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| A big hole in the ground, like an old salt mine. But there is a fundamental thermodynamics problem. Energy of compression raises the temperature of the compressed air. Store it and that heat wanders away. Expanding the air cools it and the available energy is not all there because that need of heat to complete the expansion. So it probably is less energy efficient than 85% storage batteries, but has the appeal of simplicity and longevity.
Gerald J. | |
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