With a capacity of 2,499 passengers and 202 vehicles, the m/v Tacoma, m/v Wenatchee and m/v Puyallup are the largest of the 21 vessels in the Washington State Ferries fleet. These diesel-electric Jumbo Mark II class ferries, which were built in Seattle and entered service between 1997 and 1999, have provided reliable service on the Seattle–Bainbridge Island and Edmonds–Kingston routes for over 20 years. However, as the largest consumers of diesel in the WSF fleet, they also come with a hefty operational cost and environmental footprint.
Over the last decade, WSF has explored a number of potential technologies to reduce costs and emissions. Strides in the technological development of marine batteries led to a renewed focus on hybrid propulsion, and in 2017 the state completed feasibility studies for both the vessel and the shoreside charging infrastructure.
WSF elected to convert the fleet to battery-hybrid propulsion after it became clear that the financial, environmental and operational advantages it presented far outshined other solutions. In 2018, Washington Gov. Jay Inslee signed Executive Order 18-01, which directed the agency to begin the transition to a “zero-carbon-emission ferry fleet, including the accelerated adoption of…ferry electrification.”
The state was already planning to replace the obsolete components of the vessels’ existing 20-year-old propulsion control systems, so WSF selected its original supplier, Siemens Energy Marine Solutions, as the prime contractor for the design and equipment. This would ultimately minimize cost and technical risk and capitalize on the company’s experience with battery-hybrid vessel conversions.
Siemens’ work includes the equipment and design integration for the propulsion controls; the battery hybrid system; and rapid charging system for the ferries. Naval architecture firm Glosten, which has been involved with the project since the 2017 feasibility study, was hired by Siemens to provide the preliminary and contract design integration of the propulsion controls and hybrid system. Germany-based Stemmann-Technik, known for delivering innovative marine charging solutions, is designing and supplying a unique rapid charging system. WSF’s own engineering team is working closely with the Siemens-Glosten-Stemmann team to provide some of the mechanical and structural design modifications on the vessel.
The Most Powerful Hybrid-Electric Ferry in the U.S.
The m/v Wenatchee is the first vessel to be converted to battery-hybrid power and is expected to enter the shipyard later this year. The conversion process will be made somewhat easier by the fact that each ferry already has electric propulsion via four 4,475 kW motors — one pair per end, two motors per shaft. Power is supplied by four EMD-16-710-G7A generator sets on a 4160V medium voltage bus. Two of the generator sets are being removed and replaced with two large battery banks, and the final configuration will have one battery bank and one generator per end. The Siemens BlueVault ESS batteries will have a total capacity of about 5700 kWh per shipset.
The batteries will be installed in the spaces currently designated as the shaft alley, adjacent to each propulsion motor room, and a new A-class deck and outboard bulkheads will be added to meet the installation requirements of the U.S. Coast Guard.
In October of 2019, the USCG issued Policy Letter 02-19, which establishes design guidance for commercial vessels using lithium-ion (Li-ion) batteries. The guidance primarily incorporates ASTM F3353-19, Standard Guide for Shipboard Use of Lithium-Ion Batteries, as a design standard, providing information on battery testing, fire safety, battery system design, and shipboard procedures that together establish an equivalent level of safety to existing USCG design rules.
The Jumbo Mark II vessels are USCG-inspected as 46 CFR Subchapter H passenger vessels, and onboard modifications are subject to the USCG regulatory review process. Additionally, although they’re not ABS classed, the Jumbo Mark II vessels are designed to meet ABS rules, and the hybridization project will adhere to this regulatory scheme.
Various new auxiliary systems are being added to support the new batteries, including fire suppression, fire and gas detection, air conditioning, water cooling, space ventilation and a dedicated battery ventilation system. A new foundation will support the 40 tons of batteries on each end while still allowing access and maintenance to the intermediate shafts below. Access and escape routes for equipment and personnel have been considered and incorporated into the arrangements. Power conditioning equipment including bidirectional AC/DC converters, transformers, and new medium voltage switchgear for the shore power charging system will be installed in the existing engine rooms in the approximate location of the removed generator sets. Additionally, the consoles in both pilot houses and the engineers operation station will be modified as part of the hybrid, propulsion controls, and power management upgrades.
