Japanese company PowerX is moving ahead with its strange plan to build a “mobile power station” in the form of a 140-meter (460-ft) electric “battery tanker,” which will carry 241 megawatt-hours of renewable energy across the sea over short distances.

The idea here is simple enough: renewable energy is often generated a fair distance from where it’s most needed, so let’s build an electric ship full of batteries, and jolly well ship it there.

Why not just put down an underwater cable? That’s a fine question. PowerX points out that Japan is surrounded by deep seas, and prone to earthquakes, and says in a press release that “the ship-based solution resolves issues such as long downtime from undersea cable malfunctions and repairs, as well as the high costs associated with ultra-high voltage connections and substations.”

To a man with a hammer, they say, everything looks like a nail. PowerX has a couple of battery factories, which might explain why the company thinks it’s a good idea to build a ship loaded with nothing but batteries. Ninety-six container-sized lithium-iron phosphate battery modules will be spaced around this relatively small demonstrator, as well as controllers and charge units.

Currently named “Battery Tanker X,” the prototype won’t be going very far. Pushing a vessel through draggy water is a nightmare for battery-powered electric propulsion systems, so the ship’s maximum range before it burns through too much battery to make the trip economically feasible is slated at just 300 km (186 miles).

A full production “Power Ark” the same size, says PowerX, might move about 4,190 GWh of electricity annually from renewable sources in Hokkaido to meet demand in Aomori just 100 km (62 miles) away, making use of transmission infrastructure already in place but so