Can we please, once and for all, stop decrying solar energy for being too area-intensive? See, for example, the oft-cited statistic that to power its economy, the U.S. would need "10 billion meters, squared, of land." America isn’t exactly short on square meters, and awfully sunny ones at that. But 10 billion square meters sounds a lot bigger than it really is.

10,000 square kilometers (100km x 100km) form a square you could drive around entirely, at legal highway speeds, in four hours. (Less if you speed.) 10,000 square kilometers is also roughly one-fortieth the area that the human species has already occupied for hydroelectric reservoirs — all to produce, according to the IEA, 15 percent of current global electricity demand. (This certainly overstates the efficiency of large dams, which do not produce 100 percent of the world’s hydroelectric power.)

Get that? For vastly less space than we already consume for the pittance we get from hydroelectric dams, we could power the world. Space is not the limiting factor — and soon enough, cost won’t be either. Which will leave mulish stupidity the remaining roadblock.