| 1. |
- Andersson, M, et al.
(författare)
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Dynamic Contact Angle Modeling of Droplet Reattachment at the Gas Channel Wall in Polymer Electrolyte Fuel Cells
- 2019
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Ingår i: eTransportation. - : Elsevier BV. - 2590-1168. ; , s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- Energy security, climate change and air pollution are all motivations for further development of fuel cells. Still, technical problems relating to water management, continue to hinder the marketability of polymer electrolyte fuel cells (PEFCs). The impact of dynamic contact angle (CA) boundary conditions, according to the Kistler model, is evaluated in this paper with the VOF approach, focusing on droplet reattachment at the gas channel wall. From this, it is clear that dynamic CA boundary conditions, compared to static CA boundary conditions, significantly influence the droplet reattachment characteristics, for example for the standard case with a gas velocity of 10 m/s, the first droplet awaits attachment to the channel wall on the side opposite the gas diffusion layer surface for a second droplet before merging and then moving out of the channel together, attached to the channel wall. The impact from dynamic CAs becomes even bigger for lower velocities (5 m/s in this case), where the droplet residence time increases significantly. It is clear that the channel dimensions, gas inlet velocity and value of CAs, as well as if a static or dynamic CA model is used, all have a significant impact on the droplet characteristics in PEFC GCs.
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| 2. |
- Fachrizal, Reza, 1993-, et al.
(författare)
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Smart charging of electric vehicles considering photovoltaic power production and electricity consumption : a review
- 2020
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Ingår i: eTransporation. - : Elsevier. - 2590-1168. ; 4
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Forskningsöversikt (refereegranskat)abstract
- Photovoltaics (PV) and electric vehicles (EVs) are two emerging technologies often considered as cornerstones in the energy and transportation systems of future sustainable cities. They both have to be integrated into the power systems and be operated together with already existing loads and generators and, often, into buildings, where they potentially impact the overall energy performance of the buildings. Thus, a high penetration of both PV and EVs poses new challenges. Understanding of the synergies between PV, EVs and existing electricity consumption is therefore required. Recent research has shown that smart charging of EVs could improve the synergy between PV, EVs and electricity consumption, leading to both technical and economic advantages. Considering the growing interest in this field, this review paper summarizes state-of-the-art studies of smart charging considering PV power production and electricity consumption. The main aspects of smart charging reviewed are objectives, configurations, algorithms and mathematical models. Various charging objectives, such as increasing PV utilization and reducing peak loads and charging cost, are reviewed in this paper. The different charging control configurations, i.e., centralized and distributed, along with various spatial configurations, e.g., houses and workplaces, are also discussed. After that, the commonly employed optimization techniques and rule-based algorithms for smart charging are reviewed. Further research should focus on finding optimal trade-offs between simplicity and performance of smart charging schemes in terms of control configuration, charging algorithms, as well as the inclusion of PV power and load forecast in order to make the schemes suitable for practical implementations.
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| 3. |
- Fachrizal, Reza, 1993-, et al.
(författare)
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Urban-scale energy matching optimization with smart EV charging and V2G in a net-zero energy city powered by wind and solar energy
- 2024
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Ingår i: eTransporation. - : Elsevier. - 2590-1168. ; 20
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Tidskriftsartikel (refereegranskat)abstract
- Renewable energy sources (RES) and electric vehicles (EVs) are two promising technologies that are widely recognized as key components for achieving sustainable cities. However, intermittent RES generation and increased peak load due to EV charging can pose technical challenges for the power systems. Many studies have shown that improved load matching through energy system optimization can minimize these challenges. This paper assesses the optimal urban-scale energy matching potentials in a net-zero energy city powered by wind and solar energy, considering three EV charging scenarios: opportunistic charging, smart charging, and vehicle-to-grid (V2G). This paper takes a city on the west coast of Sweden as a case study. The smart charging and V2G schemes in this study aim to minimize the mismatch between generation and load and are formulated as quadratic programming problems. Results show that the optimal load matching performance is achieved in a net-zero energy city with the V2G scheme and a wind-PV electricity production share of 70:30. The load matching performance is increased from 68% in the opportunistic charging scenario to 73% in the smart charging scenario and to 84% in the V2G scenario. It is also shown that a 2.4 GWh EV battery participating in the V2G scheme equals 1.4 GWh stationary energy storage in improving urban-scale load matching performance. The findings in this paper indicate a high potential from EV flexibility in improving urban energy system performance.
