Batteries beyond short-sea shipping

A 14.4% saving in fuel consumption on Scandlines' 'Prinsesse Benedikte' highlights the benefits of batteries in the ro-pax sector A 14.4% saving in fuel consumption on Scandlines' 'Prinsesse Benedikte' highlights the benefits of batteries in the ro-pax sector

They are finding followers among ferry, offshore and ro-pax vessels, but what will it take for batteries to breakthrough to the deep sea shipping market? Willie Wagen, global vice president of sales and marketing and managing director Europe at Corvus, argues that we are closer than many observers believe.

Conventional wisdom holds that batteries work best on ships with a wide operating profile. That way, batteries can be used alongside engines operating at a relatively constant load to provide power when demand is high, charging when energy requirements fall below the engine output.

For that reason, many offshore support vessels are now adopting battery systems: dynamic positioning, towing, lifting and rapid transit operations provide the opportunity for batteries to shave the peaks in power, reducing fuel consumption and engine maintenance.

This is also the reason why deep-sea ships such as bulkers and tankers have yet to deploy batteries in any great number. Such vessels tend to move at a more constant speed, with few peaks to be shave. There are some outliers, including a handful of recently built Baltic bulk carriers and product tankers. But the consensus remains that batteries offer limited savings on deep-sea ships.

At least one supplier of battery systems believes that this viewpoint is worth challenging. According to Willie Wagen of battery systems provider Corvus, there could be significant economies to be found on bigger ships. The company has yet to install a system on a deep-sea going merchant vessel – although Wagen reveals it is close to such a test with one of the world’s biggest shipowners – but initial results from an OSV during steaming are encouraging.

“We believe there is a case for peak shaving on ocean-going vessels,” says Wagen. “The OSV suggests that the savings could be even bigger than we imagined, up to 2%. On larger vessels that adds up quickly.”

According to Wagen, it is the business model of deep-sea merchant ship owners rather than any technical constraint that is preventing batteries’ use on such ships.

“There is no technological obstacle to deploying batteries in this way on ocean-going ships,” he confirms. “The challenge really is who pays for the fuel. If the fuel and maintenance come from the same pocket, it makes clear sense. But we need some first movers.”

The growth is coming segment by segment, Wagen explains. First it was Norwegian ferries, so often a test bed for innovative power and propulsion technologies, but hardly representative of the wide marine market. Then it was offshore vessels - not all of them Norwegian. Wagen notes that the company is supplying batteries for a Seacor vessel destined for the Gulf of Mexico. The savings for offshore vessels can be huge, he says - around a 30% cut in maintenance costs and a similar percentage in fuel savings.

ROPAX PIPELINE

The latest growth segment is ro-pax vessels. Wagen reports that Corvus has a pipeline of around 20 such vessels. Having fulfilled just two orders for ro-pax in the past, that represents a sizeable step up in interest.

The increased activity in the ro-pax sector is at least partly attributable to pioneering work by Scandlines, which now has six ro-pax ships featuring energy storage systems on its routes between Denmark and Germany. Wagen notes the financial benefits that accrued to Scandlines as a result of its projects.

“The first two vessels had large subsidies attached to them,” said Wagen. “The second pair had smaller subsidies, but still made sense financially. And the last pair had no subsidies at all. But Scandlines made the fuel and maintenance calculations and went ahead anyway. When other owners hear about that kind of decision, it causes a stir.”

The new Scandline hybrid diesel/battery propulsion systems allow the diesel generators to operate more frequently in the sweet spot of high engine efficiency. Vessels run with one diesel genset at 85-90% load at sea and in ports. While at port, excess energy generated is used to charge the batteries. A second diesel genset may also be used to charge the batteries as needed. At sea, the battery provides the power for load-balancing to allow the diesel generators to operate at a relatively consistent base load.

Analysis from Scandlines’ Prinsesse Benedikte before and after the installation of a Corvus Energy Storage System shows a 14.4% reduction in fuel consumption, representing a significant portion of the 40% reduction that Scandlines has achieved in almost two decades of fuel efficiency efforts on the Puttgarden-Rødby ferries.

The 14.4% reduction in fuel consumption equates to an annual saving of 1,200kg of heavy fuel oil. Further savings, including maintenance and lube oil expenses, mean that total annual savings from hybridisation on the ferries are approximated at €605.000 (US$710,000 USD) for each ferry.

Despite such dramatic savings shown in other segments, the global tramping fleet is not yet ready to embrace energy storage wholeheartedly. But as sector after sector sees the advantages of hybridisation, as battery technology improves and as suppliers build their impressive reference lists, it is unlikely to be long before progressive owners take an interest.

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