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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2010.06.002 Byline: Jose A. Ruiz-Arias (a), TomaA Cebecauer (b)(c)(d), Joaquin Tovar-Pescador (a), Marcel A uri (b)(c) Keywords: Solar irradiance; Satellite; Digital elevation model; DEM; Disaggregation Abstract: Downscaling of the Meteosat-derived solar radiation ([approximately equal to]5km grid resolution) is based on decomposing the global irradiance and correcting the systematic bias of its components using the elevation and horizon shadowing that are derived from the SRTM-3 digital elevation model (3 arc sec resolution). The procedure first applies the elevation correction based on the difference between coarse and high spatial resolution. Global irradiance is split into direct, diffuse circumsolar and diffuse isotropic components using statistical models, and then corrections due to terrain shading and sky-view fraction are applied. The effect of reflected irradiance is analysed only in the theoretical section. The method was applied in the eastern Andalusia, Spain, and the validation was carried out for 22days on April, July and December 2006 comparing 15-min estimates of the satellite-derived solar irradiance and observations from nine ground stations. Overall, the corrections of the satellite estimates in the studied region strongly reduced the mean bias of the estimates for clear and cloudy days from roughly 2.3% to 0.4%. Author Affiliation: (a) Department of Physics, University of Jaen, Spain (b) European Commission, Joint Research Centre, Ispra, Italy (c) GeoModel s.r.o., Bratislava, Slovakia (d) Institute of Geography, Slovak Academy of Sciences, Bratislava, Slovakia Article History: Received 10 February 2009; Revised 20 April 2010; Accepted 6 June 2010 Article Note: (miscellaneous) Communicated by: Associate Editor David Renne

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2010.06.006 Byline: Claudia Valeria Tavora Cabral (a), Delly Oliveira Filho (a), AntA[acute accent]nia SA[acute accent]nia Alves C. Diniz (b), Jose Helvecio Martins (a), Olga Moraes Toledo (a), Lauro de Vilhena B. Machado Neto (b) Keywords: Deterministic sizing; Stochastic sizing; Solar energy; Stand-alone photovoltaic systems; Probabilistic modeling Abstract: Photovoltaic systems utilize solar energy to generate electrical energy to meet load demands. Optimal sizing of these systems includes the characterization of solar radiation. Solar radiation at the Earth's surface has random characteristics and has been the focus of various academic studies. The objective of this study was to stochastically analyze parameters involved in the sizing of photovoltaic generators and develop a methodology for sizing of stand-alone photovoltaic systems. Energy storage for isolated systems and solar radiation were analyzed stochastically due to their random behavior. For the development of the methodology proposed stochastic analysis were studied including the Markov chain and beta probability density function. The obtained results were compared with those for sizing of stand-alone using from the Sandia method (deterministic), in which the stochastic model presented more reliable values. Both models present advantages and disadvantages, however, the stochastic one is more complex and provides more reliable and realistic results. Author Affiliation: (a) Department of Agricultural Engineering, Federal University of Vicosa, Av. P. H. Rolfs, s/n. 36570-000 Vicosa, Minas Gerais, Brazil (b) Group of Studies in Energy - GREEN Solar, Pontifical Catholic University of Minas Gerais - PUC Minas, Rua Dom Jose Gaspar no. 500, Predio 03, Sala 218 - Coracao Eucaristico 30535-610 Belo Horizonte - Minas Gerais, Brazil Article History: Received 28 October 2009; Revised 5 May 2010; Accepted 17 June 2010 Article Note: (miscellaneous) Communicated by: Associate Editor Elias Stefanakos

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2010.02.003 Byline: P. Geczy-Vig, I. Farkas Keywords: Solar thermal system; Thermal stratification; Water load; Modelling; Neural network Abstract: In this study an artificial neural network (ANN) model is introduced for modelling the layer temperatures in a storage tank of a solar thermal system. The model is based on the measured data of a domestic hot water system. The temperatures distribution in the storage tank divided in 8 equal parts in vertical direction were calculated every 5min using the average 5min data of solar radiation, ambient temperature, mass flow rate of collector loop, load and the temperature of the layers in previous time steps. The introduced ANN model consists of two parts describing the load periods and the periods between the loads. The identified model gives acceptable results inside the training interval as the average deviation was 0.22[degrees]C during the training and 0.24[degrees]C during the validation. Author Affiliation: Department of Physics and Process Control, Szent Istvan University, Pater K. u. 1., H-2103 GodollA, Hungary Article History: Received 21 January 2009; Revised 18 January 2010; Accepted 7 February 2010 Article Note: (miscellaneous) Communicated by: Associate Editor Halime Paksoy

