For the longest time, the Achilles heel of the passive energy generation crowd (solar and wind) is that the systems often produce more power than people are using at a given time and it winds up being wasted. Sure, utility companies will pay you for the power, but typically at some major discount as compared to what they charge users for power that is generated by their central facilities. So, the holy grail of passive generation has been to come up with ways to store the power for times when power isn’t being generated- calm days in regards to wind energy, cloudy days or nights for solar. Battery technology has lagged behind that of the solar and wind tech industries, but maybe no more. Elon Musk and his Tesla Motors are creating a $5 Billion battery R&D and production facility in the Nevada desert. Personally, I think that the ultimate solution for storage is in fuel cell technology development, which is still years down the pike. It’s highly likely that this will start the ball rolling- http://www.bloomberg.com/news/2014-12-05/musk-battery-works-fill-utilities-with-fear-and-promise.html
