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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 radiative transfer module for calculating photolysis rates and solar heating in climate models: Solar-J v7.5
摘要： Solar-J is a comprehensive radiative transfer model for the solar spectrum that addresses the needs of both solar heating and photochemistry in Earth system models. Solar-J is a spectral extension of Cloud-J, a standard in many chemical models that calculates photolysis rates in the 0.18–0.8 μm region. The Cloud-J core consists of an eight-stream scattering, plane-parallel radiative transfer solver with corrections for sphericity. Cloud-J uses cloud quadrature to accurately average over correlated cloud layers. It uses the scattering phase function of aerosols and clouds expanded to eighth order and thus avoids isotropic-equivalent approximations prevalent in most solar heating codes. The spectral extension from 0.8 to 12 μm enables calculation of both scattered and absorbed sunlight and thus aerosol direct radiative effects and heating rates throughout the Earth’s atmosphere. The Solar-J extension adopts the correlated-k gas absorption bins, primarily water vapor, from the shortwave Rapid Radiative Transfer Model for general circulation model (GCM) applications (RRTMG-SW). Solar-J successfully matches RRTMG-SW’s tropospheric heating profile in a clear-sky, aerosol-free, tropical atmosphere. We compare both codes in cloudy atmospheres with a liquid-water stratus cloud and an ice-crystal cirrus cloud. For the stratus cloud, both models use the same physical properties, and we find a systematic low bias of about 3 % in planetary albedo across all solar zenith angles caused by RRTMG-SW’s two-stream scattering. Discrepancies with the cirrus cloud using any of RRTMG-SW’s three different parameterizations are as large as about 20–40 % depending on the solar zenith angles and occur throughout the atmosphere. Effectively, Solar-J has combined the best components of RRTMG-SW and Cloud-J to build a high-fidelity module for the scattering and absorption of sunlight in the Earth’s atmosphere, for which the three major components – wavelength integration, scattering, and averaging over cloud fields – all have comparably small errors. More accurate solutions with Solar-J come with increased computational costs, about 5 times that of RRTMG-SW for a single atmosphere. There are options for reduced costs or computational acceleration that would bring costs down while maintaining improved fidelity and balanced errors.
关键词： solar heating,clouds,Cloud-J,climate models,radiative transfer,photolysis rates,scattering,aerosols,RRTMG-SW,Solar-J
更新于2025-09-23 15:22:29
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Techno‐economic analysis of applying linear parabolic and flat plate solar collectors for heating a building and their comparative evaluation
摘要： In this study, utilizing two types of solar collectors, including linear parabolic (LPC) and flat solar (FPC) collectors to heat a residential building was investigated from technical and economical point of views. The performance of these two systems were obtained and compared with each other in the cold months of the year in the South-East of Iran. The building and the heating systems were simulated in the TRNSYS software. Both the heating systems were separately analyzed from the energy and economic point of views. Results showed that the FPC and LPC heating systems delivered 51.3% and 46.7% of the received solar energy to the building, respectively. The results also showed that the solar fractions of the LPC and FPC heating systems are 22% and 8.6%, respectively. It was found that the thermal storage tank in the FPC hearing system is more useful than the LPC heating system as the LPC heating system with storage tank has a lower rate of heat loss compared to the system with no thermal storage tank. The rate of return investments in the FPC and LPC heating systems were 18.1% and 22.8%, respectively.
关键词： economic analysis,linear parabolic collectors (LPC),TRNSYS,heating load,flat plate collector (FPC),solar heating
更新于2025-09-19 17:15:36
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Solar Engineering of Thermal Processes, Photovoltaics and Wind || Design of Passive and Hybrid Heating Systems
摘要： The principles underlying passive (and active) solar processes are outlined in Chapters 1 to 11, and passive heating and cooling processes and phenomena associated with them are described in Chapters 14 and 15. In this chapter we deal with questions of estimating the annual performance of several types of passive building-heating systems. The solar-load ratio correlation method developed at Los Alamos Scientific Laboratory is first introduced. The application of utilizability methods to direct-gain and collector-storage wall systems is shown. Then design methods for two hybrid systems are outlined, for active collection–passive storage systems and for systems having significant fractions of annual loads carried by both active and passive processes. This combination of methods will allow the annual performance of a wide variety of passive and hybrid systems to be estimated.
关键词： utilizability methods,solar-load ratio,passive solar heating,hybrid systems,annual performance
更新于2025-09-19 17:13:59
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Solar Engineering of Thermal Processes, Photovoltaics and Wind || Design of Active Systems
摘要： The liquid and air system configurations described in Section 13.2 are common configurations, and there is considerable information and experience on which to base designs. For residential-scale applications, where the cost of the project does not warrant the expense of a simulation, performance predictions can be done with “short-cut” methods. Design procedures are available for many of these systems that are easy to use and provide adequate estimates of long-term thermal performance. In this chapter we briefly note some of these methods. The f -chart method, applicable to heating of buildings where the minimum temperature for energy delivery is approximately 20°C, is outlined in detail. Methods for designing systems delivering energy at other minimum temperatures, as encountered in solar absorption air conditioning or industrial process heat applications, are presented in Chapter 21.
