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.