The Experts below are selected from a list of 57222 Experts worldwide ranked by ideXlab platform
Aldo Steinfeld - One of the best experts on this subject based on the ideXlab platform.
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optical design and experimental characterization of a Solar concentrating dish system for fuel production via thermochemical redox cycles
Solar Energy, 2018Co-Authors: Fabian Dähler, Remo Schappi, Philipp Good, Carlos Larrea, Max Schmitz, Philipp Furler, Michael Wild, Thomas Cooper, Philipp Haueter, Aldo SteinfeldAbstract:Abstract The design, fabrication, and on-sun characterization of a Solar dish concentrating system for performing the two-step thermochemical redox splitting of H2O and CO2 is presented. It comprises a primary sun-tracking 4.4 m-dia. Solar dish concentrator coupled to a secondary planar rotating reflector. This optical arrangement enables the operation of two (or more) Solar reactors side-by-side for performing both redox reactions simultaneously by alternating the Solar input between them while making continuous and uninterrupted use of the incoming concentrated sunlight. On-sun characterization of the complete concentrating system revealed a peak Solar Concentration ratio of 5010 suns and an average of 2710 suns measured over the 30 mm-radius aperture of the Solar reactor. A detailed optical analysis elucidates measures to increase the optical efficiency and Concentration ratio.
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OPTICAL DESIGN OF A NOVEL 2-STAGE Solar TROUGH CONCENTRATOR BASED ON PNEUMATIC POLYMERIC STRUCTURES
2016Co-Authors: Roman Bader, Andrea Pedretti, Aldo SteinfeldAbstract:An innovative concept for fabricating Solar trough concentrators based on pneumatic polymer mirrors supported on precast concrete frames is presented. Optical aberration is corrected by means of a secondary specular reflector in tandem with the primary cylindrical concentrator. The optimal design is formulated for maximum Solar flux Concentration. The Monte Carlo ray-tracing technique is applied to determine the effect of reflective surface errors and structural beam deformations on the performance of the combined primary and secondary concentrating system. The numerical results are validated with field measurements on a 49.4 m-length 7.9 m-width sun-tracking prototype system. Theoretical maximum Solar Concentration ratio is 151 suns; the measured one with a flat secondary reflector was 55 suns
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syngas production by simultaneous splitting of h2o and co2via ceria redox reactions in a high temperature Solar reactor
Energy and Environmental Science, 2012Co-Authors: Philipp Furler, Aldo Steinfeld, Jonathan R ScheffeAbstract:Solar syngas production from H2O and CO2 is experimentally investigated using a two-step thermochemical cycle based on cerium oxide redox reactions. A Solar cavity-receiver containing porous ceria felt is directly exposed to concentrated thermal radiation at a mean Solar Concentration ratio of 2865 suns. In the first endothermic step at 1800 K, ceria is thermally reduced to an oxygen deficient state. In the second exothermic step at 1100 K, syngas is produced by re-oxidizing ceria with a gas mixture of H2O and CO2. The syngas composition is experimentally determined as a function of the molar co-feeding ratio H2O:CO2 in the range of 0.8 to 7.7, yielding syngas with H2:CO molar ratios from 0.25 to 2.34. Ten consecutive H2O/CO2-splitting cycles performed over an 8 hour Solar experimental run are presented.
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a modular ceramic cavity receiver for high temperature high Concentration Solar applications
Journal of Solar Energy Engineering-transactions of The Asme, 2012Co-Authors: Illias Hischier, P Poživil, Aldo SteinfeldAbstract:A high-temperature pressurized air-based receiver is considered as a module for power generation via Solar-driven gas turbines. A set of silicon carbide cavity-receivers attached to a compound parabolic concentrator (CPC) are tested on a Solar tower at stagnation conditions for 35 kW Solar radiative power input under mean Solar Concentration ratios of 2000 suns and nominal temperatures up to 1600 K. A heat transfer model coupling radiation, conduction, and convection is formulated by Monte Carlo ray-tracing, finite volume, and finite element techniques, and validated in terms of experimentally measured temperatures. The model is applied to elucidate the effect of material properties, geometry, and reflective coatings on the cavity's thermal and structural performances.
