TRIMET Aluminium SE started the trial operation of its virtual battery in May 2021. Initial research work began six years ago. Now the energy supply for aluminium production at the Essen plant can be controlled flexibly for the first time. This will create a huge power storage facility that will make it easier to integrate discontinuously generated electricity from renewable energy sources into the power grid. A total of around 36 million euros was invested in the conversion. With the conversion of a total of 120 furnaces in hall one of the Essen plant, 25% more or 25% less electricity can be consumed for up to 48 hours without interrupting aluminium production. The energy requirement can also be reduced to zero for up to an hour, if necessary. This means up to 2,000 megawatt hours of electricity can be stored for use in the energy revolution. The “virtual battery” thus has the capacity of a medium-sized pumped storage facility. Since its invention in 1886, the aluminium production process has been based on having a constant supply of energy. With its “virtual battery”, TRIMET is abandoning the traditional approach for the first time and is making the energy-intensive electrolysis process more flexible. To achieve such flexible control of the process, TRIMET and Bergische Universität Wuppertal have developed a controllable heat exchanger that keeps the temperature in the furnace constant despite an unsteady energy supply.