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Experimental Investigations Conducted for the Characteristic Study of OM29 Phase Change Material and Its Incorporation in Photovoltaic Panel
摘要： The solar photovoltaic (PV) system is emerging energetically in meeting the present energy demands. A rise in PV module temperature reduces the electrical efficiency, which fails to meet the expected energy demand. The main objective of this research was to study the nature of OM29, which is an organic phase change material (PCM) used for PV module cooling during the summer season. A heat transfer network was developed to minimize the experimental difficulties and represent the working model as an electrical resistance circuit. Most existing PV module temperature (TPV) reduction technology fails to achieve the effective heat transfer from the PV module to PCM because there is an intermediate layer between the PV module and PCM. In this proposed method, liquid PCM is filled directly on the back surface of the PV module to overcome the conduction barrier and PCM attains the thermal energy directly from the PV module. Further, the rear side of the PCM is enclosed by tin combined with aluminium to avoid any leakages during phase change. Experimental results show that the PV module temperature decreased by a maximum of 1.2 ?C using OM29 until 08:30. However, after 09:00, the OM29 PCM was unable to lower the TPV because OM29 is not capable of maintaining the latent heat property for a longer time and total amount of the PCM experimented in this study was not sufficient to store the PV module generated thermal energy for an entire day. The inability of the presented PCM to lower the temperature of the PV panel was attributed to the lower melting point of OM29. PCM back sheet was incapable of dissipating the stored PCM’s thermal energy to the ambient, and this makes the experimented PCM unsuitable for the selected location during summer.
关键词： PV module cooling,Thermal absorption,Organic PCM,Thermal dissipation
更新于2025-09-23 15:19:57
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Comparative analysis of different cooling fin types for countering LED luminaires' heat problems
摘要： A significant problem with high-power LED luminaires is heat. Aluminum heat sinks have been extensively used as a solution. The most common method for heat sinks that increases surface area uses fins. In the present study, pin- and plate-fins were compared and it was observed that, in equal surface areas, better cooling was achieved by pin-fins. Thus, the study’s concentration narrowed to pin-fins and the results of different pin-fins were compared. Simulations of a sample group were conducted by using different numbers of fins, and the number of fins giving the lowest Tmax value (the highest junction point temperature) was accepted to be optimum for each group; then the optimum values were compared among the different groups. Keeping the base width of fins constant, optimum values were obtained for the same number of fins when the fin height was changed. However, keeping fin height constant, surface areas of optimum values and measured Tmax values were very close to one another other, even if the base width of fins was changed. The results have practical significance in designing high-power LED luminaires.
关键词： LED cooling,fin height,junction point temperature,base width,High-power LED luminaire,plate-fin heat sink,pin-fin heat sink
更新于2025-09-23 15:19:57
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Analysis of novel passive cooling strategies for free-standing silicon photovoltaic panels
摘要： Silicon-based photovoltaic (PV) panels are sensitive to operating temperatures, especially during exposure to high solar irradiation levels. The sensitivity of PV panels is reflected through the reductions in photovoltaic energy conversion efficiency (electrical efficiency) and in PV panel lifetime due to thermal fatigue. In this study, different and novel passive cooling strategies were proposed and numerically investigated for the case of 50-W market-available free-standing silicon PV panels. The focus of the research was to examine the effect of the proposed modifications on the temperatures of the specific PV panel layers as well as on the velocity contours. The used numerical model was upgraded based on a previously developed numerical model that was validated through an experimental manner. Three different passive cooling scenarios were numerically investigated, and the most promising one was the case where the PV panel was provided with slits through the front PV panel surface resulting in a reduction of about 4 °C for the PV panel operating temperature. The other examined cases proved to be less effective with the detected temperature reduction being less than 1.0 °C. The consideration of novel PV panel frame materials was found to be a viable possibility. It was also found that all the proposed modifications can generally lead to the performance improvement in the PV panels and reduce the materials spent on the production of commercial PV panels.
