Green hydrogen is emerging as a key player in reducing carbon emissions in transportation.
A study by the University of Michigan suggests that green hydrogen, produced using renewable energy, could be crucial for decarbonizing heavy-duty transport like trucks, trains, ships, and planes.
However, it should be used strategically to maximize efficiency.
Green hydrogen is made by using renewable energy to split water into hydrogen and oxygen.
This hydrogen can then be used directly in engines or fuel cells, or converted into synthetic fuels (e-fuels) like e-gasoline, e-diesel, e-jet fuel, e-methanol, and e-ammonia.
The transportation sector is a major source of carbon emissions, responsible for about 22% of global and 37% of U.S. fossil fuel carbon dioxide emissions.
Therefore, finding ways to reduce these emissions is crucial for fighting climate change.
Researchers from the University of Michigan studied the total system energy efficiency of using green hydrogen directly or indirectly in e-fuels to power various modes of transportation. They compared this with the efficiency of battery electric options.
The study found that using hydrogen or e-fuels results in significant energy losses—about 80%-90% of the initial electrical input is lost during production, storage, transportation, and use. In contrast, electric-powered transport is three to eight times more efficient.
The study’s findings, which will be published in the journal Joule, suggest that green hydrogen should be used strategically where electric alternatives are less practical.
For example, batteries are not suitable for heavy transport vehicles that need to cover long distances, such as planes, ships, and long-haul trucks.
These vehicles require a lot of energy, and batteries would be too heavy and large to be practical. In these cases, hydrogen or e-fuels make more sense as energy sources.
Using hydrogen as a direct fuel source would require significant changes in fueling infrastructure. While using hydrogen-based e-fuels could avoid these changes, they are generally less energy efficient than direct hydrogen use.
The researchers developed a set of 25 Sankey diagrams to visualize the energy inputs and losses for each hydrogen pathway. These diagrams start with renewable electricity inputs and track the energy flows across hydrogen production and delivery to its end use in vehicles.
The study also measured the energy intensity of each hydrogen pathway, which indicates how much renewable energy is needed to move freight or people.
The findings showed that rail and shipping are the most efficient modes of transport using hydrogen, while aircraft are the least efficient because of the energy required to keep them airborne.
Renewable electricity is a limited resource, so it’s important to use it wisely. The study suggests that green hydrogen is best suited for heavy-duty transport applications where electric alternatives are less feasible.
This strategic use of green hydrogen can help maximize its benefits and support the transition to a more sustainable transportation system.
By focusing on the most efficient and least energy-intensive modes of transport, we can make significant progress in reducing carbon emissions and combating climate change.
This research highlights the potential of green hydrogen to power the future of heavy-duty transportation, paving the way for a cleaner and more sustainable world.
