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DC system will raise ship efficiencies by up to 20%

27 May, 2011

ABB has developed a DC (direct current) electrical system for ships which, it claims, can cut the fuel consumption and emissions of low-voltage onboard power systems by up to 20%.

In conventional electrically-propelled vessels, several DC connections are made from the AC circuit to the thrusters and propulsion drives, which consume more than 80% of the electrical power. The new system connects all the DC links and distributes the power through one main DC circuit.

The ship`s engines no longer need to run at a fixed speed, but can be adjusted to optimise fuel consumption. The DC system also reduces the footprint of the onboard electrical equipment by up to 30% by eliminating the need for bulky transformers and main switchboards. This, in turn, leaves more space for passengers or cargo, and allows more flexibility in the positioning of components in the vessel.

In addition, the onboard DC system allows supplementary DC sources such as solar panels, fuel cells or batteries to be plugged directly into the ship`s electrical system, for further fuel savings.

“We are seeing a revival that is making DC the technology of choice for many power transmission solutions, battery storage and other energy supply applications,” explains Veli-Matti Reinikkala, head of ABB’s process automation division. “With an onboard DC solution, we can vary generator speed to optimise fuel consumption and improve a ship`s operational efficiency by up to 20%, compared with traditional AC-powered systems.

“This forward-thinking solution will help maximise the energy efficiency and power reliability of our customers` vessels,” he adds, “and prepare them for future operating challenges like more stringent environmental regulations, higher fuel prices and the availability of new fuel sources.”

The new DC system is based on proven products such as AC generators, inverter modules and AC motors – but it eliminates the main AC switchgear and transformers.

♦ In another move that boosts its involvement in DC technologies, ABB has bought a controlling interest in US-based Validus DC Systems, which supplies DC infrastructure equipment for data centres. DC equipment has lower power conversion losses than AC systems in these applications, leading to 10–20% higher efficiencies. It is also less complex and needs less space, resulting in total savings on facility costs of up to 30%. Data centres can consume 100 times more electricity than similar-sized office buildings.

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