Different Fuels, New Systems—the
Future Is Coming Soon
Article Written in
2008
What will propel the vessels of tomorrow?
It is too early to be sure but candidates are becoming visible.
Combination of fuels and various mechanisms assembled into hybrid
systems will be common but not necessarily universal. Electricity
is a thread common to many of the systems—as one tugboat
expert summarized the future, “It’ll be diesel and
electricity.” He may be right.
This article will focus largely on systems usable by harbor tugs,
ferries, and other craft with similar duty cycles—that is,
much idling, some transit time, and periods using short bursts
of maximum power. (As an example of what is meant by “short,”
full-throttle operation of the Caterpillar main engines in two
modern East Coast tractor tugs occupies a mere 2% of total engine
hours.) Descriptions as to what is happening out there are often
short of real information, excessively vague, or close-held by
the developers but enough is known to take a first-look at what’s
out there. Let’s examine fuels first, and then briefly visit
some of the systems coming along.
What about the anti-pollution regulations?
As of January 1, 2007, all new marine engines and about 3/4 of
all remanufactured engines had to comply with Tier 2 requirements.
Tier 3 requirements are basically similar to those of Tier 2 but
tougher in some respects. Tier 4 emission standards will be phased-in
over the period of 2008-2015 and require that emissions of PM
and NOx be further reduced by about 90%. Such emission reductions
can be achieved through the use of control technologies—including
advanced exhaust-gas aftertreatment such as particulate (soot)
filtering and catalytic converters.
What is driving the switch from good-old everyday
diesel oil? Two factors: its cost as world demand
for petroleum products causes skyrocketing prices, and the general
feeling that the world has become intolerable dirty and must become
cleaner; pollution is driving the creation of increasingly tighter
regulations.
Will diesel fuel continue to be available?
Sure but at increasing cost and perhaps derived from unusual sources,
such as the oil shales of Colorado or the oil sands of Canada.
But not all diesel oil need be made from petroleum—more
on that later.
Are bio-fuels the answer? Maybe. Maybe
not. For the purposes of this article, biofuels can be said is
to fall into two categories: alcohols and biodiesel. Both can
be derived from vegetation but, as the world population increases,
the ever-present question arises: Can Mother Nature grow enough
vegetation to make lots and lots of biofuel and still feed everyone?
That answer is not yet clear.
• Alcohol powers many racecars and dragsters and an ethanol/gasoline
blend probably is in your vehicle’s gas tank. Ethanol produced
from corn is much in the news nowadays and comparisons of its
environmental/economic value and true cost are the subjects of
much controversy. But ethanol can be produced from other vegetation:
Shell, the world’s leading biofuel distributor, recently
received an $80 million dollar US government grant to build a
facility in Idaho that will produce ethanol from plant waste and
straw. And, in Brazil sugarcane-based ethanol is widely used due
that nation’s vast farming areas, favorable climatic conditions,
and extensive production of sugarcane. (It has been reported that
the exhaust fumes from alcohol-fueled vehicles in Brazilian traffic
jams tend to leave everyone with a slight buzz.)
But ethanol has a potential competitor. It is butanol, also known
as buytl alcohol, and it could be in large-scale production by
2012. Butanol is less-corrosive on engines than ethanol, easier
to mix with gasoline (and probably diesel oil), and, unlike ethanol,
can be transported via a pipeline. Unfortunately, it is more expensive
than ethanol. Butanol usually made from fossil fuels and ends
up as a solvent but biobutanol used to be and will be produced
by bacteria feeding on feedstocks (a process called fermentation)
such as wheat, paper-pulp-derivatives, and even the corn waste
from making ethanol!
• Biodiesel produces less CO2 than petroleum-based fuels,
can be safer to handle, and its exhaust fumes are easier to live
with. It may also make engines run quieter and regular diesel
can still be substituted when necessary. Negatives are lower economy,
gelling in cold weather, and increased production of NOx emissions.
The most-common method of producing biodiesel is to react animal
fat or vegetable oil with methanol in the presence of sodium hydroxide
(lye or caustic soda). Vegetable oils can be derived from corn,
soy beans, rapeseed, sugar, blue-green algae, jatropha (a kudzu-like
plant from South America that thrives in poor soil otherwise unsuitable
for farming), many grasses, woodchips, straw, etc. (Save-the-tropical-forests
advocates do not seem to have yet realized that biofuel derived
from palm tree oil often means that tropical jungles were cut
down in order to plant orderly rows of easily harvested palm trees!)
