Liquid aluminum may be used for temporary energy storage

Molten and thus liquid aluminum in the gigantic furnaces of smelters can be used to temporarily store wind energy. A large German aluminum smelter is investigating the concept.

According to the German aluminum producer Trimet Aluminum SE, the company can store a quantity of molten aluminum over a period of two days that is equivalent to 3360MWh, good for the energy needs of approximately 300,000 households for a day. Furthermore, the estimated efficiency of the process would be 90 percent, while the company says it does not need to make major changes to its production process.

Aluminum is obtained by heating aluminum oxide powder in ovens to approximately one thousand degrees Celsius. Using electrodes, the smelters send direct current through the liquid. This causes the liquid aluminum to sink to the bottom of the oven.

The production process costs a lot of energy: Trimet needs 14MWh of electricity for every ton of aluminum. This places a significant burden on the energy grid, but Trimet is currently looking at the possibility of using the liquid aluminum in the ovens as gigantic batteries.

The temporary energy storage is possible by varying the speed at which the companies melt the aluminum, Trimet believes. The 290MW the smelter normally uses can be varied up and down by 25 percent. At times when there is a lot of energy on the grid and the price is therefore low, for example because wind turbines produce electricity on a large scale, the company can melt extra aluminum. At peak times, the company can actually return power, Bloomberg writes.

In Germany, as a result of the Energiewende, a lot of money and time is being invested in research into the temporary storage of green energy. According to scientists, the principle of energy storage that Trimet is looking at can also be used for other energy-intensive production processes, such as that of cement, paper and various chemicals.