Rare is the tech story whose main development is decidedly low-tech – but not impossible. Rather than a fancy atomic clock or rat cyborgs, for instance, this tech story deals with buckets of rocks and water. Well, solar panels too, but that’s not the cool new part.

Today, at a meeting of the American Physical Society, Colgate University physicist Beth Parks described a new way to wring even more energy from a solar panel — a major development for people with no access to reliable power, s