The high proportion of fluctuating energy sources in a future energy system based heavily on renewable energies requires the comprehensive use of efficient technologies for storing energy. We are researching and developing both electrochemical storages for electricity ('batteries') as well as thermal and thermo-chemical storages for heat. In addition, a wide range of research work is being undertaken on chemical energy storages, such as hydrogen and hydrocarbons, which are characterised by high energy densities, easy handling, and exceptional versatility in their use.
The majority of the work is being carried out at the DLR Institute of Engineering Thermodynamics. The DLR Institute of Materials Research, the DLR Institute of Solar Research, the DLR Institute of Combustion Technology and the DLR Institute of Networked Energy Systems are also involved.
Our work on batteries is devoted to both the development of lithium-ion technology and that of batteries for the next and next-but-one generations, such as lithium-sulphur batteries and metal-air batteries. Within the scope of the Helmholtz Institute Ulm (HIU), we are working in close collaboration with the Karlsruhe Institute of Technology (KIT), the Centre for Solar Energy and Hydrogen Research Baden-Württemberg (ZSW) and the University of Ulm on the numerical simulation of the complex electrochemistry in batteries (and fuel cells). Furthermore, we are carrying out extensive investigations into batteries and, together with the DLR research areas of transport, space and aeronautics, we are examining the integration of batteries into complex systems.
Thermal and thermo-chemical storage
Heat can be stored purely physically in the form of sensible heat (temperature difference), latent heat (phase-change energy) and even through the use of reversible chemical reactions (reaction energy). At DLR we are addressing all three approaches. The focus is on high temperature storage between 100 and 1000 degrees Celsius, which is required for industrial and energy management applications. The aim is to develop economical and durable technologies that can also be used on a large scale. Energy efficiency can thus be increased in power plants and industrial processes, facilitating more flexible operation. Work on thermal storage is supplemented by research into high temperature heat exchangers, which are a central component of such systems.
Chemical storage and fuels
Alternative climate-friendly fuels, such as hydrogen, synthetic gases and biogases, are becoming increasingly important. A fundamental objective in this area is research into the properties of these fuels, as technical applications are not possible without this knowledge. Efficiency and reliability are aspects that are as much at the forefront as climate- and environment-friendliness. The ‘design’ of alternative fuels is playing an increasingly important part, i.e. optimising their composition with respect to their physical and chemical properties, such as the specific energy density, combustion properties and questions regarding production and storage. The methods used for this include chemical-kinetic modelling, numerical simulation procedures, chemical-analytic and laser-based measurement techniques and validation experiments of various levels of complexity. Finally, alternative fuels are assessed and optimised regarding their energetic and economic properties.
In another approach, we are researching reactors that generate hydrogen using concentrated solar radiation via chemical cycles. This offers interesting prospects for sunbelt countries.