The water around the ferry Prins­esse Benedikte shim­mers metallic blue as she leaves the harbor in Puttgarden on the German island of Fehmarn and heads for the Danish port of Rødby. What very few passen­gers know: They’re on a hybrid ferry that gets its energy from both diesel gener­a­tors and batteries. One who knows that very well is Carsten Johansen, who is standing on the ship’s bridge and taking a close look at the instru­ments instead of enjoying the sun over the Fehmarn Belt.

Johansen, who is affec­tion­ately called the “energy minister” by his coworkers, is chief engi­neer at Scan­d­lines, where he is steering the helm more and more toward effi­ciency. “Sustain­ability isn’t just part of my job, nowa­days it also dictates my personal lifestyle. That’s inevitable when you concen­trate on this subject so much.” At home, the 57-year-old there­fore replaced an old oil fired heating system with an energy effi­cient heat pump, installed solar panels on the roof and changed lighting to low energy LED lamps.

Since 2003, Johansen’s daily work has involved bringing the ferries between Puttgarden and Rødby ever closer to the goal of zero emis­sions. Back then he replaced the first of five diesel gener­a­tors with an elec­tric energy storage system. It quickly became clear to him that it would not be enough to replace the power from the ship’s diesel gener­a­tors bit by bit with battery power. The ship also needed to save elec­tricity in order to limit the number and cost of the expen­sive batteries. So Scan­d­lines replaced water pumps, converted to LED lighting, and had its captains trained in energy-saving sailing tech­niques. In 2015, the energy minister took on the ship’s climate control system. “It used an enor­mous amount of power, so we hoped we could save a lot of energy there.”

Where one big AC fan was working before the retrofit…  (Photo: Henrik Petit)

…now four smaller EC fans are helping to exchange the air. (Photo: Henrik Petit)

Fresh air for the car deck

That’s how Niels Knokgård and Torben Kirk­holt came to take a short voyage to Germany and back again. Johansen had invited the tech­nical sales repre­sen­ta­tive from ebm-papst Denmark and his managing director to an on-site visit. During the short trip, in addi­tion to exam­ining the venti­lation system in the passenger area, the two also took a close look at the system in the 12,000 cubic meter car deck, where eight large AC fans were respon­sible for air circu­la­tion. During the ferry ride, six fans brought fresh air into the closed deck from the outside while two others conveyed used air to the outside.

In port, two fans took a break while the other six aired out the ship. Since the two modes required the air to be trans­ported in opposing direc­tions, some fans had to run in reverse. “That’s a very inef­fi­cient way to operate a fan,” Knokgård pointed out to the energy minister as the three men stood in front of the AC giant. “Yes, that’s precisely the problem,” sighed the latter. “If only we could turn the fans around.” A sentence Knokgård and Kirk­holt couldn’t forget.

Not afraid to sully their hands: Carsten Johansen, Chief Engi­neer at Scan­d­lines (in the middle) and Torben Kirk­holt and Niels Knokgård from ebm-papst. (Photo: Henrik Petit)

Carsten Johansen on the car deck of the hybrid ferry. (Photo: Henrik Petit)

The venti­lation system of the car deck can now be controlled centrally and precisely. (Photo: Henrik Petit)

On the Puttgarden-Rødby route, five ferries trans­port 1.5 million cars, 400,000 trucks and 12,000 rail­road cars annu­ally. (Photo: Henrik Petit)

Pivoting fans

“It was obvious that we can’t easily turn a fan around,” says Knokgård. After puzzling over the problem a bit, he and his colleagues came up with the idea that they didn’t have to turn the indi­vidual fans at all. Together they devel­oped a pivoting square metal plate on which four fans are mounted so that they can operate in both direc­tions without running in reverse. “Since no modi­fi­ca­tions to the ship are allowed, there wasn’t much room for us to work with. That means the fans can’t be pivoted by exactly 180 degrees,” explains Knokgård, but the idea works anyway.

But with this new concept, ideas for increased effi­ciency were far from exhausted. Replace­ment of the AC fans with fans using EC tech­nology seemed an obvious next step. The latter can be smoothly adjusted to the output that is actu­ally required, so they can be oper­ated very econom­i­cally. To generate even more pres­sure in the same amount of space, Knokgård suggested using FanGrids with four smaller fans instead of large single fans, increasing the area over which the air is conveyed and further improving the air exchange on the car deck. When Johansen heard about the idea at the next meeting, he was enthu­si­astic and commis­sioned a tech­ni­cian to install a test unit with a pivoting metal plate and four EC HyBlade fans.

Explo­sion protec­tion included

A glance at the car deck shows that not only globe-trot­ting tourists and seasoned commuters use the connec­tion between Denmark and Germany, but also a lot of truck drivers. Some of the trucks trans­port flam­mable substances, and that places another impor­tant demand on the fans. “Of course it was a big plus for us that ebm-papst is the only manu­fac­turer that offers EC fans in an explo­sion-proof ATEX design,” says Johansen. After refit­ting the test unit, the chief engi­neer made some compar­a­tive measure­ments and found that the savings actu­ally exceeded the expected values.

The payback period for the change from AC to EC tech­nology is just one year.
Carsten Johansen, Chief Engi­neer at Scan­d­lines

A finding with conse­quences: During the next routine main­te­nance, Johansen had another three FanGrids installed in the ferries while they were in the docks. And Scan­d­lines also switched to EC fans for the venti­lation system in the passenger area. The results are very impres­sive. Thanks to the venti­lation changes, Scan­d­lines now achieves total energy savings of two million kilo­watt-hours per year and ship; the payback period for the project is a little over one year. “That’s a giant leap for us,” says Johansen. Following up on the successful pilot project, Scan­d­lines will imple­ment the solu­tion on the other three ferries that ply the route between Puttgarden and Rødby as well.

Mean­while, the Prins­esse Benedikte has docked in Rødby. Johansen is stretching his legs on the pier as an unending stream of cars and trucks flows out of the ship. “Our goal is to achieve emis­sion-free and fully elec­tric-powered travel within the next few years,” he says. “If all goes well, we might already get there by 2019.” The energy minister already has an idea for the next step. After all, the ferry has another car deck…