Smoothing the flow: This sodium-sulfur battery, developed by Xcel Energy, can store 7.2 megawatt-hours of electricity and is designed to compensate for wind power fluctuations.
Electricity, unlike fuel, cannot be stockpiled. For the most part, it must be created at almost the instant it is consumed. This means that generating plants must be able to accommodate the largest possible spike in demand, even if such a spike occurs only once or twice a year. And much electrical energy goes to waste, as when wind farms are taken offline because they are producing more electricity than is needed.
Industrial and academic researchers are trying to solve these problems with new large-scale energy storage technologies. Notable contenders include scaled-up lithium-ion batteries and liquid metal batteries. To date, lithium batteries have been relatively expensive and short-lived. To try to overcome these drawbacks, startup Seeo (see TR35, September/October 2010) is replacing the batteries’ usual liquid electrolyte with solid polymers. As well as lasting longer, solid polymers allow the batteries to store more energy, giving more bang for the buck.
Liquid metal batteries, developed at MIT (see TR35, September/October 2010), employ a liquid electrolyte made from metals such as magnesium and antimony. They are heated to 700 °C to keep the electrolyte molten. The result is a battery that can handle the very high current that utility-scale storage entails.