The variability of power on a solar cell is why you take the “peak watt” value but only consider 5 hours per day of sunlight. Obviously there are many more hours than that of sunlight, but the 5 hour figure is a way to average the efficiency over the whole day of weak-strong-weak insolation.
Yes, you would have environmentalist opposition. But that wasn’t the original statement. The original statement was that if the entire state of Nevada was covered with PV, it would barely power Las Vegas. That was an exageration. There are over 109,000 square miles of land in Nevada, and using only 10% of it would more than power Las Vegas — it would power all of Nevada and several other states.
Its variability means solar PV can never be alone, but storage doesn’t have to be in electrical form. Imagine you had unlimited cheap solar PV electricity. You could combine that with hydropower by using the solar PV to pump water from a lower reservoir to a higher reservoir while solar was available and let the water run through the hydro system at night. Or you could set huge flywheels spinning and let them drive generators when solar was unavailable. It doesn’t matter how inefficient any of those cycles would be, only that the total average cost works out.
This is actually a pet peeve of mine. People write articles about how this or that needs to be more efficient, when efficiency is irrelevent. What matters is the cost. Having solar PV cells that are 30% efficient but cost twice as much as others that are 15% efficient is not really progress, because the 15% cells are already more “efficient” than necessary in terms of area available vs. area needed. We’d be better off with 15% cells that cost half as much, or even 10% efficient cells if they cost only a third as much.
Pumped storage hydro has been proposed but most often it is shot down by environmentalist objections. Not a lot of people know it, but many technology historians trace the origins of the modern environmentalist movement to a fight over a proposed pumped storage reservoir, that being the Storm King Mountain project in the Hudson Valley. And the opposition was led by stinky, ratty, flea-bitten, pony-tailed wackos like you see today. The original "environmentalists" were extremely wealthy landowners along the Hudson River valley, who objected not so much to the idea of a reservoir as to the visual pollution the transmission lines would bring to their views of the picturesque Hudson Valley. Sounds familiar? Think Teddy Kennedy and the proposed Cape Wind project. So I don't have a lot of hope either for large-scale storage systems being built anytime soon. Its all coming down to NIMBYs and NOPEs and BANANAs.
Ask people today what Storm King Mountain was all about, and 9 out of 10 will say it was a nuclear plant. Little do they know that it is something related to that darling of the environmentalist movement, solar energy. Most solar energy advocates will disavow any knowledge of the issue, but that doesn't stop the NOPEs and NIMTOOs from opposing something like it.