If you have ever ridden a ferry in the San Francisco Bay, you know it can be one of the most pleasant commuting experiences. You’re out on the water with enjoyable and sometimes beautiful middle- and long-distance views. The ride is usually smooth, with some wave action once in a while. There aren’t any honking cars, trucks, SUVs, or motorcycles, and there is no snarled or stopped traffic. In life, sometimes there are downsides, and one for conventional passenger ferries is the noxious, if not nauseating, diesel fumes and exhaust. More importantly, there are greenhouse gas emissions. What if there could be a zero-emission ferry?
Welcome to Sea Change, a Bay Area ferry that uses fuel cell technology combined with electric propulsion with no such diesel fuel use nor its attendant air pollution.
SWITCH Maritime manufactured the zero-emissions 75-passenger ferry. The company’s CEO Pace Ralli provided many details about the new vessel for CleanTechnica.
Can you explain how the hydrogen fuel cells, the hydrogen storage tanks, the electric propulsion system, and the lithium-ion battery system work together to move Sea Change?
Hydrogen Storage: The ferry’s bunker panel is designed to be able to accept compressed hydrogen gas from existing hydrogen transport trailers, with a hose reel that extends from the ferry’s top deck and connects to a hydrogen transport trailer on land for a truck-to-ship transfer. Gas dispensed from the truck flows into ten Type 4 composite storage tanks that are located on the top deck of the ferry and hold 242 kg of hydrogen at a pressure of 3,600 psi or 250 bar.
Fuel Cells: Next, the hydrogen flows from the storage tanks to the 360-kW fuel cell system, where electricity is produced to power electric motors. A hydrogen fuel cell functions based on an electrochemical reaction without direct combustion, that creates useful electrical output. In the fuel-cell power “racks” used in the Sea Change, individual fuel-cell power modules of nominal power 30 kW are integrated together into stacks of four individual fuel cell modules for a combined power of 120kW per rack. The operation of each fuel cell power rack is monitored by the control system. For maintenance purposes, the individual fuel cell modules within each rack are easily removed and replaced, typically through a service contract with the fuel-cell Manufacturer.
Hydrogen is the simplest element consisting of only one proton and one electron and is extremely high in energy. Hydrogen as a fuel source is similar to natural gas but does not contain carbon. Hydrogen fuel cells directly convert hydrogen to power with zero emissions. Hydrogen has been around for decades as a commodity with a proven track record for handling and safe usage in countless commercial and industrial applications. The only byproducts of a fuel cell reaction are electricity and water that is clean enough to drink.
Batteries: When the vessel is idling or traveling at low speeds, excess electricity is generated by the fuel cells. This excess electricity is stored in the 100-kWh lithium-ion battery storage system. When the vessel needs to travel at higher speeds, the energy stored in the batteries is then used to boost the output from the fuel cells, enabling the electric propulsion system to generate more power. The batteries are housed in 2x 50kWh racks, one situated in each of the two hulls of the catamaran ferry. Each rack is comprised of smaller individual 7.1 kWh cells, which are scalable when connected together.
Electric Propulsion System: The electric propulsion system consists of 2x 300 kW electric AC Traction Motors and various control units. Electricity that flows out of the fuel cells is efficiently delivered to power the hotel loads, the energy storage system, or paralleling with other power sources for greater power demand and system flexibility.
The electric propulsion system interfaces with the hydrogen fuel cell system as well as the lithium-ion batteries to power the vessel without the need for a traditional combustion engine. The all-electric system eliminates diesel fuel use and reduces engine maintenance to create a clean mode of transportation.
Summary: The result is a clean, quiet ride for passengers onboard, lower maintenance for operators due to fewer moving components, and no emissions or particulate matter polluting the environment.
Would you say the vessel’s range is 300 nautical miles for the full hydrogen storage capacity, plus the electric battery’s 100kWh? Or is the battery depleted at a different rate from the hydrogen tanks?
Building on the above systems description, the batteries are charged by electricity from the fuel cells. Once charged, the batteries work in concert with the fuel cells to provide optimal power to the electric propulsion system. If during vessel operations the batteries are depleted, the fuel cell charging will kick on again to bring them to a higher state of charge. Because the fuel cells are used to charge the batteries, the range calculation is principally based on the hydrogen available in the storage tanks (for reference — the usable hydrogen in the the tanks is equivalent to 7,000 kWh or 7 MWh of energy.
How long does it take to refuel the Sea Change between trips?
2-3 hrs overall: 1 – 1.5 hrs to fuel. 1 – 1.5 hours for set-up and breakdown.
If the top speed is 15 knots, what is the cruising speed?
12-13 knots.
Is Sea Change considered a zero-emissions vessel?
Yes, this fuel cell electric ferry will generate zero direct GHG emissions. The only “emission” is pure (H20) water.
What is Water Emergency Transportation Authority (WETA) San Francisco Bay, and when and where will Sea Change begin operating?
WETA is a regional public transit agency tasked with developing, operating, and expanding ferry service on the San Francisco Bay and with coordinating the water transit response to regional emergencies. San Francisco Bay Ferry, a service of WETA, operates ferry routes connecting the cities of Alameda, Oakland, Richmond, San Francisco, South San Francisco, and Vallejo. More information is available at San Francisco Bay Ferry.
