A team of researchers from the Massachusetts Institute of Technology (MIT) is developing a new ‘disruptive’ technology that could not only improve the transport and storage of hydrogen but may help to decarbonise the fossil-fuel intensive long-haul trucking sector.
The technology works to improve the efficiency of liquid organic hydrogen carriers (LOHCs) – chemical compounds used in the field of energy storage and transportation.
Typically consisting of hydrogen-rich organic molecules that can absorb and release hydrogen gas reversibly, LOHCs have the ability to store and transport molecular hydrogen.
The high hydrogen storage density of LOHCs combined with reduced safety concerns compared to gaseous hydrogen have seen them garner interest for long-distance transportation and distribution of hydrogen for applications such as fuel cells and industrial processes.
LOHCs work within existing retail fuel distribution infrastructure and are used to deliver hydrogen gas to refuelling stations, where it is then compressed and delivered onto trucks equipped with fuel cells or combustion engines.
According to lead researcher William H. Green this approach incurs ‘significant’ energy loss due to endothermic hydrogen release and compression at the retail station.
“To address this, our work is exploring a more efficient application, with LOHC-powered trucks featuring onboard dehydrogenation.”
To do this, the team aims to modify the truck’s powertrain to allow onboard hydrogen release from the LOHCs, using waste heat from the engine exhaust to power the ‘dehydrogenation’ process.
This process happens within a high-temperature reactor, which continually receives hydrogen-rich LOHCs from the fuel storage tank.
Proposed process flow diagram for onboard dehydrogenation. (Source: Green Group)
After passing through a separator to remove any lingering LOHC, hydrogen released from the reactor is then fed to the engine.
On its way to the engine, some of the hydrogen is diverted to a burner to heat the reactor, which the team says helps to augment the reactor heating provided by the engine exhaust gases.
“We present an alternative option that addresses a lot of the challenges and seems to be a viable way in which hydrogen can be used in this transportation context,” said Sayandeep Biswas, part of the research team.
“Hydrogen, when used through LOHCs, has clear benefits for long-hauling, such as scalability and fast refuelling time. There is also an enormous potential to improve delivery and refuelling to further reduce cost, and our system is working to do that.”
As the hydrogen-fuelled transport industry continues to grow, McKinsey & Co predicts that – by 2035 – as many as 850,000 hydrogen-fuelled medium- and heavy-duty trucks could be on the road in Europe.
Between them, they would consume 6,900 metric kilotonnes of hydrogen per year and require up to 4,800 hydrogen refuelling stations.
