Molslinjen A/S is investing in a potential game-changer. The company has bought into Wattsup Power A/S, which produces so-called flywheels that, in theory, can fill up fast ferry entirely with green energy.

A flywheel is a rotor built into a cylinder, where it floats freely in a magnetic field. Green electricity can spin the rotor at such high speeds that the green energy can be tapped. With enough flywheels they can power a ferry, acting as a green, mechanical battery without the problematic metals used in traditional batteries.

The technology still needs to mature and then developed for Molslinjen's fast ferries.

The first step towards approval will be an imminent test in the USA to verify if the theoretical calculations hold in practice. Following that, the technology will be installed on Express 4, where the flywheels will generate power for some of the ship's systems.