High-temperature heat storage with liquid metal technology
A contribution by Dr.-Ing. Klarissa Niedermeier, Head of the High-Temperature Heat Storage and Process Technology Working Group at the Karlsruhe Liquid Metal Laboratory (KALLA)
The Karlsruhe Liquid Metal Laboratory (KALLA) is researching the use of molten metals, known as liquid metals, as heat transfer media in high-temperature heat storage systems. The use of liquid metals enables heat to be stored in a wide temperature range from around 100°C to 1000°C. Thanks to their high thermal conductivity, they transfer heat up to 100 times more efficiently than conventional liquids or gases. This allows for the development of more compact and efficient storage and transfer systems – ideal for the storage, provision, and recovery of high-temperature heat in industrial processes.
Preparing the pilot storage tank for testing at the Karlsruhe Liquid Metal Laboratory – view inside the heat storage tank during filling with ceramic beads (Picture: KIT/KALLA)
How is it researched?
KALLA is developing an innovative heat storage concept in which liquid metals are passed through ceramic fillings. These solids store heat efficiently over long periods of time. During charging, hot metal flows through the material and transfers energy; during discharging, cooler metal absorbs the stored heat and transports it to where it is needed—for example, in industrial processes. After successful demonstration on a laboratory scale, a pilot storage facility with a heat storage capacity of 100 kWh is currently being installed. More than 100 temperature measuring points in the tank will be used to analyze the charging and discharging behavior. At the same time, we are researching cheaper storage materials that are compatible with liquid metal, such as slag from the steel industry, in order to reduce material costs. We are also testing and qualifying important system components such as pumps and valves for use with liquid metal.
Thermocouple probe for measuring the temperature in the tank (Temperature: KIT/Brahmsiepe)
What is the benefit for society?
The energy transition poses major challenges for industrial high-temperature processes: fossil fuel sources must be replaced by emission-free alternatives. Thermal energy storage systems offer a cost-effective way to store heat on demand – particularly useful when waste heat is available or process heat is required. Since process heat accounts for around two-thirds of industrial energy demand in Germany but has so far hardly come from renewable sources, there is great potential for CO₂ savings here – especially at temperatures above 500°C, for which there are currently hardly any market-ready storage solutions.