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2010.01.006 Byline: Wenjun Tang (a)(b), Kun Yang (a), Jie He (a)(b), Jun Qin (a) Keywords: Global radiation; Quality control; Sunshine duration; Hybrid model Abstract: Measurements of surface radiation in China are too sparse to meet demand for scientific research and engineering applications. Moreover, the radiation data often include erroneous and questionable values though preliminary quality-check has been done before the data release. Therefore, quality control of radiation data is often a prerequisite for using these data. In this study, a set of quality-check procedures were implemented to control the quality of the solar radiation measurements at 97 stations in China. A hybrid model for estimating global solar radiation was then evaluated against the controlled data. The results show that the model can estimate the global radiation with accuracy of MBE less than 1.5MJm.sup.-2 and RMSE less than 2.8MJm.sup.-2 for daily radiation and RMSE less than 2.0MJm.sup.-2 for monthly-mean daily radiation at individual stations over most of China except at a few stations where unsatisfactory estimates were possibly caused by severe air pollution or too dense clouds. The MBE averaged over all stations are about 0.7MJm.sup.-2 and RMSE about 2.0MJm.sup.-2 for daily radiation and RMSE about 1.3MJm.sup.-2 for monthly-mean daily radiation. Finally, this model was used to fill data gaps and to expand solar radiation data set using routine meteorological station data in China. This data set would substantially contribute to some radiation-related scientific studies and engineering applications in China. Author Affiliation: (a) Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100085, China (b) Graduate School of Chinese Academy of Sciences, Beijing 100049, China Article History: Received 9 July 2009; Revised 29 December 2009; Accepted 6 January 2010 Article Note: (miscellaneous) Communicated by: Associate Editor Christian Gueymard

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2009.01.018 Byline: J. Polo (a), L.F. Zarzalejo (a), L. Martin (a), A.A. Navarro (a), R. Marchante (b) Keywords: Linke turbidity factor; Clear sky models; Solar radiation models Abstract: This work presents a methodology for estimating daily Linke turbidity factor for clear sky days from global horizontal irradiance information at solar noon and monthly mean values of the Linke turbidity factor. The analysis of the method proposed here have been made using the ESRA clear sky model to recalculate the direct normal irradiance using as input the new Linke turbidities. Ground data of three BSRN and six AEMet radiometric meteorological stations have been used for assessing the method. Linke turbidity factor estimated here exhibits higher fluctuations than the monthly means and the comparison of the solar irradiance recalculated with the ground data have shown a noticeable reduction of the root mean square deviation. On the other hand the new Linke turbidity estimations have been compared to those values obtained from normal beam irradiance measures. The discrepancies found point out the high dependence of the reliability of this method with the quality of the ground measurements used. Author Affiliation: (a) Renewable Energy Division (Energy Department), CIEMAT Avda. Complutense, 22, 28040 Madrid, Spain (b) Investigaciones y Recursos Solares Avanzados, IrSOLaV Santiago Grisolia, 2, 28760 Tres Cantos, Madrid, Spain Article History: Received 30 July 2008; Revised 22 January 2009; Accepted 24 January 2009 Article Note: (miscellaneous) Communicated by: Associate Editor Christian Gueymard

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2009.01.004 Byline: G. Montero, J.M. Escobar, E. Rodriguez, R. Montenegro Keywords: Solar radiation; Beam, diffuse and reflected radiations; Clear-sky; Real-sky; Shadows; Adaptive meshes Abstract: In this work, we propose a numerical model for generating solar radiation maps with the use of 2-D adaptive meshes of triangles. These triangulations are constructed by using a refinement/derefinement procedure in accordance with the variations of terrain surface orography and albedo. This discretization has the advantage of defining the terrain characteristics with a minimum number of points, which reduces the computational cost for a given accuracy. Moreover, the model takes into account the effect of shadows for each time step, which are detected by analysing the crossing of the trajectory of the shaft of light with the triangles of the mesh. Thus, the solar radiation is first computed for clear-sky considering the different components of radiation, that is, beam, diffuse and reflected radiations. From the results of clear-sky radiation, the real-sky radiation is computed daily in terms of the clear-sky index. The maps of clear-sky index are obtained from a spatial interpolation of observational data that are available for each day at several points of the zone under consideration. Finally, the solar radiation maps of a month are calculated from the daily results. We illustrate the performance of the model with a numerical experiment related to an episode on the island of Gran Canaria. Author Affiliation: University Institute for Intelligent Systems and Numerical Applications in Engineering, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira, 35017 Las Palmas de Gran Canaria, Spain Article History: Received 25 March 2008; Revised 4 January 2009; Accepted 7 January 2009

