by a fully virtual product development, where each development step is supported by simulation methods.

Shares of the total costs of a hydrogen storage system, based on a yearly production of 100.000 units. [1]

The most relevant manufacturing strategy for composite pressure vessels is the filament winding process. The main advantages of this process technology are its high process reliability, scalability, and the possibility to design the laminated optimized for the load case. For this purpose, a virtual development circle is crucial, to define a best-suited layup. In addition, virtual product development allows comparing a large number of different concepts on an equal basis and with significantly lower costs than for real-world prototyping.


Additionally, an important point in the development of new storage systems, as for all engineering challenges, is to ensure a high quality of the design before the actual manufacturing is started. For an efficient product and process design within a digital product development cycle, the simulation of the manufacturing process through winding simulation is an important aspect. These simulations allow not only for the validation of manufacturability but also for the optimization of process parameters as well as the prediction of fiber orientations. This informaction can then be used in subsequent simulations steps, such as a stress simulation, to improve their prediction accuracy.


SIMUTENCE is a spin-off company from the Karlsruhe Institute of Technology (KIT) in Germany with a strong background in composite simulation. Within an internal study, we explored the opportunities to extend our expertise to the virtual design of composite pressure vessels. In the following, we’ll outline some of our insights.

Conceptual design

For hydrogen storage in automotive applications, different concepts have been developed. The following figure provides an overview of the different general design approaches and gives an estimated weight-saving potential for the different concepts.

Different types of hydrogen storage units and comparison of wall thickness for similar pressure indicating weight saving potentials. [2]

Besides the illustrated type-1 to type-4, a new type is under development. The goal of the development of this type 5 hydrogen storage system is a liner-less system, which is easier to manufacture and has a lower number of individual components. Regarding the total system weight, only slight changes are expected. Therefore, lightweight is not the main driver for this development but cost reduction. From a design point of view focusing on structural performance, the required steps are similar for type-4 and type-5.


Currently, the most promising approach in terms of lightweighting is the type-4 design. This design consists of a plastic liner, in combination with carbon fiber-reinforced layers. Additionally, the outer layers are made from a glass fiber-reinforced composite material, adding additional damage tolerance.

Analytical design

The most efficient way to identify a suitable design to start from for given load and dimensional requirements are analytical equations. First, optimum dimensions of the CPV can be estimated through:

After the dimensions of the CPV are set, a layer-by-layer stress and failure analysis enables the identification of suitable layups and required thicknesses of the hoop and helical layers. Based on this, a large number of different concepts can be analyzed quickly. Based on this, a first concept can be obtained efficiently before doing any detailed winding or stress simulations.

Winding simulation

Once the laminate is defined, a kinematic winding simulation can be conducted, which enables a priori validation of the manufacturability. Based on this, feasible winding patterns can be identified and optimized. Moreover, NC data can be created, which can be directly used in the winding machine.

Results of the winding simulation for a CPV including helical, high angle helical, and hoop layers.

Moreover, the actual fiber orientations in the individual layers are predicted, which is used as an input for the subsequent structural simulation. This step is essential for high-accuracy structural analyses.

Structural analysis

A structural analysis is required to validate load requirements and to achieve an optimized design. This analysis can be done on different levels of detail.

Axisymmetric model

Conventional shell model

Continuum shell model

An axisymmetric model is used for detailed stress analysis in the individual layers, as well as for a detailed analysis of the influence of ply drops and thickness changes. This model allows to analyze stress states in each layer, as well as a layer-wise failure analysis to identify critical layers. However, this model does not account for circumferential stresses.


To analyze the overall behavior of the CPV, conventional and continuum shell models are used. These models simplify local thickness changes and ply drops, but allow for the analysis of plane stress and three-dimensional stress states, respectively. Both three-dimensional models are used to predict the stress states for different pressure conditions. Here, a failure index can be used to identify the most critical areas of the current design.


Efficient development of composite pressure vessels, which are optimized for manufacturing as well as for structural performance, requires a virtual analysis of the winding processes and the structural behavior. This challenge can be met through the developments in the context of Industry 4.0 by using a continuous and functional virtual process chain.

SIMUTENCE is using simulation approaches based on the latest state-of-the-art in combination with analytical equations, to meet these challenges. The presented case study shows an exemplary procedure to identify a suitable lightweight design for a CPV.

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  1. Houchins and B. James: 2019 DOE Hydrogen and Fuel Cells Program Review – Hydrogen Storage Cost Analysis (ST100), Annual Merit Review and Peer Evaluation Meeting (AMR), Crystal City, Virginia, USA, 2019
  2. Mori and K. Hirose: Recent challenges of hydrogen storage technologies for fuel cell vehicles, International Journal of Hydrogen Energy, Vol. 34, Issue 10, Pages 4569-4574, 2009