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Membrane project to store green energy in soil mounds

Not only batteries can store wind energy. Two master of science in engineering students from Aarhus University are working on a project that, using a huge balloon, and tonnes of ordinary soil and water, will make a giant battery for renewable energy.

One of today’s major problems is to find smart, low-tech solutions to store renewable energy, for example from wind turbines. Because if it is windy at night, when Denmark is asleep, what do we do with the large amounts of energy generated by the wind turbines?

Today Denmark sells the energy to other countries, but this means there may be a shortage of green power when it is needed. Therefore, two civil engineering students from Aarhus University, Peter Norlyk and Kenneth Sørensen, started a project that may completely revolutionise the way we manage electrical energy in Denmark.

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"The concept entails taking the surplus energy from wind or solar power that can’t be used when it is generated, and storing it in a system. For example, you can store it at hydro plants in Norway by pumping water from reservoirs back up behind dams. When the energy is needed, the water is fed back through a turbine/generator, which supplies electricity to the grid. We can’t do this Denmark because we have no hydro-electricity plants, but the idea is almost the same - just on flat ground," says 31-year-old Peter Norlyk, who is studying for an MSc in civil and architectural engineering.

A 14-metre-high mound

The project has been started by the entrepreneurial business, AquaNamic, and innovator, Asger Gramkow. In simple terms, it uses surplus energy to pump water from a reservoir into a huge, specially designed membrane buried under an enormous amount of soil.

And the figures involved are certainly impressive. AquaNamic aiming at a full-scale balloon of 330 x 330 metres, buried under thousands of cubic metres of soil that will be raised by up to 14 metres when the balloon is filled up. This will store 230 MWh.

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