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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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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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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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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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Energy and exergy efficiencies enhancement analysis of integrated photovoltaic-based energy systems
摘要： Integrated energy systems (IESs) take advantage of the complementarity of their subsystems to improve the overall system functionality, sustainability and performance. Presently, the cost of the recovery of thermodynamic losses from photovoltaic modules has not been addressed. In this study, novel energy and exergy efficiencies enhancement analysis (EEEEA) is proposed for the study of the implications of recovering the conversion and usage losses from a photovoltaic (PV) module. Four evolutionary IES were analysed: a PV-Battery (System 1); a Photovoltaic-thermal (PV/T)-Battery (System 2); a PV-Battery-Electrolyser-Fuel cell (System 3) and a PV/T-Battery-Electrolyser-Fuel cell (System 4). Actual solar radiation and temperature data coupled with synthesised data were applied. Results show that both the energy and exergy efficiencies of System 2 upgraded by 27.89% and 5.42%, respectively, over System 1. The energy and exergy efficiencies of System 3 degraded by 3.11% and 4.10%, respectively, over System 1; whereas the energy and exergy efficiencies of System 4 degraded by 21.92% and 7.72%, respectively, over System 2. Furthermore, the thermodynamic efficiencies of the IESs did not naturally upgrade with system complexity. The EEEEA can help scientists, engineers and policymakers to analyse IESs with a parent-offspring relationship in order to establish the optimum efficiency and thermo-economics.
关键词： Photovoltaics,Integrated energy systems,Energy and exergy analysis,Exergy centred design,Distributed systems
更新于2025-09-12 10:27:22
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AIP Conference Proceedings [AIP Publishing XIAMEN-CUSTIPEN WORKSHOP ON THE EQUATION OF STATE OF DENSE NEUTRON-RICH MATTER IN THE ERA OF GRAVITATIONAL WAVE ASTRONOMY - Xiamen, China (3–7 January 2019)] XIAMEN-CUSTIPEN WORKSHOP ON THE EQUATION OF STATE OF DENSE NEUTRON-RICH MATTER IN THE ERA OF GRAVITATIONAL WAVE ASTRONOMY - Exergy efficiency study case of photovoltaic/thermal hybrid cooling refrigeration system using organic fluid mixtures
摘要： At present, much interest is being shown in hybrid absorption refrigeration cycles driven by low temperature heat sources, such as solar energy or low-grade waste-heat. In the present work, an exergetic investigation of a novel configuration double-lift absorption/compression refrigeration system is developed. The potential of the organic mixture (R236fa/DMAC) in the low grade heat pump is discussed. In this paper, a modeling and simulation of the proposed configuration is presented. The ammonia-water system was used for comparison purposes. The results show that the performances of the proposed configuration are improved significantly when using the above mentioned organic mixture. Coefficient of performance of the cycle with R236fa/DMAC is 15% higher than with ammonia/water. Exergetic performances of the system are also improved by about 10% with the use of the proposed new mixture. The most important result given in this study is that the above system operates at low generator temperatures between 50°C and 80°C, which makes it a good alternative of the ammonia-water systems in the low grade heat refrigeration field. The use of such an organic fluid makes it possible to adapt the machine to sources of low energy value, among the possible solutions it was considered to install a hybrid photovoltaic unit that will meet the electrical needs of the heat pump. A simulation was also done to consolidate the results. Results of such a system show that the energy demand of absorption / compression refrigeration machines can be insured by about 80 % by solar energy. The proposed model is efficient in predicting the performance of the machine at different working conditions such as: temperature variation of the generator and evaporator, change in climatic conditions... To conclude, this study will allow making an economic optimization, an approximation on the lifetime as well as the annual production capacity of the unit.
关键词： hybrid heat pump,exergy analysis,organic absorbent,photovoltaic
更新于2025-09-12 10:27:22
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Three-dimensional numerical investigation of a hybrid low concentrated photovoltaic/thermal system
摘要： Concentrated photovoltaic/thermal hybrid collectors have received ever-increasing attention due to the simultaneous output of electric and thermal energy. For further improvement of concentrated hybrid PV/T systems, a simulation method combining the multiphysics fields is necessary to accurately analyze the optical, thermal, and electric performance. Herein, a three-dimensional numerical study has been conducted on a low concentrated photovoltaic/thermal system utilizing a heat transfer fluid as the cooling medium and a compound parabolic concentrator as the mirror field. A finite volume (FV)-CFD code has been employed to simulate the entire model, where the optical modelling is validated theoretically with the Monte Carlo ray-tracing method. The influences of employing various heatsink designs (U-type and Z-type) and coolants (water, ethylene glycol, and therminol VP-1) are numerically investigated. The economic feasibility of the hybrid PV/T system is also assessed in comparison with the standalone PV-cell. Good compatibility with the empirical data was obtained when the appropriate modelling tunings were applied. It is also shown that, on a typical day, the total energy and exergy efficiencies of the system are up to 57.66% and 7.94%, respectively. The Z-type heatsink decreases the average PV-cell temperature than the U-type design, and also the output power is slightly enhanced.
