Hydrogen has the potential to ignite a green revolution in the travel sector since it is a clean, long-term alternative to fossil-fuel vehicles.
However, hydrogen must be kept in tanks that can endure high pressure and low temperatures, which has slowed the development of fuel cell electric cars so far (FCEVs). Professor Holger Ruckdäschel, Mr. Fabian Hübner, and their team at Bayreuth University are creating super-strong materials for hydrogen fuel tanks. FCEVs might carry more fuel and travel further thanks to cutting-edge technology that uses carbon fiber and epoxy resin polymers.
Many politicians and policymakers see hydrogen as a viable alternative to fossil fuels in the face of the global climate catastrophe. The chemical reaction of hydrogen and oxygen in hydrogen fuel cells produces electrical energy. They don’t generate harmful waste products like carbon dioxide (CO2), nitrogen oxides (NOx), or soot particles like traditional combustion engines.
Despite its potential to begin a green energy revolution, hydrogen-based technology faces a number of obstacles, including environmentally friendly fuel production, simplicity of transportation, secure storage, and widespread infrastructure availability. To grasp the magnitude of the storage and transportation issues, imagine that a hydrogen fuel cell electric vehicle (FCEV) would require several cubic meters of the element in its gaseous, uncompressed condition for a normal range of 600 kilometers. Hydrogen is compressed to 700 bars at room temperature so that its molecules may be condensed together in a fuel tank and utilized effectively.
Professor Holger Ruckdäschel and Mr. Fabian Hübner of the University of Bayreuth, Germany, developed high-specific-strength materials made of carbon fiber composites to withstand the high pressure and low temperature of hydrogen stored in high-performance cars, aircraft, or space travel in order to meet hydrogen fuel requirements.
Composites are materials that are made up of two or more different types of materials. The Ruckdäschel laboratory’s hydrogen storage tanks are built of a plastic mesh with huge chain-like structures of repeating molecular units embedded in a myriad of robust and heavy carbon-fiber strands. The result is a lightweight but extremely stiff structure that preserves the low density of most plastic materials while being five times stronger than steel. The team optimizes nanomaterial composites for safety, weight, and durability, examining the structure-property connection in depth across nanoscale dimensions and under high-temperature settings.
The hydrogen revolution is sparked by space
Several countries have chosen battery-powered transportation to achieve stringent environmental goals set in recent years, as well as to reduce CO2 emissions’ impact on global warming. However, electric transportation is not without its drawbacks. The extended charging periods necessary to power travel over a small range is one of the key issues impacting potential buyers. Storing enough energy to improve range (while reducing charging time) necessitates the correct balance of fuel and fuel storage materials. Hydrogen fuel cells offer the benefit of being recharged while in use, removing the need for lengthy charging periods. Liquid hydrogen storage, on the other hand, necessitates the use of materials that can withstand high temperatures and pressures without shattering.
Ruckdäschel, Hübner, and their team were inspired by the space industry and created hydrogen storage tanks composed of lightweight materials that maintain strength and endurance. Epoxy resins are extensively used polymers that are utilized in the manufacture of adhesives, coatings, and housings. They are an excellent material for making lightweight composites because of their low viscosity. Epoxy composites are made up of a resin and a hardener that, when combined together, establish stable linkages that prevent the polymers from melting and give them great strength. When building vessels to hold pressurized fuels, it’s vital to think about the vessel shape and size, as well as crucial epoxy resin functional attributes including tensile strength (the amount of stress a material can withstand before breaking) and fracture toughness (the capacity of cracked material to resist further fracture).
Getting to the bottom of the container dilemma
Ruckdäschel and Hübner explore the physical and chemical resistance of toughened epoxy-amine compositions in a variety of chemical and environmental environments. In an article published in 2021, they present the results of their research, concentrating on the mechanical behavior of toughened composites at low temperatures and comparing it to non-toughened reference material. At –50°C and 20°C, the fatigue crack propagation, a characteristic showing a solid’s potential to fracture under mechanical stress through tension, pressure, bending, or torsion, was examined. The low temperature was chosen as a first step toward determining parameters relevant to vessel-filling techniques used in space flight when liquid hydrogen is held at cryogenic temperatures of roughly -253°C.
At cryogenic temperatures, increased resistance to microcracking is a unique need for pressure vessels. The objective is to develop resin-based tank systems that are exceptionally stable and leakproof. The microcracking phenomena might be caused by a thermal expansion mismatch between the fibers and the resin matrix. The scientists discovered that toughening epoxy resins resulted in a significant improvement in functional qualities such as strength under tension and compression. More crucially, when the material is hardened at -50°C, the rate of fracture formation is dramatically reduced. However, the experts warn that additional study is required. To avoid catastrophic failures, more research on cracking processes in epoxy resins at low temperatures is required.
Hydrogen fueling for long-term sustainability
Many concerns concerning how to use hydrogen fuel cell technology efficiently and responsibly remain unanswered. For instance, how to create, store, and utilize the energy required to manufacture hydrogen at a large enough scale to operate common automobiles. Despite these obstacles, various types of hydrogen fuel cell-powered engines are currently being utilized effectively on buses, trains, and ships. Hydrogen fuel cells, with more study, might lead to the widespread adoption of environmentally benign electric motors for public and private transportation.
The Ruckdäschel laboratory’s experts warn that the source of hydrogen generation must be carefully evaluated before environmental advantages can be calculated. Green hydrogen, or CO2-neutral hydrogen, is the most ecologically benign source of valuable gas. Green hydrogen is created by separating water (H2O) into the two components that make it up – hydrogen (H2) and oxygen (O2) – using a process known as electrolysis, which is driven by renewable energy. Hydrogen can be ‘grey’ or ‘blue’ in color. Grey hydrogen is produced from a natural gas combination using the steam reforming process, which emits a lot of CO2 and has a detrimental influence on the environment, especially when large amounts of hydrogen are needed in the future. The generation of blue hydrogen, a more environmentally friendly option, results from the prompt removal and sequestration of CO2 generated by steam reforming.
New super-strong materials have been developed
Ruckdäschel, Hübner, and their polymer engineering team are using materials used in space flight to create hydrogen storage tanks that will allow people to drive hydrogen-fueled automobiles on a daily basis.
While uncompressed fossil fuels can be utilized, hydrogen must be greatly pressurized in order to be stored and used efficiently. The researchers produced toughened epoxy amine resin systems for this purpose, evaluating their mechanical behavior and fracture resistance at low temperatures relevant to cryo-compressed hydrogen gas vessel filling methods. Even with an overall tank-wall thickness of less than 10mm, these carbon-fiber-reinforced composite materials can bear normal pressures of 700 bars and maintain structural integrity at severe temperatures.
Hydrogen fuel cell technology will be established in the car sector thanks to these robust, lightweight materials. The accomplishments of Ruckdäschel and his team constitute a huge step forward in increasing the sustainability of ordinary transportation.