Long-haul trucking is a tough to decarbonize sector owing to its high energy requirements and price sensitivity. Because of the continually increasing demand for goods, the demand for trucking is ever-growing. Hydrogen (H₂) is a promising alternative fuel for trucking, however, distribution as a compressed gas or cryogenic liquid makes it prohibitively expensive at retail fueling stations. Additionally, the considerable capital investments necessary to build H₂ delivery infrastructure hinder its adoption, particularly in developing nations.
Liquid Organic Hydrogen Carriers (LOHCs) are molecules that can be reversibly hydrogenated and dehydrogenated, thus providing inexpensive means for retail H₂ distribution as inert room-temperature liquids. Currently explored supply chains, perform the endothermic H₂ dehydrogenation at the truck stop and then compress the H₂to high pressures for storage on the trucks. These steps require substantial clean energy input which is likely to be supplied by burning around half of the hydrogen released from the LOHC.
Our concept involves LOHC dehydrogenation on the truck. The released H₂is burned in a combustion engine to extract work and the “waste” heat in the exhaust is used to provide most of the energy required to sustain the H₂release. The heat-integrated system boosts system efficiency to 87% and it is computed to be less expensive than running a long-haul truck on diesel today, with a much lower carbon footprint, and inexpensive to deploy across the globe!
However, these conclusions are all from calculations; and it has never been successfully demonstrated in the lab. Here we report our design of a reactor to enable this concept and the results of our recent experiments measuring its performance. We explore a complex reaction system that includes multiple phases: solid catalyst, liquid LOHC, hydrogen gas along with LOHC vapor which evolve as bubbles; leading to significant heat and mass transfer limitations. This study allows us to clarify the real performance requirements a hydrogen carrier must satisfy to enable this real-world climate solution for long-haul trucking, and some of the key issues in reactor and overall system design.

Sayandeep Biswas

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