Back during the 1970's my Grandfather Shelby Gordon spent much of his retirement in his wood working shop. He made wooden swings, shelves, and - most impressively - grandfather clocks. Here's the one I have in my dining room:

You don't plug these clocks into the wall. They use weights. About once a week you pull the chains to raise the weights up and they slowly work their way down.

I thought about that clock when I read this article about storing wind mill energy:

...one of the most serious issues raised by the [wind power] naysayers was that the wind does not always blow when you need it.

But a New Jersey company plans to announce on Tuesday that it is working on a solution to this perennial problem with wind power: using wind turbines to produce compressed air that can be stored underground or in tanks and released later to power generators during peak hours.

Its a great idea in part because its so simple. It doesn't require expensive batteries or capacitors to store power. Just an air compressor. Its a totally mechanical solution.

With similar ease weights like in my grandfather clock could store power. These windmills are very tall. For perspective, check out the stairs/service entrance at the bottom right of this windmill:

If the wind is blowing hard when the price of electricity is low (like at night), why not have the windmill pull weights up to the top of the tower? It could be engineered to pull several weights or geared to slowly pull one very large weight up the tower. When the electricity is needed the weights would fall.

One of my economics professors once told me that the purest application of supply and demand theory he ever saw was at a hydroelectric dam control center. The controller watches an indicator that tells what the supply is - water behind the dam - and another indicator shows the price of electricity. These indicators were probably analog dials back when my professor toured that plant. I'm sure its computerized now. But they try to match power generation to that time when the price of electricity (and the need for electricity) is highest. Unless, of course, the water gets too high behind the dam. Then they'll generate regardless of the price of electricity.

Whether the answer is compressed air or weights, mechanical storage would allow windmills to function like hydroelectric dams and be better at providing power when its needed. And that would also improve the profitability of these power plants.