Flexible electrolysis process for aluminium by TRIMET

Aluminium manufacturer TRIMET wanted to make the energy-intensive process of producing aluminium more sustainable. To this end, it devised a way to make the manufacturing process more flexible and utilise the fluctuating electricity from renewable energy sources that is available. Thanks to this innovative solution, the company is contributing to the stability of our grid and making production more sustainable in the aluminium industry.

Manufacturing aluminium is one of the most energy-intensive industrial processes out there. TRIMET’s plants alone convert around one per cent of Germany’s electricity, and a constant supply of energy is the prerequisite for an efficient manufacturing process. By introducing flexible electrolysis of aluminium, the company is now demonstrating how these conditions can be overcome while boosting its energy and resource efficiency and reducing CO2 emissions.

Innovation: adjustable heat exchanger, magnetic field compensation and digital process control

The transition to a flexible aluminium manufacturing process is essentially made possible by three technical innovations: First, fluctuating energy inputs are balanced using adjustable heat exchangers in the electrolytic furnaces to ensure a stable process temperature. In addition, the magnetic field that occurs due to the flow of current is compensated for via conductor rails that run around the furnace so the aluminium melt is not negatively impacted. Finally, a digital process control system is used for flexible production and continually records and evaluates large volumes of process data. This makes it possible to determine the level at which balancing power can be produced to support the grid at any time.

‘We have reinvented the electrolysis process for producing aluminium. For the first time, we’re able to vary the supply of energy during ongoing operation to a significant extent. In this way, we are responding to the increasing share of fluctuating feed-ins from wind and solar power plants in a manner that benefits grid stability and the security of supply for all consumers in North Rhine-Westphalia and beyond.’

Philipp Schlüter, Chief Executive Officer at TRIMET

Efficiency: optimal adaptation to the conditions of the energy transition

Following years of research, TRIMET has been operating a flexible electrolysis process for aluminium at its site in Essen since May 2019. To this end, it converted 120 furnaces, which are now capable of consuming up to 25 per cent more or less electricity. An output of approximately 750 kilowatts per furnace yields a flexibility in capacity of +/– 23 megawatts and thus a buffer capacity of over one gigawatt-hour over a maximum duration of two days – by comparison, the storage capacity of all pumped hydroelectric storage systems in Germany is currently around 40 gigawatt-hours. In addition, TRIMET’s converted production line also offers the option of a complete shut-down for 90 minutes. This last resort for stabilising the grid was required 31 times at TRIMET’s sites in June 2019 alone. The company is thus responding to the challenges posed by the energy transition in order to ensure it can maintain its competitive edge in future. In addition, this flexible process control approach, which does not rely on continuous current from base load power plants, is boosting resource efficiency and thereby reducing the company’s CO2 emissions.

Impact: stabilising the grid and integrating renewable energies

Its large buffer capacity enables the flexible electrolysis process to compensate for grid bottlenecks caused by the over or underproduction of electricity from renewable energy sources. In doing so, this innovation contributes to the stability of our grid and thus the further expansion of renewable energy sources. Converting all of Germany’s aluminium plants would reduce annual emissions of CO2 by more than 1,000,000 tonnes.