Jae Wan Park

The performance of proton exchange membrane fuel cells (PEMFC) can be significantly influenced by the physical properties of the flow field design. In this study, nickel foam with varying physical parameters—compression (porosity), pore size, hydrophobicity, and anti‐corrosion surface treatments—are systematically investigated to evaluate their influence on PEMFC electrochemical performance, water management, and corrosion resistance. The results reveal that moderate compression (67%), corresponding to a porosity of 85%, offers the optimal balance between electrical conductivity and mass transport, achieving the highest power density of 0.918 W cm ⁻² and a conductivity formation factor 23% higher than uncompressed samples. Excessive compression may cause ligament fractures and occluded cavities, reducing water management capabilities, and increasing parasitic loss and mass transport resistance. Furthermore, smaller pore sizes result in increased concentration losses, primarily due to higher fluid resistance, complex diffusion pathways, and water retention. Hydrophobic surface modification via polytetrafluoroethylene increased water removal efficiency but at the expense of ohmic losses, with excessive loading hindering water transfer and blocking pores. Among various anti‐corrosion coatings, graphene emerged as the optimal choice, providing superior hydrophobicity, corrosion resistance, and electrical conductivity. These findings offer valuable insights for enhancing PEMFC performance and durability.

As lithium-ion battery (LIB) cells degrade over time and usage, it is crucial to understand their remaining capacity, also known as State of Health (SoH), and inconsistencies between cells in a pack, also known as cell-to-cell variation (CtCV), to appropriately operate and maintain LIB packs. This study outlines efforts to model pack SoH and SoH CtCV of nickel-cobalt-aluminum (NCA) and lithium-iron-phosphate (LFP) battery packs consisting of four cells in series using pack-level voltage data. Using small training data sets and rapid testing procedures, partial least squares regression (PLS) models were built and achieved a mean absolute error of 0.38% and 1.43% pack SoH for the NCA and LFP packs, respectively. PLS models were also built that correctly categorized the packs as having low, medium, and high-ranked SoH CtCV 72.5% and 65% of the time for the NCA and LFP packs, respectively. This study further investigates the relationships between pack SoH, SoH CtCV, and the voltage response of the NCA and LFP packs. The slope of the discharge voltage response of the NCA packs was shown to have a strong correlation with pack dynamics and pack SoH, and the lowest SoH cell within the NCA packs was shown to dominate the dynamic response of the entire pack.

In this study, a lithium-ion soft-pack battery used in an electric vehicle was taken as the research object. Based on the actual working condition of the traction battery, the regularity of the evolution of the overcharge thermal runaway experiment of the sample was deeply analyzed by taking the charging rate and the ambient temperature as variables. The results showed that the larger the overcharge current was and the higher the ambient temperature was, the lower the overcharge thermal stability of the battery was. Furthermore, based on the concept of the introduction of battery energy during charging, by analyzing the total amount of energy input and the rate of energy input, a unified index was established to measure the change of the battery overcharging stability under different experimental conditions.

Hybrid electric vehicles have different performance depending on power distribution and energy management. For heavy-duty vehicles, in particular, these differences will be more pronounced. This paper presents a hybrid powertrain design framework for a heavy-duty multi-purpose vehicle assuming driving conditions. A diesel-powered conventional vehicle was adopted for the hybridization target, and a series hybrid system was suggested as a suitable hybridization topology with an in-wheel motor (IWM) system. The introduced framework supplied the adequate power distribution and the IWM specification based on the speculated drive cycle and a simple energy management strategy. In particular, the reduction ratio of IWM was determined to minimize the gross mass of the motor and reduction gear. The hybridization reduced the vehicle weight by 213 kg while increasing the peak power by 53 kW. Finally, the vehicle simulation was performed using the advanced vehicle simulator for the design result from the proposed framework. The acceleration performance and gradeability limits were improved by 18 % and 10 %p, respectively, compared to the conventional vehicle. In addition, the gasoline equivalent fuel economy of the series hybrid powertrain was 53 % higher than conventional diesel powertrain for the target drive cycle.

The operation of residential solar photovoltaic arrays are typically dependent on net energy metering (NEM) tariffs or feed in tariffs that allow the array owner to treat the electricity grid as an energy storage device. This study presents a model and simulation results of a photovoltaic array paired with a second life battery pack, a partially degraded lithium battery pack from an automotive application, for stabilizing the electricity grid interactions of residential photovoltaic systems and reducing the overall residential demand placed on the electricity grid. Two numerical simulations are performed on the operation of a second life battery pack. The first used an equivalent system model for the battery pack and measured solar production and residential loads to evaluate the system performance using one second time steps. The second model used hourly time steps and round trip efficiency for the battery, coupled with weather data and residential demand, to determine the system performance over the course of a year. The numerical investigation shows that the PV and battery system can substantially reduce the quantity of solar electricity that is exported to the distribution grid and decrease the impacts of sudden fluctuations in photovoltaic output due to cloud cover while providing significant reductions in the electricity demand placed on the grid. Copyright © 2015 John Wiley & Sons, Ltd.