(Ilmenau) – Researchers at the Technical University of Ilmenau have succeeded in improving electro-chemical energy conversion for the use of renewable energies. The results of research work in the Institute of Thermo- and Fluid Dynamics could be used to make hydrogen production more efficient and to develop better fuel cells. The research project was funded by the German Research Foundation with a total of 2014 million euros from 2021 to 1,4.
At the Technical Thermodynamics Department at TU Ilmenau, basic research into new storage technologies such as thermal energy storage and liquid metal batteries is underway under the direction of Christian Cierpka. Chemical energy storage is particularly promising for long-term energy storage. The aim was to “research the physical processes underlying electrochemical energy conversion in order to increase the efficiency of the technology and thus the performance of future generations of fuel cells and electrolysers,” explain the scientists. During electrochemical energy conversion, water is split into its components hydrogen and oxygen, which form as gas bubbles on the electrodes. The hydrogen produced in this way can then be converted back into electricity in fuel cells in a climate-neutral manner.
More efficiency without bubbles on the electrodes
However, the gas bubbles adhering to the electrodes reduced the efficiency of the electrolyzer. In experiments that they carried out together with scientists from the TU Dresden, the Helmholtz Center Dresden-Rossendorf and the Leibniz Institute for Solid State and Materials Research IFW Dresden, the researchers in Ilmenau demonstrated for the first time the influence of the so-called thermal Marangoni flows on bubble growth, says a message. To prevent bubbles adhering to the electrodes from reducing the efficiency of water electrolysis, they also investigated how these currents influence the growth of the bubbles and their detachment behavior from the electrodes. They used external “Lorentz force magnetic fields” to generate additional forces to specifically detach the bubbles from the electrode surface. Result: “More hydrogen was produced in a shorter time.”
“Microfluidic fuel cells” do not require a membrane
In order to measure the flow processes in the gas bubbles and in a fuel cell, the researchers developed measurement techniques that were used in collaboration with scientists from the Center for Fuel Cell Technology Duisburg to improve the quick-start behavior of direct methanol fuel cells. These could, for example, be used in mobile devices instead of a battery. In another sub-project, the Ilmenau scientists developed the prototype of a “microfluidic fuel cell”. This works “without the expensive membrane that is usually required to separate fuel and oxidizer.” This made it possible to increase their performance and fuel yield.
Photos
Prototype of a membrane-free microfluidic fuel cell during electrochemical and fluid mechanical characterization on the microscope / © TU Ilmenau, Wiebke Rösing