Shell will soon start creating synthetic diesel fuel (biodiesel)
in Europe from waste plant material such as woodchips and straw.
Animal oils are classed as yellow grease and can be used deep-fat-frying
oils or fat from livestock and poultry-processing plants.
On the West Coast, Brusco’s Wynema Spirit and Lulapin at
Port Hueneme, California, Campbell Maritime‘s several small
tugs in the Seattle area, and Pacific Tugboat Services’
tugs are among tugs using biodiesel.
What about natural gas? Natural gas
is basically methane but usually includes varying amounts of ethane,
propane, butane, and pentane. Widely used on land for many years
in internal-combustion engines in place of gasoline or diesel
fuel, natural gas is lean-burning, clean-burning, and provides
long engine life (up to 100,000 hours before overhaul). The gas
is usually transported in two forms. Liquified natural gas (LNG)
is stored and carried in the liquid state at extremely low temperatures
and converted back to its gaseous state at the destination. Compressed
natural gas (CNG) remains in the gaseous state but is compressed
at high pressures for carriage and storage. CNG is widely used
for land-side operations such as propelling buses. At sea, the
boil-off from tanker cargoes of LNG is often used to fire boilers
producing steam to drive turbines and some of newer LNG tankers
have dual-fuel diesel engines. On smaller vessels, natural gas
has propelled the Norwegian ferry Glutra since 2000, two supply
boats since 2003, and is appearing on other supply boats. In BHP
Billington’s application for a floating offshore LNG-unloading
facility off Southern California, it promised that all escort
tugs, crew boats, and associated land vehicles would be powered
by natural gas. (The application was denied.)
Hydrogen? Nice stuff. Highly energetic
(ask your local Space Shuttle for a reference here). Clean-burning
but note that if you ever have to fight an onboard hydrogen-leak
fire, it burns with an invisible flame. But hydrogen is not yet
available at your local marina or refueling point. Hydrogen can
be made from methane, petroleum, and coal via various chemical
reactions, and from biomass (landfill waste, wastewater sludge,
and livestock waste). It can also be made from water by electrolysis
but is currently made primarily from natural gas (methane). Although
hydrogen is used in the Space Shuttle rocket engines, hydrogen
is more likely to power fuel cells on vessels like tugboats. Honda
has just revealed a zero-emissions car that is powered by electricity
generated by a hydrogen fuel cell. Two hundred examples of this
Honda FCX Clarity model will be leasable in California next year.
And coal? Coal is perhaps the most-common
fuel in the world and the US has tremendous reserves. So why not
use it as it comes from the earth, perhaps ground into a flour-like
powder and burned in something like a fluidized-bed boiler? There
are those who believe that coal is the fuel of the future. Bob
Hill at Ocean Tug & Barge Engineering (OT&BE) was recently
approached by a European who wanted OT&BE to design a tug
using the latest coal-burning technology to generating steam for
an improved version of the Skinner Uniflow steam engine.
But liquid fuels can be synthesized from coal using the Fischer-Tropsch
process. Never heard of it? Have you ever wondered how Nazi Germany
fueled those tanks and fighter plane during World War II when
Germany was denied access to crude oil? Or how did South Africa
kept functioning when sanctioned for its apartheid policies? The
answer lay in coal-derived synthetic fuels and they created by
the Fischer-Tropsch process, invented in the Thirties and since
improved with better catalysts. Maybe we’ll see marine diesel
fuel derived from coal.
And even trash? An Italian engineer
presented a paper at the recent World Maritime Technology Conference
stating that Rome’s Worldwide Ecological Shipping &
Transport had developed a patented process for driving ships with
steam from a rubbish-fired boiler. He figured that a 4,800-teu
container ship would consume 176,000 tons of waste in 275 days
of annual navigation. Air emissions would be cut by up to 98%
and there would be freedom from oil’s price fluctuations.
But trash does seem an unlikely fuel for tugboats and the like.
That completes the fuel story. Hybrids
are now being used in seemingly everything including automobiles,
locomotives, container gantry vehicles, and even Formula 1 racecars—BMW
will have one next year. Electricity generated by the racecar’s
braking will be stored in a battery or super-capacitor, and released
in a burst of eighty additional horsepower for up to six seconds.