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2009.01.013 Byline: Somsak Chaiyapinunt, Supakit Worasinchai Keywords: Venetian blind; Optical properties; Slat curvature and thickness; Radiosity method; Mathematical model Abstract: This article is about the development of a mathematical model for a venetian blind. The model is used for determining the performance of the glass window installed with a venetian blind in term of heat transmission. The blind, whose optical properties are considered nonspecular, is modeled as an effective layer. The optical properties of the effective layer are mainly dependent on the slat angle, slat properties and solar profile angle. The effect of slat curvature and the effect of slat thickness are included in the developed model. The shortwave optical properties of the effective layer, transmittance, reflectance and absorptance, are classified as the optical properties for direct radiation and the optical properties for diffuse radiation. The analysis for optical properties due to the interreflection of the direct radiation between the adjacent slat surfaces is done by using radiosity method on a 6 surface closed enclosure. The effect of the slat curvature and thickness causes the shaded area blocked by the blind itself increased in certain cases. The optical properties for diffuse radiation of the effective layer are determined considering the incident diffuse radiation from the sky and from the ground. The optical properties calculated from the developed model are also compared to the results obtained from the three previous models. The validation of the results predicted by the developed mathematical model is performed by comparing the predicted results with the experimental results. The results that used to validate in this study is the ratio of the transmitted radiation through the glass window installed with venetian blind to the incident radiation on the glass window. It is shown from the comparison that the developed mathematical model for the venetian blind included the curvature and thickness effect yields quite accurate predicted results. Author Affiliation: Department of Mechanical Engineering, Faculty of Engineering, Chulalongkorn University, Phayathai, Bangkok 10330, Thailand Article History: Received 15 October 2007; Revised 7 November 2008; Accepted 23 January 2009 Article Note: (miscellaneous) Communicated by: Associate Editor Matheos Santamouris

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2008.12.002 Byline: A. Madhlopa, C. Johnstone Keywords: Back wall; Beam solar fraction; Diffuse solar fraction; Effective irradiance; View factor Abstract: A new model that calculates the distribution of solar radiation inside a single-slope solar still has been proposed. In this model, the solar fraction on a vertical surface is divided into beam and diffuse parts and the optical view factors of surfaces inside the still are taken into account. To validate the model, outdoor tests of a conventional solar still were conducted under different weather conditions at the University of Strathclyde. The proposed model is compared with the previous one. It is found that the beam solar fraction is affected by both the geometry of the solar still and position of the sun in the sky. In contrast, the diffuse solar fraction is only dependent on the geometry of the solar distiller. The present model exhibited a lower root mean square error than that of the previous model. It appears that splitting the solar fraction into beam and diffuse parts improves the accuracy of modelling the performance of a single-slope solar still. Author Affiliation: Energy Systems Research Unit, Department of Mechanical Engineering, University of Strathclyde, 75 Montrose Street, Glasgow G1 1XJ, United Kingdom Article History: Received 6 June 2008; Revised 17 November 2008; Accepted 8 December 2008 Article Note: (miscellaneous) Communicated by: Associated editor G.N. Tiwari

