A low cost high flux solar simulator

A low cost, high flux, large area solar simulator has been designed, built and characterized for the purpose of studying optical melting and light absorption behavior of molten salts. Seven 1500 W metal halide outdoor stadium lights are used as the light source to simulate concentrating solar power (CSP) heliostat output. Metal halide bulbs and ballasts are far less costly per-watt than typical xenon arc lamp solar simulator light sources. They provide a satisfactory match to natural sunlight; although ‘unfiltered’ metal halide lights have irradiance peaks between 800 and 1000 nm representing an additional 5% of measured energy output as compared to terrestrial solar irradiance over the same range. With the use of a secondary conical concentrator, output fluxes of approximately 60 kW/m² (60 suns) peak and 45 kW/m² (45 suns) average are achieved across a 38 cm diameter output aperture. Unique to the design of this simulator, the tilt angle and distance between the output aperture and the ground are adjustable to accommodate test receivers of varying geometry. Use of off-the-shelf structural, lighting and electrical components keeps the fabrication cost below $10,000.     

Gaussian solar flux model

The Gaussian Solar Flux model (GSFM) predicts instantaneous hourly and integrated daily direct and diffuse solar flux upon sloped as well as horizontal surfaces for clear and cloudy days. Comparison with Davis SEMRTS data from the first six months of 1981 indicates a mean relative error of +/−3.5% and a correlation coefficient of 0.999 for instantaneous global flux during clear days.The GSFM improves upon previous monolayer models with cloud transmittance functions generalized for different surface albedos and a fast Gaussian quadrature based estimate for water vapor pathlengths. Advantages over multilayer models are its speed and lack of need for soundings. Input may be made entirely from standard surface meteorological measurements.     

An improved solar cell circuit model for organic solar cells

The validity of conventional circuit model for interpreting results obtained using organic solar cells is examined. It is shown that the central assumption in the model that photo-generated current remains constant from short-circuit to open-circuit condition may not hold for organic cells. An improved model based on the photovoltaic response of organic solar cells is proposed and a method of extracting the parameters of the model is presented.     

Simple nonlinear solar irradiation estimation model

A simple nonlinear model with three parameters is proposed for global solar irradiation estimation from sunshine duration ratio measurements. Two of the parameters have almost the same interpretations for extreme weather conditions as in the classical Angström model but the third parameter appears as the power of the sunshine duration ratio. This model reduces to the classical Angström equation when power is equal to one. It contains the possible nonlinear effects in solar irradiation and sunshine duration relationship as a first-order mathematical approximation to the linear Angström equation. Power values different than one imply nonlinear models. The model parameter estimates are achieved through the nonlinear least-squares analysis. The application of the methodology is performed for eight irradiation measurement stations in Turkey.     

A flat-plate calorimeter for concentrated solar flux evaluation

In order to evaluate the energy arriving at the focus of a solar concentrator named DEFRAC (from its Spanish acronym, Device for the Study of Concentrated Radiative Fluxes) a calorimetric study was carried out. We studied the heat transfer in the receiving plate of a calorimeter; the distribution of temperatures during the transient and steady states were obtained both theoretically and experimentally. We show that the calorimeter is close to ambient temperature which validates the use of the cold water calorimetry technique. Since the heat losses are reduced it is possible to increase the exactitude and precision during the thermal evaluation. Based on an energy balance, the solar energy absorbed by the receiver of the DEFRAC and the global heat losses to the environment are quantified.     

A presentation of solar irradiation data suitable for solar energy application

Temporal global solar radiation patterns are discussed for two climatically different U.S. stations (Phoenix, Arizona and Geneseo, New York). A concept of the solar utilization season is developed along with methodology to assess the frequency of periods of consecutive days when solar irradiation values do not attain specified threshold values. This analysis is considered more appropriate in applications of solar energy than the common use of means and assumed Gaussian data properties that can be obtained from several compilations and summaries of national solar irradiation data.     

A new correlation for the limiting quality of critical heat flux at low mass fluxes and low pressures

The limiting quality (or limiting critical quality) was studied experimentally. We used a test section made of Inconel‐600 with 8 mm OD, 170 mm length and 1 mm wall thickness. The experiments were carried out with water at up flow for mass fluxes from 100 to 400 kg m^?2 s^?1, at low pressures (1.0–7.0 bar) and subcoolings (up to 70 K). The limiting quality is characterized by a sharp drop of the critical heat flux (CHF) in a diagram CHF versus critical quality with fixed values of pressure and mass flux and with change of the inlet subcooling. It was observed that the limiting quality appeared in our experimental results. There is a disagreement in the literature on how this phenomenon occurs. According to the present study the limiting quality phenomenon takes place due to a change of CHF mechanisms between DNB and dryout in agreement with Doroshchuk's findings. Existent correlations from literature have been compared with the experimental data. However, no correlations agree with our data because of their different validity ranges. Therefore a new correlation for the limiting quality phenomenon is developed for a large range of pressure. Furthermore the critical heat flux is calculated via a heat balance in which the value of the limiting quality is included. Copyright © 2004 John Wiley & Sons, Ltd.     

