energy sources (solar energy)
technologies to reach this ambitious goal. One materials costs must be reduced because they technologies. Another is that module efficiency parameter if different thin films each optimize similar level.
major conclusion is that will dominate in mature could be the overriding their manufacturing to a
Method for analyzing series resistance and diode quality factors from field data Part II: Applications to crystalline silicon del Cueto, J. A. Solur Enrrgr MoIPI.~(I/.~ & Solar Cd/s, 1999. 59, (4). 39?& 405. 00101462
The method described in a prior journal publication is applied to the determination of module series resistance and diode quality factors for several crystalline silicon (c-Si) technology photovoltaic (PV) modules. This method makes use of the functional dependence of the slope of the currentvoltage (I-V) characteristics at open circuit (Rot) against the reciprocal of the short-circuit current density (Jsc) from multiple I-V curves taken under variable illumination. It is shown that calculations of the series resistance for six modules yield values in the range 1.0-1.6 R-cm*, expressed in unitcell area terms. The derived values for the series resistance (Rs) determined from the data are investigated for their effect on the module fill factor (FF) values and their dependence at higher light intensity levels. The diode quality factors also derived from the same data are shown to be somewhat larger than those obtained from the more canonical method slope of the fit of the open-circuit voltage (Voc) versus logarithm of Jsc. The differences between the two methods are explored within a two-diode model for c-Si. Deriving average values of diode quality factors for seriesconnected cells using either method is shown to exhibit problematic issues.
00/01463 New approaches for estimating global solar radiation across Sudan Elanib,N. A. and Mansell, M. C. Ertrr~r -. Convers. & Mancr~e.. 2000,41, (5). 4 191434. This study investigates the possibility of establishing monthly-specific equations for estimating global solar radiation across Sudan. Using data from 16 stations, stretching along sub-humid, semi-arid, arid and hyper-arid zones, the derived equations embrace the dependence of global solar radiation on a single or a group of parameters, namely latitude, altitude and ratio of actual-to-maximum possible bright sunshine hours. Five kinds of regression have been tried, namely linear, exponential, power, polynomial and multiple linear. Extensive statistical comparisons between these country wide equations have been performed in order to rank them. A general conclusion is that the addition of geographical parameters to the classical oredictor variable. i.e.. the fraction of sunshine duration. imoroves the estimation of global solar’ radiation. Furthermore, using the rklative duration of sunshine as a single independent variable is workable only if the regression equation is expressed in a nonlinear form, basically a second order relation. Estimating global solar radiation by the adopted approaches have proved sufficiently reliable. The developed equations could, thus, be used to predict this parameter in areas with no measuring systems or in equipped areas where there are missing data, so that a geographical distribution of global solar radiation across the country may be obtained.
On the clear sky model of the ESRA-European Radiation Atlas-with respect to the Heliosat method
Rigollier, C. ef ~11.Solar Energ,r, 2000. 68. (I). 33-48. This paper presents a clear-sky model, which has been developed in the framework of the new digital European Solar Radiation Atlas (ESRA). This ESRA model is described and analysed with the main objective of being used to estimate solar radiation at ground level from satellite images with the Heliosat method. Therefore it is comoared to clear-skv models that have already been used in the Heliosat mkthod. The diffuse clear sky irradiation estimated by this ESRA model and by other models has been also checked against ground measurements for different ranges of the Linke turbidity factor and solar elevation. The results show that the ESRA model is the best one with respect to robustness and accuracy. The r.m.s error in the estimation of the hourly diffuse irradiation ranges from 11 to 35 Wh mm2 for diffuse irradiation up to 250 Wh m-*. The good results obtained with such a model are due to the fact that it takes into account the Linke turbidity factor and the elevation of the site, two factors that influence the incoming solar radiation. In return, it implies the knowledge of these factors at each pixel of the satellite image for the application of the Heliosat method.
go/O1465 Optical properties of sol-gel deposited Al2O3 films Ozer, N. et al. S&r Energ,v Mrrtcrials & Solor Cell.s, 1999, 59, (4). 355-366. Highly transparent, uniform and corrosion resistant AlzOJ films were prepared on stainless-steel and quartz substrates by the sol-gel process from stable coating solutions using aluminum-set-butoxide (AI(OBus)a) as precursor, acetylacetone (AcAcH) as chelating agent and nitric acid (HNOx) as catalyser. Films up to 1000 nm thick.were prepared by multiple spin coating deposition, and were characterized by X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopv (SEM), thermoaravimetric analvsis (TGA), differential scanning calorimetry (‘DSC), Fo;rier transform infrared spectroscopy (FTIR), optical spectroscopy and micro Vickers hardness test. XRD of the film heat treated at 400°C showed that they had an amorphous structure. XPS confirmed that they were stoichiometric Alz03. The refractive index (n) and extinction coefficient (k) were found to be n = 1.56f 0.01 and k = 0.003 f
Fuel and Energy Abstracts
0.0002 at 600 nm. respectively. The surface microhardness and corrosion resistance investigations showed that Al,Oa films improved the surface properties of stainless-steel substrates.
