> Since the propellors are driven by electric motors anyways, the integration in the ship should be reasonably straightforward. Oh hell no. In large container

> Since the propellors are driven by electric motors anyways, the integration in the ship should be reasonably straightforward. Oh hell no. In large container freighters, they usually have the engine crankshaft directly attached to the prop shaft. Something like the RTA96 - that thing has a rated continuous power output of 80 megawatts. No gears, no nothing. That's also part of the reason why you need tugboats in ports or rivers like Hamburg's Elbe. The only thing that is electric are the maneuvering thrusters. A ship of that size has a few of them but they are only used when precision navigation is needed. > So in principle you should be put a couple of container batteries on top and swap those in locks. At cruise speed large container ships burn thousands of liters of fuel. Even assuming you could get a quarter of the energy density of petroleum from batteries, one 40 ton container worth of batteries would be only one hour worth of runtime. The power and energy involved in maritime traffic is absurd on an absolute scale, but the sheer size and transport capacity makes more than up for it (IIRC even the dirtiest container ship run on the dirtiest possible fuel has less emissions per kilometer and ton than the cleanest euro6 truck). [1] https://en.wikipedia.org/wiki/W%C3%A4rtsil%C3%A4-Sulzer_RTA96-C https://en.wikipedia.org/wiki/W%C3%A4rtsil%C3%A4-Sulzer_RTA9... [2] https://en.wikipedia.org/wiki/Emma_M%C3%A6rsk https://en.wikipedia.org/wiki/Emma_M%C3%A6rsk