A quick back of the envelope calculation
A Lithium battery has an energy density of about 2.63 MJ/l, whereas fuel oil is 35.8 Mj/l, 14 times as dense.
The Tesla Powerwall has 10 kWh capacity and is
1300 x 860 x 180 mm (0.2 m3). A standard 20 foot shipping container is 38.5 m3, which would fit about 191 Powerwalls, with 1.91 MWh. The largest ships can carry 18,270 containers, with 3,500 MWh. A HV DC cable can carry 6,000 MW, so there would need to be a ship arriving every half hour t provide this capacity.
However, a major issue with renewable power is storage. The power provided by a storage battery is much more valuable than that from a cable, as the battery stores power. If renewable power has to be stored in batteries anyway, then it might be feasible to transport them in some circumstances.
ps: None of this had anything to do with the event I was at, which was a debate about programming languages and the eternal golden braid. ;-)