Energy bags store wind power underwater

New Scientist : One method that has been proposed to store the excess power generated by wind turbines is to use it to pump compressed air into inflatable balloons lashed to the sea floor. Researchers at the University of Nottingham in the UK are currently testing the Energy Bag, which is made of a high-performance fabric developed for the aerospace industry. The required thickness of the containment vessel is kept to a minimum by submerging the bags deep in the water off Scotland’s Orkney Islands and using the intense water pressure to contain the compressed air. “At a depth of 600 m, a 20-m-diameter bag could store around 70 megawatt hours of energy, the equivalent of roughly 14 hours of energy generation from one of the world’s largest offshore wind turbines,” writes Phil McKenna for New Scientist. The challenge, in this and other projects, is to achieve the highest efficiency possible and still remain economically viable.