关键词： Photovoltaics,Numerical analysis,Passive cooling,Renewable energy,Energy efficiency
更新于2025-09-23 15:19:57
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Temperature Effect on Capillary Flow Dynamics in 1D Array of Open Nanotextured Microchannels Produced by Femtosecond Laser on Silicon
摘要： Capillary ?ow of water in an array of open nanotextured microgrooves fabricated by femtosecond laser processing of silicon is studied as a function of temperature using high-speed video recording. In a temperature range of 23–80°C, the produced wicking material provides extremely fast liquid ?ow with a maximum velocity of 37 cm/s in the initial spreading stage prior to visco-inertial regime. The capillary performance of the material enhances with increasing temperature in the inertial, visco-inertial, and partially in Washburn ?ow regimes. The classic universal Washburn’s regime is observed at all studied temperatures, giving the evidence of its universality at high temperatures as well. The obtained results are of great signi?cance for creating capillary materials for applications in cooling of electronics, energy harvesting, enhancing the critical heat ?ux of industrial boilers, and Maisotsenko cycle technologies.
关键词： Maisotsenko cycle,cooling of electronics,silicon,open capillary microchannels,microstructures,nanostructures,femtosecond laser processing,capillary flow
更新于2025-09-23 15:19:57
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Solar gain mitigation in ventilated tiled roofs by using phase change materials
摘要： Several passive cooling design techniques are known for reducing solar heat gain through building envelope in summer season. These include the use of phase change materials (PCM), which has received an increased attention over the last years, and the strategy of increasing the above-sheathing ventilation (ASV) in ventilated roofs. However, few studies combine both technologies to maximise the building resilience in hot season. The effect of including a PCM layer into a ventilated roof is numerically analysed here in two different configurations: firstly, laid on the roof deck (PCM1 case) and, secondly, suspended in the middle of the ASV channel (PCM2 case). A computational fluid dynamics model was implemented to simulate airflow and heat transfer around and through the building envelope, under 3 days of extreme hot conditions in summer with high temperatures and low wind speed. Results showed slight differences in terms of mean temperatures at the different roof layers, although temperature fluctuations at deck in the PCM1 case were smaller than half of those estimated for the benchmark case. However, PCM2 configuration achieved a daily reduction of about 10 Wh/m2 (18%) in building energy load with respect to the benchmark case, whilst PCM1 got only 4% due to the lower ventilation at night time. Therefore, a suspended PCM layer in the ASV channel would be a better measure in terms of energy performance than laid on the deck surface, although this last option significantly decreases thermal stress of the insulation layer.
关键词： passive cooling technique,ventilated pitched roof,computational fluid dynamics,phase change material
更新于2025-09-23 15:19:57
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Colloidal Synthesis and Charge-Carrier Dynamics of Cs2AgSb1-yBiyX6 (X: Br, Cl; 0 ≤y ≤ 1) Double Perovskite Nanocrystals
摘要： A series of lead-free double perovskite NCs: Cs2AgSb1-yBiyX6 (X: Br, Cl; 0≤y≤1) NCs are synthesized. In particular, Cs2AgSbBr6 NCs is a new double perovskite material that has not been reported for the bulk form. Mixed Ag-Sb/Bi NCs exhibit enhanced stability in colloidal solution compared to Ag-Bi or Ag-Sb NCs. Femtosecond transient absorption studies indicate the presence of two prominent fast trapping processes in the charge carrier relaxation. The two fast trapping processes are dominated by intrinsic self-trapping (1~2 ps) due to giant exciton-phonon coupling and surface defects trapping (50~100 ps), respectively. Slow hot-carrier relaxation is observed at high pump fluence, and the possible mechanisms for the slow hot-carrier relaxation are also discussed.
关键词： nanocrystal,double perovskite,carrier-phonon coupling,hot-carrier cooling,trap state
更新于2025-09-23 15:19:57
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Colloidal Synthesis and Charge-Carrier Dynamics of Cs2AgSb1-yBiyX6 (X: Br, Cl; 0 ≤y ≤ 1) Double Perovskite Nanocrystals
摘要： A series of lead-free double perovskite NCs: Cs2AgSb1-yBiyX6 (X: Br, Cl; 0≤y≤1) NCs are synthesized. In particular, Cs2AgSbBr6 NCs is a new double perovskite material that has not been reported for the bulk form. Mixed Ag-Sb/Bi NCs exhibit enhanced stability in colloidal solution compared to Ag-Bi or Ag-Sb NCs. Femtosecond transient absorption studies indicate the presence of two prominent fast trapping processes in the charge carrier relaxation. The two fast trapping processes are dominated by intrinsic self-trapping (1~2 ps) due to giant exciton-phonon coupling and surface defects trapping (50~100 ps), respectively. Slow hot-carrier relaxation is observed at high pump fluence, and the possible mechanisms for the slow hot-carrier relaxation are also discussed.