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2008.12.003 Byline: A. El Fadar (a), A. Mimet (a), M. Perez-Garcia (b) Keywords: Parabolic trough collector; Adsorption; Refrigeration; Activated carbon/ammonia; Continuous cycle; Simulation Abstract: This article suggests a numerical study of a continuous adsorption refrigeration system consisting of two adsorbent beds and powered by parabolic trough solar collector (PTC). Activated carbon as adsorbent and ammonia as refrigerant are selected. A predictive model accounting for heat balance in the solar collector components and instantaneous heat and mass transfer in adsorbent bed is presented. The validity of the theoretical model has been tested by comparison with experimental data of the temperature evolution within the adsorber during isosteric heating phase. A good agreement is obtained. The system performance is assessed in terms of specific cooling power (SCP), refrigeration cycle COP (COP.sub.cycle) and solar coefficient of performance (COP.sub.s), which were evaluated by a cycle simulation computer program. The temperature, pressure and adsorbed mass profiles in the two adsorbers have been shown. The influences of some important operating and design parameters on the system performance have been analyzed. The study has put in evidence the ability of such a system to achieve a promising performance and to overcome the intermittence of the adsorption refrigeration systems driven by solar energy. Under the climatic conditions of daily solar radiation being about 14MJ per 0.8m.sup.2 (17.5MJ/m.sup.2) and operating conditions of evaporating temperature, T.sub.ev =0[degrees]C, condensing temperature, T.sub.con =30[degrees]C and heat source temperature of 100[degrees]C, the results indicate that the system could achieve a SCP of the order of 104W/kg, a refrigeration cycle COP of 0.43, and it could produce a daily useful cooling of 2515kJ per 0.8m.sup.2 of collector area, while its gross solar COP could reach 0.18. Author Affiliation: (a) Energetics Laboratory, Sciences Faculty, Abdelmalek Essaadi University, BP 2121, 93000 Tetouan, Morocco (b) Dpto. de Fisica Aplicada, Universidad de Almeria, Spain Article History: Received 26 May 2008; Revised 26 November 2008; Accepted 3 December 2008 Article Note: (miscellaneous) Communicated by: Associated editor Ruzhu Wang

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2008.08.006 Byline: P.P. Kastendeuch (a), G. Najjar (b) Keywords: Urban climate; Canyon; Radiative transfers; Heat fluxes; Simulation model; Validation Abstract: The energy balance at the soil-atmosphere interface is the fundamental equation to simulate the microclimate of urban areas. It implies the equilibrium of several energetic terms, such as: radiation (in the solar and infrared wavelengths), conduction (soil heat flux), convection (sensible heat flux) and evapotranspiration (latent heat flux). This article deals with the 3D-numeric simulation of heat transfers in an urban canyon and the validation of the appropriate algorithms and results. The simulation procedure and parameterisation of the surface elements are briefly described. All the heat transfer algorithms are taken from the existing literature. Among the mechanisms, the terrestrial infrared radiation is the most difficult term to be simulated, because realistic surface temperatures must be obtained. For this reason, at each time step, a special iterative treatment is applied to solve the energy balance equation until complete stabilisation of the surface temperatures. As a result, the simulation model is able to give all the components of the energy balance equation for every mesh. The aim of the paper is to demonstrate the validity of this approach by comparing the simulation results with the experimentation. The reliability of the simulated radiative fluxes is judged against a data set specially acquired during a dedicated experimental campaign that took place in an urban canyon of a French city (Strasbourg) during summer 2002. Author Affiliation: (a) Centre de Geochimie de la Surface (UMR 7517 ULP/CNRS), 1 rue Blessig, 67084 Strasbourg Cedex, France (b) Laboratoire des Sciences de l'Image, de l'Informatique et de la Teledetection (UMR 7005 ULP/CNRS), PA[acute accent]le API, Bd Sebastien Brant, BP 10413, 67412 Illkirch Cedex, France Article History: Received 23 October 2007; Revised 16 June 2008; Accepted 18 August 2008 Article Note: (miscellaneous) Communicated by: Associate Editor Matheos Santamouris

