Compressed air is another means of storing wind energy that is getting looked at again. The CAES schemes need large geological structures such as salt mines or depleted gas fields, but there are quite a lot of viable structures in places like Texas and Ontario where there is also interest in wind energy. It is not economical on a small scale since a large part of the compression cost is independent of the reservoir size.

According to the US Department of Energy "nearly two-thirds of the natural gas in a conventional power plant is consumed by a typical natural gas turbine because the gas is used to drive the machine's compressor. In contrast, a compressed-air storage plant uses low-cost heated compressed air to power the turbines and create off-peak electricity, conserving some natural gas."

In the last 20 years only two facilities have ever been built - a 110-megawatt plant in Alabama and a 290-megawatt plant in Germany. Iowa is building a new plant "expected to cost $200 million and operate by 2011 with the capacity to store 200 megawatts of power, enough for several days. Both the Iowa and Alabama installations can draw air to make power within 15 minutes and make a gas turbine roughly 40 percent more efficient. "

http://www.eere.energy.gov/de/compressed_air.html
http://arstechnica.com/news.ars/post/20081224-full-of-powerful-wind-bury-it-in-the-ground-for-later.html
http://www.thestar.com/business/article/553702
http://www.isepa.com/index.asp Iowa Stored Energy Park
http://news.zdnet.com/2100-9595_22-178929.html

I think it was the early Dr Who series that created the biggest impression. I'm 43 and can remember viewing Dr Who from behind the sofa when I was about 5 or 6 years old. The Cybermen seemed scary then ! I've discussed Dr Who with people of my generation a few times, with work colleagues, school friends and relatives and everyone my age could remember hiding behind the sofa when Dr Who was on, so no wonder it left an impression on us.

I can imagine later generations had other sci-fi to compare Dr Who and would not be as innocent as we were then. I also think the later Dr Who's were much more jokey and less serious, rather like what happened with the James Bonds !