Results 1 - 10 of 21
Results 1 - 10 of 21. Search took: 0.019 seconds
|Sort by: date | relevance|
[en] On October 21st, 2005 the U.S. Environmental Protection Agency (EPA), establishes AERMOD as regulatory model to be used for the dispersion of pollutants at local scale, in substitution of the ISCST3 model used up to that moment. Whenever a new dispersion model appears, it is necessary for the scientific community to make a comparison in order to discover the differences between the results obtained with the new model and the previous one. Considering the above mentioned fact, this work makes a preliminary comparison between the maximum concentrations calculated by each model (ISCST3 and AERMOD) for a specific case study that consists of eleven batteries of generation sets distributed throughout Havana City which will operate in base load mode and will use a fuel oil with 4% of sulphur. The modelling domain is the 50 xs 37 km with 1 x 1 km cells for a total of 1 850 calculation points (receptors), located in all Havana City and the bordering municipalities of Havana province. In each one of these receptors the dispersion of SO2 and NOx were modelled
[en] Thermal batteries are one of the devices employing solid electrolyte that are not nonconductive at ambient temperature, and activated by electrochemical reaction when the sufficient heat is supplied to electrolyte to melt. The demand of thermal batteries would be increased because it is cost effective and highly reliable in that no maintenance is necessary, electric power can be generated as necessary and no self discharge unlike the other primary batteries. These thermal batteries are used to the military purposes and satellite communication systems and as an emergency power sources, applied to the important places where power supply should not be interrupted, such as hospital, powder plants, ships and portable communication devices. Therefore, the purpose of this study was focused to obtain the manufacturing technologies of thermal battery on our own, after manufacturing the CaCrO4 produced by GNP and investigating the electrochemical characteristics of Ca/LiCl-KCl+CaCrO4/Ni
[en] Highlights: • Novel 3D electrochemical model with heat generation, gives thermal field in prismatic cells. • Advance is coupled electrochemical-thermal field, in past, thermal generation separate. • Thermal profiles determined in new 30 A h cells for US06 drive cycles, with cooling. • Liquid cooling gives temperature increase of 2C, 9C for forced air, 15C for passive air. - Abstract: This study combines a two-dimensional Ohm’s law finite-volume approach determining the current distribution in prismatic battery cells with a simplified electrochemical model for the thermal state of automotive battery packs. The objective was to develop a simulation tool for assessing the effect of cooling effort applied to automotive battery packs under real-life usage conditions. The Ohm’s law model was enhanced by imparting a chemical and physical basis to source terms previously found empirically. This simulation was applied to 2D electrode sheets, determining thermal generation values that were mapped volumetrically into a thermal simulation, which in turn, updated the electrochemical simulation. Battery parameters, along with capacity fade kinetics were determined by fitting experimental data to simulated results. Dynamometer data from tests under reference drive cycles provided current demands on battery cells. Thermal profiles simulated for 30 A h prismatic cells at different cooling levels. Passive and forced air cooling simulations both gave endpoint temperatures upwards of 40 °C (313 K), considered excessive for preserving the battery life. A simulation scenario which reflected a liquid cooling system kept the temperature gain for a US06 drive cycle to about 2 K. With liquid cooling, an automotive battery is better protected against thermally driven degradation.
