Onboard DC Power Grids

By Keith Henderson at March 01, 2012 07:41
Filed Under: Company News

Norwegian ship owner Myklebusthaug Management has placed an order with ABB for the supply of what is claimed to be the first ever direct current (DC) power grid on board a ship. The  5,000 ton multi-purpose oil field supply and construction vessel has a LOA of 305 ft (93 m) and is due for delivery in the first quarter of 2013.

Caption: The Onboard DC Grid provides a highly efficient power distribution system that allows a wide range of sea- faring vessels to cut their fuel consumption as well as incorporate DC energy sources such as solar panels and fuel cells.
Image credit: ABB

There is nothing new about using electric propulsion of ships; most are AC systems. What is new is that modern technology is able to ensure that the protection and control of a DC grid system is able to be maintained with high reliability.

The problem with existing AC systems is that it lacks flexibility, requiring engines and generators to run at a fixed speed to maintain the constant frequency. Startup is longer to allow time for speed synchronisation to stabilize. Fuel consumption is consequently higher and the AC system is not directly compatible with some future energy sources.

Using a DC grid offers several advantages including lower installed power thereby reducing fuel bills while producing up to 20 per cent less emissions. The reduction of the space and a weight of transformers leaves more available volume for a larger payload. The total weight saving of electrical equipment alone can be as high as 30 per cent.

Building a new ship is a long term investment typically a period of 25-30 years. There are many new higher efficiency energy source options coming in the future such as solar panels, fuel cells, batteries etc. and when they become available, will be easy to connect and integrate into an onboard DC grid

Depending on the ship’s usage profile, ABB claims that up to 20% fuel savings can be achieved using a DC grid. Looking to the future, their projection is that by the year 2020, about 20 per cent of ships will be powered by electric propulsion systems,  of which DC grids will play a significant part.

The ship classification society DNV has been working with ABB to evaluate the protection function of DC grid as applied to IMO regulations.


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