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Photovoltaic panel cooling by atmospheric water sorptiona??evaporation cycle
摘要： More than 600 GW of photovoltaic panels are currently installed worldwide, with the predicted total capacity increasing very rapidly every year. One essential issue in photovoltaic conversion is the massive heat generation of photovoltaic panels under sunlight, which represents 75–96% of the total absorbed solar energy and thus greatly increases the temperature and decreases the energy efficiency and lifetime of photovoltaic panels. In this report we demonstrate a new and versatile photovoltaic panel cooling strategy that employs a sorption-based atmospheric water harvester as an effective cooling component. The atmospheric water harvester photovoltaic cooling system provides an average cooling power of 295 W m–2 and lowers the temperature of a photovoltaic panel by at least 10 °C under 1.0 kW m–2 solar irradiation in laboratory conditions. It delivered a 13–19% increase in electricity generation in a commercial photovoltaic panel in outdoor field tests conducted in the winter and summer in Saudi Arabia. The atmospheric water harvester based photovoltaic panel cooling strategy has little geographical constraint in terms of its application and has the potential to improve the electricity production of existing and future photovoltaic plants, which can be directly translated into less CO2 emission or less land occupation by photovoltaic panels. As solar power is taking centre stage in the global fight against climate change, atmospheric water harvester based cooling represents an important step toward sustainability.
关键词： atmospheric water harvester,cooling strategy,energy efficiency,sustainability,photovoltaic panels
更新于2025-09-23 15:21:01
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Design and investigation of cooling system for high-power LED luminaire
摘要： This paper is concerned with development of cooling system for high-power LED luminaire, including design, simulation, production and investigation. Dimension, shape, and topology optimization algorithms and their program realization are developed with the use of MathCad. Thermal design by Comsol Multiphysics showed that the system on the base of heat pipes is the most effective system for cooling of high-power LED luminaire. The numerical simulation was employed to valid the designed-in engineering solution of cooling system for high-power LED luminaire under elevated temperature operating conditions and different orientation in space. In accordance to simulation data cooling system on the base of heat pipes is designed. Theoretical results are well validated by experimental data and numerical simulation and can be widely utilized for designing of cooling system related to various LED products.
关键词： Cooling system,Heat pipe,Thermal design,High-power LED luminaire
更新于2025-09-23 15:21:01
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Novel parabolic trough solar collector and solar photovoltaic/thermal hybrid system for multi-generational systems
摘要： A novel hybrid system, comprising a parabolic trough solar collector and solar photovoltaic/thermal collector units, is proposed and structured for useful multi-generational purposes with hydrogen production. The designed system comprises a parabolic trough solar collector for electricity generation, hydrogen production, and cooling applications. The solar photovoltaic/thermal collector modules serve the purposes of hydrogen production and space heating. A thermodynamic analysis was conducted for practical applications and implementation. The overall energy and exergy efficiencies of the system were calculated to be 12.90% and 54.72%, respectively, for a solar fluid exit temperature of 477 K. The hydrogen production could reach up to 8.226 g/s from the parabolic trough solar collector electrolyzer and 0.07518 g/s from the solar photovoltaic/thermal collector electrolyzer, which could be used for various useful domestic, medical, and industrial applications. The effects of varying the solar fluid exit temperature, incident solar irradiation, ambient temperature, and working fluids on the working system capability were examined. The proposed system demonstrated that the standalone solar hybrid system could serve as a vital tool for essential energy output purposes that are physically practical and economically viable.
关键词： Heating,Solar energy,Power generation,Hydrogen production,Exergy,Efficiency,Cooling
更新于2025-09-23 15:21:01
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Experimental study for the application of different cooling techniques in photovoltaic (PV) panels
摘要： This article contains the experimental investigations of different cooling methods used for photovoltaic (PV) panels. Phase change material (PCM), thermoelectric (TE) and aluminum fins were chosen as the cooling methods. The CaCl2·6H2O is chosen as one of the PCM which is widely used in the cooling of PVs and the other is the PCM with melting temperature above the surface temperature of the PV panel. By using TE material in different numbers (6, 8 and 12) and aluminum fins in different layouts, surface temperatures and output powers of PV panels were compared. It is observed that the PCM which is not chosen appropriately has insulation feature in the PV panel and enhances the temperature of the panel and decreases the output power. When the most successful cooling methods were tested under the same environmental conditions, PV with fin system produced the highest power generation of 47.88 W while PV with PCM and TEM produced the lowest power generation of 44.26 W.