关键词： nanocrystal,double perovskite,carrier-phonon coupling,hot-carrier cooling,trap state
更新于2025-09-23 15:19:57
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Thermal and electrical performance evaluation of PV/T collectors in Southern India
摘要： Combination of Photovoltaic and solar thermal collectors is used for the simultaneous production of electricity and heat. The proposed research work evaluates the thermal performance of Photovoltaic/Thermal (PV/T) hybrid collectors for the hot and humid weather condition of North Tamilnadu, South India. It is done by providing the cooling arrangement under the collector using wooden duct with baffles. Various parameters influencing the performance of the collector such as solar irradiance, ambient, glazing and tedlar temperatures, air inlet and outlet temperatures at the duct, velocity and mass flow rate of air inside the duct are analysed. The thermal and electrical performances of the PV/T collectors are evaluated under natural and forced circulation of air through the thermal collector. The experimental results are presented in this paper.
关键词： thermal performance,cooling arrangement and wooden duct with baffles,PV/T collectors,electrical performance
更新于2025-09-19 17:15:36
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A Wide Dynamic Range NUC Algorithm for IRCS Systems
摘要： Uniformity is a key feature of state-of-the-art infrared focal planed array (IRFPA) and infrared imaging system. Unlike traditional infrared telescope facility, a ground-based infrared radiant characteristics measurement system with an IRFPA not only provides a series of high signal-to-noise ratio (SNR) infrared image but also ensures the validity of radiant measurement data. Normally, a long integration time tends to produce a high SNR infrared image for infrared radiant characteristics radiometry system. In view of the variability of and uncertainty in the measured target’s energy, the operation of switching the integration time and attenuators usually guarantees the guality of the infrared radiation measurement data obtainted during the infrared radiant characteristics radiometry process. Non-uniformity correction (NUC) coe?cients in a given integration time are often applied to a speci?ed integration time. If the integration time is switched, the SNR for the infrared imaging will degenerate rapidly. Considering the e?ect of the SNR for the infrared image and the infrared radiant characteristics radiometry above, we propose a-wide-dynamic-range NUC algorithm. In addition, this essasy derives and establishes the mathematical modal of the algorithm in detail. Then, we conduct veri?cation experiments by using a ground-based MWIR(Mid-wave Infared) radiant characteristics radiometry system with an ?400 mm aperture. The experimental results obtained using the proposed algorithm and the traditional algorithm for di?erent integration time are compared. The statistical data shows that the average non-uniformity for the proposed algorithm decreased from 0.77% to 0.21% at 2.5 ms and from 1.33% to 0.26% at 5.5 ms. The testing results demonstrate that the usage of suggested algorithm can improve infrared imaging quality and radiation measurement accuracy.
关键词： Infrared radiation,Cooling infrared focal plane array,Non-uniformity correction,Wide dynamic range
更新于2025-09-19 17:15:36
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Characteristics enhancement of one-section and two-stepwise microchannels for cooling high-concentration multi-junction photovoltaic cells
摘要： This paper presents the development of simple, effective, and economic microchannel systems for cooling high-concentration multi-junction photovoltaic (HCMJPV) cells. The developed cooling system uses a short cooling fluid path concept with either one or two microchannel sections per the fluid path. The work is conducted using a 3D numerical model that is based on the finite volume method. The effects of design parameters on the thermal characteristics of one and two-section microchannels and output power of the HCMJPV cells are comprehensively investigated. Cooling systems that attained the largest net output power of HCMJPV cells are identified. Developed cooling systems achieved superior characteristics compared to the existing state of the art system. The two-stepwise microchannel cooling system achieves the best temperature uniformity, whereas the constant-width one-section microchannel cooling system achieves slightly better characteristics than the two-stepwise system. The proposed constant-width one-section cooling system achieves comparable standard deviation and lower surface temperature (35.65 °C), pressure drop (68.41%) and microchannel thermal resistance (49.57%) along with higher generated power (8.27%), net output power (8.44%) and overall heat transfer coefficient (175.8%) than the existed cooling system in literature. The developed cooling system allows the cells to produce an extra 820.5MWh/m2 of cells during their lifetime.
关键词： Hybrid jet impingement-microchannel cooling,Pumping power,High-concentration multi-junction photovoltaic,Stepwise microchannel cooling,High power integrated circuits,Net output power
更新于2025-09-19 17:13:59