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| 4. |
- Grunditz, Emma, 1980, et al.
(författare)
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Thermal capability of electric vehicle PMSM with different slot areas via thermal network analysis
- 2021
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Ingår i: eTransportation. - : Elsevier BV. - 2590-1168. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, the effect that a varied stator slot size has on the efficiency and thermal capability of a permanent magnet synchronous machine for an electric vehicle, is evaluated and quantified. A machine with four differently sized slot areas was electromagnetically evaluated with finite element analysis, and thermally with a lumped parameter network model. By decreasing the slot size while keeping other dimensions fixed, the core losses reduce due to the wider magnetic path, whereas the winding losses increase. Additionally, a higher maximum torque is reached due to reduced saturation. Results are compared in the machine's torque-speed operating area regarding machine-part and total losses, continuous torque and transient overload capability, as well as during 19 low, middle and high-speed drive cycles regarding energy losses and peak winding temperature. The largest slot showed the lowest winding losses and thus the highest thermally limited torque capability. In contrast, the energy losses with the largest slot were the highest in 13 of the drive cycles, and the lowest in 11 of them with the smallest slot due to its lower part load (i.e. core) losses. The smallest slot would also result in the lowest material cost since it has the least copper.
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| 5. |
- Mademlis, Georgios, 1992, et al.
(författare)
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Multidisciplinary Cooling Design Tool for Electric Vehicle SiC Inverters Utilizing Transient 3D-CFD Computations
- 2021
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Ingår i: eTransportation. - : Elsevier BV. - 2590-1168. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- This paper proposes a new design tool that can be used for the development of a proper cooling component for high-power three-phase SiC module-packs for electric vehicles. Specifically, a multidisciplinary approach of the design process is presented that is based on the accurate electrical, thermal and fluid-mechanics modeling as well as computational testing of a high-power three-phase SiC modulepack under transient-load conditions, so that it can effectively meet the highly-demanding cooling requirements of an electric vehicle inverter. The cooling plate is initially designed by using steady-state based 3D-computational-fluid-dynamic (CFD) tool, as in a conventional method. Then, the proposed design algorithm fine-tunes it through transient 3D-CFD computations by following a specific iterative improvement procedure considering the heat dissipation requirements for the SiC power switches during the official driving cycles for passenger vehicles and during abrupt acceleration tests under several ambient environments. Therefore, not only overheating at all operating conditions is avoided, but also, accurate thermal modeling of the individual inverter modules is provided that can be used for lifetime estimations and for calculating the overload capability of the inverter. The design improvement attained with the proposed procedure against the conventional steady-state approach is validated on a traction 450 A SiC inverter with the model of a real passenger vehicle.
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| 6. |
- Qi, Yuanxin, et al.
(författare)
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Polymer electrolyte fuel cell system level modelling and simulation of transient behavior
- 2019
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Ingår i: eTransportation. - : Elsevier BV. - 2590-1168. ; 2
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, a system level model for a polymer electrolyte fuel cell (PEFC) system, which is capable of characterizing transient behavior using the control volume method, is developed. Three different cases based on different mass transfer assumptions in the cathode channel are explicitly discussed, i.e., considering the presence of 1) only oxygen, 2) both oxygen and nitrogen or 3) oxygen as well as nitrogen and water vapour in the cathode control volume. The analysis illustrates that the model developed predict in adequate manner the dynamic behavior of a PEFC system. It is demonstrated that the presence of nitrogen and water vapour in the cathode volume significantly affects the PEFC's overall performance. Additionally, the model was modified to test the PEFC system's application for start-up, power step-up and shut-down response with the simulation results that show good agreement with experimental data.
