Gas-powered VLCC on the horizon?
(Dec 9 2010)
More than half the vessels ordered from 2020 could be powered by natural gas, a
leading class society forecast.
DNV CEO Henrik Madsen said: "I am convinced that gas will become the dominant
fuel for merchant ships. By 2020, the majority of owners will order ships that
can operate on liquefied natural gas (LNG). As a leading class society, DNV has
an important role to play in finding more environmentally friendly solutions
for the shipping industry."
He was speaking at the launch of an environmentally friendly VLCC design
powered by LNG. The conceptual design project Triality has a hull shape
that removes the need for ballast water, thus eliminating ballast water
treatment systems, will almost eliminate local air pollution and will also
recover hundreds of tonnes of cargo vapours (VOCs) per voyage, he claimed.
Triality has been developed through a DNV innovation project. As its name
indicates, DNV said that it fulfils three main goals: It is environmentally
superior to a conventional crude oil tanker; its new solutions are feasible and
based on well known technology and it is financially attractive compared to
conventional crude oil tankers operating on heavy fuel oil.
DNV compared its concept with a conventional VLCC. Both ships will have the
same operational range and can operate in the normal spot market.
Compared to the traditional VLCC, the class society claimed that the Triality
VLCC will:
- Emit 34% less CO2.
- Eliminate entirely the need for ballast water.
- Eliminate entirely the venting of VOCs.
- Use 25% less energy.
Less harm will also be caused to the health of people living close to busy
shipping routes and ports as NOx emissions will be reduced by more than 80%,
while emissions of SOx and particulate matter (PM) will fall by as much as 95%.
The new concept tanker has two high pressure dual fuel slow speed main engines
fuelled by LNG, with marine gas oil as pilot fuel. The next phase of the
Triality concept development will review the use of dual-fuel medium speed
engines and pure gas engines, DNV said.
Two IMO type C pressure tanks capable of holding 13,500 cu m LNG - enough for
25,000 nautical miles of operation - are located on the deck in front of the
superstructure. The generators are dual fuel (LNG and marine gas oil) while the
auxiliary boilers producing steam for the cargo oil pumps operate on recovered
VOCs.
A traditional tanker on a ballast voyage needs ballast water to obtain full
propeller immersion and sufficient forward draft to avoid bottom slamming. The
new V-shaped hull form and cargo tank arrangements completely eliminate the
need for ballast water in the VLCC version. There will also be much less need
for ballast water on other kinds of crude oil tankers, such as Suezmax, Aframax
and smaller vessels.
The new hull shape results in a reduced wetted surface on a round trip and has
a lower block coefficient and thus a more energy efficient hull, DNV claimed.
A VLCC in ballast will normally carry between 80,000 and 100,000 tonnes of
seawater containing organisms that can cause damage when released into foreign
ecosystems. In addition, a lot of fuel is needed just to transport this extra
water. And finally, the initial coating and later maintenance of ballast tanks
during operations are among a shipowner's main concerns, DNV said.
The Triality VLCC can collect and liquefy more than 500 tonnes of VOCs during
one single round trip. These liquefied petroleum gases will then be stored in
deck tanks and up to 50% will be used as fuel for the boilers during cargo
discharge, while the rest can be returned to the cargo tanks, or delivered to
shore during oil cargo discharge.
When it comes to the additional cost of building a vessel such as the Triality
and the reduced cost of operating it, Madsen's conclusion was clear: "It is
possible to develop an environmentally superior ship and be profitable at the
same time. Our best estimate is an additional capital expenditure of 10-15% for
a Triality VLCC newbuilding compared to a traditional VLCC. Even with this
extra cost included, we estimate a reduced life cycle cost equal to 25% of the
newbuilding cost for a traditional VLCC.
"Triality is a concept vessel and a shipbuilder will need to prepare a detailed
design before the first Triality crude oil tanker can be constructed. The
Triality concept is based on well known and proven components and systems, so
in principle a Triality crude oil tanker introducing all or some of the
innovative elements in the concept can be designed today. I am convinced that
the Triality concept will create great interest among shipbuilders and crude
oil tanker operators, so that the first Triality crude oil tanker will leave a
shipyard before the end of 2014," Madsen said.
He also said a few shipowners and at least three South Korean shipyards, plus
MAN Diesel had already looked at the concept with interest.
====== fm tanker operator ===========
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