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Application of polar solvent effects in absorption spectra for determination of lowest electron-excited states of phthalide
摘要： The optical absorption spectra of phthalide in polar (methanol) and nonpolar (n-hexane) solvents are recorded. The electronic phthalide spectrum was calculated by TDDFT B3LYP/6-311+G(d, p) using the polarisable continuum model. Based on an analysis of calculation data and the displacement of absorption bands in a polar solvent, it was established that the absorption bands of phthalide at energies of 3.51 and 3.96 eV correspond to singlet-triplet transitions to the T1 and T2 states, respectively.
关键词： Triplet excited states,Electronic absorption spectra,PCM TDDFT,Solvent effect,Phthalide
更新于2025-09-23 15:23:52
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Numerical and outdoor real time experimental investigation of performance of PCM based PVT system
摘要： Photovoltaic power generation is a suitable option to counter depleting and environmentally hazardous fossil fuels. However, increased cell temperature of the photovoltaic module reduces the electrical performance. Therefore, for enhancing the electrical performance as well as to obtain the useful thermal, a combined photovoltaic thermal system is suitable technology. Furthermore, the addition of phase change materials into photovoltaic thermal systems adds more dual benefits in terms of cooling of PV cell as well as heat storage. Hence, there are still issues to transfer heat from the system efficiently, which cause lower performance of PVT and PVT-PCM systems. In this paper, the aluminium material of thermal collector is used by introducing a novel design to enhance heat transfer performance, which is assembled in PVT and PVT-PCM systems. Experimental validation is carried out for the 3D FEM-based numerical analysis with COMSOL Multiphysics? at 200 W/m2 to 1000 W/m2 varying irradiation levels while keeping mass flow rate fixed at 0.5LPM and inlet water temperature at 32 °C. The experiment is carried out at outdoor free weather conditions with passive cooling of the module by an overhead water tank scheme. A good agreement in numerical and experimental results is achieved through experimental validation. Cell temperature reduction of 12.6 °C and 10.3 °C is achieved from the PV module in case of the PVT-PCM system. The highest value of the electrical efficiency achieved is 13.72 13.56% for PV and 13.85 and 13.74% for PVT numerically and experimentally respectively. Similarly, for PVT-PCM, electrical efficiency is achieved as 13.98 and 13.87% numerically and experimentally respectively. In the case of the PVT system, electrical performance is improved as 6.2 and 4.8% and for PVT-PCM, it is improved as 7.2 and 7.6% for numerically and experimentally respectively.
关键词： PCM,PV/T,Performance,Solar irradiation
更新于2025-09-23 15:23:52
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Characterization of form-stable phase-change material for solar photovoltaic cooling
摘要： Solar PV panel cooling is essential to achieve maximum efficiency of PV modules. Phase-change material (PCM) is one of the prominent options to cool the panel and reduce the temperature, since PCMs have low thermal conductivity. Expanded graphite particles are used to enrich the structure and stability as well as to increase the thermal properties. In the present research work, polyethylene glycol (PEG) 1000 is used as a base material and expanded graphite for inclusive particle. A novel form-stable PEG1000/EG composite PCM mixture is prepared, using impregnation and dispersion method. Expanded graphite and PEG1000/EG sample phase compositions are investigated, using X-ray diffraction technique. No new peak is identified in the composite PCM sample. The surface morphology and structure of EG and PEG1000/EG are investigated, using scanning electron microscopy (SEM). Chemical stability analysis is done by Fourier-transform infrared spectroscopy. Thermal properties of the prepared composite PCMs are analysed by differential scanning calorimetry, thermogravimetric analysis (TGA) and KD2 pro analyser. Results show that addition of EG in various propositions (5%, 10% and 15%) enhances the thermal conductivity of PCM samples from 0.3654 to 1.7866 W mK?1, while melting point and latent heat of fusion of PCM samples are getting reduced. TGA thermographs are used to investigate the thermal stability of the composite PCM samples. TGA curves show that loss of mass happens above the operating temperature, and it is varied with different mass ratios of EG. Characterization of the prepared composite PCM samples is compared and found that PEG1000-85%/EG-15% is the best form-stable PCM, suitable for cooling the solar PV panel as well as to improve the electrical efficiency coupled with a decrease of temperature in the range of 35 °C to 40 °C.
关键词： PEG1000 PCM material,Solar PV cooling,Expanded graphite,Thermal storage,DSC,Characterization
更新于2025-09-23 15:19:57
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Theoretical investigation using DFT of quinoxaline derivatives for electronic and photovoltaic effects
摘要： Photovoltaic properties of solar cells based on fifteen organic dyes have been studied in this work. B3LYP/6-311G (d,p) methods are realized to obtain geometries and optimize the electronic properties, optical and photovoltaic parameters for some quinoxaline derivatives. The results showed that time dependent DFT investigations using the CAM-B3LYP method with the polarized split-valence 6-311G (d,p) basis sets and the polarizable continuum model PCM model were sensibly able to predict the excitation energies, the spectroscopy of the compounds. HOMO and LUMO energy levels of these molecules can make a positive impact on the process of electron injection and dye regeneration. Gaps energy ΔEg, short-circuit current density Jsc, light-harvesting efficiency LHE, injection driving force ΔGinject, total reorganization energy λtotal and open-circuit photovoltage Voc enable qualitative predictions about the reactivity of these dyes.
