Economy Through Air Power

Yugoslav Geologist Bozidar Djordjevitch had an ingenious idea. Every spring, he said, water from melting snow pours into Yugoslavia's Karst caves, compressing air that whistles out through vents in the earth's surface. Why not seal the caves and funnel the escaping air to gas turbines, which could convert it into useful energy? Djordjevitch soon had an answer: the caves are vented in too many places; they are almost impossible to seal off.

To Professor Hans-Joachim Martini, director of West Germany's Federal Geological Survey, the basic idea still seemed sound, so he cleverly worked out a new version of Djordjevitch's plan. For melting snow, Martini substituted electric pumps to compress the air. For the Karst caves, he substituted abandoned salt or potash mines surrounded by nonporous rock that is easy to seal. Cheaper electricity is available during off-peak (usually early morning) hours when the demand is low, and Martini figured it could be used to pump air into the mines. The compressed air could be released during hours of peak electrical demand to drive gas-turbine-powered generators providing additional power when it is most needed.

Pumping Water Up. Geologist Martini already had evidence that his scheme would work. There was no doubt that compressed air could be stored underground; it is often used for testing the sealing of caverns that many nations use to store natural gas. In addition, off-peak-hour electricity is already used to pump water up into a reservoir above the level of a water-driven turbine. During hours of peak demand, the water is released to flow down against the blades of the turbine, which drives an electric generator.

After extensive studies of mines and natural caverns, the Federal Geological Survey concluded that compressed-air storage of electricity was not only practical but could be cheaper than water storage. An association of German power companies has already given cautious approval to the plan, and Martini is currently consulting with both French and German public power companies that are interested in trying it out.

Flushing Salt Out. Martini is sure that his plan has great potential, especially for Germany. Just north of the Ruhr industrial complex, where peak power needs are acute, there are many abandoned salt and potash mines, plus some 200 enormous salt domes between 150 ft. and 6,000 ft. below the surface. When all of the available mines have been filled with compressed air, Martini says, salt can be flushed out of the domes with water, giving the Ruhr natural reservoirs with a vast capacity for storing electrical power.

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