On Clean Energy, the Wind Blows From Germany

As world leaders prepared to discuss a major climate change treaty in Paris, Germany had a couple of especially windy days, which drove the share of wind energy in the German grid above 50 percent and the spot price of electricity to zero, or so close to it as to make no difference.

All that's missing to make 100 percent renewable energy feasible is cheap and ample storage that would help to smooth supply. That requirement no longer looks impossible.