Royal DSM, a global science-based company active in health, nutrition and materials, has introduced a material solution for high-pressure composite tanks for hydrogen storage. Hydrogen has the highest energy per mass of any fuel. One kg of hydrogen is equivalent to 33.3 kWh—three times more energy than conventional fuel. However, hydrogen’s low ambient temperature density results in a low energy per unit volume. This requires the development of advanced storage methods that have the potential for higher energy density.
DSM is working to apply its materials expertise to make safe, effective and very lightweight hydrogen tanks. The two-part tank design features a proven, blow-molded liner made of Akulon Fuel Lock, a polyamide-6-based engineering plastic with a very high barrier to hydrocarbons.
Akulon Fuel Lock offers significantly improved fuel barrier properties and impact strength than conventional polyamide 6 (PA6). Solutions created with the material are more cost-effective and reliable than solutions in fluorinated HDPE, and barrier performance does not diminish over time. Overall performance is also better than that achievable with other competing materials, including acetals (POM) and PA6-based nanocomposites and blends. Total system costs are lower than for fluorinated HDPE and for multilayer tanks.
A “barrier package” highly dispersed in the Akulon PA6 matrix creates the special properties. Phases created at a microscopic level significantly improve the fuel barrier as well as impact properties, by creating a sort of labyrinth through which fuel vapors need to pass to escape from the tank. Unlike some other barrier solutions, fuel tanks made with Akulon Fuel Lock contain no toxic chemicals.
The tank can then potentially be further reinforced by wrapping it in unidirectional (UD) continuous fiber-reinforced thermoplastic tapes made of EcoPaXX polyamide 410. This combination of commercially available materials has already proven to be very effective in CNG tanks, and DSM is now actively testing the concept in hydrogen tanks.
The result would be the lightest-weight plastic tank available for hydrogen storage applications. Reducing weight is key, since every 10 kg removed from a vehicle roughly translates into a reduction in CO2 emissions from the vehicle on the road of one gram per km.
For the liner, Akulon Fuel Lock greatly reduces weight compared to metal. It also offers improved permeation versus polyolefin liners—i.e., the gas stays in the tank. The liner material, which is 100% recyclable, is safe with no debuckling.
Furthermore, the material is optimized to remain ductile and tough even at extremely low temperatures (-40°C). This was important for CNG, but is even more vital for hydrogen storage, as the working pressures are much higher.
DSM will be showcasing the new material solutions for Hydrogen tanks at the IAA show in Frankfurt.