Elisa Magnanelli, whom I have served as a co-supervised for together with Prof. Signe Kjelstrup (main supervisor) and Eivind Johannessen (co-supervisor), successfully defended her PhD entitled “Understanding and Reducing the Entropy Production in Membrane Systems”. The purpose of her thesis work was to understand how energy is dissipated in various systems, in order to find general guidelines that can help increasing the energy efficiency of such systems. The thesis mainly focused on membranes for separation of CO2 from natural gas.
A first important step was to gain a better understanding of how the CO2 permeates through the membrane. In particular, part of the thesis explored the possibility to use a heat source to improve the membrane separation performances through nonequilibrium coupling effects. This possibility is quite attractive, since large amounts of “free” waste heat are available at the sites of extraction of natural gas. A second important step was to identify the operation of membrane systems that dissipates the least energy (i.e. operation that gives the minimum entropy production). By studying the characteristics of the optimal systems, the thesis identifies operating and design guidelines that can lead to more energy efficient membrane separation processes.
A second and wider objective of the project aimed at increasing the energy efficiency of engineering designs by gathering knowledge from natural systems that are very energy efficient. Reindeer are known to be able to survive under very difficult conditions. In the winter, temperatures at Svalbard can be as low as -40 degree Celsius, food is scarce, and water is available only in the form of snow. Therefore, reindeer living at Svalbard need to lose as little energy as possible, and their special breathing system helps them in that. Further knowledge on this system might guide the development of new and more efficient Nature-inspired processes. As an example, recovery ventilators in buildings have very similar tasks and operate under similar conditions. Thus, knowledge from the first system can be used to improve the second.
Professor Karl-Heinz Hoffmann from the Department of Physics at Chemnitz University of Technology in Germany served as the main opponent and Professor Natalya Kizilova from the Department of Theoretical and Applied Mechanics, University of Kharkiv in Ukraine served as the second opponent of the PhD. The Administrator of the committee was Professor Truls Gundersen from the Department of Energy and Process Engineering at NTNU. The picture below was taken at the defense and shows from left to right: Signe, Natalya, Elisa, Karl, Truls, me and Eivind.