Giant batteries

http://www.popsci.com/technology/article/2010-04/giant-gravel-batteries-could-make-wind-power-consistent-energy-option

The unpredictability and non-uniformity of wind is one of the largest technical problems facing wind farms. A company in Britain thinks it has figured out how to use argon gas and 200ft barrels of gravel to store electricity in a high volume, low loss, low cost manner. If it works, the devices would capture excess energy in windy times for use when the skies are calm.

Their pilot project is only 23 feet tall. This is still too big for a house, but a large apartment block or shopping center could have some solar panels and small wind turbines hooked into something like this. They could also be useful in a smart grid set up accepting extra energy if a broken link causes a surge. Rather than cascading surges and blowouts, the batteries could absorb the extra energy and return it once the grid is stabilized.