With hybrid power packages popping up in practically every arena, it was inevitable that the tugboat industry would soon come forth with its own version, especially considering the long history of diesel-electric power for tugboats in the last century and for other types of workboats in the current century.
Now it looks as though concern over air pollution in the adjacent Southern California ports of Los Angeles and Long Beach is helping to create the first hybrid diesel-electric-battery-powered engine room for a tugboat.
Foss Maritime, with its own shipyard and design staff and with partial funding from local port agencies, has stepped forward with a plan to build the first one. Hybrid-electric power plants combine the benefits of two or more power sources. In the case of automobiles, this would be a reciprocating engine and stored electrical energy in batteries. In the case of this tugboat, it would be reciprocating diesel engines and stored electrical energy in batteries.
Foss engineers figure they can build and operate a prototype 5,000-hp low-emissions tugboat for about $8 million — about $3 million more than the cost of one of their own Foss-built tractor tugs. The company reports that the base cost for a Dolphin is $5 million to $6 million, depending on outfitting.
This so-called “green” tug, at 78 feet, would be a modified version of one of Foss’s Dolphin-class azimuthing-stern-drive tugs, built by the company’s shipyard in Rainier, Ore. Instead of a pair of 2,500-hp diesels, its engine room would be fitted with smaller main engines that can be detached from the main propulsion shafts, plus a pair of battery packs capable of storing up to 1,000 kW of power, and a pair of diesel generators churning out power as needed by the batteries.
Depending on its power needs, the tug could operate on batteries alone (through motor-generators linked to each declutched propeller shaft) or on power produced by its diesel-generators, or on combinations of battery power plus generators, or direct power from one or both main engines, or, for full-out power needs, direct power from both engines with a boost from the battery packs.
The key to this design, according to Foss Director of Engineering Elizabeth Reynolds, is the versatile motor-generator that can either use stored electrical power to turn the shaft to each z-drive, or can accept mechanical power from the main engines and convert it to electrical power for the batteries. The main engines can also turn the propulsion shafts directly with or without additional power from the batteries and motor generator.
“There are times when this will be just an electric boat,” said Reynolds. “And there will be times when this is a diesel-electric tug, and there will be times when it’s a direct propulsion tug. There are even times when the stored electric power is used to supplement the direct power. That’s how we get up to a 5,000-hp tug while having main engines rated at only about 1,700 hp each. Those batteries can give you bursts of higher power, which is usually all that is needed for ship-assist work.”
While tugboats are not the primary source of air pollution in Los Angeles/Long Beach — the nation’s busiest port complex — officials are looking for any and all proposals that might help to reduce the pall of smog that can often be seen hanging over the landscape. The Los Angeles/Long Beach port complex has been identified as the worst air polluter in Southern California, accounting for almost a quarter of particulate-matter pollution in the region. It’s no wonder, with thousands of ship calling at the port each year and vast numbers of workboats, trucks, locomotives and service vehicles tending to the cargo of those ships. This will give you a feel for the problem: Approximately 16,000 diesel trucks, many of them aged, are at work on a daily basis around the combined ports.
Against this we have the combined emissions output of two dozen ship-assist tugs that service ships and barges in the port. These tugs engaged in ship-assist and barge work in the port are about evenly represented by AmNav Maritime Services, Crowley, Foss Maritime, Millennium Maritime and Sause Bros. The majority of these are tractor-style tugs. While the tugs may not be primary contributors, there’s no denying that they are part of the problem — hence, the willingness of the ports to finance part of Foss’s proposed hybrid tug.
In November 2006, the ports of Los Angeles and Long Beach approved an unprecedented joint action to improve air quality in the region called the Clean Air Action Plan. The five-year plan aims to reduce health risks posed by air pollution from port-related ships, trains, trucks, terminal equipment and harbor craft. Port officials
|The tug Millenium Dawn, operated by Millennium Maritime, escorts a ship out of Los Angeles. Millennium is one of five tug companies providing escort services in the L.A./Long Beach port complex. [photo by Jasper Walsh]
have allocated millions of dollars toward programs that can reduce pollution caused by all machinery related to the port. Among steps being taken are reducing speed of approaching and departing ships, encouraging shore-side power connections to allow ships to shut down their diesel engines while in port, use of cleaner fuel for ships and shore vehicles, introduction of electric-powered trucks and terminal vehicles, and phasing in low-emissions diesels for working craft throughout the port.
