Originally Posted by
SMT Member
Without being an engineer, let alone of the naval persuasion, it does not seem beyond the realm of possibility, that large cargo carrying vessels ditch their diesels in favour of electric propulsion driven by a bank of batteries in the bottom of the vessels, charged by natural gas driven lean turbines and a large solar array fitted on the top deck.
When I see folks hereabouts proudly stating that they are not an engineer, and then confidently explaining how things are "possible" I tend to pull out my calculator.
A typical large container vessel (say the Maersk EEE vessels) is approx 60m wide x 400m long. Even if every bit of the deck were given up to solar ( = 24,000 m2) and even if the sun were directly overhead, and if very high quality 22% efficiency solar cells were used yielding 0.22kW/m2, then such a vessel would only generate 5.4MW. In contrast the Maersk EEE class uses 60MW of main propulsion to achieve its max speed of 25kts, but at about 18kts which is its optimum designed 'slow steaming speed' it is using approx half that, i.e. 30MW.
So at midday in peak sunshine, such a ship carpeted in solar, would only be able to generate about 1/6 of the power it actually needs. Please pull out a calculator yourself before saying that it can use batteries to make up the difference. First figure out the distance between ports, then the required battery size, then the available ship size, then the batery fraction as a % of the ship volume/mass fraction ........... (it is not so different than the Breuget range equation in a different environment).
Bottom line is: Short sea can reasonably go to battery & electrical systems, fed by shoreside renewable generation. Deep sea for large vessels at 18kts cannot. It is not a given in a fully-renewables world that the relatively meagre amounts of liquid fuels would be preferentially burnt in aircraft. It is not beyond consideration that they might be preferentially burnt in deep sea shipping over those routes that cannot be economically substituted by either local manufacture, or by trans-continental (renewables-fed) freight rail.
https://en.wikipedia.org/wiki/Maersk...container_ship
https://www.sunpowercorp.co.uk/produ...n-solar-panels