Unlike fossil-fuel methods, the hours of peak generation for wind or solar power barely align with peak usage patterns; the industry term is that wind and solar are not “dispatchable”. A New York Times article from July ’07 named “Storing Sunshine” looks at moving beyond the battery as a means of bridging the gap between the creation and distribution of green electricity.
All methods covered in the article are in use, all have their drawbacks and some are damned clever. As it turns out, large-scale battery storage comes off as the least attractive method presented, its best use being as a shock-absorber/safety margin in a system that uses wind, solar and diesel.
Other than storing the energy outright, two methods work at using up to a third less fossil-fuel than conventional generating systems. They both buy electricity at night, when it’s cheap, and store it for peak hour usage when rates are higher.
What’s a gas (sorry) is the form in which it’s stored; one does it in large, underground caverns as compressed air to help drive daytime turbines, another as 500-gallon blocks of ice in big-building basements, frozen cheaply by night and cutting AC costs by day.