Sandia Labs has begun the second leg of its study focusing on liquid hydrogen fuel cells used in passenger ferries.
The San Francisco Bay Renewable Energy Electric Vessel with Zero Emissions study (SF-BREEZE) will focus on the optimal combination of vessel design, speed and passenger capacity, which, once determined, could reduce uncertainty in the industry; and the technical evidence to support new safety codes for hydrogen fuel-cell vessels.
The initial feasibility study focused on a 150-passenger ferry traveling at 35 knots per hour. Now, mechanical engineer and project lead Joe Pratt is asking whether it makes sense to design ferries that are faster or slower, larger or smaller.
Sandia Labs started by plotting typical speeds and passenger capacities of about 600 passenger ferries in the U.S., and found that the ferry studied in the SF-BREEZE project was actually an outlier, being faster and having fewer 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,” said Curt Leffers, project manager at Elliott Bay Design Group, who is leading the naval architecture work in the new study. “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.”
The lab on its part is reviewing International Maritime Organization (IMO) codes for liquid natural gas-powered vessels and developing a technical basis for codes that could be created for hydrogen fuel-cell vessels. Currently, liquid natural gas codes are the closest regulations that can be applied to hydrogen-powered vessels, but they may not accurately represent the properties of hydrogen.
For example, the LNG code requires LNG vessels to have a clearance of 30 feet around all sides of their vents. Hydrogen is lighter than natural gas and much lighter than air, so it does not sink in air like LNG does. Thus, a 30-foot clearance underneath a vent might not be a necessary requirement for a hydrogen ferry, said Sandia Labs mechanical engineer Myra Blaylock, technical lead for the project.
Labs researchers are using computer simulation to explore and analyze four common vent and leak scenarios in which hydrogen could be released on-board vessels to show actual hydrogen behavior. This allows them to confidently explore various scenarios in a quicker and less-expensive way than conducting experimental work for each individual case.
Image credits and content: Sandia National Laboratories