by Doug Woodyard
electrics
New DC power system earns pilot project
vessel booked by the Norwegian owner Myklebusthaug
A Management from
debut delivery for ABB’s innovative Onboard DC Grid concept, launched last May, will serve a platform supply
the
domestic Kleven yard. ABB will also supply all power, propulsion and automation systems for the 93m-long/4,800gt MT 6015-type multipurpose supply and construction vessel, due for handover in first-quarter 2013. “Myklebusthaug was keen to build an innovative vessel that was ready to accept future
energy-saving solutions, including
energy storage and renewable energy sources,” says Heikki Soljama, head of ABB’s marine and cranes business unit. “The vessel also had to be very fuel efficient, with low emissions. The owner became convinced that our Onboard DC Grid was the best option to achieve these goals.” The Onboard DC Grid concept facilitates
a high efficiency power distribution and electric propulsion system suitable for diverse applications, including offshore support vessels, tugs, ferries, yachts and cargo tonnage, featuring low voltage systems up to 20MW. Such a system retains the proven elements of electrical propulsion systems, including AC generators and inverter modules, but eliminates the main AC switchboards and propulsion transformers.
A more flexible power and propulsion system results, claims ABB, enabling equipment weight savings of up to 30 per cent and fuel consumption and emissions reductions up to 20 per cent. A key merit cited for Onboard DC Grid is that the engines no longer have to run at a fixed speed, allowing them to be adjusted to optimise fuel consumption: a ship’s operational efficiency can thereby be improved by up to 10 per cent over traditional AC-powered systems, ABB reports. This
facility is particularly beneficial for switchboard Key to symbols G G
AC system: transformers variable frequency inverter
DC grid with no switchboard, no transformers
AC consumers AC consumers M Comparison of AC and DC power transmission systems
offshore vessels operating in dynamic positioning (DP) mode, where average electric thruster loads are normally low but, for safety reasons, the number of engines running is high. In demanding DP operations, the electrical
plant is generally operated in a split mode so that the vessel can keep its position even if there is a failure in one side of the plant. Onboard DC Grid also reduces the footprint of the electrical machinery installed by eliminating the need for bulky transformers and main switchboards. More space can thus be created for passengers or cargo and greater flexibility provided in positioning system components. Additionally, says ABB, its new power generation and supply solution enables supplementary DC energy sources, such as solar panels, fuel cells batteries or super-capacitors, to be plugged directly into the ship’s DC electrical systems, providing scope for further fuel savings. Hybrid power systems will become more important in future ship designs, with batteries or other energy storage devices being tapped to provide short bursts of higher power when required.
Significant interest in the new DC system is reported by ABB and projects for other ship
types are anticipated soon. A fuel-efficient 2,000 TEU feeder container ship design concept from Knud E Hansen and ABB specifies the system to enable optimum running of engines at any ship speed from two to 21 knots. • ABB’s Onboard DC Grid solution was developed to mount a revival in direct current power solutions, exploiting modern technology to overcome the limitations of earlier DC systems and replace traditional AC power distribution systems. The inefficiencies inherent in AC systems are reportedly avoided to yield lower fuel consumption and emissions propelled
tonnage ranging
for electrically- from
offshore
vessels to ferries and container ships. In traditional electric propulsion configurations, multiple DC connections are made from the AC circuit to thrusters and propulsion drives, which account
for more
than 80 per cent of power consumption. ABB’s new DC concept – initially for vessels with low voltage power systems – connects directly to all DC links and distributes power through a single 1,000V DC circuit, which eliminates the need for large AC switchboards and heavy duty transformers. MP
Stadt system will serve Samsung LNG carriers
Electrical propulsion based on the Stadt Stascho No-Loss Drive system will be adopted by Samsung Heavy Industries for LNG carrier projects at the Korean yard. The patented fifth-generation system from the Norwegian specialist
www.mpropulsion.com
Stadt covers power applications from 100kW to 100MW and voltages from 220V to 15kV.
No large power transformers are incorporated in a compact and robust system,
yielding savings in space, weight and losses for installations.
Another benefit cited is the elimination of disturbances such as electromagnetic interference, reduced acoustic noise and vibrations (of particular value in military applications).
Marine Propulsion I February/March 2012 I 77 M rectifier
circuit breaker DC system:
variable frequency inverter rectifier
fixed frequency inverter Isolator
DC power distribution
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