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Modeling of Daily Global Solar Irradiation in Timisoara by Using a Fuzzy Approach

Abstract

This paper proposes a new simple model to forecast daily global solar irradiation one day ahead using the Takagi-Sugeno fuzzy methods. The model is based on solar radiation data measured in Timisoara, Romania. The daily clearness index represents the direct variable used by the fuzzy algorithm. The model forecasts the clearness index at the moment of time t on basis of two previous values measured at time t-1 and t-2. An assessment of the model accuracy is performed.

Open access
Online Forecasting of the Solar Energy Production

Abstract

Forecasting the solar energy production is a key issue in the large-scale integration of the photovoltaic plants into the existing electricity grid. This paper reports on the research progress in forecasting the solar energy production at the West University of Timisoara, Romania. Firstly, the experimental facilities commissioned on the Solar Platform for testing the forecasting models are briefly described. Secondly, a new tool for the online forecasting of the solar energy production is introduced. Preliminary tests show that the implemented procedure is a successful trade-off between simplicity and accuracy.

Open access
Optical Modeling and Simulation of Tandem Metal Oxide Solar Cells

Abstract

An investigation of silicon-based tandem solar cells incorporating Al-doped ZnO (AZO) and Cu2O metal oxides, via two of the most efficient methods of optical modeling, specifically ray tracing and transfer matrix algorithms, was performed. The simulations were conducted based on specialized software, namely Silvaco Atlas and MATLAB, as well as on OPAL2 simulation platform. The optical analysis involved the calculation of the spectral curves for reflectance, absorptance and transmittance for different thicknesses of the thin film layers constituting the cell. It was established the optimum thickness of the AZO layer based on the minimum reflectance and maximum transmittance. Moreover, several materials were investigated in order to determine the optimum buffer layer for the tandem solar cell, based on optical modeling. The optical parameters of the ZnO/Cu2O top subcell were optimized, in order to achieve the highest conversion efficiency of such heterojunction solar cell.

Open access
Review of Surface Solar Radiation Projections in Bias-Corrected Euro-Cordex Regional Climate Models

Abstract

Regional climate models (RCMs) are used in a wide range of climate applications as they can provide high resolution (up to 10 to 20 km or less) and multi-decadal simulations of the climate system describing climate feedback mechanisms acting at the regional scale. However due to different forcing data and physics parametrisations regional climate models might produce different results. This study aims to achieve a state-of-the-art knowledge of bias-corrected surface solar radiation projections coming from 11 EURO-CORDEX regional climate models. First a comparison against 63 GEBA observations is elaborated indicating a general overestimation of surface solar radiation (SSR) in the RCMs by 6.12 W/m2 (4.4%). Next changes in surface radiation between the period of 2031-2060 and 1971-2000 are presented on annual and seasonal time scale. The model projections indicate robust increase in SSR mainly in the western part of the Mediterranean region, while the northern part of the continent is characterised by decreases in SSR till the middle of this century. The study emphasis the need of an overall validation of different climate models before introducing them in impact studies in order to have an overview regarding the uncertainties.

Open access
Channel Flow and Flood Estimate

Abstract

The movement of water on the land surface, within channels and through the soil is dependent on some hydrological factors. For surface flow, the velocity of flow increases with the bottom gradient of the channel and the flow depth, but when roughness increases, it decreases. For a given flow depth, the velocity decreases as the channel height increases. The construction of sub-surface drainage helps to remove excess soil water that can cause flood. To model overland flow, a kinematic-wave approach is applied so that flood prediction could be made.

Open access
Determination of Maximum Horizontal Distance (XMHD) Travelled by Landfill Leachate from Lapite Dumpsite in Ibadan, Southwestern Nigeria

Abstract

This study was designed to determine Maximum Horizontal Distance (XMHD) travelled by landfill leachate. Twenty - nine Schlumberger Vertical Electrical Soundings (VES) were conducted at 10.0m intervals away from four sides A, B, C and D of Lapite dumpsite. One VES point conducted outside the vicinity of the dumpsite served as a control. VES data were processed. Lowest resistivity values (Y) of VES points and the control point (Yc) were extracted. Curves of Y against X fitted best to yield an equation. XMHD was determined from the generated equation when Y = Yc. The determined (XMHD) on the four sides ranged from78.95m to 179.86m.

Open access
Laser Heating of the Core-Shell Nanowires

Abstract

The induced thermal stress in a heating process is an important parameter to be known and controlled in the magnetization process of core-shell nanowires. This paper analyses the stress produced by a laser heating source placed at one end of a core-shell type structure. The thermal field was computed with the non-Fourier heat transport equation using a finite element method (FEM) implemented in Comsol Multiphysics. The internal stresses are essentially due to thermal gradients and different expansion characteristics of core and shell materials. The stress values were computed using the thermo elastic formalism and are depending on the laser beam parameters (spot size, power etc.) and system characteristics (dimensions, thermal characteristics). Stresses in the GPa range were estimated and consequently we find that the magnetic state of the system can be influenced significantly. A shell material as the glass which is a good thermal insulator induces in the magnetic core, the smaller stresses and consequently the smaller magnetoelastic energy. These results lead to a better understanding of the switching process in the magnetic materials.

Open access
Pulsed Laser Ablation of the Solid Targets in a Liquid Environment

Abstract

In this paper, the viability of laser ablation of gold target immersed in medical distillated water used to produce nanoparticles having morphological, structural and compositional properties for medical applications is explored. The morphological properties were investigated by means of scanning electron microscopy (SEM). Energy-dispersive X-ray spectroscopy (EDX) analysis was used to reveal the composition of resulting particles. The absorbance in the wavelengths range of 300-800 nm can be assigned to the small gold nanoparticles.

Open access
Quantification of the Solar Radiative Regime Variability Based on the Clearness Index

Abstract

The fluctuation of solar radiation at ground level represents a challenge in modeling the time series of solar irradiance. A procedure for the quantification of the instability of the solar radiative regime is reported. This procedure is based on the clearness index, as the ratio of the horizontal solar irradiance measured at ground level and the estimated one at extraterrestrial level. New quantities for classifying the days from the radiative stability point of view are being introduced. A procedure for classifying days according to their stability regime as stable, variable and unstable is presented.

Open access