If we discover the mechanism, we could theoretically manufacture a room-temperature superconductor (above 0 C). This would really be a leap forward :)
Why?
MRI machines are a second use case. Currently, most MRI's use a superconductive metal to run gigantic currents through a coil to create gigantic magnetic fields which they measure. In order to do this, the MRI needs to be cooled enough to make the coil superconductive which requires at least liquid nitrogen and sometimes liquid oxygen. This is what makes MRI's expensive. Without the cooling requirements, they would likely be as expensive and thus as common as X-ray machines.
In West Texas there is a huge amount of wind power installed but it's difficult to get that power from West Texas to anywhere that people use it like Houston or Dallas.
Right now people pay different amounts for electricity depending on where they are in the globe because electric power is actually a locally produced, locally consumed good. It's a commodity to be sure, but it's actually harder to transport than oil is. So oil prices are fairly flat worldwide but electricity prices can vary by a factor of 10 or more.
High temperature superconductors would make it really feasible to interconnect the world's energy grids and allow anyone with the ability to generate utility-scale power to sell into the wholesale market.
That means you could cover the Sahara, the outback in Australia and the deserts in the Americas with solar panels and run a fairly flat and smooth solar-only electric grid.
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
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.
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.
It is one and the same improvement. Though you're right the second implication is much more important.
Not that I know much more I just skimmed The Basics of MRI: http://www.cis.rit.edu/htbooks/mri/chap-9/chap-9.htm