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Radiative energy and exergy analyses of spectrally-selective surfaces for CSP systems
摘要： This work presents a new methodology for calculations of spectral radiative energy and radiative exergy to evaluate the performances of concentrated solar power (CSP) systems. Spectral radiative properties and the operating temperature of selective surfaces, along with the temperature of the environment, are taken into account in analyses. The fundamental expressions needed for the spectral radiative energy and exergy analyses are introduced first. Then, the two approaches are used to assess the spectral performance of five selective coatings. The spectral analysis is performed in the wavelength range of 250 nm to 20,000 nm, while thermal analysis is carried out for the temperature range of 325 K to 800 K. NREL 6A coating was found to result in the highest radiative energy and radiative exergy for both efficiencies and gains, and for the best thermal stability compared to the other coatings.
关键词： selective coating,spectral radiative energy analysis,concentrating solar power systems,spectral radiative exergy analysis
更新于2025-09-23 15:23:52
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Design and analysis of a multigeneration system with concentrating photovoltaic thermal (CPV/T) and hydrogen storage
摘要： Concentrated photovoltaics (CPV) is an auspicious technology to overcome the high cost problem of highly efficient multi-junction solar cells. However, due to huge concentration of light energy, high heat flux dissipation from a confined space is a challenge. The proposed system here is first of its type to apply and thermodynamically analyze the Nucleate Pool Boiling Heat Transfer (NBHT) for thermal management of CPV. In order to increase overall efficiency of CPV system, a multigeneration system using concentrated photovoltaic thermal (CPV/T) and hydrogen storage is designed and thermodynamically analyzed to fulfill electricity, hot and cold water, heating ventilation and cooling (HVAC) requirement of a residential community with continuous operation. A part of the generated electricity from CPV is used to power the electrolyzer to produce hydrogen and oxygen. The produced gases are stored, and reused by proton exchange membrane fuel cell (PEMFC) to fulfill the system's electrical energy requirement during night time and unfavourable energy conditions in day time. The resultant thermal energy from CPV/T is used for the heating, hot water and cooling requirement of the buildings by employing lithium bromide absorption chiller (AbC). A humidity harvesting system is connected, at the outlet of the absorption chiller, to convert humid air into water and ventilation air requirement of the building. The designed system performs at 67.52% overall energy efficiency, 34.89% of overall exergy efficiency and up to 1862 times concentration ratio at designed steady-state conditions. The results show that with an increase in boiling temperature of NBHT from 353 K to 373 K, the maximum concentration ratio ability increases significantly from 1392 to 2400 times due to increase in critical heat flux, while the electrical efficiency of the CPV system decreases from 28.65% to 27.09% because of increase in cell temperature. To verify the performance of the designed system for different locations, operating conditions and capacities, the effects of Direct Normal Irradiance (IDNI), ambient temperature, relative humidity ratio and the installed capacity are also analyzed by the parametric studies.
关键词： Concentrated photovoltaics,Multigeneration system,Hydrogen storage,Exergy,Solar photovoltaics/thermal system,Electrolyzer and fuel cell
更新于2025-09-23 15:23:52
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Designing and exergetic analysis of a solar power tower system for Iskenderun region
摘要： In this paper, a steam cycle assisted solar tower power system is designed and parametrically optimised for Iskenderun region by considering the weather conditions. After the optimisation, exergy-based analysis of the compounds and overall plant is performed for the best-performing cycle conditions. As a result of the annual-based monthly parametric optimisation, the design parameters, working performance, energy and exergy efficiencies of system are compared to obtain the best-performing cycle conditions which are found in July at the tower outlet pressure and temperature of 100 bar and 1,000°C. The net power production and thermal efficiency of the system at the best-performing conditions are calculated as 47,046.60 kW and 45.814%, respectively. After the exergetic analysis of compounds and overall system, the highest exergetic efficiency is evaluated in 2nd turbine (T-2) as 99.23% and the lowest exergetic efficiency is found in 1st heat exchanger (HeX-1) as 74.16%. Moreover, the overall exergetic efficiency is calculated as 47.19%.
关键词： SPT,steam cycle,solar power tower,exergy analysis,parametric optimisation,energy analysis
更新于2025-09-23 15:22:29
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Solar radiation exergy and quality performance for Iraq and Turkey
摘要： The present study is conducted with two primary objectives: First, a new formulation for the maximum efficiency of the solar radiation conversion is developed by considering the radiative energy transfer between two surfaces at different temperatures for a constant volume system. Second, a new methodology is introduced for estimating the exergy value of the monthly average daily horizontal global radiation, including many parameters, such as monthly average daily value of the horizontal extraterrestrial radiation, the number of sunny hours, the day length, the mean temperature and the mean wind velocity. Seven statistical parameters are used to validate the accuracy of all models. The results of the two new models are found to be more reliable than the results obtained from other models. This study, which was conducted for four locations in Iraq and Turkey. The findings would help in predicting the maximum availability of solar radiation based on weather parameters.
