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Performance Evaluation of Short Parabolic Trough Collectors Integrated with a Small-Scale Solar Power and Heating System
摘要： An investigation is presented on the performance of a small-scale solar power and heating system with short parabolic trough collectors (PTCs). The steady-state model of the short PTCs is evaluated with outside experiments. The model mainly contains the heat loss of the receiver, the peak optical efficiency and the incident angle factor consisting of incident angle modifier and end loss. It is found that the end loss effect is essential in this model when the length of the PTCs is less than 48 m, especially in the winter. The standard deviation of the steady-state model is 1.4%. Moreover, the potential energy efficiency ratio of the solar power and heating system is considerably larger than the coefficient of performance (COP) of general air-source heat pumps, and increases with the decrease of the condensation temperature. An overall system efficiency of 49% can be reached. Lastly, the existence of a water storage tank improves the flexibility of heating the building, and the volume of the water storage tank decreases with the increase of the heating water temperature.
关键词： practical operating characteristics,parabolic trough solar collector,thermal performance,testing method,small-scale
更新于2025-09-23 15:23:52
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Design and characterization of the non-uniform solar flux distribution measurement system
摘要： It is important to accurately measure the solar flux distribution on the heated surface for the utilization of solar energy. To this end, in this paper a new measurement system was proposed to measure the solar flux distribution of the absorber tube surface by taking advantage of the end loss effect. The new measurement system does not disturb the collected lights path and influence the operation of the solar collector. The solar flux distribution at different angles can be measured with a few number of heat flux gage by rotating the proposed solar flux measurement system. Compared with existing measurement techniques, the proposed solar flux measurement system has distinct advantages such as simple structure, flexible and reliable operation and easy application. An experimental platform was designed and constructed, and the solar flux distributions on the outer surface of the absorber under different conditions are measured. The feasibility and effectiveness of the proposed measurement method are validated by comparing the experiment results and the numerical simulation results.
关键词： solar flux distribution,solar flux measurement system,parabolic trough solar collector,experimental investigation
更新于2025-09-23 15:23:52
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Analysis of optical and thermal factors’ effects on the transient performance of parabolic trough solar collectors
摘要： Solar resources are inherently unsteady and their energy density on the earth is low. Thereby, when the solar energy is converted into thermal energy through concentrating the sunlight, how to predict the transient performance of parabolic trough solar collectors under the operating conditions is necessary for the steady useful output and the efficient use of the energy. So this paper describes a mathematical model of the transient thermal behaviors of parabolic trough solar collectors. Then, to validate this transient model, its numerical results are compared with the experimental data. These data were collected from a utility-scale loop of parabolic trough solar collectors. The comparison between the model predictions and the experimental data shows a consistent and reasonable agreement. Furthermore, the primary interest of this study is to determine how the temperature distributions of the absorber, the glass envelope and the heat transfer fluid evolve from initial conditions with specified optical and thermal parameters. Thus, this model is used to carry out parametric studies to make analyses of essential impact factors on transient behaviors of parabolic trough solar collectors. These factors include the temperature of the heat transfer fluid at the inlet, the initial conditions, and the optical efficiency. Moreover, this model has the function of continuous adjustment of the flow rate to satisfy the requirement of the temperature of the heat transfer fluid at the outlet according to varying boundary conditions. Hence, another analysis is performed to investigate transient processes when the flow rate is continuously adjusted at various DNI ramp rates.
关键词： Concentrating solar power,Transient model,Parabolic trough solar collector,Solar heating and cooling
更新于2025-09-23 15:23:52
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A performance and technoeconomic study of different geometrical designs of compact single-pass cross-matrix solar air collector with square-tube absorbers
摘要： This manuscript presents a performance study on a forced convection single-pass solar air heater channel with compact cross-matrix absorber (CMA) incorporating metal hollow square-tube absorbers. Four different geometries of CMA (Type I, II, III and IV) were investigated experimentally to evaluate their efficiency, pressure drops and heat transfer parameters. The experiments were conducted with uniform heat flux (indoor) and outdoor solar radiation as heat source. The air mass flow rates used were between 0.0142 kg/s and 0.0360 kg/s. Techno-economic feasibility studies were conducted using cost-benefit ratio (AC/AEG) method. Thermal efficiency of the CMA obtained by Type I with 76%, being the highest. CMA Type I also exhibited the highest temperature elevation than other configurations with 15.3 °C and thermal capacity of 38.7 kJ. Maximum pressure drop obtained was 1.33 Pa in turbulent condition with Reynolds number of 50,794. Type I has the advantage of high performance CMA and has comparatively lower cost-benefit ratio (AC/AEG) of 0.15 RM/kWh than other type of thermal absorbers.
