Compensating for grid fluctuations with bivalent furnaces

Melting and holding furnaces are significant contributors to costs during casting. In cooperation with several partners, the Fraunhofer Institute for Manufacturing Engineering and Automation (IPA) is developing a bivalent version of a furnace. This is supposed to be able to dynamically switch from gas to electricity as a power source. This would put companies in a position to utilise energy with greater flexibility and lower costs.

An energy-flexible operation is made possible by the bivalent design of furnace technology. “Furnaces are typically operated using only one energy source – either fuels such as gas and oil or alternatively electricity. Bivalent crucible furnaces, however, can switch dynamically between electricity and gas during operation. This technology has not been available until now”, says Alexander Mages, a researcher at Fraunhofer IPA in Stuttgart. “It means that we can use different energy sources to cover the energy requirements of crucible furnaces in any operating state.”

In cooperation with Hindenlang GmbH, Bark Magnesium GmbH and the Institute for Energy Efficiency in Production (EEP) at the University of Stuttgart, the research team has modelled various heating concepts, optimised the plant designs using thermal simulations and implemented the bivalent design of a crucible furnace. The crucible furnace is part of a plant centre in the die-casting foundry Bark Magnesium GmbH. The crucible furnace was successfully tested in April 2023 and commenced operation in May.

Now the operation of the bivalent furnace can be switched to gas when the price for electricity is especially high – for example caused by the recurring high consumption of electricity in the mornings and evenings. When the price is low, however, operation is switched to electricity. “An energy-flexible demand for electricity can contribute significantly to reorienting our electricity system toward renewable energy generation. Industrial companies account for 44 percent of our total electricity consumption”, says Mages.

The switch between sources of energy can be triggered manually through the furnace control system or automatically through a signal at the level of the hall network. Likewise, there is an option to switch once the electricity provider transmits a signal. “By switching the energy source, the the process start time does not have to be postponed to when the electricity prices are low, nor do shifts have to be adapted to accommodate break times. These are common measures to achieve flexibility in terms of energy”, says the researcher.

The furnace was developed as part of the Kopernicus project SynErgie II, funded by the German Federal Ministry of Education and Research (BMBF). An application has already been submitted for the follow-up project, SynErgie III, which aims to optimise the furnace, including its heating and network design. With the help of thermal measuring elements, the project partners determine parameters like the distribution of heat inside the furnace, in order to draw conclusions regarding its energy efficiency. They are also testing whether the furnace might operate on hydrogen. “It’s almost as if we are conducting research on a live object”, says Mages.