Home' Work Boat World : October 2015 Contents Am I clean yet?
Cutting-edge developments affecting the work boat world. By ANDREW BAIRD.
The Bow Wave
Can a designer really trumpet a vessel as being “eco” because it
uses electric podded propulsion? A Russian oligarch wanting to
improve his green credentials demanded that his super yacht, or
perhaps mega yacht given the size of the thing, utilise electric
propulsion and have onboard waste treatment equipment.
The onboard treating of waste is certainly admirable but the use
of podded propulsion struck me as being nonsensical. Using diesel
engines to generate electricity and then using that electricity to
turn a pair of big screws must have significant inefficiencies. If this
set-up were in any way more efficient than direct drive I’m certain
that all vessels would have their engines in-line, and located low
and central in the hull to optimise weight distribution.
I was a bit unsure of the e-Kotug system developed by
XeroPoint Energy and Aspin Kemp and Associates, both of Canada,
which uses in-line electric motors along the main shafts such that
engines and/or propellers can be de-clutched. This allows one
engine to power two propellers or even use batteries to provide
power with no engines engaged.
I first heard of the concept at the International Tug and Salvage
show in 2012 and wasn’t skeptical for long as I soon had the
chance to speak with a tug captain who raved about the system.
The captain informed me that when departing the harbour to meet
an arriving vessel he would use one engine, but engage two
thrusters and, when combined with a large battery pack, found
that it easily reached operating speed. Upon meeting the ship, the
captain would start the remaining two engines and utilise three
thrusters. The escort into the harbour would be sufficient time for
the battery bank to recharge and the tug would be good to go
again for another escort.
Electric propulsion for larger workboats
So it seems that electric propulsion may have a place amongst
workboats, but what about something larger? In this column last
month I wrote about new developments in wind power for fixed,
terrestrial power generation, but what opportunities are there for
ships to give up the black gold? A bulk carrier or VLCC plastered in
solar cells isn’t likely to be moving anywhere in a hurry. Add to
this the irony of a vessel carrying thousands of tonnes of oil or coal
attempting to be “green” and you soon reach the conclusion that
it would be cheaper to just buy lots of green paint.
Fuel cells are more than a century old now but first gained fame
when they were launched into space to power the US space shuttle
whilst in orbit. Rather than burning a fuel to produce expanding
gas, a-la internal combustion, a fuel cell is able to react a fuel with
oxygen in a manner similar to a battery so that an electrical
current is generated within the unit, without needing to go via the
mechanical generation step.
Fuel cells are able to convert fuel to electricity with a much
higher efficiency than internal combustion (>50 percent compared
to ~35 percent) but a few problems still exist for shipboard use:
• You have to convert electrical energy back to mechanical
energy via a motor; however the added efficiency of the fuel cell
should exceed the losses described in the super yacht example.
• You won’t be using bunker oil in a fuel cell. Different models of
fuel cells use different fuels but the most appropriate for maritime
use will be the ones that can use CH4, more commonly known as
methane, or natural gas.
• The size of fuel cells will require a redesign of ships. A multi-
megawatt installation will probably be installed low in the hull
along the keel to place the weight low down. Being able to
distribute parts of the fuel cell system around the ship will
probably be a boon, but the sheer volume and mass of the
installation will, with current technology, exceed the volume and
mass of an engine and gearbox. Bloom Energy, a manufacturer of
systems for data centres lists a 250kW system as weighing in at
17.6 tonnes. A 250kW genset from Kohler weighs 2.4 tonnes.
• The cost is just too high right now. At between US$7-8/W of
installed power, a 14,000TEU container ship with a 72,000kW
engine will be spending US$504-576 million, just for the fuel
cells! Considering that Maersk recently ordered nine 14,000TEU
vessels for US$1.1 billion, it is doubtful that shipping companies
will be rushing to switch their power supply anytime soon.
Various organisations including eBay, FedEx and NASA are
using fuel cells to provide power to their data-centres and it’s likely
that people are paying close attention to how well that works out
for them. Perhaps if Google or Apple were to enter the LNG
shipping industry we may see a bit more urgency in the
development and implementation of large fuel cell systems.
That being said, is it time to rethink nuclear? Perhaps a topic for
Any comments, or perhaps you’ve come across something interesting?
Feel free to conta ct me at the. bow.wave@gmail. co m
The e-Kotug system uses in-line electric motors along the main shafts.
A solid oxide fuel cell
18 October 2015 WORK BOAT WORLD
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