关键词： Thermal absorber design,Solar air collector,Cross-matrix absorber
更新于2025-09-23 15:23:52
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Performance improvement of baffle-type solar air collector based on first chamber narrowing
摘要： This paper proposes a novel idea to optimize thermal performance of baffle-type solar air collector by narrowing the first chamber through rearranging the baffles in the collector. The collector with five chambers divided by four baffles was investigated numerically and experimentally, and the mechanism of performance improvement was revealed by flow and heat transfer analysis. The simulation results show that the width of first chamber has significant influence on thermal efficiency, while has little influence on pressure drop. The maximum thermal-efficiency growth rate can be achieved when the width of the first chamber is 200 mm with the total chamber size of 2000 mm × 1000 mm × 120 mm, and the value is up to 16.90% compared with the model with evenly distributed baffles during the Reynolds number ranges from 1.8–5.5 × 10^3. A test rig was developed at the ratio of 1:0.5 to the numerical model. Four collector models were studied under three working conditions, and effectiveness of this method is verified. The results show that the first-chamber narrowing method has relatively stable optimization effect with a thermal-efficiency growth rate ranges from 9.73% to 16.10% in the experiment. It means that this method is not sensitive to scale change and has certain adaptability.
关键词： Experimental verification,Numerical simulation,Performance optimization,First chamber narrowing,Solar air collector
更新于2025-09-23 15:23:52
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Direct absorption solar collector with magnetic nanofluid: CFD model and parametric analysis
摘要： Direct absorption collectors (DAC) with nanofluid are among the most promising yet least studied in solar energy technology. There are numerous micro- and macroscopic factors that determine their efficiency. This complicates in situ optimization of DACs using physical prototypes. The present paper describes a multiphase CFD model of the collector, which was validated against two independent experimental datasets. The model was used for a multiparametric numerical analysis, where we altered concentration and size of the nanoparticles, as well as the geometry and inclination of the collector. The optimization resulted in up to 10% improvement in the collector's efficiency. Finally, we considered the process of thermomagnetic convection in the collector using a magnetic nanofluid. This resulted in a 30% increase in the collector performance.
关键词： multiphase,nanofluid,thermomagnetic convection,CFD,direct absorption collector
更新于2025-09-23 15:23:52
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Comparative investigation of performances for HIT-PV and PVT systems
摘要： Crystalline silicon heterojunction solar cells are a promising candidate for high efficiency solar cells, and the heterojunction photovoltaic (HIT-PV) module is strongly dependent on the temperature. In this study, we design three heterojunction photovoltaic modules to improve the performance by preventing from over-heating, with, glass, Tedlar/Polyethylene terephthalate/Tedlar (TPT) and aluminum substrates, respectively. The efficiencies of those HIT-PV modules are investigated under four different outdoor climates. The aluminum-module shows the best thermal dissipation; while the glass-module/TPT-module have the better electrical efficiency and electrical energy, since there is the high reflectivity layer on the surface of the glass (and TPT) substrates rather than the aluminum substrate. In order to increase the output power of HIT-PV modules, we design a heterojunction photovoltaic thermal (HIT-PVT) system based on HIT solar cells and aluminum thermal collector. The measured results of HIT-PVT system show that the coolant circulation increase the output power, and the HIT-PVT module can provide the domestic hot water supply (up to 51.2 °C) under outdoor conditions. In addition, the cost of HIT-PVT systems are much lower than those of the conventional photovoltaic systems, and the investment payback time can be less than 3 years.
