Silencing some skeptics’ doubts, two researchers at Sandia National Laboratories have found it is technically feasible to build a high-speed, zero-emission hydrogen-powered ferry in California with full regulatory acceptance.
The feasibility study for the San Francisco Bay Renewable Energy Electric vessel with Zero Emissions (SF-BREEZE) was conducted by Joe Pratt and Lennie Klebanoff in Livermore, Calif., and its results published in September. Since then, Sandia, in cooperation with the U.S. Maritime Administration (MarAd), has been focusing on optimizing vessel specifications to minimize the cost and maximize emissions benefits.
The study was funded by a $470,000 grant from MarAd. Other project participants include Red and White Fleet of San Francisco, the American Bureau of Shipping (ABS), the U.S. Coast Guard and Elliott Bay Design Group.
The fast-ferry project comes in anticipation of hydrogen becoming more available in the next few years as more stations serving fuel-cell vehicles come into existence.
Joe Burgard, vice president of operations for Red and White Fleet, said the SF-BREEZE study began with one of the most demanding operating profiles in the U.S. ferry sector. The study showed the profile could be met with commercially available proton exchange membrane (PEM) fuel-cell technology running on liquid hydrogen.
Hydrogen-powered ferries already exist, but most are smaller, slower vessels used for tours on lakes and rivers. In this study, the team drew up conceptual specifications for a 150-passenger commuter ferry that would make four 50-mile round trips each day while operating at 35 knots about 60 percent of the time. The ferry could refuel at midday, between the morning and afternoon commutes.
By studying speed and capacity, optimization will determine whether there are other vessel types in the U.S. market with more favorable cost and emissions on a per-passenger basis, Pratt said. It will consider the different demand profiles of ferries, such as short-route, low-speed car ferries, larger-capacity passenger ferries with low-speed demands, and water taxis, Burgard said.
“This kind of boat has never been built before,” Curt Leffers, project manager for Elliott Bay Design Group, said in a prepared statement from Sandia. “Hydrogen fuel cells are heavier than diesel engines for a given power output, so achieving the right power-to-weight ratio for the vessel was tricky.”
The cost of building a hydrogen ferry would be 1.5 to 3.5 times higher than a comparable diesel ferry, according to the study. Much of the difference is due to the current high cost of PEM cells. Fuel costs also would be higher given today’s prices, but reducing nitrogen oxide, particulate matter and greenhouse gas emissions would yield an estimated societal economic benefit of $2.6 million to $11 million over the 30-year lifetime of the ferry, the study said.
Sandia is conducting a gas dispersion analysis to address hydrogen safety concerns. “While hydrogen and natural gas have many similarities, hydrogen has much higher buoyancy in air even at temperatures approaching the liquid state. This means that hazardous and exclusion zone requirements established for LNG may not accurately reflect hydrogen behavior,” Pratt said.
The researchers are producing computer simulations that compare natural gas and hydrogen vent and leak scenarios of interest to regulators and vessel designers. This will allow accurate regulations to be established for the safe use of gaseous and liquid hydrogen, Pratt explained.
The hydrogen fast-ferry project was conceived in 2014 by Tom Escher, president of Red and White Fleet. He believes that reducing vessel emissions to zero is imperative if the maritime industry is to have a meaningful effect on climate change and airborne pollutants, the study noted.