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design of a 10 mw particle flow reactor for syngas production by steam gasification of carbonaceous feedstock using concentrated Solar energy
Energy & Fuels, 2010Co-Authors: Gilles Maag, Aldo SteinfeldAbstract:Steam-gasification of carbonaceous feedstock is carried out in a Solar reactor consisting of a cavity-receiver containing an array of tubular absorbers, through which a two-phase flow of water vapor laden with μm-sized carbonaceous particles reacts to form H2 and CO (syngas). Concentrated Solar radiation, entering through the cavity’s aperture, is supplied as the source of high-temperature process heat to the endothermic reaction. A heat transfer model is formulated by coupling radiation/convection/conduction heat transfer to the chemical kinetics for a solid−gas reacting flow. It is solved numerically by Monte Carlo and finite volume techniques. Experimental validation is accomplished for biochar gasification with a 3 kW prototype reactor subjected to high-flux thermal irradiation. The model is applied to analyze the performance of a 10 MW industrial-scale reactor mounted on a Solar tower configuration. For an optimized reactor geometry and a desired outlet temperature of 1500 K, a Solar-to-chemical energy conversion of 37% is predicted for 1500 suns Solar Concentration.
Antonio Calvo Hernandez - One of the best experts on this subject based on the ideXlab platform.
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Solar driven sodium thermal electrochemical converter coupled to a brayton heat engine parametric optimization
Renewable Energy, 2021Co-Authors: Jincan Chen, Wanli Peng, Julian Gonzalezayala, Antonio Calvo HernandezAbstract:Abstract A novel high-efficiency device comprised of three subsystems, a Solar collector, a sodium thermal electrochemical converter, and a non-recuperative Brayton heat engine, is modeled by taking into account the main internal and external irreversibility sources. The model extends previous works in which the heat waste of the electrochemical converter is used as heat input in a Brayton gas turbine to study its performance and feasibility when a Solar energy input is added. The operative working temperatures of three subsystems are determined by energy balance equations. The dependence of the efficiency and power output of the overall system on the Solar Concentration ratio, the current density, the thickness of the electrolyte, and the adiabatic pressure ratio (or temperature ratio) of the Brayton cycle is discussed in detail. The maximum efficiencies and power output densities are calculated and the states of the maximum efficiency-power density are determined under different given Solar Concentration ratios. The parametric optimum selection criteria of a number of critical parameters of the overall system are provided and the matching problems of the three subsystems are properly addressed. It is found that under a Solar Concentration around 1350, the maximum efficiency and power output density of the proposed hybrid system can reach, respectively, 29.6% and 1.23 × 10 5 W/m2. These values amount approximately 32.7% and 156% compared to those of the Solar-driven sodium thermal electrochemical converter system without the bottoming Brayton cycle. The Pareto front obtained from numerical multi-objective and multi-parametric methods endorses previous findings.
Wanli Peng - One of the best experts on this subject based on the ideXlab platform.
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Solar driven sodium thermal electrochemical converter coupled to a brayton heat engine parametric optimization
Renewable Energy, 2021Co-Authors: Jincan Chen, Wanli Peng, Julian Gonzalezayala, Antonio Calvo HernandezAbstract:Abstract A novel high-efficiency device comprised of three subsystems, a Solar collector, a sodium thermal electrochemical converter, and a non-recuperative Brayton heat engine, is modeled by taking into account the main internal and external irreversibility sources. The model extends previous works in which the heat waste of the electrochemical converter is used as heat input in a Brayton gas turbine to study its performance and feasibility when a Solar energy input is added. The operative working temperatures of three subsystems are determined by energy balance equations. The dependence of the efficiency and power output of the overall system on the Solar Concentration ratio, the current density, the thickness of the electrolyte, and the adiabatic pressure ratio (or temperature ratio) of the Brayton cycle is discussed in detail. The maximum efficiencies and power output densities are calculated and the states of the maximum efficiency-power density are determined under different given Solar Concentration ratios. The parametric optimum selection criteria of a number of critical parameters of the overall system are provided and the matching problems of the three subsystems are properly addressed. It is found that under a Solar Concentration around 1350, the maximum efficiency and power output density of the proposed hybrid system can reach, respectively, 29.6% and 1.23 × 10 5 W/m2. These values amount approximately 32.7% and 156% compared to those of the Solar-driven sodium thermal electrochemical converter system without the bottoming Brayton cycle. The Pareto front obtained from numerical multi-objective and multi-parametric methods endorses previous findings.
J D Phillips - One of the best experts on this subject based on the ideXlab platform.
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heterojunction band offset limitations on open circuit voltage in p z n t e n z n s e Solar cells
IEEE Journal of Photovoltaics, 2015Co-Authors: Alan Teran, Chihyu Chen, E Lopez, P G Linares, I Artacho, A Marti, A Luque, J D PhillipsAbstract:Limitations on the open-circuit voltage of p-ZnTe/n-ZnSe heterojunction Solar cells are studied via current–voltage ( I – V ) measurements under Solar Concentration and at variable temperature. The open-circuit voltage reaches a maximum value of 1.95 V at 77 K and 199 suns. The open-circuit voltage shows good agreement with the calculated built-in potential of 2.00 V at 77 K. These results suggest that the open-circuit voltage is limited by heterojunction band offsets associated with the type-II heterojunction band lineup, rather than the bandgap energy of the ZnTe absorber material.
