UA civil engineers are designing hollow structural members that could be used to store compressed air in load-bearing components, such as foundation piles or the frames of buildings and houses.

"The key to our system is that the loads on structural components coming from compressed air are small compared to building loads, such as the weight of the building and wind loads," said George Frantziskonis, a professor of civil engineering and engineering mechanics. "This makes CAES storage in buildings economically and aesthetically feasible."

The larger the building, the more economical the CAES system and the greater the energy cost savings both in the short and long term, Frantziskonis said.

Underground storage reservoirs

Researchers in the UA's Laboratory for Advanced Subsurface Imaging, or LASI, are developing high-resolution underground imaging systems that can be used to find salt deposits, porous rocks and other natural underground storage reservoirs. These sites could be used to hold large amounts of compressed air to drive utility-scale turbines.

While salt deposits have traditionally been associated with CAES technology, "you don't need a large cavern," said Sternberg, a professor of mining and geological engineering and director of the LASI program. "Rocks that have lots of pores also can provide energy storage. A third option is alluvium in basins, such as those found throughout the Southwest."

All of these possibilities require mapping the Earth's subsurface in high resolution with ground-penetrating electromagnetic waves. "That's where our work comes in because accurate imaging is needed to determine if there are discontinuities in these underground storage areas that will allow too much air to escape," he said.

Sternberg said porosity within the Earth, either from caverns or lots of interconnected pore space, has tremendous potential for low-cost storage that would make renewables cost competitive with fossil fuels.

Recent breakthroughs in the LASI program could help drive exploration and development of these resources. "We're getting data that's an order of magnitude more sensitive than conventional measurements," Sternberg said. "It's a combination of a new approach to collecting data, a new type of antenna array and a very different way of analyzing the data."

Sternberg is anxious to rapidly expand this technology to utility-size exploration. "Right now, so much of our energy is coming from volatile areas of the world, and we've got to overcome that," he said. "Energy security is our biggest risk. That's why this is so pressing. We cannot afford to drag this out and sit on the new developments in energy independence that are being created here in the LASI and CAES programs, as well as in other programs at universities across the country."

Science Foundation of Arizona and the Arizona Research Institute for Solar Energy, or AzRISE, are funding UA's CAES projects. The small-scale project also is being funded by the U.S. Department of Energy and has received help from several local businesses.