Powering the Planet With Sun-Harnessing Balloons

There are plenty of good ideas for moving the world beyond fossil fuels, but most of them aren’t practical with current technology or don’t scale well. (You would have to build something like 10 million conventional windmills to produce 100 percent renewable electricity in the United States.) A few years back, a group of West Coast engineers were puzzling over a practical way to tackle the problem, looking for a hydrocarbon-free, clean, and renewable energy system that required no major technical breakthroughs and could be put to work in the next few years. The result: the start-up Cool Earth Solar, now based in Livermore, California, and its new-think technology, an inexpensive plastic-film balloon a bit over eight feet tall. Millions of these balloons could hover low over the landscape, each concentrating sunlight onto a photovoltaic cell inside, and pumping out electricity more cheaply than power from fossil fuels, the company ...