Harvesting power for a fitful lady

Running simulations on a computer is one thing, getting your hands on real-life data is another. When the two matched, in the case of the Viking Lady, Wärtsilä could confirm that it had cut yearly fuel expenditure for its green-minded client Eidesvik by 15 percent.

About three years ago Wärtsilä announced that it would fit a hybrid system on the off-shore supply vessel the Viking Lady, which shuttles back and forth in the North Sea and Barents Sea. The technology was in essence the same as the hybrid cars loved by green-minded Hollywood celebrities like Ashton Kutcher. Keep the engine load from dipping and reroute the surplus to charge a battery, which in turn can fill in when needed.

But transplanting and refining such technology for the off-shore industry had its own challenges, and chief among them was developing new classification rules.

“Because we brought on board new technology, which is quite different from traditional engines, there was a need to establish new rules,” explains Norway-based Ingve Sørfonn, Technical Director, Electrical & Automation, Research, Wärtsilä Ship Power, about the co-operation with classification society DNV and Viking Lady owners Eidesvik.

“It’s been a long process but during the project new rules have been established, including safety procedures.”

The 92-metre platform supply vessel, which runs on four LNG-powered Wärtsilä 32DF dual-fuel engines, was a perfect case study, because the Viking Lady does different things all the time. To anthropomorphize a bit, she’s fitful.

“Sometimes it’s sitting out on the field, then it’s dynamic positioning operations, sometimes it’s in transit, then it’s in harbour,” notes Sørfonn of the different tasks that will see engine load swing from 80 percent down to as low as 10 percent. “This vessel has a very variable operation profile so the potential for fuel saving is huge. They’re good objects to install these hybrid systems on.”

In broad strokes, the Viking Lady test installation can be run in several modes – the Island Mode, when the fuel cell and battery alone power the vessel; Transit Mode, when the vessel is en route and the battery reduces engine transient load variations: and finally, Dynamic Positioning Mode, when the battery is used as power redundancy, and allows the engine to run at its most efficient load.

“The next step is to use the battery as a power source in harbour. And that means you can stop the engines,” says Sørfonn.

In essence, a totally clean and remarkably silent ship would shuttle into port.

“Yes, but then we have to develop or extend the battery capacity and we also have to look at what kind of measure we can use to review the power consumption of the vessel,” he explains. “But the system as such is prepared for it.”

Before installing the hybrid system, Wärtsilä kept tab on the Viking Lady, measuring fuel use, emissions, and a wide range of other factors in order to collect control data. When the system was put in place last year, the hybrid solutions team simply kept on measuring. By the spring, when what was hopefully the most environmentally-sound vessel on the planet had been in operation with its new hybrid system for a year, the team got ready to check if fact was better, or at least as good, as fiction. Had their predictions come true?

“The project team did a lot of simulations before we tested it and they were more or less in line with the measurements, so we were quite happy that they fit so well,” Sørfonn recalls.

The new system has cut the Viking Lady’s fuel needs by 15 percent, which means the investment in the new hybrid system will pay for itself within a few years. It represents cost-cutting potential for many different potential clients.

“The payback time is about four years on a new vessel and maybe five to six years on a retrofit,” says Sørfonn.

And saving money on fuel is just one of the benefits.

”The hybrid systems tend to balance the whole system to be more stable and the dynamics will be less for the engine,” says Sørfonn, explaining that maintenance costs should reduce as a result.

The team found that nitrogen oxide (NOX) emissions were down by 25 percent. Such reductions mean that ship operators have to set aside less cash for NOXtax, another money-saver. And all in all, the Viking Lady in one year may save the atmosphere from around 1000 tonnes of carbon dioxide (CO2).

What makes this particular vessel all the more remarkable is that she was already a very clean lady. It runs on LNG and has an oil recovery capacity of 3500 m3, which meant the Viking Lady complies with classification notation Clean Design. The Viking Lady was also the very first merchant ship that used a fuel cell in its propulsion system, generating some 330 KW.

Offshore supply vessels might be the perfect fit for the hybrid system, but they are not the only would-be customers out there at sea.

“It is suitable for all vessels with a variable operational profile; ferries, fishing vessels, coastal vessels,” says Sørfonn. But it doesn’t stop there. He also mentions drilling units and special operations like crane operations.

“We have some interesting ideas how to use this on, for instance, drilling platforms which in a way have the same type of dynamics and also the same type of redundancy, where you always need to have backup power for your operation,” he explains.

“There are different processes where you can harvest power, where it’s a good investment to use this kind of energy storage.”

 

Twentyfour7. Speaks with Inge Rune Kallevåg, Development Manager at Eidesvik Offshore, which owns the Viking Lady.

What makes the Viking Lady so special?

"The Viking Lady has been part of the FellowSHIP cooperation between Det Norske Veritas (DNV) and Wärtsilä, which has used her in a research and development project. By using dual-fuel engines from Wärtsilä, you’re reducing CO2, NOX and particles.

She also has a fuel cell installed, which reduces the emission footprint of the vessel even more. The fuel cell’s advantages are that you gain a very high fuel efficiency, which again gives reduced emission.

And now she also has a battery pack."

Can you explain some of the benefits?

"Usually, the vessel has peaks in power requirement, especially in bad weather. The battery pack can take these peaks, resulting in much more stable load on the engines. In that way the engines will become more efficient and consumption and emissions will be reduced.

The captain has said the battery should be a part of all future energy systems on board. The battery also gives significant operational advantages, improving response time, and making the power plant even more stable during operations.

The crew, and especially the captain, is very satisfied with the new solutions."

What are other benefits?

"With the battery pack you get better utilization of the fuel cell and the engines, because you can store energy on the battery pack and use it whenever you want."

Can the Viking Lady run only on the Wärtsilä battery?

"The battery pack is not as big as the engine but you can use it. If you have for example a 500 kWh battery and the engine is 2,000 kW, then the battery can step in for an engine for 15 minutes.

But of course you can increase the battery size on future installations.

We hope and expect in the future to use the battery as a backup for engines. We can maybe run on one engine when we are alongside platforms. Then we can increase the load on the remaining engine and we get a much more efficient energy system. If anything goes wrong the battery can be the backup until you manage to start the standby engine.

In the future, the energy storage capacity of the batteries will probably increase. We have already seen that the battery functions very well. It will be the future solution for these vessels, until you take the ultimate step into renewable energy.

Then the battery will also open new possibilities that we haven’t seen before, because renewable energy can be stored on the battery system, which decreases the consumption of fossil fuels."

Has the work environment become less noisy?

“Not yet. We’ve had the hybrid battery system on board for a year but we need to increase the capacity in future installations to stay on batteries only.

Some years from now, we’ll be able to stay on battery when we are alongside the quay. Which also has benefits for people living near the offshore bases and cities that we are using when staying alongside quay. We’ll have a completely silent ship when we shut down the engines and stay only on battery.”

Does the Viking Lady give you a competitive edge in the oil and gas industry?

“Already now, we’ve measured that fuel consumption has dropped by maybe 15 percent and we think we’ll come up to a 20 percent reduction. Our customers, who pay for the fuel, reduce their costs and we are also reducing our environmental footprint. Longer term, we expect this to give a competitive edge when negotiating future contracts."

© 2016 Wärtsilä