In this study, five most commonly used single span shapes of greenhouses viz. even-span, uneven-span, vinery, modified arch and quonset type have been selected for comparison. The length, width and height (at the center) are kept same for all the selected shapes. A mathematical model for computing transmitted total solar radiation (beam, diffused and ground reflected) at each hour, for each month and at any latitude for the selected geometry greenhouses (through each wall, inclined surfaces and roofs) is developed for both east-west and north-south orientation. Computed transmitted solar radiation is then introduced in a transient thermal model developed to compute hourly inside air temperature for each shape and orientation. Experimental validation of both the models is carried out for the measured total solar radiation and inside air temperature for an east-west orientation, even-span greenhouse (for a typical day in summer) at Ludhiana (31[degrees]N and 77[degrees]E) Punjab, India. During the experimentation, capsicum crop is grown inside the greenhouse. The predicted and measured values are in close agreement. Results show that uneven-span shape greenhouse receives the maximum and quonset shape receives the minimum solar radiation during each month of the year at all latitudes. East-west orientation is the best suited for year round greenhouse applications at all latitudes as this orientation receives greater total radiation in winter and less in summer except near the equator. Results also show that inside air temperature rise depends upon the shape of the greenhouse and this variation from uneven-span shape to quonset shape is 4.6[degrees]C (maximum) and 3.5[degrees]C (daily average) at 31[degrees]N latitude. Keywords: Greenhouse; Solar energy; Solar radiation; Greenhouse shapes; Thermal modeling

In this paper, a MODIS-derived daily PAR (photosynthetically active radiation) simulation model from cloud-free image over land surface has been developed based on Bird and Riordan's model. In this model, the total downwelling spectral surface irradiance is divided into two parts: one is beam irradiance, and another is diffuse irradiance. The attenuation of solar beam irradiance comprises scattering by the gas mixture, absorption by ozone, the gas mixture and water vapor, and scattering and absorption by aerosols. The diffuse irradiance is scattered out of the direct beam and towards the surface. The multiple ground-air interactions have been taken into account in the diffuse irradiance model. The parameters needed in this model are atmospheric water vapor content, aerosol optical thickness and spectral albedo ranging from 400 nm to 700 nm. They are all retrieved from MODIS data. Then, the instantaneous photosynthetically available radiation (IPAR) is integrated by using a weighted sum at each of the visible MODIS wavebands. Finally, a daily PAR is derived by integration of IPAR. In order to validate the MODIS-derived PAR model, we compared the field PAR measurements in 2003 and 2004 against the simulated PAR. The measurements were made at the Qianyanzhou ecological experimental station, Chinese Ecosystem Research Network. A total of 54 days of cloud-free MODIS LIB level images were used for the PAR simulation. Our results show that the simulated PAR is consistent with field measurements, where the correlation coefficient of linear regression between calculated PAR and measured PAR is 0.93396. However, there were some uncertainties in the comparison of 1 km pixel PAR with the tower flux stand measurement. Keywords: MODIS; PAR; Albedo

This paper deals with a combined approach for assessing the thermal performance of radiant barriers under field conditions, based both on dynamic simulations and field measurements. The methodology involves the combination of model predictions and experimental results of a complex roof including a radiant barrier installed on a dedicated test cell. During the empirical validation of the building thermal model and more particularly thanks to the results of sensitivity analysis, simplifications of the model were made. These considerations lead to successive simplified versions of the model and finally a very simplified one, which is used to determine the thermal resistance of the complex roof. We first present the detailed thermal model, elaborated with a prototype of building simulation code. We then describe the experimental test cell and put the emphasis on the details of the roof. The simplification of the detailed model is then explained and the results presented. A value of the thermal resistance is finally obtained and confirms the potential of radiant barriers for a tropical climate. Keywords: Radiant barriers: Thermal simulation; Model validation; Sensitivity analysis: Thermal resistance

REST2, a high-performance model to predict cloudless-sky broadband irradiance, illuminance and photosynthetically active radiation (PAR) from atmospheric data, is presented. Its derivation uses the same two-band scheme as in the previous CPCR2 model, but with numerous improvements. Great attention is devoted to precisely account for the effect of aerosols, in particular. Detailed research-class measurements from Billings, OK are used to assess the performance of the model for the prediction of direct, diffuse and global broadband irradiance. These measurements were made in May 2003 during a sophisticated radiative closure experiment, which involved the best radiometric instrumentation currently available and many ancillary instruments. As a whole, these exceptional measurements constitute the only known modern benchmark dataset made specifically to test the intrinsic performance of radiation models. Using this dataset as reference, it is shown that REST2 performs better than CPCR2 for irradiance, illuminance or PAR predictions. The availability of the turbidity data required by REST2 or other similar models is also discussed, as well as the effect that turbidity has on each component of broadband irradiance, PAR irradiance and illuminance, and on the diffuse/global PAR ratio. Keywords: Solar radiation; Irradiance; Illuminance; Photosynthetically active radiation; Radiation model; Validation; Radiative closure; Performance assessment; Radiometry; Diffuse radiation; Turbidity; Aerosols

