Test facility for heat storage in molten salt

TESIS

The Test Facility for Heat Storage in Molten Salt (TESIS) at the DLR Institute of Engineering Thermodynamics in Cologne is the first large-scale research facility in Germany in which molten salt storage facilities and associated technologies are investigated on a relevant scale. It is used to develop new storage technologies and to improve materials, components and processes for the use of molten salt storage systems in the field of renewable energies.

Test facility TESIS
With TESIS (Test Facility for Thermal Energy Storage in Molten Salt), DLR is providing a test facility at the Institute of Technical Thermodynamics in Cologne that can be used to further develop storage technologies on an application-specific and industrial scale.
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The plant is specifically designed to move away from the laboratory scale and test the technology on a megawatt-hour scale. Research is therefore being conducted under conditions that are close to industrial implementation and later utilisation. The aim is to address technical issues at an early stage in realistic operation and to ensure transferability to large-scale applications.

Potential fields of application lie in particular in energy-intensive industrial processes, for example in steel and iron production, the manufacture of non-ferrous metals, glass, cement, paper, food or chemical products. Molten salt storage systems can help to increase energy efficiency or decarbonise industrial processes through the use of power-to-heat (PtH) technologies.

Molten salt storage systems are already commercially established in solar thermal power plants and are used to generate electricity in line with demand. In addition, molten salt storage systems in conventional fossil-fuelled power plants offer the potential to make existing plants more flexible through integrated heat storage or to convert them into heat storage power plants in the future.

Operating experience

The continuous operation of the TESIS plant since 2019 has provided us with extensive practical experience in all relevant aspects of molten salt technology. This accumulated knowledge is already being channelled into the consulting, planning and implementation of further molten salt plants. The TESIS plant is thus an example of reliable, step-by-step technological progress that builds on tried-and-tested principles while opening up new avenues.

Functionality and subsystems at a glance

The TESIS facility is designed as a central large-scale research infrastructure for molten salt technologies. In the tried-and-tested engineering tradition, it combines experimental research with practical testing under realistic operating conditions. Since its commissioning in 2019, the facility has been continuously utilised and further developed. The experience gained forms a reliable basis for the planning and implementation of future molten salt applications.

The overall facility is divided into three specialised sub-facilities, each with a clearly defined focus and complementing each other in their function.

1. TESIS:store - development of new single-tank storage concepts
TESIS:store forms the centrepiece of the TESIS facility and is the world's largest large-scale research facility for the development of single-tank storage systems for high-temperature heat storage based on molten salt. In contrast to conventional two-tank systems, the heat is stored in just one tank - an approach that builds on earlier, robust storage principles and combines them with modern research.
 
Excess heat is absorbed directly in the liquid salt storage medium and released again as required. By reducing the number of tanks, capital costs can be cut by up to 40 per cent, while heat losses are halved.
 
Research work in TESIS:store is focussing on material compatibility at high temperatures, heat and mass transport in the storage tank, thermomechanical loads and the integration of the storage tank into overall systems. The aim is to develop viable storage solutions for industrial applications and future energy systems.
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2 TESIS:store.ext - Qualification of large-scale components
TESIS:store.ext is designed as an extension of TESIS:store and closes the gap between component testing and real plant operation. In this sub-system, large-scale components are analysed and validated under real operating conditions.
 
For example, electric heaters or large-scale heat exchangers can be tested here. Compared to TESIS:com, TESIS:store.ext allows operation with significantly higher outputs, voltages and mass flows. This makes it possible to work on issues that are of particular importance on an industrial scale.
 
The objective basically corresponds to that of TESIS:com, but is consistently transferred to larger dimensions. The result is an end-to-end test and development environment - from individual components to large-scale applications.
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3 TESIS:com - Qualification of components and process engineering
The TESIS:com sub-system is designed to qualify components and process engineering concepts for use with molten salt. It serves as a flexible test platform on which pumps, valves, pipework and other components can be tested under realistic conditions.
 
A key feature of TESIS:com is the ability to quickly set up and convert components and carry out fully automated test programmes. Temperatures and mass flows can be varied in a targeted manner so that both typical and extreme operating conditions can be modelled.
 
The tests take place in an air-conditioned building that is equipped with extensive safety features. This means that even demanding tests can be carried out in a protected environment. TESIS:com thus makes an important contribution to the technical validation of molten salt systems and the transfer of research results into practice.
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Contact

Prof. Dr.-Ing. Annelies Vandersickel

Head of Department Thermal Process Technology
Institute of Engineering Thermodynamics
Thermal Process Technology
Pfaffenwaldring 38-40, 70569 Stuttgart