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| 7. |
- Streb, Moritz, et al.
(författare)
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Investigating re-parametrization of electrochemical model-based battery management using real-world driving data
- 2023
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Ingår i: eTransporation. - : Elsevier BV. - 2590-1168. ; 16
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Tidskriftsartikel (refereegranskat)abstract
- Li-ion batteries in electric vehicles must be utilized more efficiently to lower their economic and environmental cost. To achieve this increase in efficiency, it is of large interest to develop more thorough battery management that can predict internal states in online settings and update usage and control accordingly. Electrochemical models are an important tool in achieving this, and their implementation in battery management systems is the topic of ongoing research. However, electrochemical battery management relies on accurate parametrization and thus requires re-parametrization as a battery ages. We therefore studied viability of re-parametrization for electrochemical model-based battery management. To this end, we performed global sensitivity analysis on selected Doyle-Fuller-Newman model parameters using on-board current measurements. Representative driving data was collected from several types of heavy-duty vehicles. This elucidated which model parameters should be updated periodically to conserve model accuracy and which parameters are sensitive enough to be estimated from the on-board data. Additionally, we studied how parameter uncertainty affects estimation of internal states and highlight how model-based state estimation relying on a beginning-of-life parametrization degrades as electrochemical parameters change with aging.
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| 8. |
- Zhang, Hongtao, et al.
(författare)
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Power management optimization in plug-in hybrid electric vehicles subject to uncertain driving cycles
- 2020
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Ingår i: eTransporation. - : Elsevier BV. - 2590-1168. ; 3
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Tidskriftsartikel (refereegranskat)abstract
- Optimization of power management in plug-in hybrid electric vehicles (PHEVs) with dual-power-source plays a critical role in achieving higher fuel economy and less pollutant emissions. In this study, power management and optimal control strategies in PHEVs have been investigated subject to uncertain driving cycles of individual drivers for particular trips. First, a stochastic driving cycle is constructed to more accurately model the dynamic characteristics of the uncertain driving cycles, derived from the historic record of individual drivers. Finite-horizon stochastic dynamic programming is adapted to globally optimize the vehicle performance in stochastic sense. Simulation results show that the proposed strategy significantly improves fuel economy, indicating the present optimization approach is very effective in exploring the potential of the hybridization of power train. A higher discretization of (that is, with smaller step sizes in) vehicle dynamics state variables (vehicle velocity, power demand and battery state of charge) has a positive impact on the fuel economy while the limitation of driving operability actually degrades the fuel economy. The commuting time with doubly truncated normal distribution slightly enhances the fuel economy in comparison with uniform distribution. In addition, there exists a tradeoff between the fuel economy and the pollutant emissions. These results could be utilized as a guideline for the design of PHEVs with different objectives.
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| 9. |
- Zhang, Yongzhi, 1991, et al.
(författare)
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Aging characteristics-based health diagnosis and remaining useful life prognostics for lithium-ion batteries
- 2019
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Ingår i: eTransportation. - : Elsevier BV. - 2590-1168. ; 1
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Tidskriftsartikel (refereegranskat)abstract
- This paper developed methods for improving the practicability of battery health diagnosis and remaining useful life prognostics. Battery state of health was estimated using a feature extraction-based method based on the charging voltage curve. Battery remaining useful life was predicted by identifying recognizable aging stages. Acceleration aging test data for 9 cells at constant current rates including 0.5C, 1C, 1.5C, and 2C, and dynamic current rates were used to validate the developed methods. The capacity estimates were accurate with estimation errors less than 1% at most cycles. The remaining useful life was predicted within 0.3 s at dynamic current rates, with the prediction errors at most cycles less than 10 after 300 cycles and the 95% confidence intervals covering about 20 cycles for each prediction.
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