关键词： Electrical energy,HIT-PV module,Three substrates,Aluminum thermal collector
更新于2025-09-23 15:23:52
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Thermal performance analysis of a novel linear cavity receiver for parabolic trough solar collectors
摘要： The trough solar thermal power generation system is one of the most mature solar thermal power generation systems. A novel major arc-shaped linear cavity receiver with a lunate channel based on the black cavity effect principle for parabolic trough solar collectors is proposed in this work. The effects of the inclination angle, collecting temperature, surface emissivity and aperture width on the heat loss are thoroughly analyzed with a two-dimensional numerical model coupling natural convection with surface radiation. In addition, the thermal performance of the proposed linear cavity receiver is compared with that of the Solel’s UVAC series evacuated collector tube. The results show that: (1) The natural convection heat loss is significantly affected by the inclination angle, while the radiation heat loss is mainly affected by the surface emissivity and the collecting temperature. (2) The aperture width of the receiver has a great impact on the thermal performance. The larger the aperture width is, the greater the heat losses. However, the aperture width can also affect the optical performance and the manufacturing cost. The reasonable aperture width for this kind of linear cavity receiver is about 50–70 mm with consideration of all these factors. (3) The proposed linear cavity receiver demonstrates comparative or even better thermal performance as traditional evacuated collector tubes, especially in high temperature range. In general, the proposed linear cavity receiver has the comparative shape and size as the traditional evacuated collector tubes. More importantly, it has the advantages of raising the collecting temperature and reducing the production and maintenance costs. Therefore, it can be used to replace the evacuated collector tube which has poor performance due to long-term operation.
关键词： Cavity receiver,Parabolic trough solar collector,Surface radiation,Natural convection,Thermal performance,Linear receiver
更新于2025-09-23 15:23:52
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A dynamic model based on response factor method and seasonal performance analysis for integration of flat plate solar collector with building envelope
摘要： Integrating solar thermal collectors into building envelopes (e.g. walls or roofs) is very promising due to no need of additional site to place solar collectors. When a solar collector is integrated with a building, the working conditions for both the solar collector and the building envelope are changed. This paper proposed a new dynamic thermal model based on the response factor method. The new model combines the conventional analysis method for solar collectors with building envelopes, therefore it is easy to be understood and is more convenient to be realized by programming in a computer than state space model. The calculated results by the dynamic model agreed well with those calculated by the state space model and the measured experimental data, suggesting a satisfying validity of the model proposed. The seasonal performance of a solar wall (integrating of solar collectors and walls) in Beijing was studied by the new model. The results showed that: (1) In winter, the useful heat gain by the solar wall was always a little higher than the separate wall by about 6.7–8.8%, and the heat loss through solar wall is reduced by 90% or more, this is very favorable to reduce space heating load. (2) In summer, the useful heat gain of solar wall was higher than the separate collector by about 2.1–10.2%, the heat transferred through walls was less or higher than the separate wall depending on the inlet water temperature.
关键词： Dynamic model,Building heat transfer,Response factor method,Integration of solar collector with building,Useful heat gains
更新于2025-09-23 15:23:52
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Investigative study of the thermal performance of a trial solar air heater
摘要： Solar collectors need to be inclined at the optimum angle to maximize the receiving energy. The evaluation of the thermal performance of solar air collectors is important for the proper design and sizing of the collector for a given application. In our experimental/theoretical study, which consists of a thermal performance investigation, we have sought to optimize the efficiency–temperature rise couple of the designed solar air heater by considering the appropriate assembling materials regarding the absorber, the glazing and the insulation. Obviously, efficiency is dependent on the orientation of solar collectors and the measured parameters climate conditions such as wind speed, solar radiation and ambient temperature. In order to achieve possible performance optimization of the receiver plane using a low number of variables and equations, the calculations were carried out considering four values of azimuth angle, γ = 0°, 22.5°, 45° and 67.5°, and by varying the tilt angle β by 5 degrees from 15° to 70°.
关键词： Insulation,Efficiency,Absorber,Optimization,Experimental solar air collector
更新于2025-09-23 15:23:52