The experiment has been carried out by engineers at the Technical University of Denmark who, roughly, would inject compressed air in large bags buried under the dunes of Jutland. The bags were inflated by a compressor operated by wind power.
With a view to future applications for the storage of large-scale wind power, a group of Danish engineers have managed to do a small scale (several kilowatts) using large reinforced plastic bags, according to Ingeniøren, local newspaper specializing in engineering. The degree of efficiency during the tests reached figures in excess of 97%, according to the same source.
The experiment was based on previous projects that also use compressed air. This time, however, instead of using large underground caverns for storage of compressed air, the air is injected into a large synthetic bags are inflated by means of some electrical compressors activated by wind energy.
In initial tests, researchers have measured an efficiency of 97% to 99.5% passing on subsequent tests. The forthcoming project will use larger bags, about 50 meters x 50 meters in its deflated/inflated, designed to store the energy produced by a 34 kW wind turbine.
The researchers explained that one of the challenges has been to ensure that the bags can withstand repeated Inflation/Deflation. The synthetic material has managed to overcome this challenge, according to researcher Ole Hededal, which ensures that the bag can be stretched to a tension of 14% while the tests have required a voltage of only 0.5%.