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[IEEE 2018 IEEE 7th World Conference on Photovoltaic Energy Conversion (WCPEC) (A Joint Conference of 45th IEEE PVSC, 28th PVSEC & 34th EU PVSEC) - Waikoloa Village, HI (2018.6.10-2018.6.15)] 2018 IEEE 7th World Conference on Photovoltaic Energy Conversion (WCPEC) (A Joint Conference of 45th IEEE PVSC, 28th PVSEC & 34th EU PVSEC) - Improving the performance of thermophotovoltaics using stabilized porous media combustion
摘要： A novel cylindrical porous media combustion-based thermophotovoltaic is proposed and experimentally studied. A mixture of methane-air is burnt at an equivalence ratio of 0.7 in a packed bed made of two layers of different alumina balls which are coated with ytterbia (Yb2O3) and erbia (Er2O3) for spectral control with gallium antimonide (GaSb) photovoltaic (PV) cells. A radiant reflector is used to increase the electrical output and the radiant efficiency. The experiments revealed it was possible to achieve a superadiabatic temperature of 1538 °C and a high radiant efficiency, 63%. Overall, this systematic analysis for lean Air/CH4 mixtures represents a new direction for TPV technology.
关键词： porous media combustion,selective coatings,Thermophotovoltaics
更新于2025-10-22 19:40:53
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Asphaltenes dissolution mechanism study by <i>in-situ</i> Raman characterization of a packed-bed microreactor with HZSM-5 aluminosilicates
摘要： Asphaltenes, the most aromatic component of heavy oil, are responsible for the fouling and impairment in flow lines, wellbores, and other production facilities in the petroleum industry. Aromatic solvents such as xylenes are commonly used for the asphaltenes’ cleaning process. Understanding the mechanism of asphaltenes’ dissolution in aromatic solvents is significant for the development of a remediation strategy. The reduction of a reactor’s characteristic length scale leads to the decrease in experimental period while providing high throughput information. Microfluidic systems with in-situ spectroscopy is an excellent platform for time-effective studies of the molecular behavior of asphaltenes in simulated sandstone reservoirs. Here, we injected the HZSM-5 zeolite nanoparticles (707 nm ·aggregate-1 in isopropanol solution) with varying Al2O3/SiO2 ratios (from 0 to 1/26) into the quartz porous media to represent reservoirs with different characteristic acidity. In-line UV-Vis spectroscopy enabled the direct measurement of the dissolution percentage, while in-situ Raman spectroscopy revealed where the dissolution took place within the porous media. In addition to bed occupancy, sheet sizes of asphaltenes molecules can also be determined by in-situ Raman spectroscopy. Our results show that the average sheet size of deposited asphaltenes molecules decreased from 2.97 ± 0.25 nm to 2.74 ± 0.26 nm after cleaning the porous media with xylenes. This trend is confirmed with the fluorescence emission spectra of dissolved asphaltenes molecules, where a 10-30 nm red-shift is present when referenced to asphaltenes source samples. These results provide an explanation to why the dissolution percentage of asphaltenes in aromatic solvents increases from 20.15 wt% to 51.00 wt% as the Al2O3 content increases. We can speculate that this increase in weight percentage is attributed to the differences in deposited asphaltenes molecules’ sheet size. These results reveal the importance of π-π interactions during asphaltenes dissolution process in the aromatic solvent. Our results provide the fundamental understanding of asphaltenes dissolution, which otherwise would be challenging to observe using any other analytical methods.
关键词： in situ Raman spectroscopy,Asphaltenes dissolution,Porous media
更新于2025-09-23 15:21:01
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Effects of bluff-body on the thermal performance of micro thermophotovoltaic system based on porous media combustion
摘要： To improve thermophotovoltaic system efficiency, a porous media combustor with a bluff-body as the flame holder was proposed. A two-dimensional numerical simulation of premixed hydrogen/air combustion inside a planar porous media channel with the local thermal non-equilibrium model was conducted. Effects of the bluff-body flame holder on mean wall temperature and system efficiency were examined. By inserting the bluff-body, the blowout limits of the planar porous media combustor for ? = 0.6, 0.8, 1.0, 1.2 are increased by 33%, 19%, 12%, 20%, respectively. Numerical results show that the flame stabilization is dominated by flow and heat recirculation. Further analysis reveals the mechanism of heat transfer on flame stabilization due to three heat recirculation paths. Considering the view factor and the external quantum efficiency, the system efficiency with the bluff-body is increased by 14.72% as compared to the one without the bluff-body at ? = 0.8, vin = 4 m/s.
