United States looks to gas power

Natural gas propulsion could soon take-off in the US. The San Francisco Bay Water Transit Authority has launched an environmental impact study into the operation of fast ferries on the bay, which includes evaluation of alternative fuels and alternative propulsion. And next month, the US Maritime Administration will commence a program intended to produce an effective comparison of natural gas and diesel fuel. Mary Frances Culnane, manager of marine engineering for the San Francisco Bay Water Transit Authority (WTA), explains that its environmental impact study “? will include researching ethanol, methanol, propane, natural gas (CNG & LNG), dual-fuel, biodiesel, fuel cells, hybrid engines, electric motors, photovoltaic cells (solar), wind turbines and flywheels.” The environmental study forms part of a broader initiative by the WTA looking at an expanded ferry system on San Francisco Bay. This could ultimately result in up to 120 new fast ferries. The US Maritime Administration?s office of shipbuilding and marine technology will carry out its program on two near identical ferries operated by Hampton Roads Transit in Norfolk, Virginia. “We are conducting a comprehensive measurement of energy efficiency and emissions from natural gas and diesel fuelled sister vessels,” explains Richard Volker, chief of the advanced technology division in the office of shipbuilding and marine technology. The program will compare the emissions of the replica paddlewheel riverboat James C Echols, which was converted to CNG operation in 1995, against emissions from one of its two sisters. James C Echols has two six-cylinder Caterpillar 3406 gas engines, rated at 147kW each. Its sisters have two six-cylinder Detroit Diesel 671 engines, rated at 147kW each. The testing is part of a five-year program formulated to address maritime energy and clean air emissions. This will evaluate baseline measurement of existing diesel fuelled power plants, the use of alternate fuels, auxiliary equipment to reduce emissions and fuel cells, says Volker. These organisation?s research coincides with the launch of a fast ferry campaign by the influential US-environmental organisation, Bluewater Network. Bluewater claims higher speeds, combined with a lack of regulation, have increased the environmental impact of fast ferries ? something it is striving to change. The organisation has targeted San Francisco and has already won the support of city supervisors, who earlier this year passed two resolutions designed to bring in more environmentally-friendly ferries. These call for the introduction, by December 2002, of a natural gas demonstration vessel on one of the longer commuter routes and the use of hybrid solar-electric and wind-powered vessels, by 2005, in place of diesel-powered vessels on tourist routes to Alcatraz Island. CNG in dual fuel The British Columbia Ministry of Transportation and Highways (and latterly the Greater Vancouver Transportation Authority ? TransLink) has had a ferry, Klatawa, operating on a dual fuel mix of diesel and compressed natural gas, since 1985. A second ferry Kulleet, has been operating on dual fuel since 1988. Both ships make a ten-minute crossing of Vancouver?s Fraser River. In addition to their diesel fuel tanks, they have compressed natural gas cylinders, stored on deck, taking natural gas every 4.5 hours from a compressor station ashore. This is fed from a regular natural gas pipeline. The company responsible for securing regulatory approval for these ships is Canadian firm Marine Design Associates (MDA). Ralph Marwood, a naval architect with MDA, says the company now has approval from Lloyd?s Register to store gas cylinders in the void compartments down below, thus freeing up deck space. Thus MDA?s most recent gas-fuelled ferry project ? the 80 car, 250 passenger, 15-18 knot Osprey 2000, which entered service on the 20-minute crossing of British Columbia?s Kootenay Lake in August 2000 ? is configured for conversion to dual fuel operation, with the gas cylinders stored in the void spaces. Approval has been given for conversion of the ship?s four Caterpillar 3512B DITA electronic diesel engines to dual fuel operation. And a contract has been awarded to Florida-based Gas Technologies, Inc. “There is no modification needed,” explains Ken Green, president of Gas Technologies. “Ours is an add-on system fumigated into the air intake on the side of the engine.” Pure LNG experience Norwegian operator M?re og Romsdal Fylkesbåtar (MRF) introduced the natural gas-powered double-ended car ferry Glutra onto a 20-minute fjord crossing between S?lsnes and Åfarnes in February 2000 (see The Motor Ship, May 2000). Glutra has four Mitsubishi GS12R-PTK engines fuelled solely by natural gas. Liquefied gas (LNG) ? stored in vacuum-isolated tanks ? passes through an evaporation plant, which returns it to its gaseous form prior to injection. In normal operating conditions only two generating sets are required. “We have had trouble with pre-chamber gas nozzles/valves (poor regulation),” admits John Aage Rasmussen, technical marine manager at MRF. “But due to the concept [of four generating sets], we have been able to cope with and solve the problem without harming operation. “With the generating sets on the boat deck and a very high airflow through the engine rooms, making them a non-gas zone, it allows us to troubleshoot and work on the units in service,” he adds. In its 18 months to date, Glutra has been out of service for just 2.5 hours and that because of a manoeuvring problem. He says measurements taken thus far indicate NOx emissions are reduced by 80% while CO2 output is down by 15-20%, compared to MRF?s newest diesel electric ferry. This is achieved without any negative impact on fuel consumption, he adds. As far as advocates of a fleet of natural gas powered ferries in San Francisco are concerned, the successful precedent set by Glutra means a set of draft class rules is now available for the construction of a similar fleet of ferries powered solely by natural gas. These rules entered force on July 1, 2001 and are contained within Part 6, chapter 13 of DNV?s Rules for Classification of Newbuildings. Fast on gas Both of these examples involve relatively slow ferries on short routes. On San Francisco Bay a number of the routes are longer and demand faster speeds. Local authorities have expressed interest in Iguana Seacraft?s natural gas fast ferry design, the EcoFerry (see The Motor Ship, October 2000). The concept design carries 60 passengers and eight light goods vehicles at speeds of up to 25 knots. Paulo Bernardes-Silva, senior naval architect at Iguana Seacraft says this is suited to certain runs ? like Alcatraz and Oakland ? but he concedes that properly serving the bay?s transport needs will require larger derivatives. Bernardes-Silva feels the Norwegians behind Glutra are in a very strong position should the San Francisco authorities pass legislation requiring the use of cleaner fuels. Per Magne Einang, research manager for internal combusion engines at Marintek, the Norwegian research institute, says the Norwegians have not conducted a great deal of research into natural gas fuelled smaller fast ferries ? smaller fast ferries being the mainstay of the San Francisco ferry system. Its research in this area has thus far focused on larger ships powered by gas turbines, he says. The absence of in-depth research, he explains, is based on concerns about the availability of an engine with the required power to weight ratio for a smaller fast ferry. A natural gas fuelled diesel engine, on the whole, would impact the overall weight of a small ferry to an extent that would inhibit its ability to go fast, says Einang. And marinised gas turbines are not available in outputs below 16-18MW (ie those required for smaller fast ferries); although they can be de-rated this would just involve adding weight, he adds. Thoughts from the Bay This doubt about small natural gas fuelled fast ferries, from such a prominent authority, somewhat contradicts the optimistic views of naval architects like Iguana Seacraft and environmental organisations. However it supports the views of a sceptical core among San Francisco Bay?s commuter ferry operators. Baylink Ferries, which runs a fast commuter service to Vallejo, is one example. Its general manager Martin Robbins has listened to the arguments for natural gas power but he still expresses concern about the complexity, cost, reliability and additional weight of natural gas powered vessels. “A natural gas powered vessel may offer some environmental benefit, but I am quite convinced that the total earth-benefit would be small when compared to the total cost involved,” comments Robbins. Bernardes-Silva is adamant that weight isn?t an issue for a small natural gas fuelled fast ferry. He says that while there may be weight penalties with a dual fuel arrangement, a purely natural gas fuelled vessel has little or no weight disadvantage, thus meaning the requirements for fast operation are broadly similar to those of diesel-fuelled vessels. Areas of agreement While there are many contradictory arguments to the use of natural gas fuel, there are areas where there is broad agreement. On the environmental side, there is no questioning the reduction in particulate matter, nitrous oxides and sulphur emissions through burning natural gas (although other emissions, such as methane, increase). And even the strongest advocates of natural gas fuel admit that creating the supply infrastructure is a potentially huge cost standing in the way of progress. On slower ships, the accumulated operating experience of natural gas fuelled ferries is supported by cost analysis that comes out in favour of the use of natural gas fuel, either stored in its compressed or liquefied form. Precedents exist and there is now a set of predefined regulations available from which operators and builders can work. For longer routes, where speed is required, the jury is still out. Ultimately, though, a transition from diesel to natural gas is likely to come down to the regulators and the local authorities and their desire to push through what is seen – at least for now – as a more environmentally-sensitive way of powering the United State?s ferries. n