关键词： Thermoelectric module,Photovoltaic,Fin,Cooling,Phase change material
更新于2025-09-23 15:21:01
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Abrasive flow machining (AFM) finishing of conformal cooling channels created by selective laser melting (SLM)
摘要： Conformal cooling channels are widely adopted in the mold industry because of rapid and uniform cooling during injection molding. These complicated cooling channel geometries become feasible via selective laser melting (SLM) technology. However, the SLM fabricated internal channel surface shows high surface roughness of about 10 μm Ra. This rough surface can cause stress concentration, reducing the fatigue life of the mold. Therefore, the objective of this study is to investigate the surface finish of the SLM fabricated conformal channels by abrasive flow machining (AFM), which is widely used in the surface finishing of internal channels. To fulfill this objective, a combination of single/multiple and straight/helical channels for conformal cooling channel geometries are employed. Seven different types of conformal cooling channels (?3mm) inside the bar are fabricated using SLM. The bar is put in the AFM fixture, and the internal channels are polished by flowing AFM media (ULV50%-54) through the channel at the same extrusion pressure of 80 bars for ten cycles. Fourteen bars (seven before AFM and seven after AFM) are machined to have the internal channel surfaces exposed for surface roughness measurement. Surface topographies of the exposed surfaces of seven types of internal channels are obtained using focus variation microscopy. The areal roughness parameters, such as arithmetical mean height (Sa) on the internal channel surfaces before and after AFM. By comparing SLM as-built conformal channel surfaces with AFM finished ones, AFM is shown to be effective in improving all SLM conformal cooling channels’ arithmetical mean height, Sa. Areal roughness parameters, such as developed interfacial area ratio (Sdr), root mean square gradient (Sdq), reduced peak height (Spk), reduced valley height (Svk), and skewness (Ssk), on those internal surfaces, were found to be sensitive to surface finishing by AFM.
关键词： Conformal cooling channel,Selective laser melting (SLM),Abrasive flow machining (AFM),Straight/helical and single/multiple channels,Areal roughness parameters
更新于2025-09-23 15:21:01
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Numerical simulation of temperature field of B1500HS steel/Q235 laser tailored blanks by external thermal action
摘要： Taking high-strength B1500HS steel/Q235 laser tailored blanks as the research object, this paper established the finite element model of the laser welding process of high-strength B1500HS steel /Q235 laser tailored blanks based on the theoretical model of laser welding temperature field. The temperature field of laser tailored blanks was numerically simulated under the conventional condition and External Thermal Action (ETA). The thermal cycle curve of welded joints was compared and analyzed, and the influence of welding power and welding speed on the welding width was analyzed. The results show that, under ETA condition, the cooling rate of weld and heat affected zone decreases greatly, and the residence time above the phase transition temperature becomes longer. And it is conducive to the homogenization of austenite structure at high temperature and the coordination of mechanical properties of welded joints. In addition, under the same welding power, the welding width of ETA is wider than that of conventional welding, and the larger the welding speed is, the smaller the welding width is. In order to ensure the penetration of welding, the welding speed should between 2mm/s and 7mm/s.
关键词： laser welding,external thermal action,cooling rate,numerical simulation,temperature field
更新于2025-09-23 15:21:01
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Temperature uniformity enhancement of densely packed high concentrator photovoltaic module using four quadrants microchannel heat sink
摘要： The dense solar radiation received by a high concentration photovoltaic module (HCPVM) causes a high cell temperature. In this module, multiple solar cells were electrically connected in both series and parallel. The higher temperature of the solar cell in the series string limits the generated power for the whole string. Therefore, it is crucial to employ a uniform cooling mechanism for higher electrical performance along with a longer lifespan. The uniform cooling is required to attain safe operating temperature and prevent the hot spot formation. Hence, in the current work, a four-compartment microchannel heat sink is proposed for the thermal management of HCPVM under high solar concentration of 1000 suns (1 sun = 1000 W/m2). A three-dimensional (3D) conjugate heat transfer model with exergy analysis is developed and validated. This model was used to investigate the effect of inlet and outlet orientation of four quadrants microchannel heat sink as a cooling method for HCPVM. Eight different orientations of parallel-flow and counter-flow conditions were investigated and compared in terms of temperature non-uniformity, module power, and exergy performance. The results showed that the inlet and outlet orientation was a key role affecting the module temperature non-uniformity. For the counter-flow operated heat sinks, the HCPVM can be operated under a temperature non-uniformity of 3.1 °C at total inlet module mass flowrate of 350 g/min and solar concentration ratio of 1000 suns. In addition, the attained HCPVM electrical, thermal, and overall exergy efficiency were 37.2%, 8.2%, and 45.4% respectively at the same conditions.
