TRIMET: Aluminium electrolysis as a virtual battery

Primary aluminium is recovered using electricity in an electrolysis process. Since the invention of aluminium production in 1886, a constant supply of energy has been the guarantee of an energy-efficient process. TRIMET has overcome this premise for the first time and enabled the use of aluminium electrolysis as a virtual battery by increasing the flexibility of the process. With the help of the electricity storage this technology provides, the integration of volatile renewable energy sources into the German power grid is supported while at the same time maintaining the security of supply.

Primary aluminium production requires approximately one per cent of the energy produced worldwide and fused-salt electrolysis is the only available efficient production option. The energy is required to transform aluminium oxide, which is particularly chemically stable, into metallic aluminium. But intelligent handling of the substantial energy requirement can also contribute to the success of the transformation of the energy system, as is demonstrated by TRIMET Aluminium with its "virtual battery".

Engine for progress:

  • provision of 3,360 MWh of storage capacity in Essen alone
  • contribution to the grid integration of renewable energies and network stabilisation
  • development of an innovative process to make production more flexible
  • positive economic effects through participation in the balancing power market

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Photo: Trimet

Hall with electrolysis furnaces. At the Essen site, there are three halls of this size with a total of 360 electrolysis furnaces.

The storage capacity of pumped storage

At the TRIMET Aluminium smelting works in Essen, 450 tonnes of aluminium are produced in 360 electrolysis furnaces every day. "We want to make the electrolysis furnaces flexible for use as energy storage," says Roman Düssel, Technical Production Manager at the site. The aim is to be able to vary performance within a range of 25%. The resulting storage capacity of approximately 3,300 MWh is comparable to that of a large pumped storage facility," adds Düssel. All four aluminium smelting works in Germany, three of which are in NRW, could increase the existing pumped storage capacity for Germany of 40 GWh by one third.

The challenge of flexible aluminium production

A controllable heat exchanger has been developed for flexible furnace control, with the task of keeping the energy balance constant in the furnace despite fluctuating energy input. Another challenge is that, regardless of the flexible energy input, the product output has to be kept constant, so that the foundry process is not interrupted and delivery commitments can be met. Due to the characteristics of the process, each cell contains an aluminium reserve of 10 tonnes of molten aluminium. In the case of higher or lower production, this content should vary in order to decouple further processing from the production fluctuations.

The aim is to combine industry and the transformation of the energy system

With the help of the energy storage this technology provides, the integration of volatile, renewable energy sources such as wind and PV into the German power network is supported in an environmentally-friendly and structurally-sustainable manner while maintaining security of supply. This drives the transformation of the energy system forward and at the same time secures TRIMET's market position.

Photo: Trimet

"We have a vision: NRW is to become Germany's energy storage facility."

Roman Düssel, Head of Production Electrolysis

Partners and sponsors

  • TRIMET Aluminium SE
  • Bergische Universität Wuppertal
  • EU-Förderung