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Design and Performance of Two Axes Solar Tracker
Get PDFThe possible energy gain in the case of two axes tracking as well as a fixed system with Equator facing tilted solar PV module with latitude angle and daily optimum slope is calculated basing on Hottel clear sky radiation model (HM) and ex-terrestrial solar radiation model (ESRM). The calculated results are compared with the data obtained from a PV system with 252 Wpeak power module installed on a two axes solar tracker which was designed and constructed locally. The main components of the tracker are introduced. It was found that, the maximum possible energy gain calculated basing on HM and ESRM are practically identic. For example, on 25 August from 8 O’clock to solar noon, the hourly energy gain values of HM are 1.672, 1.336, 1.170, 1.098 and 1.097 while they are 1.677, 1.337, 1.170, 1.098 and 1.098 in the case of ESRM. The corresponding measured values on the same day are 1.746, 1.36, 1.16, 1.043 and 1.027. Thus, the theoretical data are consistent with the measured ones. Moreover, it was found that the tracked system is more economic feasible than latitude tilted similar one with a relative solar energy gain of 0.32%
Solar Azimuth Angle in the Tropical Zone
Get PDFBasing on the concept of sun position, appropriate relationships for determining the solar azimuth angle were derived. The derived formulas were compared with those available in literature and proposed to determine the solar azimuth angle all over the year and all over world. Some comments were given on some of them. Here it was found that the formulation of Braun and Mitchell [1], recommended by Duffie and Beckman [2] in their respectful book could not be applied in the tropical zone. The calculated results using the derived formulas were compared with the available results in literature
The Application of Process Mapping to Create Improvements in Production Logistics at the Example of the Shipbuilding Industry Plant
Get PDFThe hereby article presents an example of application of the process mapping method in analysis of barge production logistics. The method was described briefly and the logistics of production of a barge produced in the shipyard industry were characterized. Three possible modernizations were suggested on basis of the prepared production process map that consist in technological, organizational improvements and an option that combines both of these solutions. AnyLogic program was used for comparative analysis of the suggested options in relation to the process in the base option. This is particularly important for proper drafting of the process computer models in applications for their modeling and simulation
The Solar Panel’s Performance Dependence on Incident Radiation Intensity and its Surface Temperature
Get PDFThe effect of radiation intensity and temperature on the performance parameters of a solar panel is investigated experimentally using an indoor experimental setup, designed and constructed locally at Higher Institute for Applied Sciences and Technology, Damascus. The experiments have been carried out under various intensity levels of radiation in the range of 700- 2000W/m2. The experimental results indicate that, radiation intensity has a dominant effect on current parameters. It is found that photocurrent; short circuit current and maximum current have been increased linearly with increasing radiation intensity. So, concentrating system may be regarded as a best choice to enhance the power output of solar system. The power density of the solar panel at 30oC increased from 1.86 mW/cm2 at 1300W/m2 to 3.59 mW/cm2 at 2000W/m2. The role of temperature on the electric parameters of solar panel is also considered. The practical local possible solar panel’s temperature was considered to be in the range of 10–70oC. The experiments cover this temperature range. Experimental results show that all electrical parameters of solar panel such as maximum output power, open circuit voltage, short circuit current, efficiency and fill factor have changed with temperature variation. As well as the amount of changes in these parameters in terms of temperature value have been obtained. According to results, the most significant is the temperature dependence of the voltage which decreases with increasing temperature while the current of the solar panel slightly increases by temperature. On the other hand, it has been observed that solar panel’s temperature has a dramatic effect on voltage parameters. Open circuit voltage and maximum voltage are decrease with increasing solar panel’s temperature. So, the maximum power density of the mono-crystalline and poly-crystalline silicon solar module decreased from 43.4 and 48.76/cm2 to 36.32 and 41.88mW/cm2 for temperature 10oC and 70oC respectively. When testing the effect of temperature on French Photo watt solar cells, obtained 20 years ago and encapsulated in a solar panel locally, in the temperature range of 10–90oC, it was found that, the open circuit voltage decreases by 1.87mV/ oC which is equivalent to 0.3% of the nominal value. The short circuit current intensity decreases by 20mA/oC which is equivalent to 1% of the nominal value. When comparing these values with those of the company presented at its electronic cite, Isc = +0,06%/°C; Voc = -0,34%/°C, one can conclude that aging effect is important on short circuit current intensity
Self-Assembled Growth of Tail-Like Cluster Composed of Flower-Shaped ZnO Microwires by Chemical Vapor Deposition Method
