Efficient Storage of Wind Energy is in the Bag

The research project, based in Southern Jutland, has been filling massive air bags buried under sand dunes using wind-powered compressors.

The compressed air is then released to generate power using a pump and turbine system similar to those used for storage in lakes, according to the newspaper’s account.

An initial test, carried out in a 5-metre by 5-metre engine room, rated the efficiency of the storage method at 97%. A later, larger-scale test recorded a figure of 99.5%.

Researchers said the toughest challenge is making sure the massive air bags can cope with repeated inflation and deflation.

"‘But the synthetic membrane has proved to be unproblematic," Ole Hededal, a lecturer at the Technical University of Denmark, told the paper.

"In our tests the bags only stretched 0.5%, and they're made to tolerate tension of up to 14%."

The final phase of testing will use a 50-metre by 15-metre air bag, intended to hold up to 34 kW of wind energy.