One recent solution to the traffic congestion that troubles coastal cities is maritime transportation. But with urban passenger ferries running in tourist areas and sensitive environments, hydrogen fuel cell-powered passenger ferries offer a noiseless, zero-emission alternative to conventional diesel vessels.
In its San Francisco Bay Renewable Energy Electric Vessel with Zero Emissions study, known as SF-BREEZE, Scientists at Sandia National Laboratories decided liquid hydrogen fuel cells are viable on technical, economic and regulatory bases. Currently, Scientists are working towards reaching the next level in a second study that concentrates on:
- the best combination of vessel design, passenger capacity, and speed, which, once established, could decrease uncertainty in the industry; and
- the technical confirmation to support new safety codes for hydrogen fuel-cell vessels.
The research is funded by the U.S. Department of Transportation’s Maritime Administration’s Maritime Environmental and Technical Assistance program.
The Maritime Administration sees immense potential in the use of hydrogen fuel cells to provide efficient, clean, domestically produced power for the maritime sector. The current effort to improve the economic viability using fuel cells in a commercial vessel will bring this vision one step closer to reality.
John Quinn, Maritime Administration Associate Administrator for Environment and Compliance
Optimizing how renewable hydrogen can best reduce carbon emissions
The first feasibility study concentrated on a 150 passenger ferry moving at 35 knots per hour. At present, Mechanical Engineer and Project Lead Joe Pratt is questioning whether it makes sense to build ferries that are slower or faster, smaller or larger.
Sandia Labs began by plotting typical passenger capacities and speeds of around 600 passenger ferries in the U.S., and discovered that the ferry investigated in the SF-BREEZE project was essentially an outlier, being faster and having a smaller number of passengers than most.
Although previous work on the SF-BREEZE project demonstrated the feasibility of utilizing hydrogen fuel cells for propulsion power on a high-speed passenger vessel, it became apparent that there may be better economic returns when applied to slower speed vessels. The next logical step in the process is to examine the effect of speed and passenger count on the overall cost and per-passenger emissions for hydrogen fuel cell-powered passenger vessels, which is why the optimization study is important.
Curt Leffers, Project Manager at Elliott Bay Design Group, who is leading the Naval Architecture work in the new study
Pratt added, “How do you achieve the best economics compared to conventional diesel technology and the best gain in environmental impact? Answering these questions is how we’ll be quantifying the merit of different designs.”
The research aims to make the trade-offs for the ferry and shipbuilding industries clear. The faster and heavier the vessel, the more power is necessary. To acquire more power, fuel cells — the most costly part on a hydrogen-powered ferry — must be incorporated, which increases the cost, Pratt said.
“You get a double benefit by going slower: you reduce the power required by the fuel cells and the cost of the fuel cells, and you reduce the fuel consumption, so you reduce your operating expense,” Pratt said, “That’s an example of why we’re thinking about this and looking at other designs.”
Sandia hopes to create many ferry concepts to show which are most cost-effective and which will make the greatest impact on protecting the environment, he said.
Tom Escher is President of a San Francisco Bay operator, the Red and White Fleet, which was a partner in the first study. He said he is keen to move ahead with new ferry designs.
The maritime industry needs to move to zero emissions for the sake of our globally shared environment. This study is tremendously helpful by pointing out how to do that in the smartest way possible, and we look forward to using the results to build the first zero emission hydrogen passenger vessel in the U.S.
Tom Escher, President of a San Francisco Bay operator, the Red and White Fleet, which was a partner in the first study
Updated regulations could clarify path forward for industry
Sandia is appraising International Maritime Organization codes for liquid natural gas-powered vessels and forming a technical standard for codes that could be made for hydrogen fuel-cell vessels. Presently, liquid natural gas codes are the nearest regulations that can be applied to hydrogen-powered vessels, but they may not accurately signify the properties of hydrogen.
For instance, the LNG code stipulates LNG vessels to possess a clearance of 30 feet around all sides of their vents. Hydrogen is much lighter than air and lighter than natural gas, so it does not sink in air like LNG does. Therefore, a 30 foot clearance beneath a vent might not be an essential requirement for a hydrogen ferry, said Sandia Labs Mechanical Engineer Myra Blaylock, technical lead for the project.
Labs Researchers are using computer simulation to investigate and test four common vent and leak setups in which hydrogen could be discharged on-board vessels to exhibit actual hydrogen behavior. The computational simulations have underlying physics models that have been endorsed through experiments and allow Researchers to assertively explore numerous scenarios in a quicker and less-expensive manner instead of conducting experimental studies for each individual case. The results can be used by the International Maritime Organization to guarantee the accuracy of the codes when applied to hydrogen vessels.
The possibility of spreading the applications of hydrogen fuel cells, demonstrating to the industry the ideal path forward and providing the technical foundation for new hydrogen regulations, all have “the potential for impact across the entire maritime sector,” Pratt said. “A lot of these vessels can travel in ecologically sensitive areas where there is an extra motivation for making them clean. So it’s about localized as well as global emissions benefits.”