I don't understand. Doesn't wind energy account for just a fraction of one percent of our generated electricity? Where is the surplus coming from that needs to be stored? Even at times of optimal wind power generation and low demand, it seems to me there would still be more than enough demand that it wouldn't go to waste.

If the demand isn't local, it might not be cost-effective to transmit power to where the demand is. Just speculation on my part, though.

This is not energy storage, it is a natural gas power plant.

The storage system is a solution to the main reason Wind, solar, and other periodic energy supplies are not now very practical. By using a storage system energy can be stored when available, IE the wind is blowing or the sun is shinning, and used as needed. There is a considerable loss due the energy efficiency of the turbines. There is a law in thermodynamics that says in a heat engine, like the turbines, 50% is the best efficiency you can get. That works out to about 40% of 50% in the real world. Even with that loss it may be worth it to free our selves from the CO2 release and having energy for electric vehicles.
We have Altir with a quick recharge battery, and EEstor with their hyper capacitor in the near future. If these could be used for storing large amounts of energy they would be much more efficient than turbines.
Lets hope these projects work and the future will be much brighter.

Yeah.. I don't understand how it could possibly be worth the expense to do this.. and then theres the question of the possibility of causing trouble with the soil if the pressure in the "balloon" is too much. It could just be my ignorance, and I hope it is.. could anyone shed some light on this? I could just google it either way.

@Denny

Compressed Air Energy Storage (CAES) is not expensive. It's actually one of the cheapest large-scale energy storage technology. (for comparative cost analysis, see this)

Here's how it works out: Energy prices are not always the same, so if you capture wind energy at night and use it at peak demand the next day, you could make some serious profit.

Here's why it's needed: As Bill above pointed out, wind is a variable energy resource - which means sometimes it's there and sometimes it's not, whereas we need energy 24/7. So storing energy in any form is a good idea to smooth out constant energy output.

There's even a wind turbine company called General Compression which makes wind turbines that compress air directly (rather than producing electricity which in turn runs compressors) for storage underground : General Compression.

It makes sense to me. Storing wind energy will give it access to the most lucrative part of the market, traditionally a place dominated by on-demand technologies such as coal. Doing it with air pressure seems at least more sensible on a large scale than massive battery arrays. It makes even more sense when wind is such a small part of our generating capacity. Going after the highest profits will make the best use of the money investors are pouring into it and help the industry grow. It will also dampen peak energy prices and start pulling the rug out from dirtier technologies, making them less profitable as a whole.

This has practically nothing to do with wind power, this is just a way for any power generator to store energy when the price is low so they can sell it when the price is high. This helps them make more money, but doesn't actually conserve anything. Say I have a coal burning power plant; when it's very windy, and the local wind power turbines are producing a lot of electricity, I just store mine as compressed air --if I sell it now, there will be even more of a supply, without a corresponding change in demand, so prices will sink lower. Thus I (as a power generator) am able to help control prices and maximize my profit. Since the this option is available to any power producer, I don't see how it would give wind turbines in particular any advantage.

There are some possible advantages to this if all energy production were organized under a central authority (not a good idea for other reasons), but when it's up to individual producers/corporations they'll just use it to maximize their profits.

On a small scale, though, doing something similar is a good idea: if I have a wind turbine on my farm, I could sell any excess power I generate to the power company at their wholesale price (far less than what i'll pay to buy it back when I need it on a windless day), but if I use that excess power to instead pump water into an elevated reservoir (or water tower), then I won't need electricity for my pump at odd times (watre pressure will always be there), and if I do need extra power I can just let it run out of the reservoir through another (hyro)turbine, and turn it back into electricity again.

This same concept can be applied to automotive engines. Stored pressurized air (from regenerative braking or idling at stoplights) can be injected into combustion engines which increases power (like a turbo or supercharger).

There have been numerous studies about the integration of wind energy into the grid. They mostly agree that at least 20% of the electricity can come from wind turbines without the need for extra back-up or storage. However, it doesn't hurt to prepare for the future.

One more thing. Storage always means (at least) two conversion steps in which energy is lost. So it should be used as little as possible. It is therefore not ideal to make a a combination of one windturbine with one storage unit that together act as a conventional baseload powerplant. Instead the storage should work for the whole system.

Example 1) There is a strong wind, and a windturbine is working at full capacity. If you have the windturbine-storage combination you will store the energy for times when there is no wind. But maybe at that time there is also a high demand, a conventional powerplant has failed or undergoes maintenance. So it would be better to feed the windenergy into the grid directly and not to use the storage.

Example 2) There is no wind, but also demand is low, or it has rained a lot and hydropowerplants need to get rid of their water. In this case it make no sense to release electricity from the storage, it may even be useful to store some electricity.

So to manage electricity storage you should look to the whole system of all production and consumption, rather than just windenergy.

Although not a mechanical engineer, wouldn't the conversion losses be less if the turbine directly drove the air compressor instead of converting the energy to electricity and then compressing it? In fact, if you did this, you could always use the direct turbine to compressor all the time, and grab the energy from the stored air whenever it was needed.

If there's no wind the motor won't run so what's the difference other than we can get energy during the night???