Get PDFA self-assembled ZnO tail-like cluster (TC) had been successfully synthesized by a simple chemical vapor deposition method. Scanning electron microscopy observations show that ZnO TC is composed of bushy ZnO microwires with flower-shaped cross sections. Long and narrow furrows can be clearly observed on the surface of the ZnO TC. A possible growth model is proposed to discuss the formation mechanism. The analytical result indicates that the flower-shaped ZnO microwires are formed by the lateral coalescence of ZnO wires at high temperature. The room temperature PL spectrum shows a prominent UV emission band around 380 nm, and no green emission is found, implying that the unique flower-shaped ZnO microwires have high optical quality. This controlled growth of ZnO TC may have implication for potential applications in novel optoelectronic micro/nanodevices in the near future
A Note on Heat Transfer Unsteady Similar Boundary Layer Flow Over a Streatching Surface with Power Law Temperature
Get PDFThe aim of this paper is to investigate the effects of thermal radiation and viscous dissipation on unsteady two dimensional viscous and incompressible boundary layer flow and heat transfer from a stretching surface. The governing partial differential equations are transformed into a system of ordinary differential equations by using similarity transformation. The governing equations are solved through the use of Spectral relaxation method. The solution is found to be dependent on the governing parameters including the Prandtl number, unsteadiness parameter, thermal radiation parameter, Eckert number and power law temperature parameter. Flow profiles are presented graphically for various values of the problem parameters
Steady Free Convection Boundary Layer Flows at a Vertical Plate with Variable Fluid Properties
Get PDFThis paper investigates the similarity solutions of the steady two-dimensional flow of a stream of viscous fluid with far field viscosity past a vertical plate. The variable viscosity, thermal conductivity and heat sink in momentum and energy equations are incorporated. The governing system of equations are transformed into dimensionless equations and solved numerically by using Maple-13 software for different boundary conditions and for various values of parameters. The effects of different values of physical parameters on the velocity and temperature profiles as well as on the skin-friction coefficient and Nusselt number are discussed
Preparation and Optimization of NbCrN/NbCrON/SiO2 Solar Selective Absorbing Coating
Get PDFA novel Cu/NbCrN/NbCrON/SiO2 solar selective absorbing coating was successfully prepared by magnetron sputtering. In this coating, Cu, NbCrN, NbCrON and SiO2 act as the infrared reflector metal layer (and as substrate too), high metal volume fraction layer, low metal volume fraction layer and anti-reflection layer, respectively. The effects of the reactive gas flow rates of the absorption layers and the thickness of each layer were investigated and the optimal deposition parameters for the coatings were obtained. Finally the main result is that the best spectral properties with the absorptance of 0.93 and the emittance of 0.07 (25oC) are achieved. The experimental results indicate its potential applications in solar collectors
Corrosion of Simple Cobalt-Chromium Alloys, Bases of Real Dental Alloys Devoted to Prosthetic Dentistry, in a NaCl Solution Simulating Human Saliva Specified by Stationary Electrochemical Techniques and EIS
Get PDFCobalt-based alloys containing chromium in quantity high enough represent a cheap alternative to dental alloys involving high quantities of noble metals (Au, Pt, Pd…). However, their general corrosion behaviour is not necessarily excellent and their use in the buccal milieu, which supposes contact with saliva, may lead to the release of ions to which the patient may be particularly sensible: allergic reaction, disease due to cobalt ions, associated troubles… In this work it was wished to investigate the electrochemical behaviour of extremely simplified versions of commercial cobalt-based dental alloys in a solution featuring among the ones usually used for simulating saliva. The aim was to explore the possible effects on the corrosion rate of the chromium content and of an eventual plastic deformation issued from fabrication or from mastication. Two binary alloys, Co-15wt.%Cr and Co-30Cwt.%Cr, mounted as electrodes, without or with preliminary hardening in compression, were subjected to EIS and cyclic polarization runs in a threeelectrode cell heated at the human body temperature. Both alloys demonstrated high resistance against corrosion, with Icorr values significantly lower than 1 μA/cm2, without real effect of the chromium content (15wt.% seems enough) or of preliminary plastic deformation
02-D Magnetohydrodynamics Boundary Layer Flow of Cu-Ag-TiO3-Al2O3-H2O-C2H6O2 Mixtures: Explicit Numerical and Stability Approach
Get PDFAn analysis is present for an unsteady, viscous incompressible flow with four types of nanoparticles, namely (Cu, Ag, Al2O3, TiO3). It also considers water and Ethylene Glycol (C2H6O2, EG) as base fluids which are electrically conducting in the presence of a transverse magnetic field. The transformed nonlinear governing equations which are non-similar are solved with suitable transformations and a robust explicit finite difference method. The controlling flow characteristic parameters such as Prandtl number (Pr), Magnetic parameter (M), Richardson number (Ri), Reynolds number (Re) and volume fraction of nanofluids (φ) are discussed for dimensionless velocity and temperature flow profiles. Stability and convergence of the derived solutions are considered. It is observed that in the momentum profiles, the magnetic field has a great impact on Reynolds number. Richardson number has a significant impact in the momentum boundary layer thickness. The effect of different nanoparticles with different base fluids is analyzed and compared between steady and non-steady states. Shear stress and Nusselt number are also discussed for different parameters. This study has applications in propulsion system and magnetic nanomaterials processing