关键词： residential-scale applications,f-chart method,design procedures,solar heating systems,thermal performance
更新于2025-09-19 17:13:59
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Artificial neural network based assessment of grid-connected photovoltaic thermal systems in heating dominated regions of Iran
摘要： In this paper, an artificial neural network (ANN) is developed to assess hybrid photovoltaic thermal (PVT) systems for grid-connected (GC) electricity generation, space heating and domestic hot water providing in heating dominated regions of Iran. To do so, monthly and annual performance of a 5 kWp GCPVT system is simulated for a single-family house. The simulation results show that the GCPVT system is very promising whereas the annual yield factor varies from 1506 kWh/kWp to 1891 kWh/kWp. Also, an appropriate solar fractions for covering hot water are achieved in a range from 74.5% to 49.4%. A multilayered perceptron feed-forward neural network which is trained by Levenberg-Marquardt algorithm is used to predict AC electrical energy and solar thermal output of the GCPVT system. The developed ANN is based on global horizontal irradiance, ambient temperature, ambient relative humidity and wind speed as inputs. The proposed configuration of ANN presents a high accuracy in predicting output energy of the GCPVT system according to minimum mean square error and maximum correlation coefficient. Analysis of variance is performed to determine the significant control parameters influencing the output energy of the GCPVT system.
关键词： Solar heating,AC electricity,Grid-connected PVT,Artificial neural network,Performance assessment
更新于2025-09-19 17:13:59
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Economic and environmental potential for solar assisted central heating plants in the EU residential sector: Contribution to the 2030 climate and energy EU agenda
摘要： Aligning with the ambitious EU 2030 climate and energy package for cutting the greenhouse emissions and replacing conventional heat sources through the presence of renewable energy share inside efficient district heating fields, central solar heating plants coupled with seasonal storage (CSHPSS) can have a viable contribution to this goal. However, the technical performance variation combined with inadequate financial assessment and insufficient environmental impact data associated with the deployment of those innovative district heating systems represents a big challenge for the broad implementation of CSHPSS in Europe. In this context, our paper presents a comprehensive evaluation for the possibility of integrating CSHPSS in the residential sector in various EU member states through the formulation of a multi-objective optimization framework. This framework comprises the life cycle cost analysis for the economic evaluation and the life cycle assessment for the environmental impact estimation simultaneously. The technical performance is also considered by satisfying both the space heating demand and the domestic hot water services. The methodological framework is applied to a residential neighborhood community of 1120 apartments in various EU climate zones with Madrid, Athens, Berlin, and Helsinki acting as a proxy for the Mediterranean continental, Mediterranean, central European, and Nordic climates, respectively. The optimization results regarding the energy performance show that the CSHPSS can achieve a renewable energy fraction above 90% for the investigated climate zones. At the same time, the environmental assessment shows significant improvement when using the CSHPSS in comparison to a natural gas heating system, in those cases the environmental impact is reduced up to 82.1–86.5%. On the other hand, substantial economic improvement is limited, especially in the Mediterranean climate zone (Athens) due to low heating demands and the prices of the non-renewable resources. There the total economic cost of the CSHPSS plants can increase up to 50.8% compared to a natural gas heating system. However, considering the incremental tendency in natural gas prices all over EU nowadays, the study of future plant costs confirms its favorable long-term economic feasibility.
关键词： Life cycle assessment (LCA),2030 climate and energy EU targets,Multi-objective optimization,Life cycle cost (LCC),Central solar heating plant with seasonal storage,Solar community
更新于2025-09-10 09:29:36
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[IEEE 2018 IEEE PES/IAS PowerAfrica - Cape Town (2018.6.28-2018.6.29)] 2018 IEEE PES/IAS PowerAfrica - Design of a Solar Powered Desalination Plant
摘要： Owing to the lack of perennial streams in the semi-desert to desert parts, two-thirds of South Africa’s surface area is largely dependent on groundwater. This ground water may at times be found to be brackish. Thus, hampering the development economy. A reliable water purification process would be an invaluable tool to those who do not have access to clean drinking water. This paper sets out to trade off this requirement of fresh water with the practical considerations of water quality, quantity, and the energy requirement of affected communities. The goal is to present a meaningful design of a water desalination unit for use in remote and water scarce parts of RSA. The desalination plant will be designed using an outcomes focused methodology and an estimated MATLAB model will be formulated.
关键词： Energy Conversion,Computer Simulation,Water Storage,Desalination,Solar Heating
更新于2025-09-09 09:28:46