Weather is annoyingly fickle, and so is the wind. If massive offshore wind farms are going to become reality, we need better ways to store the extra energy from windy days for the windless ones. One a bizarre-sounding idea floating around: giant balloons of compressed air stored deep underwater.
Like many good ideas, the seeds of compressed-air energy storage, or CAES, were sowed long ago, in the 1870s. Today, a handful of operations store energy as compressed air in sealed-off caves or pipe systems. But that's all on land. Bringing CAES deep underwater, where water pressure naturally keeps air compressed, is a novel and tantalising idea for the massive offshore wind farms of the future.
In August, IEEE Spectrum reports, the Toronto-based Hydrostor will make the first commercial deployment of underwater CAES technology. It will use electricity to fill several balloon-like bags tethered to the bottom of Lake Ontario with compressed air. To turn that stored air back into electricity, they will run the compressed air through a turboexpander.
Proponents of CAES have their sights set on grand scales. Maxim de Jong, CEO of Thin Red Line Aerospace — a company that also makes the energy bags — recently calculated how underwater CAES would be used to store energy from the London Array, currently the largest offshore wind array in the world. One day's worth of energy from the array would require 812,000 cubic metres of compressed air, or a whopping 27,500 of his company's 5m diameter balloons. If we made much bigger balloons, say 41 metres in diameter, de Jong calculates you'd only need 23 of them.
De Jong tells IEEE Spectrum his calculations are meant to provoke us into thinking about underwater CAES, which will have to be deployed at pretty massive scales. The UK recently approved a new offshore wind farm that will be twice the size of the London Array. As wind energy projects get ever more ambitious, the infrastructure that support them will need ambitious ideas too. [IEEE Spectrum]
Picture: Keith Thomson/Thin Red Line Aerospace