HSL Technologies (formerly known as HySiLabs), a French hydrogen energy startup founded in 2015, has developed liquid siloxane hydrogen carriers for hydrogen transportation and storage.
Challenges: hydrogen storage
Hydrogen (H₂), the most abundant element in the universe, is not just a fundamental building block of stars—it's also a vital ingredient in the synthesis of ammonia. Production of ammonia plays a crucial role in producing a wide range of products we use on a daily basis, including fertilizers for crop nourishment and plastics for modern life.
Traditionally, the world has relied heavily on steam methane reforming (SMR) to produce over 60 million tons of hydrogen annually. However, this method comes with a significant environmental cost. It's an energy-intensive process that contributes approximately 2% to global carbon dioxide (CO₂) emissions, releasing between 5 and 9 tons of CO₂ for every ton of hydrogen it generates.
There are cleaner paths to producing hydrogen, such as water electrolysis and methane pyrolysis.
After production, transporting hydrogen to end-users is necessary. Gaseous hydrogen is commonly delivered by trucks called tube trailers. These vehicles compress hydrogen to high pressures (180 bar or higher) in long cylinders stacked on the trailer. Hydrogen is also liquefied and transported in specially insulated trucks or ships.
Alternative solutions to hydrogen transport are emerging, including hydrogen carriers. Hydrogen carriers are either solid-state or liquid-state materials that have the ability to store hydrogen and release it when needed.
Solid-state carriers include metallic hydrides that enable the uptake of hydrogen by adsorption onto metal particles, resulting in metal hydride. Among them, magnesium hydride is stable at low pressure and standard temperature, making it convenient to transport and store. When needed, the material is heated to release the hydrogen gas. Solid-state solutions have been identified as best suited for same-site reversible processes of energy storage from renewable energies. Indeed, handling solid materials is not as convenient as handling gas or liquid ones.
Liquid hydrogen carriers can be any liquid-state material able to release hydrogen under specific conditions. Among the liquid hydrogen carriers, Liquid Organic Hydrogen Carriers (LOHC) are the most represented. Typically, the organic hydrogen carrier is unsaturated or aromatic hydrocarbons, such as toluene and fluorenone.
During the hydrogenation process, hydrogen is chemically bonded to the liquid organic carrier in the presence of a catalyst under heating. The resulting saturated hydrocarbon is transported in a liquid state at standard temperature and pressure. Then the hydrogen is released from the saturated hydrocarbons by a process called the dehydrogenation reaction, which occurs in the presence of a catalyst and heating.
HSL Technologies Technology
HSL Technologies has developed liquid cyclic siloxane hydrogen carriers. The liquid siloxane hydrogen carriers are stable, non-toxic, and non-explosive. They release hydrogen in large quantities with high efficiency in a short time. The resulting solid byproducts can be reused to regenerate liquid siloxane hydrogen carriers. HSL Technologies allows for low-cost and safe hydrogen transport and delivery, enabling on-site hydrogen production for a variety of applications.
HSL Technologies hydrogen carriers
The diagram below depicts the molecular structure of HSL Technologies liquid siloxane hydrogen carriers.
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