关键词： empirical models,solar radiation,solar radiation exergy
更新于2025-09-23 15:22:29
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A year-round study of a photovoltaic thermal system integrated with phase change material in Shanghai using transient model
摘要： In the study, the daily and monthly performance of a photovoltaic thermal system integrated with phase change material is investigated in Shanghai, China. A three-dimensional model of photovoltaic thermal system integrated with phase change material system is developed and numerically simulated. Water is considered as working fluid, and the fluid flow regime is laminar and incompressible. Both quasi-steady and transient models are compared together, and the transient model is selected because of its higher accuracy. Validation analysis is performed on the numerical model to show the reasonable agreement of current research compared to some other research. After obtaining the suitable operating time for the system, the performance of the system is studied from both energy and exergy viewpoints during the year. An environmental analysis is also conducted to show the annul carbon dioxide mitigation potential. The results show that July is the best month for operating of the system in shanghai with an operating time period of 13.5 h per day on average, while November, December, and January have the lowest operating time period. The percentage of melted phase change material in January, February, March, November and December is zero which means that the melting process does not occur in these months, due to the low ambient temperature and incident solar radiation in Shanghai. Though the overall energy efficiency of the system is higher in summer, the overall exergy efficiency is lower in this season.
关键词： Quasi-steady and transient models,Environmental analysis,Daily and monthly analysis,Energy and exergy analysis,PVT systems
更新于2025-09-23 15:21:01
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Exergy and energy analysis of wavy tubes photovoltaic-thermal systems using microencapsulated PCM nano-slurry coolant fluid
摘要： To develop a more efficient water-cooled photovoltaic-thermal system, energy and exergy analysis of a photovoltaic-thermal system with wavy tubes are investigated numerically using different coolant fluids. A comparison between the straight tube and wavy tubes is conducted for various wavelengths and wave amplitudes. The geometrical parameters of the wavy tubes as well as the velocity of the coolant fluid are examined. Besides, the consequences of coolant fluid including water, Ag/water nanofluid, microencapsulated phase change material slurry, and also a new type of cooling fluid called microencapsulated phase change material nano-slurry are studied. The results show that the electrical, thermal, and exergy efficiencies of the photovoltaic-thermal module enhance by using the wavy tubes compared with the corresponding straight tubes. By declining wavelength in a constant wavelength/amplitude, the heat absorbed by the heat transfer fluid raises. For the best configuration, the primary and exergy efficiencies of the module increase by 6.06% and 4.25%, respectively, for the wavy tubes system compared with those for the straight unit. Furthermore, in both configurations, by increasing the inlet velocity, the overall performance of the photovoltaic-thermal module increases due to a higher heat transfer rate. The results also reveal that among different types of cooling fluids, the microencapsulated phase change material nano-slurry has higher performance in terms of both energy and exergy efficiencies due to having higher thermal conductivity and heat capacity. By employing the wavy tube and the novel proposed coolant fluid, the primary and exergy efficiencies increase in comparison with a typical photovoltaic-thermal module.
关键词： Energy,Microencapsulated phase change material slurry,Wavy tube,Nanofluid,Photovoltaic-thermal module,Exergy
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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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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Numerical and experimental investigation of the energy and exergy performance of solar thermal, photovoltaic and photovoltaic-thermal modules based on roll-bond heat exchangers
摘要： This paper presents numerical and experimental energy and exergy performance assessments of solar thermal (ST), photovoltaic (PV) and photovoltaic/thermal (PV/T) modules based on roll-bond heat exchangers having three different channel geometries: serial, parallel and bionic. The validation of a coupled numerical simulation encompassing the thermo-hydraulic and electrical properties shows that 78% of all the data lies within a ± 10% uncertainty. The thermo-hydraulic simulation shows that the lowest outlet-water temperature inside the absorber is for the case of the bionic absorber (average 44.1 °C vs. 46.5 °C for the serial). This geometry is also beneficial when considering pressure losses, since compared to the parallel configuration (average 778 Pa) the bionic has significantly lower pressure losses (average 385 Pa). The simulation of the electrical properties of PV/T with all three absorber types showed the highest average solar-to-electrical efficiency (14.5%) in the case of the bionic absorber compared to the PV/T with parallel and serial absorbers (14.4% and 14.3%, respectively). Finally, a set of experiments using the ST, PV and PV/T2 (the index 2 denotes a PV/T collector variant with a foil thickness of 0.3 mm, compared to the thickness of 0.4 mm for PV/T1, positioned between the absorber and the PV cells) modules showed that the PV module, coupled with a bionic absorber plate, achieves the highest average electrical (PV – 8.5% vs. PV/T2 – 9.9%) and exergy (ST – 4.4% vs. PV – 9.2% vs. PV/T2 – 12.7%) efficiencies. Only in terms of the thermal efficiency, the PV/T is at a disadvantage to the ST (PV/T2 – 33.5% vs. ST – 61.4%) due to the air gap between the front glass and the absorber of the latter module.
关键词： Simulation,Solar,Roll-bond heat exchanger,Absorber,Exergy,PV/T
更新于2025-09-23 15:19:57
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Exergoeconomic and Envirnoeconomic Analysis of Building Integrated photovoltaic Thermal (BIPVT) System and its Optimization
摘要： This paper gives an idea about advantage of semitransparent photovoltaic system over opaque system. In an inclined system. Considering different parameters of the cell, room, duct and tedlar effect has been made to increase the overall efficiency of the total system. Thermal Model has been designed and mathematical analysis has been done. Electrical as well as thermal energy calculation has been compared with other system from different outputs of different places. If we compare a normal PV system definitely the hybrid PVT system has an edge over PV as in PVT system we consider thermal energy too. A soft computing technique has been developed to optimize the exergy of the system by varying the velocity and length of channel. For the proposed system, it has found that air at 4.5 m/s and channel length of 0.2083 m gives maximum exergy. A total thermal energy gain of 54716kWh and electrical energy gain of 15838kwh is obtained
关键词： Optimization,Electrical and Thermal Exergy,Energy,Building Integrated PVT (BIPVT)
更新于2025-09-23 15:19:57