Optimization of a wickless heat pipe flat plate solar
Hussein, H. M. S et (I/. Eriergr Coni7er.s. & Monoge., 1999. 40. (18). l9491961. The transient thermal behaviour of wickless heat pipe flat plate solar collectors has been analysed with regard to various parameters. These parameters include global solar radiation intensity, inlet cooling water temperature, absorber plate material and thickness, ratio of pitch distance to wickless heat pipe diameter and ratio of condenser section length to total wickless heat pipe length. The results show that the selection of an absorber plate having a high value of conduction heat transfer rate per unit temperature difference is limited by the pitch distance.
00101467 Performance analysis of a hybrid photovoltaicl thermal (PWT) collector with integrated CPC troughs Garg, H. P. and Adhikari, R. S. htr. J. Energy Res., 1999, 23. (15). l2951304. In the present investigation a theoretical analysis has been presented for the modelling of thermal and electrical processes of a hybrid PVE air heating collector coupled with a compound parabolic concentrator (CPC). In this design, several CPC troughs are combined in a single PV/T collector panel. The absorber of the hybrid PViT collector under investigation consists of an array of solar cells for generation of electricity, while collector fluid circulating past the absorber provides useful thermal energy as in a conventional flat plate collector. In the analysis, it is assumed that solar cell efficiency can be represented by a linear decreasing function of its temperature. Energy balance equations have been developed for the various components of the system. Based on the developed analysis, both thermal and electrical performance of the system as a function of system design parameters are presented and discussed. Results have been presented to compare the performance of hybrid PVn collector coupled with and without CPC.
00/01466 Performance of a low cost solar paraboloidal dish steam generating system Kaushika, N. D. Energ.r Cor~ser,v. Marrtrge. 2000. 41, (7). 7 13~ 726. This paper presents the design, development and performance characteristics of a low cost solar steam generating system, which incorporates recent design and materials innovations of parabolic dish technology. The concentrator is a deep dish of rather imperfect optics, made of silvered polymer reflectors fitted in the aluminium frame of a satellite communication dish. Conventional cavity receivers tend to be inadequate for this concentrator. Semi-cavity and modified cavity receivers, thermally optimized, with the fuzzy focal image have, therefore, been investigated. Preliminary field measurements and cost, as well as performance analyses of the system, indicate a solar to steam conversion efficiency of 70-80% at 450°C and a collector system cost of RsSOOO-9000/m* (US%1 = Rs40.0).
Performance of a solar water pump with n-pentane and ethyl ether as working fluids
Wang, Y. W. and Sumathy, K. Dtergr Coirrersion & Ma~~crgcwxwt, 2000. 41, (9), 9155927. In this study, the performance of a solar thermal water pump with two different working fluids such as n-pentane and ethyl ether, is reported. The theoretical comoarison is made in terms of the number of cvcles the oumo can work per day, the amount of water that can be pumped per day an’d thk overall efficiency of the system. It is found that the efficiency of the pump with ethyl ether is about 17% higher than that with n-pentane at a discharge head of 6 m. It is shown that ethyl ether seems to be a better choice for operating a non-conventional solar thermal water pump in terms of efficiency and economics.
00/01470 Photoelectrochemical response and differential capacitance of poly(3-methylthiophene) Micaroni, L. er 01. So/w Erwrg.r Moterids & So/m Cc/l.\. 200060, (I ). 27-41. Following the theory used to study the semiconductor/electrolyte interface the differential capacitance of poly(3-methylthiophene) films has been determined from measurements with a lock-in amplifier and by electrochemical impedance spectroscopy (EIS). According to the findings, the best results were obtained by EIS because the space charge capacitance can be separated from the other capacitances. Using Mott-Schottky plots (C-2 versus E) the flat band potential Efb = 80 mV and the carrier density N = 6 x 1017 cm-3 for the PMeT film in contact with the electrolyte were obtained, where dissolved Oz played the role of the electron acceptor. The determined width of the depletion layer is 0.04 ,lrn. Also investigated here is the photoelectrochemical response of the PMeT film. The plot of the square of the photocurrent versus potential yields Efb = 90 mV, in good agreement with the EIS measurement. The dependence of the photocurrent with the frequency of the incident light shows that PMeT has a long response time (order of ms), compared to an inorganic semiconductor. The band gap was also determined from the photocurrent spectra. The value obtained, for a direct transition is 1.9 eV and is coincident with the value obtained from the absorption spectra.