WSF "a step closer" on LNG conversions

LNG fuel tanks will be mounted on top deck of each ferry LNG fuel tanks will be mounted on top deck of each ferry

NOVEMBER 22, 2013 — Washington State Ferries says it is "another step closer" to convert six Issaquah Class vessels to LNG fuel. The proposal was officially submitted to the U.S. Coast Guard on Nov. 18 in a formal letter of intent (LOI) and waterways suitability assessment (WSA). The submission of the LOI and WSA marks the official starting point of the Coast Guard's review process. WSF expects the Coast Guard to issue a finding regarding the LNG conversion proposal in 2014.

"Fuel is WSF's fastest growing operating expense," said David Moseley, assistant secretary for the Washington State Department of Transportation, Ferries Division. "Replacing diesel with LNG on the Issaquah Class ferries could result in very substantial savings on fuel over the remaining 30 years of their service life. This will also mean a cleaner, more efficient future for our fleet by significantly decreasing emissions."

The average Issaquah Class vessel carries up to 124 cars and 1,200 passengers, serving on some of the state's busiest ferry routes. Converting the fuel systems from ultra-low sulfur diesel to LNG would significantly reduce emissions according to WSDOT's Air Emissions Model, including:

89 percent reduction in particulate matter
61 percent reduction in nitrous oxide
28 percent reduction in carbon dioxide
59 percent reduction in sulfur dioxide

For the proposed LNG conversions, WSF would install main propulsion engines to use natural gas and retrofit LNG fuel tanks on the top decks of the six vessels.

According to the LOI, the LNG tanks will be located on the upper deck of the Issaquah Class ferries, and will not accessible to passengers. These two skid mounted tanks will be located on either side of the existing exhaust stacks. The tanks will have an integrated assembly with a cold box and control system to control bunkering and vaporization of the LNG to gas for use in the engines. The tanks will be manufactured using the same technology used in over the road LNG truck trailers. The capacity of each tank will be 100 cu.m (26,000 gal), resulting in a total capacity of 200 cu.m (52,000 gal). LNG will be transported to the vessels by dedicated over the road tractor trailers that carry 10,000 gallons of LNG.

The proposal calls for a phased approach for conversions to avoid schedule changes or delays. Once vessels are converted and back in service, they would begin a routine overnight, out-of-service refueling process similar to current diesel refueling.

Since 2010, WSF has been studying the benefits of alternative fuels and evaluating the feasibility and safety of using LNG to fuel its vessels. The process included the U.S. Coast Guard, multiple agencies at the state and local level, private industry organizations, the Washington State Joint Transportation Committee and consultants including Cedar River Group and Det Norske Veritas.

WSF concluded its study process by issuing the final waterways suitability assessment, which includes a safety and security assessment and a risk-management plan. The study found that the LNG proposal is inherently safe with risks as low as reasonably practicable.

Use of LNG to power passenger ferries has been proven technically and operationally feasible worldwide for more than a decade, with Norway operating LNG-fueled passenger vessels since 2000. LNG is also fast becoming an efficient alternative fuel for buses and semi-trucks.