[hyp0]

I'm thinking this falls out as: we only see losses up to 20%, because for transmissions where it would be higher, it's not feasible, so not done, so we don't see it.

I guess your scenario of outback solar powering the world would work with undersea (why not?) superconducting cables. But orbital power stations need a space elevator (perhaps more feasible, if it's just a cable, not people/goods transport).

I worry about room-temperature superconductors... what if they carry massive power and get a tiny bit hotter? I suppose there's the same solution of circuit breakers as for regular cables, but seems more dangerous with little head room and no environmental cooling. Don't touch that! You'll warm i ka-BOOOM

[msandford]

There will be engineering challenges no doubt, but they're technically quite easy to overcome. Expensive and a bit impractical, but very doable.

A few thoughts:

1. Make the total capacity up of multiple superconducting strands. That prevents a single failure from totally blowing everything up.

2. Create variable loads at the power generation equipment as well as distributed throughout the grid. They could be giant resistors or single-use loads that are designed to burn up, or probably some combination of both. If/when something goes wrong they can be brought online to absorb the energy currently in the grid and prevent really nasty failures.

3. Any kind of really long distance transmission is likely going to be HVDC and that means capacitance isn't a huge problem. Which means you can bury the cables underground (perhaps 500 or more feet) where the ground temperature is relatively constant in the 50-90f range (depends on latitude). http://en.wikipedia.org/wiki/Geothermal_heat_pump

4. There probably won't be too many of them and that means you can go to some pretty serious lengths to ensure that they're highly reliable.

I would envision a single cable from Australia to China to Russia to Europe. A dogleg down through Africa and head onwards to cross North America horizontally with another dogleg down to South America. If we've got crazy money, maybe even connect back up over the Pacific and have the South American and African doglegs connect over the Atlantic.

The whole thing would easily cost hundreds of billions but the benefits would be really big. New power generation could be done where it's easiest rather than near/in population centers.

[tbrownaw]

4. There probably won't be too many of them and that means you can go to some pretty serious lengths to ensure that they're highly reliable.

I would envision a single cable from Australia to China to Russia to Europe. A dogleg down through Africa and

You need 2- or 3- way redundancy, or one drunk backhoe operator (or aircraft cargo pilot) could knock out power to half a continent.

[msandford]

You'd definitely encase them in a pipeline. Something durable. That would be much cheaper than multiple pulls. 1/2" wall 8" diameter steel pipe is real strong and pretty cheap compared with doing a second pull for a redundant cable. But you make a good point about redundancy.