No abstract

No abstract

A B S T R A C TQuantifying incident solar radiation on a surface is a complex task that requires the knowledge of geometric, geographical, astronomical, physical and meteorological characteristics of the location.The aim of this paper is to analyze the attenuation processes of the solar radiation and to review the scientific works in this field, specifically the analytical models for solar irradiance calculation, as well as to establish an alternative method to compute the magnitude of the overall atmospheric transmittance.Analytical models have been developed since 1940 and they have been improving in precision and complexity. Up until now, the Bird & Hulstrom model is the most complete and accurate of them all. The main disadvantage of this model is that a great number of equations and parameters such as temperature, sunshine hours, humidity, etc. are required.In this paper, a very fast and accurate new method is developed to quantify solar irradiances at any site. The analysis shows that the parameters required are only the type of climate, altitude and state of the atmosphere. This method also allows to quantify the influence of the turbidity degree in both direct and diffuse irradiances. That information is essential to select which solar technologies are suitable in each place.As an application, the new method has been implemented and characterized in Mexico. Solar energy is an abundant resource in Mexico, and there are some studies about the solar energy potential in that country, but the influence of physical and meteorological factors on the solar radiation have not been related. In this study, the meteorological information of 74 weather stations located in different climates of the country were used to determine the parameters required. The results have been validated with experimental data available for different locations.

No abstract

Cadmium sulphide (CdS) and Cadmium sulphide/Zinc sulfide (CdS/ZnS) thin films have been extensively investigated as an n-type buffer layer to form thin film heterojunction solar cells with pCdTe absorber layers. The buffer layer affects the electrical properties of the junction and protects it from chemical reactions. From the electronic point of view, the CdS and CdS/ZnS layers can optimize the band alignment of the device [1 and 2]. Also, these can build a sufficiently wide depletion width that minimizes tunneling and establishes a higher contact potential that allows higher open circuit voltage [2]. Recently, a particular attention of the researches has been focused on the heterostructures involving CdS and CdS/ZnS multilayers [3]. Because of its band gap, it could be an excellent window layer in CdTe thin film solar cells. Since Chemical Bath Deposition (CBD) is known to produce solar cells over a large area at a low cost and low temperature. The effect of deposition parameters of CdS and CdS/ZnS thin films developed by CBD technique were investigated in [4 and 5], principally, the influence of pH control of the reaction solution on the structural and optical properties of chemically deposited CdS and CdS/ZnS thin films. Different films thicknesses of CdS and CdS/ZnS thin films were deposited onto a glass substrate. The structural surface morphology of as-deposited CdS and CdS/ZnS thin films was characterized by SEM. The physical conditions were kept identical while growing of the samples. The investigation of the effect of the synthesis method on the change the ammonium hydroxide by buffer pH (from 10.1 -13) contributed in increases the growth kinetics, resulting in thicker films. In this paper, a comparative study of CdS and CdS/ZnS thin films deposited by CBD as a buffer layer solar cell was carried out. The CdS and CdS/ZnS thin films were fabricated by CBD technique on a glass substrate for a deposition time of 60 minutes at a bath temperature of 90 ºC. These thin films were synthesized by chemical bath deposition using acid as a complexing agent with pH values between 10.1 to 11.3 for the CdS thin films and for the CdS/ZnS thin films with pH values between 11.4 to 13, these can be seen in the Figures 1a and 1b, respectively. The SEM photos (see figure 1a) show the surfaces of CdS films grown at 60 minutes deposition time and to different solution pH values. Based on the optical transmission measurements, the square of absorption coefficient (α 2 ) is plotted as a function of phonon energy (hν) in figure 1c, one can see the energy band gap, Eg, values 2.38, 2.58 and 2.44 eV for pH values, 10.1, 10.6 and 11.3, respectively. In the other case, for the CdS/ZnS thin films grown at 60 minutes time deposition, one can see the SEM photos of the samples surfaces in the figure 1c. Also, we found different energy band gaps for different pH values; for pH=11.4, Eg equals 2.74 eV and at pH=11.8, Eg equals 2.7 eV, these values are pretty similar of the literature [6]. Finally, these studies show that the pH contribut...