When the conversion is complete, the vessel will have the ability to operate as a hybrid or as a battery-electric vessel. The battery capacity will allow full zero-emissions operation on both routes; however, if shore power were not available, the remaining two generators and batteries will provide the vessel with enough power to maintain service. This failsafe is also important in the event that the ferry does not have time to fully recharge, or if it needs to speed up to stay on schedule. In both cases, the batteries may not receive a full charge within the available time at the dock, but the onboard generators will be able to supplement the shore power and allow service to continue.
When completed next year, the vessels will be among the largest battery-hybrid vessels in the United States in terms of power and battery capacity.
Charging Ahead with Shore Power
One of the most challenging aspects of any battery-electric project is the charging system. Once the shore power system is installed, the vessels will be able to charge on each side of the Seattle–Bainbridge route and on the Kingston side of the Edmonds–Kingston route. The time the ferry spends at the dock is assumed to be 20 minutes, which starts after the lines have been lashed to shore. Once the lines are secured, the charging process can begin. However, time must be allowed for both connection and disconnection, as well as time for the power to ramp up and down.
The design basis allows for 90 seconds of connection and disconnection and 60 seconds of ramp up/down time, leaving only 15 minutes of charging time at full power. Since the vessels will be pushing the dock while charging, the shore power will need to provide not only energy for the full route, but also propulsion and hotel power while pushing the dock. For the Seattle–Bainbridge run, which has the highest power demand, the shore must provide 10MW of power with a standardized voltage of 12.4 kV. While the details of the onshore equipment have not yet been finalized, it will require a significant amount of real estate at or near each terminal.
Understanding the physical requirements for the charging device and inventing a mechanism for it has presented the most significant challenge. To minimize environmental impacts and simplify the permitting process, the charging system needs to utilize existing infrastructure rather than installing any piles or other support structures on the seabed. Furthermore, WSF requires the moving parts of the charging system to be installed on the vessel rather than on shore, so that equipment maintenance may be performed by the vessel’s engineering staff. After much study, it was determined that the shoreside receptacle box will be installed on the ferry terminal’s wingwall and the charging device will be installed under the pickle fork on each end of the vessel.
The final charging solution will be an articulating arm that can autonomously locate and connect to the receptacle box on the wingwall. Once the vessel is secured and it has been established that charging can safely commence, the pilothouse will start the process with the push of a button. To meet technical and operational requirements, the charging arm must accommodate dynamic changes in draft due to loading, tides and waves, and successfully connect at least 90% of the time.
The design team solicited input from vessel crews and support staff throughout the design process to ensure that the new design will meet WSF’s operational demands and be supportable throughout the ferries’ service lives.
Sailing Toward an All-Electric Future
The project is currently wrapping up the contract design phase, which includes all shipyard modification documents and regulatory design submittals. Once the system becomes fully operational with shore power, the vessels will have a substantially reduced carbon footprint and are expected to lower WSF fleet emissions by as much as 25%.
Assistant Secretary of Transportation Patty Rubstello, who took the helm of Washington State Ferries in January, has hailed the project as an example of both fiscal and environmental stewardship.
“These three vessels were due for needed mid-life preservation,” she said. “By incorporating this energy storage technology into the project, we’ll save about five million gallons of fuel per year. This will result in a significant reduction in stack emissions and lower our lifecycle costs over the next 40 years.”
While the preservation portion of the project is funded with state money, the hybrid conversion is funded by a grant from the Washington State Department of Ecology’s Volkswagen Settlement Fund, the Federal Highway Administration’s Congestion Mitigation and Air Quality Program, and the U.S. Maritime Administration’s Marine Highway Program.
The conversion of the Jumbo Mark II vessels is just the beginning of a larger initiative: WSF’s 2040 Long Range Plan and System Electrification Plan. The 2040 vision is a fleet of 26 vessels, 22 of which are plug-in hybrid electric. This includes building 16 new vessels, converting six existing ferries, and completing 17 terminal electrification projects. The first phase began with the Jumbo Mark II conversions and a contract with Vigor’s Seattle shipyard for the construction of up to five hybrid Olympic-class vessels.
While many challenges still lie ahead, the benefits of electric and hybrid propulsion are clear and provide the marine industry with another important tool in reducing pollution and fighting climate change.
Sean Caughlan is a senior marine engineer with naval architecture and marine consulting firm Glosten. Since joining Glosten in 2003, Sean has led the firm’s efforts in design and retrofits of alternative-fueled and hybrid powered vessels.
Matthew von Ruden is Director of Vessel Engineering and Maintenance for the Washington State Department of Transportation’s Ferries Division. He has 35 years’ experience in the government and private sectors, including 23 years in the U.S. Coast Guard.
