Carbon dioxide isn’t the only thing that might get injected underground in response to climate change. Wired is reporting on how storing compressed air could help utilities deal with the irregular output from renewable generation options, such as wind farms. When energy supply exceeds demand, these facilities would pump air into underground structures like salt domes. When the grid demands more power than renewable sources can supply, the high-pressure air can be released to regenerate electricity.
A facility in Alabama has been storing 19 million cubic feet of air at 1,100 pounds per square inch since 1991:
The plant’s output is 110 megawatts at full capacity, which is fairly typical of power plants now coming on line. It can run for 26 hours from a fully charged cavern and supply the demands of 11,000 homes, the institute says. Typically, however, it would run 10 hours a day or less, when demand is high. Another advantage, Mr. Meyer said, is that it can increase and decrease its power level quickly.
The facility can recover 870 watts from every 1,000 it stores – a higher proportion than is possible with either pumped hydroelectric storage or batteries. It also cost only $550 per kilowatt of capacity, compared with about $1,000 per kilowatt for pumped hydro. Despite those advantages, the Alabama facility remains the only one of its kind in the United States. A similar facility in Huntorf, Germany has been operating since 1978.
While air is an easier thing to store underground than CO2 (which forms acid in contact with water, and is riskier if suddenly released), it is conceivable that innovations in compressed air storage could be applied to carbon capture and storage operations, and vice versa.
Technologies and facilities like these will help to even out the peaks and troughs associated with renewable generation. Along with compressed air and pumped hydroelectric storage, promising energy storage options include pumped and multi-lagoon tidal facilities, as well as fleets of electric vehicles that can be charged when energy is ample and tapped as an energy reserve at times of maximum demand. Linking widely-separated generating sites using technologies like high voltage direct current (HVDC) transmission could also be an important way of dealing with fluctuations in output. When the sun isn’t shining in California or New Mexico, the wind may well be blowing in the Dakotas or along the Pacific Coast.