Harnessing hydrogen’s potential to address long-haul trucking emissions

MIT researchers work to transform truck powertrain design with support from the MIT Climate and Sustainability Consortium, Molly Chase writes.

The transportation of goods forms the basis of today’s globally distributed supply chains, and long-haul trucking is a central and critical link in this complex system. To meet climate goals around the world, it is necessary to develop decarbonized solutions to replace diesel powertrains, but given trucking’s indispensable and vast role, these solutions must be both economically viable and practical to implement. While hydrogen-based options, as an alternative to diesel, have the potential to become a promising decarbonization strategy, hydrogen has significant limitations when it comes to delivery and refuelling.

These roadblocks, combined with hydrogen’s compelling decarbonization potential, are what motivated a team of MIT researchers led by Willam H. Green, Hoyt Hottel Professor in Chemical Engineering, to explore a cost-effective way to transport and store hydrogen using liquid organic hydrogen carriers (LOHCs). The team is developing a disruptive technology that allows LOHCs to not only deliver the hydrogen to the trucks, but also store.

An “onboard” approach

Currently, LOHCs, which work within existing retail fuel distribution infrastructure, are used to deliver hydrogen gas to refueling stations, where it is then compressed and delivered onto trucks equipped with hydrogen fuel cell or combustion engines.

“This current approach incurs significant energy loss due to endothermic hydrogen release and compression at the retail station” says Green. “To address this, our work is exploring a more efficient application, with LOHC-powered trucks featuring onboard dehydrogenation.”

To implement such a design, the team aims to modify the truck’s powertrain (the system inside a vehicle that produces the energy to propel it forward) to allow onboard hydrogen release from the LOHCs, using waste heat from the engine exhaust to power the “dehydrogenation” process.

The dehydrogenation process happens within a high-temperature reactor, which continually receives hydrogen-rich LOHCs from the fuel storage tank. Hydrogen released from the reactor is fed to the engine, after passing through a separator to remove any lingering LOHC. On its way to the engine, some of the hydrogen gets diverted to a burner to heat the reactor, which helps to augment the reactor heating provided by the engine exhaust gases.

Acknowledging and addressing hydrogen’s drawbacks

The team’s paper underscores that current uses of hydrogen, including LOHC systems, to decarbonize the trucking sector have drawbacks. Regardless of technical improvements, these existing options remain prohibitively expensive due to the high cost of retail hydrogen delivery. The team, has been using MATLAB tools to develop models and simulations for this work

Different sectors coming together

Decarbonizing transportation modes, including long-haul trucking, requires expertise and perspectives from different industries — an approach that resonates with the MCSC’s mission. The team’s groundbreaking research into LOHC-powered trucking is among several projects supported by the MCSC within its Tough Transportation Modes focus area.

The research led by Green celebrates this cross-sector theme by integrating industry-leading computing tools provided by MathWorks with cutting edge developments in chemical engineering, as well as industry-leading commercial LOHC reactor demonstrations, to build a compelling vision for cost-effective LOHC-powered trucking.

Source: MIT News