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2005.08.004 Byline: Michael K.H. Leung (a), S.M. Tang (a), Ringo C.W. Lam (a), Dennis Y.C. Leung (a), W.C. Yam (b), S.P. Ng (b), Lilian L.P. Vrijmoed (c) Keywords: Solar; Photocatalytic; Parallel-plate photoreactor; Design optimization Abstract: This study focused on modeling and optimization of a photoreactor packed with parallel glass plates coated with sol-gel TiO.sub.2 thin films on both sides. The photoreactor design has great potential for solar photocatalytic air purification. Borosilicate glass substrate was selected because its high transmissivity facilitated the transmission and distribution of exterior solar radiation onto interior immobilized photocatalyst. Flat-plate configuration was adopted because a TiO.sub.2-coated plate could be easily set up for effective ion implantation treatment to extend the activating spectral range from UV to visible light for a higher solar photonic efficiency. In the analytical study of this research, a semi-empirical correlation model was formulated for prediction of the photoreactor performance. The correlation coefficients were obtained based on the results of photocatalytic air purification experiments conducted. Additional experimental tests were carried out for validation of the model. In the photoreactor design optimization analysis, the semi-empirical correlation model was used as an optimizer to determine the number of parallel TiO.sub.2-coated plates needed for efficient photocatalytic air purification. It was found that the optimal number of plates was dependent of the incident irradiance. The modeling and optimization methods developed for solar photocatalytic air purification are equally applicable for solar photocatalytic water purification. Author Affiliation: (a) Department of Mechanical Engineering, The University of Hong Kong, 7/F Haking Wong Building, Pokfulam Road, Hong Kong, China (b) Department of Microbiology, The University of Hong Kong, Hong Kong, China (c) Department of Biology and Chemistry, City University of Hong Kong, Hong Kong, China Article History: Received 19 May 2005; Accepted 16 August 2005 Article Note: (miscellaneous) Communicated by: Associate Editor Gion Calzaferri

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2005.04.018 Byline: Pierre Ineichen Keywords: Clear sky irradiance; Solar irradiance modeling; Model validation Abstract: A selection of eight high performance clear sky solar irradiance models is evaluated against a set of 16 independent data banks covering 20 years/stations, altitudes from sea level to 1600m and a large range of different climates. Their performance evaluated on very clear condition measurements are within 4% in term of standard deviation. The conclusions are that the accuracy of the input parameters such as the turbidity is crucial in the validity of the obtained radiation components, and that the choice of a specific model is secondary. The model selection criteria should be based upon either implementation simplicity, input parameter availability (Linke turbidity or aerosol optical depth) or the capacity of the model to produce spectral radiation. Author Affiliation: Center of Energy, University of Geneva, Battelle BAcentst. A, 7 rte de Drize, CH-1227 Carouge, GE, Switzerland Article History: Received 20 April 2004; Revised 15 February 2005; Accepted 28 April 2005 Article Note: (miscellaneous) Communicated by: Associate Editor David Renne

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2005.06.015 Byline: Mirela Robitu (a)(b), Marjorie Musy (b), Christian Inard (a), Dominique Groleau (b) Keywords: Urban climate; Vegetation; Water pond; Thermal comfort Abstract: The beneficial influence of trees and water ponds on summer comfort in urban spaces was studied experimentally in situ and in wind tunnels but the modeling needs further development to become effective in practical applications. This paper introduces a numerical approach based on coupling the CFD model of airflow, in which the influence of trees is considered as source terms, and the radiation exchange, completed with thermal conduction. The CFD, radiation and thermal conduction models use the same discretization grid at their common boundaries. The model was used to estimate the influence of trees and water ponds in a real town square. Comparison of results between two situations, with and without vegetation and water pond, indicate that surface temperatures are reduced in presence of trees and the comfort is improved. Author Affiliation: (a) LEPTAB University of La Rochelle, Avenue Michel CREPEAU, 17042 La Rochelle, France (b) CERMA -- Architectural School of Nantes, Rue Massenet, BP 81931, 44319 Nantes, France Article History: Received 3 January 2005; Revised 31 May 2005; Accepted 28 June 2005 Article Note: (miscellaneous) Communicated by: Associate Editor Matheos Santamouris