关键词： Wall temperature,Bluff-body,System efficiency,Micro thermo-photovoltaic system,Porous media combustion,Heat recirculation
更新于2025-09-23 15:19:57
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Numerical study of the geometrically graded metal foam for concentrated photovoltaic solar cell cooling
摘要： Concentrated photovoltaic cell (CPV) had gained much attention recently due to high efficiency at a competitive cost. However, efficiency of CPV is inversely proportional to the temperature. Hence, it is important to reduce the maximum temperature and variation of temperature across the CPV. Metal foam with its high specific surface area, thermal conductivity and tortuous flow path to promote mixing is an ideal candidate for thermal management for CPV. However, the thermal performance of the metal foam may drop from upstream to downstream and lead to poor cooling performance near the outlet. In this study, functionally graded metal foam is attached on the CPV to extract the heat generated. Functionally graded aluminum foam with gradual variation porosity are modelled to investigate the thermal performance and flow field using computational thermal fluid dynamics analysis. Heat transfer correlation, permeability and resistance loss coefficient are extracted from the literature and used in the simulation. The results showed that functionally graded metal foam with gradual reducing porosity offered a better temperature uniformity for the CPV. Therefore, this approach will further extend the cycle life as well as improve the overall efficiency of the CPV.
关键词： solar cell,cooling,metal foam,CFD,porous media
更新于2025-09-12 10:27:22
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Experimental study of active phase change cooling technique based on porous media for photovoltaic thermal management and efficiency enhancement
摘要： The photoelectric conversion efficiency of solar cells was significantly influenced by its operating temperature which promotes the studies in thermal management for photovoltaic (PV). This paper introduced a novel cooling method based on porous media applied in PV panel for thermal management and efficiency enhancement. An active phase change (APC) cooling system has been designed and fabricated to explore the possibility of cooling the PV panel, and ethanol was considered as the working fluid. By laboratory test, average temperature, temperature distribution, electrical performance of the PV panel as well as energy and exergy efficiency were analyzed in detail. The results demonstrated that the average temperature of the PV panel can be better managed by the APC cooling method compared with the uncooled conditions at different irradiation levels. Besides, increasing the non-condensable gas flow rates has a positive effect on the temperature reduction and maximum generated power of the PV panel. The obtained three-dimensional temperature distribution map proved that the temperature distribution was well uniform with the maximum temperature difference less than 5 °C. The maximum specific power improvement and percentage improvement in power generation were 21.37 W/m2 and 19.32%, respectively.
