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Experimental and simulation analysis of novel cooling approaches for automotive lithium-ion batteries
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Worwood, Daniel (2018) Experimental and simulation analysis of novel cooling approaches for automotive lithium-ion batteries. PhD thesis, University of Warwick.
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Official URL: http://webcat.warwick.ac.uk/record=b3473792~S15
Abstract
Previous research has identified that the ageing rate and performance of lithium-ion cells are negatively influenced by unfavourable cell thermal conditions, specifically, high ambient temperatures and large in-cell temperature gradients. Careful consideration must, therefore, be placed on the design of the battery thermal management system (BTMS) contained within electrified vehicles to ensure that thermal constraints are satisfied whilst avoiding the addition of excessive weight and volume which are detrimental to the overall battery system design.
Common cooling approaches that define the current state of the art BTMS focus on cooling the exterior of the cells. For cylindrical cells, cooling the radial surface is susceptible to the formation of large temperature gradients through the cell material, which is exacerbated as the cells heat generation rate increases. Conversely, for pouch cells, the shorter heat transfer pathway between the cell centre and surface makes internal temperature gradients less problematic. However, common cooling approaches using indirect liquid plates to contact the pouch body suffer from inherent leakage concerns.
Conduction based thermal management methods offer inherent benefits over common indirect liquid cooling solutions as the external cooling location may be positioned further away from the cell, which can reduce the risk of leakage and simplify the overall design. Further, the use of conduction elements that are incorporated directly inside battery cells offer the potential to improve temperature uniformity by increasing the heat transfer to the external surfaces of the battery. To advance the deployment of a conduction based BTMS, this thesis presents and examines the thermal performance of two novel cooling approaches employing advanced conduction methods that tackle the key thermal management issues facing both cylindrical and pouch type lithium ion cells in automotive applications. In the cylindrical cell study, a mathematical model that captures the dominant thermal properties of the cell is created and validated using experimental data. Results from the extensive simulation analysis indicate that the proposed internal cooling strategy can reduce the cell thermal resistance by up to 67.8 ± 1.4% relative to single tab cooling and can emulate the thermal performance of a more complex pack-level double tab cooling approach.
In the pouch cell study, a novel graphite-based fin material with an in-plane thermal conductivity 5 times greater than aluminium is presented for advanced battery cooling in a developed novel BTMS design. The thermal performance of the fin is benchmarked against conventional copper and aluminium fins in an experimental programme cycling commercially available 53 Ah pouch cells. Results from the rigorous experimental testing and subsequently validated thermal model indicate that under an aggressive electric vehicle duty-cycle, the new fin can reduce the peak cell surface temperature gradient by up to 55% and volume averaged cell temperature rise by 6.3 ℃ when compared to a comparably sized aluminium fin with the same weight penalty.
The innovative thermal management approaches presented in this thesis offer improved thermal efficiency relative to the current state of the art BTMS reported in the literature, providing important contributions to academia and opportunities for the sponsor company to further the advancement of next generation BTMS.
Item Type: | Thesis (PhD) | ||||
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Subjects: | T Technology > TK Electrical engineering. Electronics Nuclear engineering T Technology > TL Motor vehicles. Aeronautics. Astronautics |
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Library of Congress Subject Headings (LCSH): | Lithium ion batteries, Lithium ion batteries -- Cooling, Automobiles -- Batteries, Automobiles -- Batteries -- Cooling, Battery management systems | ||||
Official Date: | 20 December 2018 | ||||
Dates: |
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Institution: | University of Warwick | ||||
Theses Department: | Warwick Manufacturing Group | ||||
Thesis Type: | PhD | ||||
Publication Status: | Unpublished | ||||
Supervisor(s)/Advisor: | Marco, James ; Greenwood, David | ||||
Sponsors: | Engineering and Physical Sciences Research Council | ||||
Format of File: | |||||
Extent: | xxvii, 283 leaves : illustrations, charts. | ||||
Language: | eng |
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