Fabrication and Characterization of Cobalt Pigmented Anodized Zinc for Photocatalytic Application

ZnO is an n-type oxide semiconductor with a direct wide band gap greater than 3 eV. Like any other semiconductor, the optical and electrical characteristics can be influenced by doping or adjusting process conditions which broaden its applications. In this work, varying amounts of Cobalt (0.01g-0.04g) were electrodeposited on anodized Zinc thin films (ZnO) followed by heat treatment to about 2500C. Optical characterization was performed in the range 300-2500 nm to obtain reflectance data which aided in defining the absorption coefficient and band gap of the films. Photocatalytic activity of the films was explored in Methylene Blue solution degradation under UV light irradiation. Analyzed data revealed a band gap shift to the red, i.e. from 3.34 eV to 3.10 eV for pure ZnO and 0.04g-Cobalt pigmented ZnO thin films respectively. Moreover, absorption coefficient increased with pigmentation attributed to the band shrinkage effect which elucidates that ZnO:Co thin films serve as good candidates for application in photocatalysis. All the fabricated films were photocatalytic but ZnO thin films containing 0.02g of Cobalt was the most photocatalytic

Angular characterization of low concentrating PV-CPC using low-cost reflectors

The most expensive component in a conventional solar photovoltaic (PV) system is the solar module cell. The module cost could be reduced if low-cost reflector materials are used to concentrate solar energy flux across a small module area. Three reflector materials were studied for fill-factor improvements in low concentrating system. These were anodized aluminium, rolled aluminium foil and miro reflectors. From the short-circuit current measurements within +/- 10 degrees from normal incidence, the effective specular reflectance was predicted for each reflector material. The effective specular reflectance was predicted from the flux distribution profile measurements and the ray-tracing results at normal incidence. The ray-tracing and the short-circuit current results were in good agreement within 10% but rather different from spectrophotometer measured results. (C) 2008 Elsevier B.V. All rights reserved

Projected beam irradiation at low latitudes using Meteonorm database

The quantitative analysis of beam radiation received on a solar concentrator may be understood by evaluating the projected solar height angle or profile angle along the north-south vertical plane. This means that all the sunrays projected along the north-south vertical plane will be intercepted by a collector provided the projection angle lies within the acceptance angle. The Meteonorm method of calculating solar radiation on any arbitrary oriented surface uses the globally simulated meteorological databases. Meteonorm has become a valuable too for estimating solar radiation where measured solar radiation data is missing or irregular. In this paper we present the projected beam solar radiation at low latitudes based on the standard Meteonorm calculations. The conclusion is that there is potential in using solar concentrators at these latitudes since the projected beam radiation is more during winter periods than in summer months. This conclusion is in conformity with the design principle of solar collectors for worst case conditions. (C) 2008 Elsevier Ltd. All rights reserved

Mitigating the non-uniform illumination in low concentrating CPCs using structured reflectors

One problem in concentrating photovoltaic systems without active cooling is the formation of hot spots on the solar module cells. These hotspots are a result of uneven concentration of radiation within the solar module cells. The overall effect of concentrated heating is the reduction in the fill-factor of the solar module cell and the subsequent decrease in the overall efficiency of the system. In this paper, we investigate one alternative of improving the performance of a low concentrating photovoltaic system using semi-diffuse rolled reflective elements. Our results indicate that rolling marks on the reflector aligned parallel to the plane of the solar module cell improve the performance of the photovoltaic system. (C) 2009 Elsevier B.V. All rights reserved

Optical characterization of photocatalytic copper doped thin films of anodized titanium

Titanium oxide is used in a myriad of applications such as in capacitors, insulation paints among others. It is a prime candidate for water splitting due to its photocatalytic properties. In this work, undoped TiO _2 thin films were prepared by anodizing titanium foils cut into pieces measuring 60 mm by 20 mm. The specimens were anodized in an electrolyte consisting of 0.5 M H _2 SO _4 and 0.075% wt HF at room temperature. The anodizing voltages ranged from 50 V to 100 V. Anion doping of copper in as anodized TiO _2 was done electrochemically. The as anodized Ti foils were dipped in a 1 M Cu _2 SO _4 solution. All samples were annealed at 450 °C for 3 h. Near-normal total reflectance was measured on as anodized and copper pigmented samples in the solar (300–2500 nm) wavelength range. Spectrophotometric reflectance data was analyzed to obtain the absorption coefficient and using the same to determine the band gap of the films. It was noted that the films exhibited reduced solar integrated reflectance for TiO _2 samples prepared at lower anodic voltages of 50, 60 and 70 V. The copper pigmented, and annealed, TiO _2 samples exhibited both direct and indirect energy band gaps in the ranges, 3.38–3.86 and 2.50–2.74, respectively. Further, annealing and copper doping of the films lead to increased absorption. The photocatalytic activity of the films was assessed by measuring the rate of degradation of 10ppm methylene blue in UV light source. Copper doped TiO _2 exhibited enhanced photocatalytic performance in compared to pure TiO _2 . An increase in the anodization voltage caused subsequent increase in photocatalytic activity of films with 70 V as the optimum voltage above which photo degradation of methylene blue decreased