Let’s look at some proposed and planned tugs, most of which
(but not all) are hybrids. Hybrids are nothing new; they have
been afloat for many decades. For example, World War II submarines
used hybrid drives; diesel engines, electric motors and generators,
and a massive storage battery system. (Sounds vaguely reminiscent
of a Toyoto Prius, doesn’t it?) A submarine in the pre-nuclear
power days, was propelled by either its engines or its motors,
which used electricity stored in the batteries, and the engine/generator
sets recharged the batteries. Post-war, many new harbor tugs were
built using war-surplus main engines turning surplus generators
that powered surplus electric propulsion motors, and the diesels
revved up and down in response to load variations. Today’s
hybrid tugs will require clean-burning gensets operating at constant
rpm, modern control electronics, and the development of new and
radically advanced types of batteries.
Interestingly, the US Navy’s new warships will be propelled
by down-sized electric motors using superconducting magnets and
sophisticated electronic control systems. Little of this technology
seems apparent in what is being developed for commercial applications.
The all-electric, non-battery, non-hybrid tug.
Why not a pure diesel-electric tug? Later, a Dutch tug is described
that closely approximates the following setup but with the addition
of an unusual component or two.
A little background: Generating electrical power for vessel propulsion
is possible via several routes. Historically, a diesel engine
spun the rotor of a generator and the engine revved up or down
in accordance with the load imposed on the system’s electric
propulsion motor. Nowadays a constant-speed diesel turns a constant-speed
generator, whose output to the motor and other loads is controlled
either by varying the generator’s field strength or by using
a chopper arrangement to control output from a DC generator set
or a variable-frequency drive on an AC set.
On a tug, such a set-up on a tug might copy many cruise ships
that are powered by father-son combinations of diesel-powered
generators, each placed online in accordance with the load demand—one
“son” for “hotel” service while docked,
maybe a “father” while transiting to a job, then everything
online during a big push on a container ship during, say, hurricane
winds. And note that Schottel already offers electrically driven
azimuthing drives.
RailPower. Perhaps the first company
to commercially produce technology that realizes the benefits
gained by using clean-burning diesel engines with generators and
motors coupled to large battery packs was the Canadian company
RailPower Technologies. It originally set out to create a “clean-power”
switching engine but model-train buff Bob Hill recognized that
ship-assist tugs and other workboats have remarkably similar duty
cycles and so his OT&BE obtained a license of RailPower’s
technology for marine applications. The basis is one or more electric
drive motors supplied from massive battery packs (think 2,000
hp or so each) continuously recharged by one or more small gensets.
(The gensets might even be used to power a tug at light loads,
such as while under way to a job.) OT&BE’s subsidiary
company EcoMarine Propulsion LLC is designing such systems in
association with Railpower Technologies for a group of six new
5,000-hp tugs propelling articulated tug/barges (AT/B).
The Foss hybrid tug. This tug will
probably be the first hybrid tug to see service. It is based on
Foss’s series-built Dolphin-class tug but the 5,080 hp of
the standard tug will be approximated by a combination of propulsion
units. When idling or transiting, up to 2,012 hp will be taken
from two 671-hp battery packs battery packs supplemented by and
maintained by two 396-hp generator sets. Two main engines output
3,400 hp total and are used only when maximum efforts are needed.
Originally, the Foss hybrid tug was going to be hull 9 in the
Dolphin series but now it will be hull 10. The reason illustrates
the state of progress in battery design and construction. Nickel-metal-hydride
batteries were to be used but the selected brand is longer made.
Gel-based lead acid batteries will be substituted, at a lower
cost and a considerable increase in weight.
GE and C-MAR’s tug. General Electric
and Texas-based maritime engineering and management firm C-MAR
plan to provide cleaner power for nautical applications. They
will start with a hybrid tug. It will use either the GE V228 (formerly
the 7FDM engine, with powers ranging from 1,753-3,506 hp at the
900 rpm continuous rating) or the new Tier 2-compliant V250 engine
(2,725-3,626 hp under the same conditions) to drive a generator
that will keep a battery pack charged. That will supply power
to an electric motor. Neither the type of battery or motor has
been identified but it may of significance that GE Financial Services
recently invested more than $20 million into A123 Systems, a developer
and maker of lithium-ion batteries. Look for the tug in about
two years.
OT&BE’s natural-gas fueled tugs.