While new tugs everywhere are being built with EPA Tier II-compliant engines, the introduction of an actual hybrid-powered tug is purely voluntary. And why not, considering that everyone else is getting into the act, from tiny automobiles and SUVs to military vehicles and even railroad locomotives? Even traditional truck manufacturers like Kenworth and Peterbilt have introduced hybrid-style engines.
Foss’s new low-emissions tug is planned to join the company’s fleet of tractor-style tugs operating in the combined ports. An average of 16 ships a day arrive at the two ports from foreign destinations. Among many other cargoes, these ships bring in 43 percent of all containerized cargo arriving in the United States. In fiscal year 2006, this amounted to about 5 million containers.
Agencies representing these two ports have offered $1.35 million in direct support of the prototype hybrid tugboat project. Port officials believe that this first “green” tugboat will produce 44 percent less nitrogen oxide and particulate matter, compared with a conventional tug, while simultaneously reducing overall fuel consumption by as much as 30 percent. The design would allow the tug to shut down one or both of its main diesel engines during periods of low power demand.
“We did projections of the development and life-cycle costs on this, and considering the $3 million extra cost for this particular tug, even though we save on fuel and save on maintenance over the long run, it still does not pay for our capital invested in up-front development costs,” said Reynolds. “But with the development money from the ports, we can make it work,” she added. “Those contributions make the difference between a viable and a non-viable project.”
Once introduced, some time in 2008, according to plan, Foss would own the tug design and be committed to operating the tug in Los Angeles/Long Beach for five years, she said.
Foss, which contracted with a Canadian electrical engineering firm to develop the plan, is projecting that it will use Cummins QSK-50 diesels for both main engines and smaller Cummins diesels for auxiliary generators. Other big equipment items include the motor generators and something on the order of 20 tons of batteries and battery racks. The company will likely use Rolls-Royce azimuthing propeller units, as in other Dolphin-class tugs.
Like a hybrid-powered automobile, the tug could shut down the main reciprocating engine or engines when not needed, thus saving fuel and reducing emissions. As in a hybrid car, the tug’s batteries can provide all power needed for slow movements and other low-power situations.
Another form of hybrid power technology considered for this application was the “Green Goat” power system developed by Railpower Technologies of Canada, and currently being developed for marine use by Ocean Tug & Barge Engineering. These systems make use of multiple small generators constantly feeding power to large battery packs that provide motive power to railroad yard and switching locomotives. The Green Goat system does not fit the needs of a high-horsepower ship-assist tug, however, because the demands of peak power periods would require massive battery banks that would be prohibitively heavy.
“We had to go with a setup using main engines for maximum power needs, because it is not feasible to fit all those batteries in what is really a relatively small tugboat,” said Foss’s Reynolds. “But what’s different is that the main engines are not as large as they might otherwise be, and they can be shut down when not needed.”
Foss’s Dolphin-class tugs are compact tugs originally designed by Robert Allan Ltd., Vancouver, Canada. With a normal machinery package, the 78-foot hulls can produce up to 65 tons of forward bollard pull at full power of 5,080 hp. Because of the competitive nature of ship-assist work in the Los Angeles/Long Beach area, and bollard pull standards required by the ports, Foss’s new green-designed tug will have to produce similar power levels.
The company is considering either lead-acid battery packs or nickel-metal-hydride batteries that are lighter but more expensive. Either way, battery packs will play a huge role in the design of this tug, not only because of its footprint within the engine room, but also because of the effect of more than 20 tons of battery weight on stability and trim. Foss’s Dolphin tugs have all been built with Markey electric winches, so that fits well with the diesel electric design formula.
Plus the Dolphin tugs have all been built with carbon fiber shafts that lend themselves well to a system that would involve more frequent stopping and starting of the shaft than normal. The system will likely be set up so that the shaft will run right through the in-line motor generator. The engine can be clutched out so as to disconnect it from the shaft, and the motor-generator can be clutched out so that the shaft can turn through it without effect.
“The motor generator will not have to contribute power to the shaft, but there are many variations that can be used,” said Reynolds. “Suppose you need 60 percent power from a main engine, but it is more efficient to run the engine at 75 percent. Then you could just use the extra engine power to generate electricity through the motor generator to charge up the batteries.”
The entire power scenario would be managed by a computerized system.
“There will be a master power controller that would make the entire arrangement seamless to the operator, similar to the way it is when you operate a hybrid automobile,” said Reynolds.
In developing the plan for its green tug, Foss engineers conferred with consulting engineers from Aspin Kemp & Associates, Owen Sound, Ontario, Canada.