The student Manex Larrañaga Eceiza obtained an EXCELLENT grade with mention Industrial Doctorate

The student Manex Larrañaga Eceiza obtained an EXCELLENT grade with mention Industrial Doctorate

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• Thesis title: Direct liquid cooling strategy for electric vehicles focused on lithium-ion pouch type battery cells

Court:

• Presidency: Maitane Berecibar Uribe (Vrije Universiteit Brussel)
• Vocal: Bernhard Lechner (Virtual Vehicle Research GmbH)
• Vocal: Peru Fdez. Arroiabe Txapartegi (Mondragon Unibertsitatea)
• Vocal: Mohamed Ben-Marzouk (Total Energies)
• Secretary: Unai Iraola Iriondo (Mondragon Unibertsitatea)

Abstract:

In this research, a novel direct liquid cooling strategy for electric vehicles focused on large-scale lithium-ion pouch-type cells is proposed. This approach aims to control the cell temperature within the optimum range of performance and safety, meeting the demands of modern electric vehicle applications. With a modular design to reduce the fluid weight impact, the novelty of the strategy consists of directly cooling the surface of the battery cell instead of immersing the battery system in the cooling fluid.

To develop this strategy, first, a cell-level prototype is designed to analyse the performance of the cooling strategy. The feasibility of the strategy is validated by testing the prototype under current pulse tests and deep fast charge and discharge conditions. In all cases, the proposed strategy is able to maintain the battery cell within the optimum working temperature range. Subsequently, the geometry of the internal cooling circuit is numerically optimised through a multi-objective parametrisation process to maximise the energy density while minimising cell temperature and the pumping power.

Finally, the cooling strategy is scaled up to a four-cell battery module prototype, yielding gravimetric and volumetric energy densities in line with the market reference battery modules. To assess its feasibility, a comprehensive experimental comparison is made at subsystem level between the proposed direct liquid cooling prototype and a battery system based on indirect liquid cooling, the reference cooling strategy in the electric vehicle market. Both approaches are subjected to 1C pulse tests and equivalent driving cycles. At 1C pulse tests, the mean module temperature obtained by the proposed cooling strategy is 8ºC lower, and the thermal heterogeneity decreased from 7.9 to 2ºC. The equivalent driving cycle results showed the faster response of the direct liquid cooling strategy, which instantaneously reduces the battery module temperature to the cooling setpoint after semi-fast charges.

This study highlights the higher performance of the proposed strategy, which delivers more accurate thermal management without increasing power consumption nor worsening the gravimetric and volumetric energy density. Thus, this research provides a feasible high-performance thermal management solution for high-capacity batteries for electric vehicle applications based on lithium-ion pouch-typed cells.