Can the US be powered by a 100 miles x 100 miles solar grid? [duplicate]

Question

In this article Elon Musk is quoted to say that the US can be powered by a solar grid shaped as a square (in video he says "a corner of Utah or Nevada") 100 miles x 100 miles big.

“If you wanted to power the entire United States with solar panels, it would take a fairly small corner of Nevada or Texas or Utah; you only need about 100 miles by 100 miles of solar panels to power the entire United States,” Musk said during his keynote conversation on Saturday at the event in Rhode Island. “The batteries you need to store the energy, so you have 24/7 power, is 1 mile by 1 mile. One square-mile.”

I'm skeptical, since if it true, then why didn't anyone build this square already?

Answer 1

Can the US be powered by a 100 x 100 miles solar grid?

Desertec is basically the same idea, solar plants located in North Africa supplying power to Europe. The article includes a map showing the area required to power Germany, Europe, and the whole world, respectively, as estimated by the German Aerospace Center (DLR). That estimate puts 100x100 miles for the USA in the "plausible" ballpark.

Why didn't anyone built this square already?

This isn't part of the claim by Elon Musk, but some thoughts on this:

One, solar power is dependant on sunlight (obviously). Your solar plant would produce power only at daytime, and at limited capacity when it's overcast. You would need to build excess capacity to cater for bad weather, and you would need to store the energy somewhere during daytime to cater for nighttime demands. Or you'd need to keep some conventional plants on standby.[1]

Two, if all the power for all the USA were produced in Nevada, you would need to build massive power lines running all across the continent to supply the east coast, for example. Losing a lot in the transfer, so you need even more excess capacity to make up for those losses.[2]

Three, you would need to redeem your investment in that massive solar power plant, so even while sunlight is for free, your solar energy won't be. And you will be competing with existing power providers which already provide 100% of the power required by the US.[3]

Four, while you would create a lot of jobs in the solar panel and power line industry, you would also make a lot of people in other industries lose their job. Coal miners, plant workers etc., and that will run into a lot of resistance from the associated lobby groups.

There are probably a couple more items I have missed. But it's not as easy as "just plaster a couple of square miles with solar panels and we're done".

So, yes, it could be done. But it should be obvious why people are not really eager to do it just that exact way.

Answer 2

It seems possible, at least in theory. Of course, whether it possible and whether it's remotely economically feasible are completely different questions.

A decent back-of-the-envelope series of calculations here shows that 10,000 square km of solar panels could provide more energy than the US uses. This was in response to the same (or at least a similar) graphic Musk demoed when he launched the Tesla PowerWall and PowerPack batteries.

Inputs to the calculation

US electricity consumption is about 425 GW on average The EIA give a figure of 3,725,101 thousand Megawatt Hours of total electricity sales in 2013, i.e. 3725 TWh in a year. That’s equivalent to 425 GW.

The area shown is 10,000 km² in NW Texas

Looking at the map presented by Elon Musk, and comparing it with a scale map of the US, leads me to an estimate that the square, in North-West Texas, is about 100km along the side, and thus has a total surface area of 100km x 100km, i.e. 10,000 km²

Average PV yield in NW Texas is about 21%

The USA National Renewable Energy Lab (NREL) provides an online calculator for PV yields, called PVWatts. I looked at the data for location TMY2 Amarillo, TX, which seems close to the area in question. A 1 kW system would generate 1,838 kWh per year (on a 10° slope facing south), which is equivalent to 210W; that gives a ratio of generated power to capacity of 21%.

The highest efficiency we currently get from solar modules is about 24%

Table 2 of Green et al’s Solar cell efficiency tables (Version 45) gives the best PV module as being 24% efficient. And that translates to installed capacity of 0.24 GW/km², given the standard measure of 1 full sun being equal to 1 kW/m².

Calculation

10,000 km² x 0.24 GW/km² x 21% = 500 GW Which is more than current US electricity consumption of 425 GW.

Summary

Yes, the area shown is reasonable, [...]

Answer 3

I'm skeptical, since if it true, then why didn't anyone build this square already?

Just focusing on this part. The other answers already seem to indicate that such an area might be large enough to produce electricity in the order of what is needed. Now this doesn't mean, it's economically beneficial to do that.

You can only expect people to actually realize this project if the costs and other aspects are manageable. I will only focus on costs. You would need to buy that much land; prepare the land (flatten it locally and remove obstacles); produce 10,000 square miles of solar panels yourself or buy them; install them; wire them; pay for maintenance like ongoing replacement of worn out panels.

Let's only take the costs of buying 10,000 square miles of solar panels. Of course for such a huge project you could expect quite some effect of scale and much lower costs than are paid now. This will add quite a big uncertainty. Taking $0.75 per watt (mentioned as discount price for solar companies in How much do solar panels cost in the U.S. in 2017?) and a total power of 425 GW (taken from this answer), I arrive at roughly 300 billion US dollar. This is of course only a very, very rough estimate but still hints at why nobody built this square so far.

It might be just too expensive compared to producing electricity by other means. On the positive side, the figure is not totally crazy (compared for example with the national debt in the order of 14 trillions).