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2005.03.004 Byline: Jesus Polo, Luis F. Zarzalejo, Lourdes Ramirez, Bella Espinar Keywords: Solar irradiance; Meteosat satellite; Active learning; Ground database quality Abstract: A new technique of filtering solar radiation ground data is proposed for generating models for solar irradiance estimation from geostationary satellite data. The filtering processes consists of an iterative way of selecting the training data set to achieve the best model response. Although in this paper the proposed methodology has been used for solar irradiance modeling, it could be applied to any kind of empirical modeling. The iterative filtering method has proven to have fast convergence and to improve successfully the statistical model response, when applied to hourly global irradiance calculation from satellite-derived irradiances for 13 Spanish locations. Individual statistical models for hourly global irradiance were fitted using the Heliosat I method applied to Meteosat images of 13 Spanish stations for the period 1994-1996. Author Affiliation: Renewable Energy Department, CIEMAT, Avad. Complutense, 22, 28040 Madrid, Spain Article History: Received 26 January 2004; Revised 17 February 2005; Accepted 9 March 2005 Article Note: (miscellaneous) Communicated by: Associate Editor Pierre Ineichen

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2004.12.006 Byline: A. Mellit (a), M. Benghanem (b), A. Hadj Arab (c), A. Guessoum (d) Keywords: Global solar radiation data; Clearness index; Artificial neural network; Markov transition matrices; Hybrid model; Prediction; Sizing PV system Abstract: The purpose of this work is to develop a hybrid model which will be used to predict the daily global solar radiation data by combining between an artificial neural network (ANN) and a library of Markov transition matrices (MTM) approach. Developed model can generate a sequence of global solar radiation data using a minimum of input data (latitude, longitude and altitude), especially in isolated sites. A data base of daily global solar radiation data has been collected from 60 meteorological stations in Algeria during 1991-2000. Also a typical meteorological year (TMY) has been built from this database. Firstly, a neural network block has been trained based on 60 known monthly solar radiation data from the TMY. In this way, the network was trained to accept and even handle a number of unusual cases. The neural network can generate the monthly solar radiation data. Secondly, these data have been divided by corresponding extraterrestrial value in order to obtain the monthly clearness index values. Based on these monthly clearness indexes and using a library of MTM block we can generate the sequences of daily clearness indexes. Known data were subsequently used to investigate the accuracy of the prediction. Furthermore, the unknown validation data set produced very accurate prediction; with an RMSE error not exceeding 8% between the measured and predicted data. A correlation coefficient ranging from 90% and 92% have been obtained; also this model has been compared to the traditional models AR, ARMA, Markov chain, MTM and measured data. Results obtained indicate that the proposed model can successfully be used for the estimation of the daily solar radiation data for any locations in Algeria by using as input the altitude, the longitude, and the latitude. Also, the model can be generalized for any location in the world. An application of sizing PV systems in isolated sites has been applied in order to confirm the validity of this model. Author Affiliation: (a) University Center of Medea, Institute of Engineering Sciences, Department of Electronics, Ain Dahab, Mdea 26000, Algeria (b) University of Sciences Technology Houari Boumediene (USTHB), Faculty of Electrical Engineering, El-Alia, P.O. Box 32, Algiers 16111, Algeria (c) Development Center of Renewable Energy (CDER), P.O. Box 62, Bouzareah, Algiers 16000, Algeria (d) Faculty of Science Engineering, Department of Electronics, Blida University, Blida, Algeria Article History: Received 12 July 2004; Revised 12 December 2004; Accepted 22 December 2004 Article Note: (miscellaneous) Communicated by: Associate Editor Pierre Ineichen

