FINLAND ABB takes a slice of LNG
ELECTRIC propulsion for LNG carriers offers benefits in terms of overall efficiency, as well as fuel savings, according to ABB.
A
BB's power and propulsion solutions are well suited to safety and reliability
requirements for the high availability demands of LNG carriers. In 2002, ABB delivered the first 6.6kV
medium voltage power solution for the cargo handling plant for three BP LNG carriers built at Samsung Heavy Industries in 2002-2003. However, the true breakthrough came in
2005 when ABB was the first to supply electric propulsion systems for the two 153,500m3
LNG
carriers ordered from Chantiers de l’Atlantique, one apiece for Gaz de France (Provalys) and NYK Line/Gaz de France (Gaselys). These ships were the first large LNG carriers to take advantage of electric propulsion with a dual- fuel diesel electric (DFDE) engine concept. Also in 2005, Samsung Heavy Industries ordered electric power and propulsion systems for nine 153,200m3
LNG carriers, of which
six will be delivered to A.P. Møller and three to “K” Line. The ships are being built by Samsung for delivery in 2008. Each ship will receive 2 x 6.6kV medium voltage switchboards (main and cargo), four generators, 4 x three- winding propulsion transformers, 2 x ACS 6000 frequency converters, 2 x 12,650kW medium
speed synchronous propulsion motors, MV distribution transformers, and a propulsion control system. In 2006, ABB received orders for diesel electric propulsion systems for two 162,400m3
LNG
carriers being built for BW Gas ASA at Daewoo Shipbuilding and Marine Engineering (DSME) in South Korea, with first vessel’s delivery due by the end of 2008. These will be the first LNG carriers at DSME to be equipped with an electric propulsion system. Also, in 2006, the company received orders for diesel electric propulsion systems for two 157,000m3
LNG carriers being built for MISC
at Mitsubishi Heavy Industries' Nagasaki shipyard, with the first vessel due delivery in December 2008. These will be the first LNG carriers in Japan to be equipped with an electric propulsion system. High voltage switchboards and transformers have
also been ordered for five LNG carriers for China LNG at Hudong-Zhonghua Shipbuilding Co. ABB can thus claim to be the leading supplier for
electrical power- and propulsion systems for LNG carriers, with systems for some 30 LNG carriers already delivered and nearly 30 on order. Dual-fuel diesel engines producing electricity for
the ship's propulsion, pumps and other consumers is becoming a preferred solution for many LNG carrier owners. Compared to steam turbines, the propulsion efficiency is significantly higher, some 48% according to ABB. Less fuel from the cargo is thus needed, and significant savings
can be achieved. With diesel-electric machinery the efficiency when running at lower power is easily optimised, and high torque and operational flexibility is achieved over the entire rpm rate. Also, when comparing dual-fuel electric propulsion (DFEP) with slow speed diesel propulsion with a reliquifaction plant (SSDR), the overall efficiency is better for the DFEP according to ABB. This is owing to the fact that the reliquifaction plant has to be run simultaneously with the propulsion plant. With DFEP there are less harmful emissions than with steam- and slow speed diesel propulsion resulting in better environmental friendliness. ABB uses ACS 6000 Marine Drives-type
variable speed drives for the electric propulsion systems. They use DTC - direct torque control - motor control technology for accurate and smooth speed and torque control. This results in minimum torque ripple at the propeller shaft and low vibration and noise levels. According to ABB, another benefit of the ABB 24-pulse drive solution is that the harmonic distortion from the propulsion system is kept within classification limits without use of harmonic filters in the main switchboards. The ACS 6000 drive is available in four base
modules of 3, 5, 7 and 9 MVA. With four sizes of inverter modules available, the optimum configuration for a specific application can be reached by combining the modules with minimum engineering effort. By linking modules in parallel, the power can be increased to 27MVA.
THE NAVAL ARCHITECT FEBRUARY 2007
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