[en] Fiberglass tape and borosilicate filter discs impregnated with molten LiCl-KCl eutectic were examined for potential use as separators for high-temperature LiSi/LiCl-KCl/FeS(sub 2) thermal batteries. Test discs were punched from these materials and evaluated at 400 C in single cells at a steady-state current of 63 mA/cm(sup 2). The performance generally improved with electrolyte loading for most of the materials. Better results were obtained with the filter discs than with the tape. The best overall results were obtained with Whatman GF/A discs. Active lives for cells with these separators were about 85% of the standard cells with pressed-powder separators. More work with other materials and electrolytes over a wider temperature range is underway, along with 5-cell-battery tests
[en] Highlights: • A simple, accurate and adaptive thermal model is proposed for Li-ion batteries. • Equilibrium voltages, overpotentials and entropy changes are quantified from experimental results. • Entropy changes are highly dependent on the battery State-of-Charge. • Good agreement between simulated and measured heat development is obtained under all conditions. • Radiation contributes to about 50% of heat dissipation at elevated temperatures. -- Abstract: An accurate thermal model to predict the heat generation in rechargeable batteries is an essential tool for advanced thermal management in high power applications, such as electric vehicles. For such applications, the battery materials’ details and cell design are normally not provided. In this work a simple, though accurate, thermal model for batteries has been developed, considering the temperature- and current-dependent overpotential heat generation and State-of-Charge dependent entropy contributions. High power rechargeable Li-ion (7.5 Ah) batteries have been experimentally investigated and the results are used for model verification. It is shown that the State-of-Charge dependent entropy is a significant heat source and is therefore essential to correctly predict the thermal behavior of Li-ion batteries under a wide variety of operating conditions. An adaptive model is introduced to obtain these entropy values. A temperature-dependent equation for heat transfer to the environment is also taken into account. Good agreement between the simulations and measurements is obtained in all cases. The parameters for both the heat generation and heat transfer processes can be applied to the thermal design of advanced battery packs. The proposed methodology is generic and independent on the cell chemistry and battery design. The parameters for the adaptive model can be determined by performing simple cell potential/current and temperature measurements for a limited number of charge/discharge cycles
[en] Highlights: • Double-cavity micro combustor is presented and numerically investigated. • Outer wall temperature of double-cavity combustor is more uniform and higher than that of single-cavity combustor. • Usable radiation energy and radiation efficiency of double-cavity combustor are relatively higher in all studied cases. • The optimum cavity gap length is determined by inlet velocity. - Abstract: The micro combustor is a key component of a micro-thermophotovoltaic (TPV) system. In this study, a novel double-cavity micro combustor is proposed for a micro-TPV system. The thermal performance of the double-cavity micro combustor is numerically investigated. We found that the new combustor can obtain higher and more uniform temperature distribution along the wall because of the second high temperature zone formed in the downstream cavity at relatively high inlet velocity, which is desirable for the micro-TPV system. When the inlet velocity is 12 m/s and the H_2/air equivalence ratio is 0.3, the usable radiation energy is increased from 2.13 W for the single-cavity combustor to 2.59 W for the double-cavity combustor. The corresponding radiation efficiency increases from 1.25% to 1.53%. Meanwhile, the combustion characteristics of the two micro combustors are studied under different H_2/air equivalence ratios at a fixed inlet velocity. The usable radiation energy and radiation efficiency of the double-cavity combustor are higher than that of the single-cavity combustor, and both values increased by increasing equivalence ratio. Furthermore, the influence of cavity gap length between the two cavities is examined at different inlet velocities. Results show that the optimum cavity gap length is determined by inlet velocity.
[en] The performance of Li-alloy/CsBr-LiBr-KBr/Ag(sub 2)CrO(sub 4) systems was studied over a temperature range of 250 C to 300 C, for possible use as a power source for geothermal borehole applications. Single cells were discharged at current densities of 15.8 and 32.6 mA/cm(sup 2) using Li-Si and Li-Al anodes. When tested in 5-cell batteries, the Li-Si/CsBr-LiBr-KBr/Ag(sub 2)CrO(sub 4) system exhibited thermal runaway. Thermal analytical tests showed that the Ag(sub 2)CrO(sub 4) cathode reacted exothermically with the electrolyte on activation. Consequently, this system would not be practical for the envisioned geothermal borehole applications
[en] Muon spin rotation/relaxation method is effective for understanding the functioning mechanism of the functional materials and will gives unique information because (1) It is sensitive to the local magnetism and (2) Positively charged muon can be regarded as a light isotope of the proton. (K.Y.)
[en] Highlights: • The principle of the thermal battery using advanced metal hydrides was demonstrated. • The thermal battery used MgH_2 and TiMnV as a working pair. • High energy density can be achieved by the use of MgH_2 to store thermal energy. - Abstract: A concept of thermal battery based on advanced metal hydrides was studied for heating and cooling of cabins in electric vehicles. The system utilized a pair of thermodynamically matched metal hydrides as energy storage media. The pair of hydrides that was identified and developed was: (1) catalyzed MgH_2 as the high temperature hydride material, due to its high energy density and enhanced kinetics; and (2) TiV_0_._6_2Mn_1_._5 alloy as the matching low temperature hydride. Further, a proof-of-concept prototype was built and tested, demonstrating the potential of the system as HVAC for transportation vehicles