Schiphol Airport in the Netherlands is testing an unusual kind of battery that could prove to be a better, cheaper way to store wind and solar energy.  Developed by US startup ESS, the device is known as an iron flow battery. The airport is currently trialling the technology to power some of its electric ground power units. These machines provide electricity to parked planes to run systems such as lights, avionics, and air conditioning.  But why is Schiphol betting on this lesser-known type of energy storage instead of mature lithium-ion batteries? The answer can be traced back over four decades…

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