From watching your favourite YouTube video to emailing a friend, the internet is made possible by a massive network of underwater cables. 1.2 million kilometres of submarine fibre-optic cables, to be precise, which ferry data around the world.
Now, imagine electricity being similarly shipped across continents. Surplus energy produced in one country could be bought and consumed in another nation thousands of kilometres away. The world, or at least parts of it, would be powered by one supergrid.