Evaluating multifunctional efficiency of a structural battery composite via thermo-electro-chemical modelling

The emerging research field of structural batteries aims to combine the functions of load bearing and energy storage to improve system-level energy storage in battery-powered vehicles and consumer products. Structural batteries, when implemented in electric vehicles, will be exposed to greater temperature fluctuations than conventional batteries in EVs. However, there is a lack of published data regarding how these thermal boundary conditions impact power capabilities of the structural batteries. To fill this gap, the present work simulates transient temperature-dependent specific power capabilities of high aspect ratio structural battery composite by solving one-dimensional heat transfer equation with heat source and convective boundary conditions. Equivalent circuit modeling of resistivity-induced losses is used with a second-order finite difference method to examine battery performance. More than 60 different run configurations are evaluated, examining how thermal boundary conditions and internal heat influence power capabilities and multifunctional efficiency of the structural battery. The simulated structural battery composite is shown to have good specific Young’s modulus (79.5 to 80.3% of aluminum), a specific energy of 158 Wh/kg, and specific power of 41.2 to 55.2 W/kg, providing a multifunctional efficiency of 1.15 to 1.17 depending on configuration and thermal loading conditions and demonstrating the potential of load-bearing structural batteries to achieve mass savings. This work emphasizes the dependency of power efficiency on cell design and external environmental conditions. Insulating material is shown to improve multifunctional efficiency, particularly for low ambient temperatures. It is demonstrated that as cell temperature increases due to high ambient temperature or heat generation in the battery, the specific power efficiency increases exponentially due to a favorable nonlinear relation between ionic conductivity and cell temperature. The simulations also demonstrate a thermal feedback loop where resistivity-induced power losses can lead to self-regulation of cell temperature. This effect reduces run-averaged losses, particularly at low ambient temperature.

The Microfabricated Alkali Vapor Cell with High Hermeticity for Chip-Scale Atomic Clock

Herein, a microfabricated millimeter-level vapor alkali cell with a high hermeticity is fabricated through a wet etching and single-chip anodic bonding process. The vapor cell, containing Rb and N2, was investigated in a coherent population trapping (CPT) setup for the application of a chip-scale atomic clock (CSAC). The contrast of CPT resonance is up to 1.1% within the only 1 mm length of light interacting with atom. The effects of some critical external parameters on the CPT resonance, such as laser intensity, cell temperature, and buffer gas pressure, are thoroughly studied and optimized. The improved microfabricated vapor cell also exhibited great potential for other chip-scale atomic devices.

An empirical investigation on the correlation between solar cell cracks and hotspots

In recent years, solar cell cracks have been a topic of interest to industry because of their impact on performance deterioration. Therefore, in this work, we investigate the correlation of four crack modes and their effects on the temperature of the solar cell, well known as hotspot. We divided the crack modes to crack free (mode 1), micro-crack (mode 2), shaded area (mode 3), and breakdown (mode 4). Using a dataset of 12 different solar cell samples, we have found that there are no hotspots detected for a solar cell affected by modes 1 or 2. However, we discovered that the solar cell is likely to have hotspots if affected by crack mode 3 or 4, with an expected increase in the temperature from 25$$^\circ $$ ∘ C to 100$$^\circ $$ ∘ C. Additionally, we have noticed that an increase in the shading ratio in solar cells can cause severe hotspots. For this reason, we observed that the worst-case scenario for a hotspot to develop is at shading ratios of 40% to 60%, with an identified increase in the cell temperature from 25$$^\circ $$ ∘ C to 105$$^\circ $$ ∘ C.

Net Water Drag Coefficient during High Temperature Operation of Polymer Electrolyte Fuel Cells

For polymer electrolyte fuel cell (PEFC) systems in vehicle applications, net water drag coefficient ( ) is an essential index and must be negative for system operation. The feasibility of PEFC operation at temperatures over 100C was examined here by measuring and comparing the current density (j) - characteristics using PEFCs with either an Aquivion or Nafion membrane. The effect of cell temperature ( ) on was evaluated at range from 80 to 120C. Results clearly demonstrated that, for both membrane types, significantly increased increasing . Results also confirmed that, at a constant flow rate of H2 at the anode, decreased with decreasing stoichiometric ratio of air ( ), although the effect of on was relatively small. Finally, the effect of relative humidity (RH) balance of supplied gases in both sides (anode/cathode) on water transport at temperature up to 120C was examined for the Aquivion cell. Results revealed that could be significantly decreased by decreasing the RH of hydrogen supplied to the anode (RHA) and that the control of RHA is an effective method for lowering at elevated temperature operation.

Modelling and Optimization of Photovoltaic Serpentine Type Thermal Solar Collector With Thermal Energy Storage System For Hot Water and Electricity Generation For Single Residential Building

Increasing surface temperature significantly affects the electrical performance of photovoltaic (PV) panels. A closed-loop forced circulation serpentine tube design of cooling water system is used to effectively manage the surface temperature of PV panels. A real-time experiment was first carried out with a PV panel with a cooling system at HTF flow rates of 60 kg h-1, 120 kg h-1, and 180 kg h-1. Based on the experimentation, a correlation for a nominal operating cell temperature (NOCT) and thermal efficiency for collector was developed for experimental validation of useful energy gained, cell temperature and electric power generation. The developed corrections are validated with electrical power and useful energy gained in photovoltaic serpentine thermal solar collector (PV/STSC) and fit into experimental results with a deviation of 1% and 2.5 % respectively. Further, with the help of developed correlations, a system was developed in the TRNSYS tool through which an optimization study was performed based on electric and hot water demand. The findings indicate that an optimal system with an 8 m2 PV/STSC area, a HTF flow rate of 60 kg h-1, and TES system having a volume and height of 280 l and 0.8 m could meet 91 % and 33 % of the hot water demand for Ac loads and 78 % or DC loads, respectively.