Known as the bivalent crucible furnace, the equipment was developed by the Fraunhofer Institute for Manufacturing Engineering and Automation (IPA) in Stuttgart, Germany.
Due to the high energy consumption of melting and holding furnaces, the price of energy represents a significant cost factor in the production of castings. The price of electricity fluctuates significantly over the course of the day, due to varying demand and supply.
“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,” said Alexander Mages, a researcher at Fraunhofer IPA. “It means that we can use different energy sources to cover the energy requirements of crucible furnaces in any operating state.”
Working with partners Hindenlang GmbH, Bark Magnesium GmbH and the Institute for Energy Efficiency in Production (EEP) at the University of Stuttgart, the research team modelled various heating concepts, optimised plant designs through thermal simulations, and implemented the bivalent design into a crucible furnace.
The crucible furnace forms part of a plant centre including punches, presses and CNC machines at Bark Magnesium GmbH’s die-casting foundry. It was tested successfully in April 2023, then commissioned in May to melt magnesium ingots.
The bivalent furnace can be switched to gas operation when the electricity price is particularly high – due to the regular increase of electricity consumption in the morning or evening, for example. When prices are low, the system switches to electricity operation.
“An energy-flexible demand for electricity can contribute significantly to reorienting our electricity system toward renewable energy generation. Industrial companies account for 44% of our total electricity consumption,” said Mages.
Operators can switch manually between electricity and gas using the furnace control system, or the furnace can switch automatically.
“By switching the energy source, the process start time does not have to be postponed to when electricity prices are low, nor do shifts have to be adapted to accommodate break times. These are common measures to achieve flexibility,” Mages said.
The furnace was developed as part of the Kopernikus project SynErgie II, funded by the German Federal Ministry of Education and Research.
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. Using thermal measuring elements, the project partners are determining parameters such as temperature distribution in the furnace to draw conclusions about energy efficiency. They are also testing whether the furnace could be operated with hydrogen.
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