Voith and Huntsman Advanced Materials formed a partnership to meet industry demand for safe, lightweight, high-quality hydrogen pressure tanks.
The collaboration aimed to achieve the best cost-performance ratio of pressure tanks by implementing a new mass production process using towpreg material.
Leveraging Voith and Huntsman’s experience and know-how in filament winding process products, the two companies are building tanks of higher storage capacity without compromising safety at high pressures, with the goal of achieving mass production.
Enabling the best cost-performance ratio through towpregs (high number of filaments pre-impregnated with an optimal amount of resin), Carbon4Tank 700-bar H2 is an improved and sustainable hydrogen storage solution that meets automotive quality standards.
H2 tanks with higher storage density
Type IV 700-bar H2 tanks developed for use in hydrogen-fueled zero-emission trucks show significant performance improvements over conventional Type IV tanks (Figure 1).
Figure 1: Results for 700-bar Type IV H2 tanks with the new Voith Composites Carbon4 Tank GEN II towpreg system – 700-bar Type IV hydrogen tank with a capacity of 15.5 kg H2, length of 2,140 mm and diameter of 555 mm.
With the performance advantages of Voith’s H2 tank design, Huntsman Advanced Materials’ new towpreg resin system has helped Voith improve the total cost of ownership (TCO) of new tanks while meeting the quality and safety standards of the automotive industry.
Strict requirements for safe storage of hydrogen
Truck manufacturers’ requirements for hydrogen tanks are clear and strictly defined.
So-called Type IV pressure tanks must ensure the storage of compressed hydrogen at high pressures, up to 700 bar.
Therefore, composite tanks must meet the following requirements:
- meet automotive standards: the UN/ECE Regulation No. 134 regulates
- technical requirements, whereby tanks must withstand impact and chemical tests and fatigue cycling at various temperatures to ensure safe storage and transportation of hydrogen;
- compatibility with mass production: the design had to meet the industry’s production and cost objectives through high-speed production and reproducibility;
- lightness: lighter pressure tanks allow for greater storage capacity and result in longer range and higher payload;
oith Composites and Huntsman Advanced Materials have joined forces and identified the towpreg production process as the best solution because it offers several advantages.
Because the towpreg impregnation line operates at speeds of up to 100 m/min, productivity is increased.
Excellent quality control ensures optimal resin content and reproducibility of high-quality, safe tanks in a clean process environment.
Additional winding options compared to conventional filament winding allow for a reduction in composite wall thickness and, consequently, material consumption and overall weight of the pressure vessel.
Both partners have combined their know-how and experience to develop a new generation of carbon fiber-based towpreg material dedicated to the production of high-performance 700-bar Type IV hydrogen tanks: Huntsman Advanced Materials focused on formulating epoxy-based resin systems with optimized thermomechanical performance and process ease, while Voith Composites worked on tank design, certifications, and automated process for cost-effective large-scale production of high-pressure H2 tanks.
Development of a new generation of towpreg
A new epoxy-based formulation was developed to give the towpreg material enhanced storage capabilities, specific rheology, adhesiveness and cohesion of carbon fiber filaments to optimize reservoir production without sacrificing thermomechanical performance.
Araldite towpreg solution can be stored for up to 3 months at 23°C after towpreg coil production, thus reducing logistical problems, energy consumption, storage costs and time-consuming operations.
The rheological profile leads to excellent impregnation of the carbon web during towpreg production at speeds of up to 100 m/min.
Specific resin adhesiveness and viscosity at room temperature are tuned to achieve an optimal balance between tow stiffness and drapability.
The carbon fiber filaments hold together during the winding process and can expand when deposited on the tank layup at low and high tension to achieve adequate tape width.
The stickiness of the towpregs allows the machine’s maximum winding speed (up to 6 m/sec.) to be achieved and the tow to be accurately positioned on the predetermined path, during pressure vessel production.
The highly accurate positioning of the fibers and the ability to achieve lower winding angles without slippage allow the winding pattern and design to be optimized (Figure 2).
Fig. 2: Specific winding diagram
Both the development of the resin system and the optimization of the pressure vessel design benefited from the kinetic polymerization simulation expertise offered by Huntsman.
Polymerization simulation provides a valuable tool for quickly evaluating the effects of changes to polymerization cycles and for obtaining information on all areas of the simulated part.
Detailed material data models have been generated to make accurate predictions of exothermic temperature, degree of cure, and glass transition temperatures (Tg).
This is a powerful tool for accelerating product development and optimizing production, resulting in increased part quality and reduced production cycle times.
Figure 3 shows the temperature distribution during the tank curing cycle to keep an eye on the exothermic temperature and predict the curing behavior.
The overall curing cycle of the tanks was optimized to increase production and achieve the optimal degree of curing of the resin system to ensure safety.
Thermomechanical, static and dynamic performance, as well as chemical resistance, are governed by the resin system and have been optimized to safely withstand extreme stresses during the life of the tanks.
Fig. 3: Simulation of polymerization of pressure vessels.
In summary, this new towpreg material enables increased productivity through rapid in-house coil production, exceptional winding speed, and controlled cure cycles; new winding possibilities for new lay-up designs; excellent control and reproducibility of production parameters to ensure quality and safety over the life of pressure vessels; and shorter cure times for increased productivity.
Optimized use of towpreg material for economical and fully automated production of lV-type H2 tanks
Voith has identified several ways to improve TCO:
- in-house production of towpreg material optimizes the H2 tank value chain, reducing cost thrusts along the supply chain and storage and transportation costs;
- Extremely low rejection rate due to impregnation processes that are controlled and monitored online for the highest automotive quality standards; reduced material consumption in the impregnation process and subsequent winding process drives down costs and reduces tank weight while achieving the best mechanical performance from the carbon material;
- the design capabilities offered by the new winding options (possibility of reduced angles) allow for reduced laminate thickness.
This will allow for greater H2 storage capacity per kg of composite.
Increased productivity throughout the entire production process is achieved through fully automated production lines; higher winding speeds (three times faster than WFW); and rapid curing with the new resin formulation; - well-designed production layout according to Composite 4.0 principles promotes cost efficiency with fewer errors and defects.
H2 plug and drive storage systems meet the requirements of truck OEMs
Voith Composites and Voith Turbo have jointly developed a complete ready-to-use H2 storage system for heavy trucks (Figure 4).
The complete system, which includes H2 peripherals and electrical control, features outstanding performance and long service life.
The plug-and-drive, modular, platform-based storage system is offered with 4-8 Type IV hydrogen tanks.
The light weight and thin walls of the 700-bar hydrogen tank increase the payload by about 5 tons and increase the space efficiency on the truck compared to the battery electric version.
The complete hydrogen storage module, from the tank nozzle to the fuel cell inlet, a proven and ready-to-install 700-bar system in automotive grade, is ready to drive after less than 10 minutes of charging.
Voith’s plug-and-drive H2 storage system is suitable for long distances and allows a range of up to 1,000 km.
“This joint project perfectly illustrates how confident collaboration can accelerate development and time to market,” said Simon Burkel.
“Sharing expertise and understanding each other’s constraints and needs have been crucial to the success of this development,” added Carolin Cichosz.
