Danish ferry reinvents and puts a modern twist on ancient technology
If a journalist in 600 BC were to write about a new invention, the flywheel would be an obvious choice.
The principle is simple: A potter’s wheel and a watermill function better when a heavy, rotating wheel stores and distributes the energy.
Today, the technology has advanced and, with the help of magnets and electricity, flywheels can act as a kind of battery that can store kinetic energy.
WattsUp Power CEO: Martin Speiermann Manufactures flywheels for various purposes. One model is to be used to integrate solar energy into the electricity grid and has a capacity of 70 kWh. The second model has a capacity of 250 kWh and is to be used in industry; it comes in an onshore and offshore version. Source: WattsUpPower.com
Molslinjen can well imagine that the alternative battery technology could fully power a ship in the future. Therefore, the company has invested an unspecified amount of money in WattsUp Power, a company which specializes in flywheels.
“It has the potential to be something extraordinary if we make it work. And we would like to be part of that journey,” Molslinjen’s CEO Carsten Jensen says.
The project will start in the USA, where WattsUp Power will carry out some tests to see whether theory matches practice.
“The faster the wheels spin, the more energy we can get out of them—it’s an exponential curve. Potentially, we could store a much larger amount of energy in them than in an electric battery. So we have to test getting them up to faster revolutions,” Carsten Jensen says.
Once the entrepreneurial company has verified the prototypes, they will be tested on the Express 4 ship, where they will supply power for some of the ship’s functions. For example, the ventilation system, Carsten Jensen says.
In the long term, the plan is for a large enough number of flywheels to be able to power an entire ship, so that green power can be stored in the “mechanical batteries” instead of the familiar lithium batteries.
Greener than electric batteries
The modern flywheels differ from the old ones in being almost frictionless:
They are held up by permanent magnets instead of a shaft and rotate inside a vacuum container, so that there is virtually no friction.
In this way, they can spin for hours and store large amounts of energy that can be tapped again within a certain time frame.
And this suits Molslinjen well, according to Carsten Jensen, since their ships operate short, quick routes.
Flywheels have many advantages over electric batteries, he says.
“Batteries have a different lifespan of five to seven years at the moment, while a flywheel has a lifespan of 20 years or something like that. They also weigh less and are more environmentally friendly as they don’t require heavy metals and a lot of processing. And in terms of energy, the storage potential is greater than anything else we have seen.”
Expert: It can get really expensive
Flywheels have previously been seen as a means of propulsion: In the 50s and 60s, the so-called gyrobus functioned as public transport in a number of cities.
However, this technology has never fully powered a ship before. Nevertheless, Carsten Jensen is optimistic about the modern, frictionless version with magnets and a wheel made of optimized composite material.
“It’s an old, proven technology in a modern package,” as he says.
However, it is far from certain that the flywheels will actually be able to fully power a ship, says Nikolaj Zangenberg, innovation coordinator at the Danish Technological Institute who has previously collaborated with WattsUp Power in the development of flywheels.
“I actually think it’s a good investment. Because it’s a technology that has matured enough to be easily usable in some areas. They are, for example, suitable to use when braking to easily store some energy and then use it later.”
“It’s too early to say whether they can be developed to the point where they can fully power a ship. In principle, it’s possible, but I would question whether there is a business case for it.”
Nikolaj Zangenberg explains that the modern magnetic flywheels are especially well developed for use in space and that NASA has obtained a model that can operate at 41,000 rotations per minute.
On Earth, things are different, because it must also be possible to build them at a reasonable price without compromising either safety or reliability. Therefore, the final solution for Molslinjen may end up being expensive, Zangenberg says.
“After all, there are also alternative means of propulsion which are energy efficient. My guess would be that it will in the end be a hybrid solution in combination with, for example, e-fuels or perhaps also electric batteries, where the flywheel has a certain role. Whether the flywheel will be able to stand alone, I don’t know.”
Great optimism
Carsten Jensen admits that it has not yet been proven that it will work and that the technology to fully power a ship is not yet mature.
Still, he is optimistic.
“If our technical experts, who work with this in practice, didn’t have a justified belief that we could make this work, and if there wasn’t a business case, then we wouldn’t have invested.”
Molslinjen already invests in many different development projects, says Carsten Jensen, and flywheels are the latest addition to the list.
“It’s kind of like if AGF’s football coach had to spend time on going through all the opinions of both the experts and the naysayers—there would be no time left to score a goal.”
Molslinjen owns three high-speed ferries that sail between Sjællands Odde and Aarhus/Ebeltoft, and starting in the spring, a brand new fourth ferry will sail between Rønne and Ystad.
