They don't take space requirements into consideration probably because it's trivial to dismiss. 40,000 square miles would provide enough energy to power the entire US with solar, in a country with 3.6 million of them. That's less than the space taken up by cemeteries.

And continental is what makes 3 hours possible. The wind is always blowing somewhere.

> They don't take space requirements into consideration probably because it's trivial to dismiss.

Ah yes, so trivial.

> 40,000 square miles would provide enough energy to power the entire US with solar

No, it wouldn't. As the document yo link shows, even countries with similar makeup have very different solar and wind profiles.

Also. You can't just wave your magic wand and say: "here, we now have 40k square miles". You're saying "oh, let's just randomly find an area larger than Austria (population: 9 million people + farmland + industry + ...) and cover it entirely in solar panels (without taking into consideration the place for all the required infrastructure to go with them".

It is so, so trivial to dismiss, true.

> The wind is always blowing somewhere.

Only... What is the amount of that wind? Is there enough wind in Denmark to cover non-windy days in Spain? Will the grid be able to switch fast enough? (answer is: no, because renewable sources are notoriously slow to ramp up production)

The power generation capacity in the US is worth trillions. That kind of money is a magic wand that can makes obstacles like 40k square miles pretty trivial.

> Only... What is the amount of that wind? Is there enough wind in Denmark to cover non-windy days in Spain?

That is the question the paper answers, but on a national basis.

>Also, three hours of storage for a continental grid? Nice dream.

Comon, if we can't store energy for 3 hours that's an armutszeugnis. The battery of my electric bycicle can store the energy needed to power my flat for 3 hours.