关键词： Densely packed module,Solar concentration ratio,Exergy analysis,Microchannel heat sink,Uniform cooling
更新于2025-09-23 15:21:01
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Directly photoexcited Dirac and Weyl fermions in ZrSiS and NbAs
摘要： We report ultrafast optical measurements of the Dirac line-node semimetal ZrSiS and the Weyl semimetal NbAs, using mid-infrared pump photons from 86 meV to 500 meV to directly excite Dirac and Weyl fermions within the linearly dispersing bands. In NbAs, the photoexcited Weyl fermions initially form a non-thermal distribution, signi?ed by a brief spike in the differential re?ectivity whose sign is controlled by the relative energy of the pump and probe photons. In ZrSiS, electron-electron scattering rapidly thermalizes the electrons, and the spike is not observed. Subsequently, hot carriers in both materials cool within a few picoseconds. This cooling, as seen in the two materials’ differential re?ectivity, differs in sign, shape, and timescale. Nonetheless, we ?nd that it may be described in a simple model of thermal electrons, without free parameters. The electronic cooling in ZrSiS is particularly fast, which may make the material useful for optoelectronic applications.
关键词： ultrafast optical measurements,electronic cooling,photoexcitation,Dirac line-node semimetal,thermalization,Weyl semimetal
更新于2025-09-23 15:21:01
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states of Rb in simultaneous magneto-optical trapping of Rb and Hg
摘要： We report the measurement of the photoionization cross sections of the 5S1/2 and 5P3/2 states of 87Rb in a two-species Hg and Rb magneto-optical trap (MOT) by the cooling laser for Hg. The photoionization cross sections of Rb in the 5S1/2 and 5P3/2 states at 253.7 nm are determined to be 1+4.3 × 10?20 cm2 and 4.63(30) × 10?18 cm2, respectively. To measure the 5S1/2 and 5P3/2 state fractions in the MOT we detected the photoionization rate of the 5P3/2 state by an additional 401.5 nm laser. The photoionization cross section of Rb in the 5P3/2 state at 401.5 nm is determined to be 1.18(10) × 10?17 cm2.
关键词： Hg,laser cooling,Rb,magneto-optical trap,photoionization cross sections
更新于2025-09-23 15:21:01
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[SpringerBriefs in Applied Sciences and Technology] Sustainable Thermal Power Resources Through Future Engineering || Experimental Investigation on Performance of Solar-Powered Attic Ventilation
摘要： An attic ventilation system has the potential to reduce cooling load and power consumption of an air-conditioning system in buildings that experience elevated temperature in the attic space during the day. For this, a solar-powered attic ventilation system, which harnesses the abundant source of solar energy from the sun, is desired to ventilate the hot attic space in an economical way. On the other hand, it is known that the ef?ciency of photovoltaic (PV) cells decreases when temperature of the solar panel increases. This chapter discusses the design and development of an ef?cient and low-cost solar-powered attic ventilation system. The novelty approach is intended to improve the PV ef?ciency and the overall performance of the system by providing air?ow for the solar panel from out?ow of the ventilation system. The designed and developed solar-powered attic ventilation system consists of an exhaust fan powered by a polycrystalline solar panel, a direct current to direct current (DC-DC) step-down converter power module, ducting system, and ventilation casing assembled together. Components like ventilation casing and angle adjustable mounting for solar panel are prepared through fabrication work. A few experiments and testing on ventilation process and PV ef?ciency are conducted to determine the performance, working condition, and functionality of the developed system. Parameters like ambient temperature and indoor temperature of the research location are studied in the experiment of ventilation process. Solar irradiance, the power produced from the PV, and the power delivered to the exhaust fan are studied through the experiment on PV ef?ciency. The developed solar-powered attic ventilation system reduces the attic temperature by 2.9 °C and keeps the temperature difference between the ambient and indoor in the range of 0.1–0.4 °C. An increment of about 17% was observed for the PV ef?ciency when there is air?ow for the PV module from out?ow of the ventilation system.
关键词： energy consumption,photovoltaic efficiency,thermal comfort,solar-powered attic ventilation,cooling load reduction
更新于2025-09-23 15:21:01