Dubai, the most populous city in the United Arab Emirates, has announced plans for what will be the world's largest solar plant. By 2020, it is expected to meet a quarter of the city's national energy needs, and outpace the U.S. in terms of renewable energy generation.

It's part of the city's overall plan to be 75-percent renewable by 2050. That's a big deal in a region with abundant oil supplies and plenty of money. But it's also forward thinking: the project they've chosen makes a lot of sense in the region too—and has the capacity to deliver energy long after any oil supplies would ever run out.

Concentrated solar works a little differently than the cells you've probably seen on rooftops. Instead of cells, a massive array of mirrors reflect light toward a central point. At that point is a tower, and where the light is focused, power is generated by the heat from all the light powering a steam turbine.

It's the perfect choice for somewhere hot that gets a lot of sunlight—similar to how Denmark depends on wind.

Total renewable energy coverage isn't really a hypothetical anymore: last month Portugal was able to sustain all its energy needs for more than 100 consecutive hours, all just on a combination of solar, wind, and hydro power.