Overcoming the electricity grid capacity and battery thermal limitations of electric vehicle fast charging using stationary energy storage and cell thermal modelling

Abstract

Electric vehicles have the potential to both provide health benefits to the population by reducing air pollution and combat climate change by reducing greenhouse gas emissions. Potential electric vehicle owners currently worry that on long distance journeys they will run out of energy in the vehicle battery and have to wait while their battery is recharged, potentially adding hours to their journey. Fast charging, defined here as a charging power greater than 120 kW, is therefore one of the challenges to overcome before the widespread consumer adoption of electric vehicles. Future advances in battery chemistry may enable the faster charging of electric vehicles, however if these advances are achieved, two challenges will remain and these are the focus of this thesis: 1. Faster charging requires higher power capacity electricity grid connections, which may not be available at the required fast charging station location. 2. Faster charging requires the batteries to operate at higher charge rates, which generates more heat meaning the battery may require active thermal management during charging. The solution to the first challenge investigated in this thesis is to use stationary energy storage at fast electric vehicle charging stations. The stationary energy storage buffers the energy between the electricity grid and the electric vehicles using the fast charging station, thereby reducing the maximum power demand required from the grid and meaning installation is possible at more locations on the grid. In this thesis, a novel method is used to predict demand at fast charging stations before a second novel method is proposed to size the required stationary energy storage. The solution to the second challenge is to use thermal modelling to design thermal management systems to deal with the excess heat generated during fast charging. In this thesis a thermal model that can be used for high rate applications, defined here as a rate that will recharge the battery in less than one hour, is demonstrated and a novel experimental method to determine the parameters required for the model is proposed.

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ORCID for Andrew Cruden: orcid.org/0000-0003-3236-2535

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