One of the biggest drawbacks with electricity produced by windmills is that the price per Kw falls the harder and longer the wind blows. Since there is no way to regulate the output from windmills it would be nice to be able to somehow store the energy until prices are high enough.

This is an interesting design challenge as well as a huge business opportunity.

The price the electrical utilities pay per kW of electricity from windmills fluctuates considerably minute by minute. During peak loads the prices are higher, at night time the prices are lower. Power stations conserve energy by turning production down at night, (un)fortunately nobody can increase or decrease the wind to regulate the output of windmills. The consequence is that windmills sell a large portion of their output at very cheap rates.