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2004.11.006 Byline: Hamdy K. Elminir (a), Faiz F. Areed (b), Tarek S. Elsayed (a) Keywords: Artificial neural network; Regression model; Infrared solar radiation; Ultraviolet solar radiation; Global solar radiation; Meteorological parameters Abstract: Field testing carried out for solar energy applications is costly, time consuming and depends heavily on prevailing weather conditions. Adequate security and weather protection must be provided at the test site. Measurements may also suffer from delays that can be caused by system failures and bad weather. To overcome these problems the need for accurate model becomes evermore important. To achieve such prediction task, an artificial neural network, ANN, model is regarded as a cost-effective technique superior to traditional statistical methods. In this paper, Levenberg optimization function is adopted to predict insolation data in different spectral bands for Helwan (Egypt) monitoring station. The predicted values were then compared with the actual values and presented in terms of usual statistics. The results hint that, the ANN model predicted infrared, ultraviolet, and global insolation with a good accuracy of approximately 95%, 93% and 96%, respectively. In addition, ANN model was tested to predict the same components for Aswan over an 11 month period. The predicted values of the ANN model compared to the actual values for Aswan produced an accuracy of 95%, 91% and 92%, respectively. Data for Aswan were not included as a part of ANN training set. Hence, these results demonstrate the generalization capability of this approach over unseen data and its ability to produce accurate estimates. Author Affiliation: (a) National Research Institute of Astronomy and Geophysics, El-Marsad Street, 11421 Helwan, Cairo, Egypt (b) Faculty of Engineering, Control and Computer Department, Mansoura University, 11421 Mansoura, Egypt Article History: Received 10 May 2004; Revised 2 November 2004; Accepted 16 November 2004 Article Note: (miscellaneous) Communicated by: Associate Editor Pierre Ineichen

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2004.10.007 Byline: Emmanuel Bozonnet, Rafik Belarbi, Francis Allard Keywords: Urban micro-climate; Solar radiation; Radiant interchange model; Zonal model Abstract: In urban areas, the climatic loads on buildings in summer conditions are largely affected by solar radiation. In this paper a modified simplified method for radiant interchange determination is used in a solar energy study. The good agreement with the radiosity method allows one to use this simplified method in the street canyon case. In a building pilot study, parametric analysis and building thermal behaviour can be assessed by simplified models which are useful for long-period simulation. Then this radiant interchange model is introduced in a zonal model of a canyon street and performed with a variable climatic conditions show case. The solar radiation is the only driving force in the street air movement. The interest of such approach for complex coupled phenomena studies is highlighted by obtained results and the assessment of variable climatic loads for different building zones can be considered with the model detailed herein. Future developments are planned in order to improve simulation accuracy by the addition of other local phenomena. Author Affiliation: Laboratoire d'Etude des Phenomenes de Transfert Appliques au BAcentstiment, Universite de La Rochelle, Avenue Michel Crepeau, 17042 La Rochelle Cedex 1, France Article History: Received 16 January 2004; Revised 15 July 2004; Accepted 25 October 2004 Article Note: (miscellaneous) Communicated by: Associate Editor Matheos Santamouris

Byline: Jyrki Tapani Kuikka The Linear No-Threshold (LNT) model has been traditionally used in the field of radiation safety. Public attention to and debate on this model increased after estimates that current Computed Tomography (CT) procedures in the USA will ultimately be responsible for up to 2% of cancers. However, there is evidence that in the mGy range, low doses not only cause a relatively low probability of deoxyribonucleic acid (DNA) damage, but may also involve adaptive protection against DNA damage. Thus, we have to realise that the dose-response relationship cannot be based on a simple mathematical equation of the first order. The LNT model should be rejected.

Using a large dataset of 135 stations encompassing very diverse geographic locations (82.5 [degrees] N to 67.6 [degrees] S) and climates, two new models are presented to predict the monthly-average hourly global irradiation distribution from its daily counterpart. It is found that a quadratic in the sine of solar elevation fits the data very well at all locations. Other parameters include the mean monthly clearness index, [K.sub.t], the average day length, and the daily average solar elevation. Based on this dataset, a detailed performance assessment is conducted for these new models, as well as for six models of the literature. Their respective performance is discussed, particularly with respect to the latitudinal effect. The proposed models appear to correctly predict irradiations even for a very low sun typical of near-polar night conditions. The accurate predictions of the newly proposed `daily integration model' translate into the lowest yearly-average and site-average Root Mean Square Difference, a statistic obtained by comparison with 21 722 measured hourly irradiations. However, it is stressed that the performance of this kind of model is seriously limited by artefacts due to shading (e.g., from mountains), and, more importantly, by strong morning/afternoon radiative asymmetries due to local or climatological influences, which cannot be predicted from just daily irradiation data. [C] 2000 Elsevier Science Ltd. All rights reserved.