Washington State Ferries and DNV Explore LNG as a Fuel
Like all commercial vessel owners, the Washington State Ferries’ (WSF) most significant expense is fuel. As the largest ferry operator in North America, and the third largest worldwide, WSF burns more than 17 million gallons of ultra-low sulfur diesel each year.
“It’s our fastest growing operating expense,” comments Washington State Department of Transportation (WSDOT) Assistant Secretary David Moseley.
It’s no wonder that the Olympia-based ferry operator is looking to retrofit a half-dozen of their vessels with engines capable of the burning liquefied natural gas (LNG). To ensure that the safety, security and operational challenges of such a move is handled in a responsible manner, Washington State Ferries has partnered with DNV, a risk management company with extensive experience of LNG-fueled ships and the infrastructure they demand.
LNG, on a per unit basis, contains less energy than diesel fuel. To be exact, 1.67 gallons of LNG contains the same energy as 1 gallon of diesel fuel. This, and the difference it the way LNG burns, explains why spark-ignited LNG, and dual-fuel engines, have a larger cylinder bore as compared to diesel engines of the same horsepower rating.
The delivered price of LNG via tank truck to a vessel, according to a report by the Washington State Ferries, has been quoted as $0.75 per gallon. Given the current price of diesel fuel is around $3.34 per gallon, the per gallon savings is approximately 56 percent.
With these potential fuel cost savings, WSF is pursuing a $75 million retrofit of the Issaquah-Class Ferries to burn LNG with an estimated 7-year payback period.
From an emissions standpoint, these vessels would see a 100% reduction in SOx and particulate matter emissions, a 90% reduction in NOx, and 20% reduction in CO2 emissions.
Working with DNV
DNV has taken the leading role in making LNG as a fuel safe and viable. 35 out of 37 LNG fueled vessels in the world, including the very first in 2000, have been built to DNV’s standards. Of these, 16 are car/passenger ferries. Particularly for short-sea shipping, LNG technology can make a big difference quickly, when it comes to reducing harmful emissions.
“As the biggest ferry operator in the US, and the third biggest in the world, WSF can really lead the way for its industry. In DNV, we can now clearly see a tipping point when it comes to global interest in LNG-fuelled ships. Knowing that LNG as a fuel helps reduce emissions and costs, our team of researchers, engineers, and business analysts are looking forward to assist WSF and other companies with managing risks related to their LNG operations,” says Kenneth Vareide, Director of DNV’s maritime operations in North America.
LNG Operational Challenges – by Cotty Fay, Chief Architect, WSDOT
Availability – Natural gas is a widely available fuel across North America. LNG is in limited use in Washington State today, but if a large enough market existed in the Puget Sound area, a gas supplier may build a local liquefaction plant.
Currently two liquefaction facilities exist on the Washington/Oregon border and another in British Columbia, Canada. All potential ferry fuel would have to be trucked to the vessel much like 70 percent of the diesel fuel is today. Presently, two commercial shipping entities – Fortis and Teekay Shipping – are developing a plan to supply LNG into Puget Sound by truck and barge. Puget Sound Energy already has a fleet of trucks that deliver LNG to their Peak Shaving Plant in Gig Harbor.
Regulatory – Since no LNG-fueled passenger vessels have yet been built in the United States (other than small retrofit pilot projects), the United States Coast Guard (USCG) does not have an established path for regulatory review. As the USCG is WSF’s primary regulator, early engagement with them to discuss an approach to gaining their approval of an LNG ferry is essential. The basic design for the Issaquah-Class boat has been approved by the Coast Guard and we are presently working on the Safety and Security Plan with consultant, Det Norske Veritas (DNV), and the local USCG district. The Safety and Security Plan will include Navigation, Risk Assessment and Operational procedures.
Storing LNG on board
The location of the storage tanks is difficult because of the nature of the tanks. The LNG is maintained under pressure at -160 deg C in an insulated tank that is a body of revolution which must be B/5 feet, which equates to 15.7 feet from the side of the vessel. The present design locates the tanks up on the sun deck to provide the B/5 clearance as well as provide a safe position for any escaping vapor to dissipate naturally away from the vessel and passengers. LNG is about half the density of diesel fuel, but has about 10 percent more heating value per pound. The result is we need about 165 percent more volume of LNG for the equivalent volume of diesel fuel.
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