Energy storage

The Carnot Battery is an energy storage concept that uses thermal energy storage systems to store excess electrical energy, which may for example be provided by volatile renewable energy sources. The thermal energy storage of a Carnot Battery can be designed either as a system with two separate storage tanks for the discharged cold and charged hot storage fluids or as a stratified one-tank system that contains both the hot and cold storage fluids in a single vessel. The latter has been shown to be more cost-effective than two-tank systems, but is subject to parasitic convective flows and heat transfer from the hot storage fluid layer to the cold one, destroying the stored exergy over time. Understanding this exergy loss mechanism is essential for the design of efficient Carnot Batteries and is therefore the objective of this project. Experimental investigations of storage tanks using water and molten salt as storage media are combined with numerical simulations to develop and validate an exergy prediction model for stratified thermal energy storage systems that accounts for different system design parameters. The project “GenEx” thus aims to contribute to the development of more efficient thermal storage tanks.

Team:  

• Prof. Dr.-Ing. Christian Cierpka (PI)
• M.Sc. Hannes Ribitza

Recent Publications:

H. Ribitza, C. Naumann, C. Cierpka (2026) On the influence of the storage wall thickness on the parasitic near-wall flow and exergy destruction in stratified thermal energy storages, Experimental Thermal Fluid Science 174, 111711, DOI: 10.1016/j.expthermflusci.2026.111711, open access

 C. Naumann, T. Käufer, C. Cierpka (2026) Improving simultaneous two-color PLIF and PIV temperature and velocity field measurements through a single three-chip color camera, Experiments in Fluids 67, 21, DOI: 10.1007/s00348-025-04167-x, open access

 C. Naumann, N. Stark, C. Cierpka (2025) On the role of parasitic convection for heat transport in stratified thermal energy storages: experiments and numerical simulation, Experimental Thermal Fluid Science 170, 111568, DOI: 10.1016/j.expthermflusci.2025.111568, open access

For the efficiency of Carnot-Batteries, the thermal energy storage (TES) is a key component. It should store large amounts of thermal energy over a long time at low cost. Often liquid materials like water or molten salt are used. The storage can be applied as a two-tank system with cold fluid in one tank and the hot fluid in the other tank, or as a stratified storage, where hot fluid is stored directly above the cold fluid. However, even in single storage tanks with initially uniform temperature, thermal stratification develops due to heat losses to the surrounding. Since the wall material typically has a larger thermal conductivity than the storage medium, heat is transferred from the hot region via the wall to colder regions an vice versa. This drives thermal convection close to the wall, which enforces mixing and thus destroys exergy. The effect can be seen in small systems, but also in larger systems in industrial scale. The understanding of these parasitic convective flows is of fundamental interest for many fluid mechanical and heat transfer problems in nature and engineering. More important, it will help to improve the overall efficiency in terms of energy and exergy of TES for Carnot Batteries, but also for TES in general for other heating applications. Thus, the project aims also to be a valuable contribution to achieve the ‘Wärmewende’. 

Team:  

• Prof. Dr.-Ing. Christian Cierpka (PI)
• M.Sc. Clemens Naumann

Recent Publications:

C. Naumann, T. Carlesi, H. Otto, C. Cierpka, D. Laboureur (2024) Dynamic characterization of Fiber Bragg Grating temperature sensors, Experimental Thermal Fluid Science 156, 111222, DOI: 10.1016/j.expthermflusci.2024.111222, open access

H. Otto, C. Naumann, C. Odenthal, C. Cierpka (2023)On the unsteady inherent convective mixing in thermal energy storage systems during stand-by periods, Physical Review X - Energy 2, 043001, DOI: 10.1103/PRXEnergy.2.043001, featured in Physics, open access

H. Otto, C. Resagk, C. Cierpka (2020) Optical Measurements on Thermal Convection Processes Inside Thermal Energy Storages during Stand-By Periods, Optics 1, 155-172, DOI: 10.3390/opt1010011, open access