OT&BE is also designing three tugs powered by diesel engines
fueled by natural gas. One tug would be the prime-mover of an
AT/B. The boil-off from its cargo of LNG would power the tug’s
engines. When the barge is empty, the tug would use stored CNG,
as would the two other tugs. The method of CNG storage is to be
determined; it may be tanks or cylinders or tight coils of piping.
No other details are available.
A Dutch fuel cell-powered tug: Inquiries
were made abroad as to what was happening outside the US and only
three projects were identified. The pedigree of the first is impeccable:
a highly knowledgeable member of a great Dutch tugboating family
who has a smart design group at his beck and call and partners
in the form of two smart tugboat companies, both Dutch and one
a world-leader in the business. Michiel Wisjmuller owns Worldwise
Marine and it is a part of the Offshore Ships Designers group.
The companies are Rotterdam’s Smit Towage and Jmuiden’s
Iskes Towing and Salvage.
Worldwise is designing an electrically-driven, azimuthing stern-drive
harbor tug that will use hydrogen fuel cells and batteries to
provide zero emissions while on standby and mobilizing/demobilizing.
“[It] will save up to 98% of SOx, NOx, and particulate matter
and 30% of CO2 emissions in total compared to a conventional harbor
tug over the whole employment cycle. This is a major step forward
for tug operators who have tugs operating in densely populated
areas," said Wijsmuller, managing director of Offshore Ship
Designers.
Hydrogen will be stored at 430 bar (over 6,000 psi) and the proton-exchange-membrane
fuel cells will use the NedStack Fuel Cell Technology. Two main
electric propulsion units deliver 1,733 hp (1300 kW) each while
four 650-kW Caterpillar C32 generator sets provide additional
power as needed to deliver the full 50-tonne bollard pull. Power
will also be created thru regeneration from winch feed-outs or
propeller rotation while the tug is in a braking or escort mode.
Interestingly, the tug is fitted with a bow-mounted retractable
Voith bow propulsion unit that is used when the tug is operating
on electric/hydrogen power. When the tug switches to the berthing/assisting
mode and is running on one or more of the four diesel generators,
the Voith unit is retracted, to cut hull drag.
As far as is known here, this project has yet to get past the
planning stage but, because of the partners involved, one should
expect tugs to be built.
A Finnish hybrid tug. Anchor-handling
tugs/supply boats (AHTS) need flexible power systems and diesel-electric
systems are becoming more popular. Finland’s Aker Yards
has orders for two big (308 feet overall) AHTS and they are said
to be “equipped with a hybrid propulsion solution”
for a bollard pull in excess of 350 tonnes (about 385 tons). Sparse
specifications provide few clues except that there are two main
engines of 8,000 kW (10,728 hp) each and an “auxiliary“
engine” of 11,000 kW (14,750 hp). One might guess that the
auxiliary engine is actually a single electric motor connected
to one shaft.
Finally, a multi-national hybrid tug. One
truly hybrid project is already in series production. Norwegian
design group VIK-Sandvik and Indonesian shipyard PT Batamec have
been cooperating on creating a large, high-powered, “clean”
AHTS and twenty of the resulting VS491 CD vessels are on order
for deliveries in 2008-2011. This hybrid vessel uses a mix of
diesel engines, generators, and electric motors. Fuel cells could
replace the diesels in powering the motors.
In a scheme somewhat reminiscent of a World War II submarine,
each of two controllable pitch propellers can be driven by a diesel
engine and/or a variable-speed electric motor. Each 10,730-hp
main engine has a power take-off in the front end that drives
a 3,000-kW shaft generator. With this arrangement, the main engine
can be used as the propulsion engine at variable speeds (but not
below the idle speed of the engines), can be the propulsion engine
at a constant generator speed, or can be a generator-driving engine
disconnected from the propeller. The variable-speed electric motors
have two nominal ratings and speeds. When operating in parallel
with the diesel engine, they turn 1370 rpm in order to match the
nominal propeller speed of 144 rpm. When operating as the only
propulsion device, the nominal speed is 800 rpm, equal to a propeller
speed of 84 rpm. This hybrid system minimizes the total installed
engine power (electrical and diesel) and provides a propulsion
system that is efficient over a mission profile that includes
extensive high-load and low-load operations including anchor-handling
and rig-towing, a transit speed of 15 knots, and precise dynamic
positioning.
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