关键词： Photovoltaic/thermal system,FV-DO radiation method,heat sink,energy and exergy analysis
更新于2025-09-12 10:27:22
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Experimental study of a micro-refrigeration system driven by photovoltaic power generation
摘要： A micro-refrigeration experimental system driven by photovoltaic power generation was established, and a study of the cooling capacity, load power, and system efficiency changes over time under sunny and cloudy weather conditions was carried out. The results show that the appendant battery makes the system run more stably, and the weather has no obvious effect on the operation of the indoor refrigeration system. The system exergy analysis indicates that the exergy loss of the compression process is the largest, accounting for more than 80% of the total in the refrigeration system; The exergy efficiency of the refrigeration system can reach about 28% under both weather conditions.
关键词： exergy analysis,Photovoltaic power generation,micro refrigeration system
更新于2025-09-12 10:27:22
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Exergy Analysis of Flat Plate Solar Air Heaters Having Obstacles and Filled with Wire Mesh Layers
摘要： Two new experimental studies are presented in this research for improving the convection heat transfer and efficiency of flat plate solar air heater (SAH). An exergetic analysis is applied for evaluating the efficiency of a flat plate (SAH) with and without porous media. It was specially designed, low height bed filled with aluminium wire mesh layers and four aluminium longitudinal obstacles that increase the air path flow through the bed and the area of the absorber plate. Six wire mesh layers as an alternative of absorber plate, the layers had an internal diameter of 0.31 cm and a cross-sectional area of 0.22 cm × 0.22 cm. The wire mesh layers and the obstacles, improve the heat transfer from the absorber mesh layers in the moving air inside the heater. The plotted exergetic efficiency curves are a function of solar intensity, ambient temperature, bed temperature and temperature rise parameter (To-Ti/ I). These efficiency curves are in bed with and without porous media through different airflow rate. The results illustrate that the heater with porous media SAH is more efficient, from exergy point of view, then the heater without porous media. The maximum exegetic enhanced efficiency with and without porous media SAH in this study has been found to be 3.42 % and 5.16 %, respectively. These results correspond to the low airflow rate of 0.015 kg/s and 2.5 cm channel depth. A significant improvement in the exergetic efficiency discovered when comparing the proposed system with other conventional SAHs.
关键词： Flat Plate Solar Air Heaters,Exergy Analysis,Obstacles,Wire Mesh Layers
更新于2025-09-12 10:27:22
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Performance evaluation of a thermoelectric ventilation system driven by the concentrated photovoltaic thermoelectric generators for green building operations
摘要： This paper proposed one novel Thermo-Electric Ventilation (TEV) system driven by the concentrated photovoltaic-thermoelectric generator (CPV-TEG), which could use the electric power converted directly from solar energy by CPV-TEG. The effects of incident solar irradiance, number of thermoelectric generators, and ambient air temperatures on the power output of CPV-TEG have been analytically investigated through energy balance and first law of thermodynamics. Furthermore, input current and number of thermoelectric coolers were sensitively varied to optimize the performance of TEV system respectively in heating and cooling modes. Finally, an integrated theoretical and numerical approach was proposed to match the power output of CPV-TEG with the power input of TEV. Modeling results indicate that the output power from CPV-TEG could satisfy the energy demand of TEV system when the input currents of thermoelectric coolers were no more than 2.5 A and 2.8 A respectively for cooling and heating modes. Minimum energy and exergy efficiencies of the system in winter heating mode were confirmed to be 1.67 and 0.24 respectively, which were far higher than that in summer cooling mode. This research may be helpful for enhancing performance and reducing exergy destruction of thermoelectric ventilation system, simultaneously.
关键词： thermoelectric ventilation system,power matching,energy and exergy analysis,concentrated photovoltaic-thermoelectric generator
更新于2025-09-12 10:27:22