Samenvatting
The reliance of our energy supply on fossil fuels leads to increasing pollution of the environment and the deterioration of human health, whereas the depletion of fossil fuels is a concern and should also be considered to reduce environmental risks such as climate change. Nowadays, it is expected that the future electricity generation mechanisms could mitigate the challenges related to fossil fuel utilization for the purpose of electrification with the replacement by clean and renewable energy sources (RESs). However, the critical problem with the RESs (solar and wind) is that the output power is intermittent in nature, and this fluctuation affects the grid stability and reliability. Therefore, energy storage technologies, specifically battery energy storage systems (BESS), have been recognized as one of the most promising approaches in a stationary application. Furthermore, the use of BESS in grid-scale stationary applications provides an advantage of increased grid efficiency, voltage stability and reliability, optimizing power flows and supporting optimal use of the RESs.
Nevertheless, a serious weakness of the BESS is their high costs, which represents a prominent barrier to their use in automotive applications or as grid-connected energy storage. To this end, an effective solution is to repurpose or reuse the battery systems after retired from vehicular services. Accordingly, second life batteries (SLBs) are still expected to store and deliver substantial energy in low-demanding stationary applications. Indeed, batteries are retired from a vehicle as soon as they no longer provide 80% of the rated capacity (needed for vehicle range). Hence, it is possible that these devices satisfy the requirements of stationary applications and serve as SLBs. However, the uncertainty on the degradation mechanisms in these SLBs is another challenge that needs deep investigations to ensure prolonged lifetime services.
Therefore, in this PhD thesis, a comprehensive lifetime investigation of the first and second life batteries have been performed by considering both electric vehicles (EVs) and stationary application scenarios respectively. To investigate the first life aging mechanism of the battery cells, an extensive cycling and calendar lifetime characterization is performed. Accordingly, a combined lifetime model is parametrized and developed for predicting the state of health (SoH) in terms of capacity fade and internal resistance growth of the cells. The lifetime model is coupled with a dual polarization equivalent circuit model (DP_ECM) based electro-thermal model, which has initially been used to identify the electrical and thermal behavior of the battery. The validation of the lifetime model is then conducted by using a Worldwide harmonized Light vehicle Test Cycle (WLTC) profile, and a promising accuracy with root mean square error (RMSE) of 2% was achieved. Beyond the study on the capacity loss and the evolution of internal resistance of EVs battery cells, the power capability of these cells was also analyzed by developing a state of power model and estimating the power in terms of internal resistance increase throughout the life of the cells.
In addition to the first life aging study, the representative SLBs are selected by considering the requirements of the stationary application, and then the cell and module level aging of SLBs is performed using a stationary cycling current profile. Prior to the SLBs aging study, the optimal sizing of batteries and RESs-based cycling current profile definition is performed by applying advanced moving average ramp rate compliance (MARRC)-based sizing method and profile synthesization technique. This comprehensive lifetime investigation enables one to evaluate the technical viability of SLBs used in grid-scale power smoothing stationary applications. Accordingly, based on the lifetime characterization and the respective model validation results, this research identified that the nickel-manganese-cobalt oxide (NMC) based lithium-ion (Li-ion) batteries under study show promising performance in both mobility and stationary applications. The result also proved that SLBs are a technically viable solution for the RESs power smoothing application considered in this thesis.
Nevertheless, a serious weakness of the BESS is their high costs, which represents a prominent barrier to their use in automotive applications or as grid-connected energy storage. To this end, an effective solution is to repurpose or reuse the battery systems after retired from vehicular services. Accordingly, second life batteries (SLBs) are still expected to store and deliver substantial energy in low-demanding stationary applications. Indeed, batteries are retired from a vehicle as soon as they no longer provide 80% of the rated capacity (needed for vehicle range). Hence, it is possible that these devices satisfy the requirements of stationary applications and serve as SLBs. However, the uncertainty on the degradation mechanisms in these SLBs is another challenge that needs deep investigations to ensure prolonged lifetime services.
Therefore, in this PhD thesis, a comprehensive lifetime investigation of the first and second life batteries have been performed by considering both electric vehicles (EVs) and stationary application scenarios respectively. To investigate the first life aging mechanism of the battery cells, an extensive cycling and calendar lifetime characterization is performed. Accordingly, a combined lifetime model is parametrized and developed for predicting the state of health (SoH) in terms of capacity fade and internal resistance growth of the cells. The lifetime model is coupled with a dual polarization equivalent circuit model (DP_ECM) based electro-thermal model, which has initially been used to identify the electrical and thermal behavior of the battery. The validation of the lifetime model is then conducted by using a Worldwide harmonized Light vehicle Test Cycle (WLTC) profile, and a promising accuracy with root mean square error (RMSE) of 2% was achieved. Beyond the study on the capacity loss and the evolution of internal resistance of EVs battery cells, the power capability of these cells was also analyzed by developing a state of power model and estimating the power in terms of internal resistance increase throughout the life of the cells.
In addition to the first life aging study, the representative SLBs are selected by considering the requirements of the stationary application, and then the cell and module level aging of SLBs is performed using a stationary cycling current profile. Prior to the SLBs aging study, the optimal sizing of batteries and RESs-based cycling current profile definition is performed by applying advanced moving average ramp rate compliance (MARRC)-based sizing method and profile synthesization technique. This comprehensive lifetime investigation enables one to evaluate the technical viability of SLBs used in grid-scale power smoothing stationary applications. Accordingly, based on the lifetime characterization and the respective model validation results, this research identified that the nickel-manganese-cobalt oxide (NMC) based lithium-ion (Li-ion) batteries under study show promising performance in both mobility and stationary applications. The result also proved that SLBs are a technically viable solution for the RESs power smoothing application considered in this thesis.
| Originele taal-2 | English |
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| Begeleider(s)/adviseur |
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| Datum van toekenning | 16 jan 2023 |
| Status | Published - 2023 |