Storing Power…In Molten Lakes!


Germany’s advance towards renewable energy is making wholesale power cheap, even free, when the sun is shining and the wind is blowing. When the weather is not to rosy though, prices rise. The system doesn’t have dedicated storage equipment capable of holding large amounts of renewable energy yet. Trimet Aluminium, Germany’s largest producer of the metal, is experimenting with one answer: using its vast pools of molten metal as storage batteries. Intrigued? So are we.


Trimet is turning aluminum oxide into aluminum by using electrolysis, the use of an electric current to stimulate a chemical reaction. Negative and positive electrodes in a tank separate the compound into aluminum and oxygen. The electrodes, in tandem with the liquid metal that settles at the bottom of the tank and the oxygen above, form an enormous battery that Trimet can use to soak power from the grid when energy is cheap. It can then resell the power when demand is at its peak.

Trimet can temporarily reduce its power consumption when prices are high by slowing the electrolysis, cutting the energy drain of its 290-megawatt smelter by as much as 25 percent. Heribert Hauck, Trimet’s head of energy management, says the plant eventually will be able to store the aluminum equivalent of as much as 3,360 megawatt-hours over a two-day period—enough to power more than 300,000 homes for a day. “The results can be transferred to the whole production process without any changes,” he says.

The principle Trimet is experimenting with may also work for other energy-intensive industrial processes including those used to manufacture cement, paper, and chemicals. Making chlorine, used to produce paper, plastic, fabric, paint, drugs, and antiseptics, also requires electrolysis. Playing a similar game with its production may be an essential lever for stabilizing the power market.