关键词： Computing methodology,TD-DFT,Energy,PCM,Optoelectronic,Particle physics,Quantum mechanics,Photovoltaic,Physics,Quinoxaline derivatives,Theoretical computer science,Solar cells,Molecular physics
更新于2025-09-23 15:19:57
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Photovoltaic Cooling Utilizing Phase Change Materials
摘要： A theoretical analysis based on mathematical formulations and experimental test to a photovoltaic system cooled by Phase Change Material (PCM) is carried out and documented. The PCM is attached to the back of the PV panel to control the temperature of cells in the PV panel. The experimental tests were done to solar systems with and without using PCM for comparison purposes. A PCM of paraffin graphite panels of thickness15 mm has covered the back of the panel. This layer was covered with an aluminum sheet fixed tightly to the panel frame. In the experimental test, it was found that when the average cell temperature exceeds the melting point temperature of the PCM, the efficiency of the system increases. However, when the cell temperature did not exceed the melting temperature of the PCM, the use of the PCM will affect negatively the system efficiency.
关键词： Photovoltaic Cooling,PCM melting point,PV panel efficiency,Phase Change Materials
更新于2025-09-23 15:19:57
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Performance analysis of solar tunnel dryer with thermal storage and Photovoltaic system for drying star fruit
摘要： The aim of this research work to analyse the performance of the proposed solar tunnel dryer and photovoltaic (PV) system to dry star fruit. Star fruit (Averrhoa carambola L.) is a native fruit in the north eastern states of India. Due to its rich nutritional composition and medicinal property, the demand for this fruit increased nationally. The proposed design consists of a tunnel type drying chamber and thermal storage unit. Paraffin wax (PCM) was used as a thermal storing material mounted in the tunnel dryer chamber to use the thermal energy at off sunshine hours. The thermal insulation coating on the outer surface of the solar drying chamber enhances the thermal performance of the tunnel dryer. The overall efficiency of this proposed design was analysed. The results indicated that drying of star fruit occurred in the falling rate period, where no constant rate period of drying rate was observed. The quality analyses data revealed that higher values of TPC (47.59 mg GAE/ gram of sample) and DPPH (73.59 μ mol of TE/ gram of sample) are obtained in the samples dried in solar dried as compared to open sun-dried samples. Sensory analysis (taste, aroma and flavour) carried out on slices of star fruit indicated that the solar-dried slices provided better scores compared to open sun-dried samples.
关键词： Star fruit,Solar tunnel dryer,Sensory analysis,PCM
更新于2025-09-23 15:19:57
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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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In-Situ Testing of the Thermal Diffusivity of Polysilicon Thin Films
摘要： This paper presents an intuitive yet effective in-situ thermal diffusivity testing structure and testing method. The structure consists of two doubly clamped beams with the same width and thickness but different lengths. When the electric current is applied through two terminals of one beam, the beam serves as thermal resistor and the resistance R(t) varies as temperature rises. A delicate thermodynamic model considering thermal convection, thermal radiation, and film-to-substrate heat conduction was established for the testing structure. The presented in-situ thermal diffusivity testing structure can be fabricated by various commonly used micro electro mechanical systems (MEMS) fabrication methods, i.e., it requires no extra customized processes yet provides electrical input and output interfaces for in-situ testing. Meanwhile, the testing environment and equipment had no stringent restriction, measurements were carried out at normal temperatures and pressures, and the results are relatively accurate.
关键词： in-situ testing,thermal diffusivity,process control monitoring (PCM),thin film
更新于2025-09-19 17:15:36
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Energy, exergy and efficiency of four photovoltaic thermal collectors with different energy storage material
摘要： Hybrid photovoltaic thermal (PV/T) is a technology with many variations and designs. The aim of this unit is cooling down PV temperature while producing hot water. In this paper, different PV/T designs are compared in terms of energy, exergy and efficiency. Data from experiments and numerical calculations conducted at Bangi, Malaysia was used for the comparisons. The proposed systems were tested in outdoor conditions. The designs in question are water-based PV/T, water-based PV/T with PCM tank, nanofluid-based PV/T with nano-PCM tank and conventional PV module. Effect of mass flow rate and solar irradiance are emphasized in this paper. The highest thermal efficiency, thermal energy and electrical exergy produced are found for PV/T with nanofluids and nano-PCM with around 72%, 14 kW and 76.152, respectively. All PV/T systems proposed exhibit better performance than the conventional PV module. These findings highlight the utility of PV/T technology and its massive potential to energize and popularize the solar energy field.
关键词： Nanofluids,PV/T,Nano-PCM,Exergy,Efficiency
更新于2025-09-19 17:13:59
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Thermodynamics assessment on cooling photovoltaic modules by phase change materials (PCMs) in critical operating temperature
摘要： Increasing the temperature of photovoltaic (PV) cells decreases their electricity generation. The use of phase change materials (PCMs) is one of the most common methods for controlling the rate of increasing the temperature of PV cells. This research focuses on thermodynamic analysis of PV/PCM systems with and without fins in maximum operating temperature of PV modules (85 °C). Polyethylene glycol 600 (PEG-600) and paraffin, with different melting points, have been studied experimentally as PCM in an indoor condition. Moreover, the effect of using fins was investigated. For this critical temperature, the results showed that using paraffin could be better for controlling the temperature of PV cells, due to its closer melting point with the module temperature. In the case of fins included, the temperature differences of 28.0 °C and 8.8 °C between the case of paraffin + fin and the case of PEG 600 + fin in comparison with the conventional PV module were measured, respectively. At this critical temperature condition, the output power of a PV module cannot exceed the half of its nominal power. The exergy efficiency of the paraffin + fin case was measured to 4.2% more than the conventional one. Also, entropy generation was calculated and reduction up to 5% was shown for paraffin + fin in comparison with the conventional one. Moreover, variations of the Rayleigh number for proposed cases are calculated too.
关键词： Energy,Critical operating temperature,Entropy,Photovoltaic,PCM,Exergy
更新于2025-09-19 17:13:59