When and where: Passenger service beginning at the start of 2024. Fares are set at $1 each way, offering transportation between Pier 41 and the downtown Ferry Terminal.
How much did it cost to build Sea Change, and about how much CO2 will be avoided by using Sea Change instead of a ferry that uses fossil fuels?
Overall Cost: ~$14M, comprising $6M SWITCH Equity, $5M construction loan (commercial bank), $3M state CARB grant. Cost includes significant one-time / first-of-kind costs that will be eliminated / reduced in future “business as usual” builds.
This fuel cell electric ferry will generate zero direct GHG emissions. It will displace GHGs that would otherwise result from use of a diesel engine used to power a ferry in the same service. The direct emissions generated from a diesel-powered passenger ferry of comparable size would generate 1,190 tons of CO2 emissions annually, which are avoided with the Sea Change.
Electric batteries used in land-based electric vehicles are heavy, so did you choose hydrogen fuel cells because they are lighter? How much lighter are they, and how much space do they require inside the vessel?
Multiple factors influence our zero-emissions vessel design decisions, and weight is definitely one of them. Generally, SWITCH maintains a technology agnostic stance and will let technical considerations (route distance, vessel speeds, dwell times (loading / unloading), hours of operation, availability of sufficient grid power etc) inform what technology solution is the best fit for a specific customer requirement. In other words, some routes and operating profiles will lend themselves well to battery electric vessels with shoreside charging infrastructure and some to fuel cell electric vessels with hydrogen fueling.
To make the weight comparison concrete, the 10 hydrogen tanks on the top deck of the Sea Change store 210 kg of usable hydrogen, equivalent to 7,000 kWh or 7MWh of energy. The total weight of that energy storage system is ~3,500 kg. By comparison, storing an equivalent amount of energy (7MWh) in standard marine batteries (e.g. Corvus) would weigh ~91,000 kg or ~26x the weight of the hydrogen energy storage system. For reference, the total weight of the entire Sea Change vessel is 48,770 kg. This example makes clear that hydrogen’s high energy density and lower weight are important to consider in zero emissions vessel design.
Where will you get the hydrogen fuel to replenish the vessel’s tanks?
The operators are adopting this technology and vessel for the purpose of achieving zero carbon operations, so their interest is in getting green hydrogen supply. There is a H2 production project under construction, to be located right in the port of SF (and backed by a DOE grant), that will produce green hydrogen right where the vessels will be operating, using renewable hydropower for H2 electrolysis. This green hydrogen then will be transferred directly into the ferry, and the project once completed has the ability to fuel 3-5 additional ferries. It takes the same time to fuel a H2 ferry as it does a diesel ferry. And our objective is to build and secure our own supply chain of green hydrogen to support the zero-carbon vessels.
Until this supply chain is completed, we are using the hydrogen that is currently available in SF, which is the same H2 that is in the car fueling stations being built in the Bay Area. Our volume is relatively small right now, so we can tap into what they have, but as soon as our volume increases with more vessels, we’ll be looking to switch to our own.
How much does hydrogen fuel cost compared to gas or diesel fuel?
Currently hydrogen is about 2-2.5x the cost of diesel. While it’s currently a significant premium to diesel, that cost premium represents only around a ~7.5% increase in the total operating cost of the vessel on an annual basis relative to the baseline. Generally, SWITCH considers total cost of ownership (TCO) the most informative view for assessing cost premiums/discounts relative to conventional vessels. The three primary categories comprising the TCO for a vessel are: CapEx, Service & Maintenance, and Fuel. We see forward-looking cost curves for both hydrogen fuel and CapEx declining overtime with increased scale of hydrogen and fuel cell production. The reduction in moving parts associated with zero emissions vessels means that service and maintenance is expected to result in discounts relative to conventional options. Overall, cost-parity is expected to be achieved in the next 5 years with grants and incentives helping to offset premiums in the near-term. Most importantly, however, we ultimately view the move to zero emissions vessels as a binary decision. For many operators, compliance with emissions regulations will mean that the cost comparison to diesel fuel is not relevant because zero emissions is mandated.
Is the Sea Change’s propulsion systems more energy efficient than the typical ferry gas or diesel engine?
Yes, the energy efficiency of fuel cells is ~50% efficient vs. traditional internal combustion engines which are around 30-35%.
How long can hydrogen fuel cell propulsion systems operate before they need to be replaced? This generation of fuel cells is expected to run approximately 10,000 hours before needing to be refurbished at ~50% of the original capital cost.
When the 100kWh of lithium-ion battery is done being used in the vessel, could it have a second use life for stationary electricity storage?
Hypothetically yes, but 100kWh isn’t a huge amount of battery so it’s not clear it would be useful on its own.
What will you use your latest funding round for?
This latest round of funding (1) helps enter the Sea Change into commercial operation, as the first such hydrogen-fueled vessel in the US with approval from the USCG for passenger service, (2) provides the equity to grow the fleet by designing larger / faster zero-emissions passenger ferries (150-, 300-, and 450-passenger) to deploy in key ferry markets across the US, with construction on the 2nd and 3rd SWITCH vessels targeted to commence mid-2024.
How soon can you make the larger ferries, the ones with capacities of 150 passengers and 350?
Target timeline is commencing construction mid 2024 to enter operations start of 2026.
