By Jason Deign
Battery-based microgrids are helping the shipping industry go through a quiet electric-power revolution, said an expert at the 5th Microgrid Global Innovation Forum last week.
Going from combustion engines to hybrid systems to fully electric systems, “what’s happening in ships is like in cars,” said Dr Josep Guerrero, a microgrid professor at Aalborg University’s Department of Energy Technology.
The move to vessel electrification is being driven by a desire for higher efficiencies, he said, which is particularly useful for delivering new shipboard features such as dynamic positioning.
This generates variable power demands of up to several megawatts in a few seconds, which energy storage systems can meet exactly.
Traditional diesel engines, on the other hand, waste a lot of energy by providing a flat power output just to meet occasional peaks in demand.
Shipboard power systems
Vessel electrification requires a re-thinking of how shipboard power systems work, though. In traditional vessels, the electrical and propulsion systems are completely segregated.
In hybrids, an AC electrical system is integrated into the propulsion setup, while in all-electric vessels the whole arrangement is based on DC.
The move to DC-only systems can help cut vessel electrification costs, Guerrero said, by eliminating the need for costly AC-DC converters.
Configuring these systems as microgrids makes sense, he said, because they ideally need to be connected to the grid when at port and then islanded when sailing.
Making the transition to a fully electric configuration is not easy, though. Electric vessels gain in complexity because of the need for multiple systems to maintain stability in the event of a failure.
Current electric vessel designs
Current electric vessel designs, said Guerrero, essentially contain four separate microgrids, each serving a different set of motors. “The complexity increases a lot,” said Guerrero.
Adding to this is the fact that electric vessels may end up using a variety of energy storage systems. While batteries have been the mainstay of prototypes to date, there is also potential to use supercapacitors, flywheels or fuel cells.
It is perhaps too early to say which of these will prove most effective in a shipboard setting. To date, only a small number of vessels have gone fully electric, and because of range concerns these are mostly ferries.
In May, the French battery maker Leclanché looked to capitalise on this emerging market with an off-the-shelf, modular lithium-ion battery system.
The Leclanché Marine Rack System was approved by DNV-GL, the international certification agency, and is due to first see action aboard the world’s largest 100% electric ferry, by battery capacity.
E-ferry to be launched in late 2017
“The E-ferry will be launched in late 2017 sailing between the island [of] Ærø and the mainland,” said Leclanché in a press release.
“The emission-free, passenger and car ferry will be able to sail a record 60 nautical miles (110 km) on a single charge.”
In Scandinavia, there is potential to convert almost 200 ferry routes to electric within the next decade, Leclanché said; Europe-wide, more than 1,000 ferries could be converted.
“The Leclanché MRS could also be used in other marine applications including hybridisation and peak shaving of auxiliary loads of cargo vessels and cruise ships,” said the battery maker.
It remains to be seen whether marine propulsion is on the cusp of an electric vehicle-style boom in electrification, though.
Electric propulsion systems for vessels
Moves to develop electric propulsion systems for vessels have been around for some time, seemingly without making much of a dent on the shipping industry.
One notable exception might be in military vessels: Leonardo DRS, a US-based defence contractor, has posted several energy-storage related contract wins over the years.
In April, for instance, the Arlington, Virginia-headquartered firm announced it had won a contract by Eastern Shipbuilding to provide hybrid electric drive systems for the US Coast Guard’s new fleet of Offshore Patrol Cutters.
And last year the company, then named DRS Technologies, delivered a hybrid electric drive system for the Korean Navy’s FFX Batch II future multipurpose frigate.
The first of many remarkable systems
“This is the first of many of these remarkable systems we hope to provide to South Korea in support of their naval programs,” said Roger Sexauer, DRS Maritime and Combat Support Systems Group president, in a press note.
According to Aalborg University’s maritime microgrids web page, “all-electric ships and next-generation ports with shore-side power supply systems have been recognised as the main trend of future maritime and related industries.”
However, it says: “Since these activities are in their early stages, a lot of work need [sic] to be done in terms of proof of concept, standardisation and demonstration.”
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