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thermal emission in type ii gasb gaas quantum dots and prospects for intermediate band Solar energy conversion
Journal of Applied Physics, 2012Co-Authors: Jinyoung Hwang, Andrew J Martin, Joanna Mirecki Millunchick, J D PhillipsAbstract:The electronic structure and thermal carrier capture and escape mechanisms are studied for GaSb/GaAs quantum dots with a type-II band alignment using admittance spectroscopy. Clear signatures are observed corresponding to confined quantum dot states with extracted activation energy of 0.337 eV and the thermal capture cross section in the range from 2.10 × 10−16 to 1.19 × 10−13 cm2. The thermal emission rates in the GaSb/GaAs quantum dots are significantly lower than prior reports for type-I systems, where optical emission is predicted to be the dominant process in an intermediate band Solar cells under Solar Concentration.
Mahmoud Ahmed - One of the best experts on this subject based on the ideXlab platform.
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influence of varying the ethylene vinyl acetate layer thicknesses on the performance of a polycrystalline silicon Solar cell integrated with a microchannel heat sink
Solar Energy, 2020Co-Authors: Abd Elmoneim A Harb, Ali Radwan, Khairy Elsayed, Momtaz Sedrak, Mahmoud AhmedAbstract:Abstract Modifying the polycrystalline silicon Solar cell by reducing the thermal resistance of the ethylene–vinyl acetate (EVA) layer is essential to enhance the thermal management process. This modification will improve the heat dissipation process from the silicon wafer especially at a higher Solar Concentration ratio (CR) and in return enhance the Solar cell performance and output power. Thus, a modified design of a Solar cell integrated with a microchannel heat sink is developed. In this new design, variations of the Ethylene-Vinyl Acetate (EVA) upper- and lower-layer thickness along with the interval width between the two consecutive silicon layers are investigated. To determine the effect of varying the design parameters on the cell temperature at various Solar Concentration ratios and coolant mass rates, a three-dimensional comprehensive model for the Solar cell integrated with a heat sink is developed. The model is simulated and validated with numerical results and measurements. Results indicate that reducing the EVA lower layer thickness has a remarkable effect on the Solar cell temperature. At a Solar Concentration ratio of 20, varying the EVA lower layer thickness from 1.0 mm to 0.2 mm results in decreasing the maximum cell temperature from 102.3 °C to 69.3 °C. With further increase of the Concentration ratio up to 30, the maximum cell temperature reduces from 138.3 °C to 87.4 °C. It is found that at a coolant rate of 2000 gm/min, and a Concentration ratio of 20, maximum temperature in the modified and conventional Solar cell with a lower EVA thickness of 0.2 mm and 0.5 mm, reaches 69.3 °C and 81.5 °C, respectively. Furthermore, the conventional cell efficiency is about 8.90%, while the modified one achieves 9.6%. At a CR = 30, the maximum temperature of the modified cell is 87.4 °C, while it is beyond the permissible temperature for the conventional cell. However, the Solar cell temperature was not affected by varying the EVA upper layer and the interval width between the silicon layers. The finding of the current results provides another direction for researchers to utilize a higher Concentration ratio with polycrystalline silicon Solar cells.
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enhancing the performance of a Solar driven hybrid Solar still humidification dehumidification desalination system integrated with Solar concentrator and photovoltaic panels
Desalination, 2018Co-Authors: Amir Mahmoud, Hassan E S Fath, Mahmoud AhmedAbstract:Abstract A new Solar driven desalination system is developed using hybrid Solar still/two effects humidification-dehumidification desalination system combined with Solar concentrator and two thermally cooled photovoltaic panels. The system performance is investigated under different operating conditions including varying the basin water height, circulating air mass flow rate, and Solar Concentration ratio. A transient mathematical model based on the conservation of mass and energy equations for the system components is developed and the predicted results are validated using the available experimental and numerical data. The results indicated that the system productivity decreases with the increase of the basin height and the circulating air mass flow rate. Integrating the photovoltaic panels along with Solar concentrator leads to a significant increase in the fresh water yield at high Concentration ratio. The maximum temperature of photovoltaic panels, electrical output power and efficiency of both panels are presented. Accordingly, selection of the optimal operating conditions is developed within the allowable maximum basin water temperature (to avoid a potential scale formation) and the maximum photovoltaic panels' temperature.