Even the most hardened anti-fossil fuelers can’t deny that science has not yet caught up to our capacity to store electricity generated by so-called renewable sources like wind and solar. Sometimes the wind doesn’t blow and last time we checked, the sun doesn’t shine at night. But sometimes the wind does blow, a lot, and the sun shines a lot, and produces far more electricity than the grid can handle. It would be nice to store that extra electricity for use later–but batteries don’t cut it. Not yet. So how can you store extra electricity from wind and solar aside from batteries?