Die effiziente elektrochemische Energieumwandlung spielt im Rahmen der Brennstoffzellentechnik in Form von Wasserelektrolyse eine signifikante Rolle. Die Energieumwandlung findet dabei immer an der Elektrodenoberfläche statt, wodurch mikrofluidische Systeme besonders geeignet erscheinen, da hier das Verhältnis von benetzter Oberfläche zum Volumen stark gesteigert werden kann. Durch die Parallelisierung solcher Mikrobrennstoffzellen und Elektrolysezellen lassen sich Einheiten mit quasi beliebiger Leistung erzeugen. Ziel der DFG geförderten Emmy Noether Nachwuchsgruppe (CI 185/3) ist es die Effizienz der elektrochemischen Energieumwandlung durch wandnahe Strömungskontrolle zu steigern und die zugrunde liegenden physikalischen Prozesse aufzuklären, um zukünftige Systeme optimieren zu können. Dazu sollen zeitlich und räumlich hochaufgelöste experimentelle Untersuchungen der Geschwindigkeits- und Skalarfelder (Temperatur, pH-Wert, Druck) in ein- und mehrphasigen Mikroströmungen durch das neu entwickelte und erweiterte 3D Astigmatismus PTV beitragen. Der Fokus der Arbeiten liegt dabei zum einen auf der effektiven Temperaturkontrolle durch Nanofluide und Partikel-Partikel Interaktion im Fluid, zum anderen auf der gezielten Beeinflussung der wandnahen Konvektionsströmung durch elektromagnetische Volumenkräfte.

Partner:

Universität der Bundeswehr München, Technische Universität Dresden, Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden, Helmholtz-Zentrum Dresden-Rossendorf, University of Washington, University of Purdue

Bearbeiter:

• Prof. Dr.-Ing. Christian Cierpka (Projektleiter)
• M.Sc. Wiebke Rösing

Aktuelle Publikationen:

W. Rösing, T. Schildhauer, J. König, C. Cierpka (2019) Passive control of the concentration boundary layer in electrochemical microfluidic devices using Dean‐vortices, Microfluidics and Nanofluidics 23, 110, DOI: 10.1007/s10404-019-2274-2, open access

J. Massing, N. van der Schoot, C. J. Kähler, C. Cierpka (2019) A fast start up system for microfluidic direct methanol fuel cells, International Journal of Hydrogen Energy 44, 26517-26529, DOI: 10.1016/j.ijhydene.2019.08.107

 J. Massing, G. Mutschke, D. Baczyzmalski, X. Yang, K. Eckert, C. Cierpka (2019) Thermocapillary Marangoni convection during hydrogen evolution at microelectrodes, Electrochimica Acta 297, 929-940

X. Yang, D. Baczyzmalski, C. Cierpka, G. Mutschke, K. Eckert (2018) Marangoni convection at electrogenerated hydrogen bubbles, Physical Chemistry Chemical Physics 20, 11542

T. Weier, D. Baczyzmalski, J. Massing, S. Landgraf, C. Cierpka (2017) The effect of the rotating MHD flow on the detachment of gas bubbles from the electrode surface. International Journal of Hydrogen Energy 42, 20923-20933

D. Baczyzmalski, F. Karnbach, M. Uhlemann, G. Mutschke, X. Yang, K. Eckert, C. Cierpka (2017) Growth and detachment of single hydrogen bubbles in a MHD shear flow. Physical Review Fluids 2, 093701

R. Irwansyah, C. Cierpka, C.J. Kähler (2016) On the reliable estimation of heat transfer coefficients for nanofluids in microchannels, Journal of Physics: Conference Series 745, 032078

D. Baczyzmalski, F. Karnbach, X. Yang, G. Mutschke, M. Uhlemann, K. Eckert, C. Cierpka (2016) On the Electrolyte Convection around a Hydrogen Bubble Evolving at a Microelectrode under the Influence of a Magnetic Field, Journal of the Electrochemical Society 163, E248-E257

D. Baczyzmalski, T. Weier, C.J. Kähler, C. Cierpka (2015) Near-wall measurements of the bubble-driven and Lorentz-force-driven convection at gas-evolving electrodes. Experiments in Fluids 56, 162