Thermal management for electric aviation: An product development approach

Abstract

Lithium-ion batteries (LIB’s) are gaining momentum as a suitable and sustainable solution which can be utilised in many different applications and market. In order to be used in electric aircraft the batteries have to be lightweight, they also should also be safe enough to support second-line of defense during an electrical outage. As the global electric aircraft markets are expected to reach 27.7 billion USD by 2030. Battery industry is also expected to evolve and grow as the need evolves. The safety, lifetime and reliability of LIBs are directly dependent on the operating cell temperature, which makes the thermal characterization of battery cells vital. Therefore, understanding the different thermal effects within the battery is of ut most importance for selecting the correct battery thermal management systems (BTMS). Understanding the heat distribution through the cell is important, as the cells exhibit orthotropic properties. This master thesis deals with understanding the dependence of different cooling strategies on the cell by creating a thermal model of a Li-ion pouch cell determining temperature distribution within the cell volume. A commercial CFD tool was utilised for performing the necessary simulations. The simulations were based on the heat generated during high discharge profiles. To validate the simulated results, experimental tests were conducted based on the pre defined profiles and the results are will be utilized to further improve the simulation approach and calibrate the model to improve its accuracy and reliability. It was observed that the thermal resistance is the highest only when the terminals are cooled and the lowest when the cells are cooled radially. The heating tests also showed similar trends in the thermal resistance characterisation. while comparing the experimental and simulated results the difference in maximum temperatures was found to be approximately 5%, with the experimental temperatures being higher than the simulated results. As the tests were carried out only on a specific discharge case while repeating the experiments for other discharge profiles might give a different perspective and more valuable information.