A study of solar irradiation data for six sites

Measurements of hourly direct normal solar radiation and total hemispherical solar radiation on ahorizontal surface for Albuquerque, New Mexico; Fort Hood, Texas; Livermore, Calif.; Marynard, Mass.; and Raleigh, North Carolina and measurements of hourly total hemispherical and diffuse radiation on a horizontal surface for Highett, Australia have been studied. The relationships between total and diffuse radiation and distributions and mean values associated with these quantities are considered.     

A simple model for estimating monthly mean daily sums of solar irradiation and its local distribution

This paper deals with linear correlations between solar irradiation sums and sunshine duration for mapping global, diffuse and direct irradiation. All values represent long-term averages of monthly mean daily sums. The first part of this paper describes a set of fourteen correlation equations based on an earlier study. The constants of all correlations depend on a common numerical triple that describes the climatic conditions. The constants, correlation coefficients and the triple are determined and discussed with reference to the example of two stations in the Federal Republic of Germany. In the second part, a general method for generating solar irradiation maps is proposed and applied for the state of North-Rhine Westphalia (FRG). The distribution of global and diffuse irradiation in terms of yearly averages is shown and discussed. © 1997 John Wiley & Sons, Ltd.     

基于改进CNN的光热电场太阳直接法向辐射预测研究

为了在实际运行中更好地利用光热电站,文章建立了一种基于改进卷积神经网络的光热电场太阳直接法向辐射的预测模型。首先,通过分析光热发电系统的运行机理,得到影响光热发电系统出力的主要因素是太阳直接法向辐射,并根据太阳直接法向辐射特点选用卷积神经网络对其进行预测;然后,针对卷积神经网络在实际应用过程中存在的预测精度较低和训练时间较长的问题,引入带有稀疏约束的损失函数和自适应学习率思想,并提出一种改进卷积神经网络;最后,利用改进卷积神经网络建立了光热电场太阳直接法向辐射的预测模型。模拟结果表明:文章提出的改进卷积神经网络能够解决一般卷积神经网络在实际应用中存在的预测精度较低和训练速度较慢的问题;基于改进卷积神经网络的预测模型可以较准确地预测出太阳直接法向辐射的变化趋势及其数值。     

A solar flux density calculation for a solar tower concentrator using a two-dimensional hermite function expansion

The calculation of flux density on the central receiver due to a large number of flat polygonal reflectors having various orientations is a basic part of the system simulation problem for the tower concept of solar energy collection. A two-dimensional Hermite function expansion is adapted to the simulation problem, and numerical results are contrasted with an analytic integration of the solar flux density at specific nodes on an image plane. Various measures of error in the flux density calculation are monitored vs distance to the image plane and orientation of the reflector. The flux densities predicted by the statistical method compare favorably with those of the analytic model and require approximately one-tenth the computer time.     

太阳能制冷系统低温储粮研究

总结了国内外太阳能制冷低温储粮的研究进展,介绍了太阳能吸收式制冷和吸附式制冷的工作原理及系统组成,分析了太阳能制冷低温储粮的优点、应用前景及尚待解决的问题。     

A comparatively low-quality silicon material improved for solar cell fabrication

A comparatively low-quality silicon wafer (with a purity of ≈99.9%) was adopted to form a silicon-on-defect-layer (SODL) structure featuring improved crystalline silicon near the defect layer (DL) by means of proton implantation and subsequent annealing. Thus, the SODL technique provides an opportunity to enable low-quality silicon wafers to be used for fabrication of low-cost solar cells.     

Performance enhancement of parabolic trough collectors by solar flux measurement in the focal region

Characterization of the optical performance and detection of optical losses of parabolic trough collectors are very important issues in order to improve the optical efficiency of these systems and to ensure the desired quality in solar power plants. Therefore two methods of measuring the solar flux in the focal region were developed: PARASCAN (PARAbolic Trough Flux SCANner) is a solar flux density measurement instrument which can be moved along the receiver axis. The sensor registers the flux distribution in front and behind the receiver with high resolution. The resulting flux maps allow to calculate the intercept factor and to analyse the optical properties of the collector at the finally interesting location, i.e. around the receiver. The camera-target-method (CTM) uses a diffuse reflecting Lambertian target and a calibrated camera which takes pictures of it. The target is held perpendicular to the focal line surrounding the receiver. With the resulting images of this fast and easy method it is possible to visualize the paths of the reflected rays close to the receiver and to detect local optical errors. Both methods are described in detail. Latest measurement results gained at the Eurotrough-II prototype collector built on the Plataforma Solar de Almería (PSA) in Spain are presented and consequences are discussed.