Fossil fuel tankers that transport oil, gas and coal across the seas play an important part in the global energy mix, but one Japanese startup is eyeing a future where these types of vessels carry a much cleaner load. PowerX's Power ARK vessels are designed to carry renewable energy from wind turbines located far off-shore back to dry land, allowing them to make the most of stronger gusts and opening up new opportunities for their installation.

PowerX's grand ambition is to accelerate the adoption of off-shore wind energy by enabling it to be shipped between any two locations on Earth. Off-shore wind farms are starting to play a bigger and bigger role in the provision of renewable energy, but there are limitations in terms of where they can be installed, as the turbines need to be anchored to the seabed.

GE's Haliade-X, for example, the world's most powerful offshore wind turbine, can only operate at depths of up to 60 m (200 ft). This problem is giving rise to a new breed of floating turbines, such as those at the Hywind farm off the coast of Scotland.

But PowerX is working on an alternative solution, particularly in its home nation of Japan, which is surrounded by deep coastal waters and therefore has limited opportunities for off-shore wind farms in close proximity to the land. Rather than relying on undersea cables to transmit the power from farms farther afield back to shore, which the company says are expensive to construct and have significant environmental impacts, it is developing watercraft to carry the load.