关键词： Photovoltaic,Efficiency enhancement,Active phase change,Thermal management,Porous media
更新于2025-09-12 10:27:22
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A comprehensive experimental characterisation of a novel porous media combustion-based thermophotovoltaic system with controlled emission
摘要： The high temperatures of combustion systems make them suitable for coupling with thermophotovoltaic systems. In practice, it is quite challenging to reduce heat losses and the spectral mismatch between the emission of the combustion source and the spectral response of photovoltaic (PV) cells. In an effort to pull these disparate energy-focussed research fields together, this paper explores the use of a low-cost erbia (Er2O3) coating on a novel porous media combustion-based thermophotovoltaic (PMC-TPV) reactor for continuous combined heat and power generation. In this work, three different configurations were analysed, including a non-coated porous foam, a coated porous foam, and a coated quartz container. As such, this study provides the first in-depth analysis and characterisation of all salient components of a PMC-TPV system. It includes a detailed characterisation of a 24-cell gallium antimonide (GaSb) array, which was attached to a heat sink and used to harvest the radiant emission from a hot (> 1200 °C), yttria-stabilised zirconia/alumina composite (YZA) ceramic foam. Since the ceramic foam does not have an ideal emissivity curve for these cells, the ability of the erbia coating to control the spectral emission was measured. The results show that by applying the erbia coating to the outer surface of the YZA foam (e.g. using a simple 2-step process of dip coating followed by curing/calcination), it is possible to increase performance, achieving a maximum in-band emission fraction of 25.4% at a firing rate of 1300 kW/m2 (i.e. around 10% of increase than that for non-coated configuration), which provides a temperature of 1285 °C. Additionally, a maximum power output of 1 W was achieved by using erbia coating on YZA foam. For the third configuration, the use of the erbia coating on the quartz tube (instead of the YZA foam) leads to an increase in the maximum core temperature of the reactor up to 1443 °C; however, this also leads to a decrease in electrical performance due to a lower in-band fraction. These findings show that applying an erbia coating on an industrial radiant emitter could enable a combined heat and power processes to gain around 30% increase of electrical output. Finally, since the PV fill factor was lower than expected, and electroluminescence measurements indicated cell damage, these findings also reveal the importance of continuously monitoring PV parameters in PMC-TPV systems.
关键词： Thermophotovoltaic systems,Direct energy conversion,Porous media combustion
更新于2025-09-11 14:15:04
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Tomography-based determination of Nusselt number correlation for the porous volumetric solar receiver with different geometrical parameters
摘要： Pore-scale numerical models of the porous volumetric solar receiver are established in this paper. By using the X-ray computed tomography and the imaging processing techniques, models of porous media with different geometrical parameters are reconstructed. The conjugate heat transfer process in the porous volumetric solar receiver is solved based on the direct pore-scale numerical simulation. The turbulent effect of fluid flow inside porous geometry is considered by the Shear-Stress Transport k-ω model and the absorbed solar energy is simulated by following the Beer’s law. The results present that the inlet velocity and the geometrical parameters influence the thermal performance of the porous volumetric solar receiver. Larger inlet velocity tends to enhance the convective heat transfer between fluid and solid phases meanwhile decreases noticeably the overall temperature. Receiver with larger porosity is preferred because it limits the reflection losses. The Nusselt number increases as the porosity becomes larger. As a result, the general correlation of Nusselt number for the porous volumetric solar receiver is derived as a function of porosity and Reynolds number. This correlation is applicable with the porosity ranging from 0.74 to 0.89 and the pore Reynolds number ranging from 3 to 233.
关键词： Solar energy,Pore-scale numerical simulation,Convective heat transfer,Volumetric solar receiver,Nusselt number correlation,Porous media
更新于2025-09-09 09:28:46
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[ASME ASME 2015 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems collocated with the ASME 2015 13th International Conference on Nanochannels, Microchannels, and Minichannels - San Francisco, California, USA (Monday 6 July 2015)] Volume 1: Thermal Management - A Study on the Thermo-Fluid Simulation Model Using Porous Media in the Power Conversion System
摘要： When converting an electric power by an insulated-gate bipolar transistor (IGBT) module, the problem which is the heat generation in the IGBT module should be prudently considered in the design process. As an engineer reviews the cooling performance of power semi-conductor devices only at the component level, it is difficult to predict the reduction of airflow rates in the heat sink when power semi-conductor devices including the heat sink are integrated into the power conversion system. As the porous media model is adopted in the IGBT stack of the PCS, the problem that the meshes are heavily concentrated in the IGBT module including the heat sink, air, and IGBT/ diode chips can be evaded and the airflow rate which is reflected in the effect of flow resistance by all interior structures including the IGBT module is calculated. For the outdoor type PCS, the hotspot temperature on the heat sink of the simulation and experiment is 99.3 and 101.6 Celsius, respectively. The proposed numerical simulation model considerably accurately predicts the hotspot temperature on the heat sink and can earn benefits in terms of efforts of mesh generation and computation time.
关键词： porous media model,heat sink,thermo-fluid simulation,power conversion system,IGBT module
更新于2025-09-04 15:30:14