Eventos Anais de eventos
ENCIT 2016
16th Brazilian Congress of Thermal Sciences and Engineering
ESTIMATE OF ANGSTROM’S TURBIDITY COEFFICIENT TO NATAL CITY
Submission Author:
Kelvin da Cruz Praxedes , Procurando endereço...
Co-Authors:
Gabriel Ivan Medina Tapia
Presenter: Kelvin da Cruz Praxedes
doi://10.26678/ABCM.ENCIT2016.CIT2016-0189
Abstract
The transmission of solar radiation through the atmosphere is dependent of three factors, the Rayleigh’s scattering, of scattering and absorption by solids and liquids particles (aerosols), the steam water absorption and atmospherics gases uniform mix. Among these factors, the aerosols are more complex due to variations in their forms, sizes and types. They have absorptive, diffusive and hygroscopic effect, exerting influence on the global energy balance, optical properties and the lifetime of clouds. The Angstrom’s turbidity coefficient, β, is an aerosols concentration indicator in the atmosphere, which informations are applied in modelling of direct, global and diffuse radiations, in the absence of clouds (clean sky condition). It is also fundamental parameter to estimate the performance maximum of solar collectors. To determine the β value generally requires spectrometric measurements of solar radiation, which is not simple to obtain mainly by necessity of equipment such as solar spectrometers and photometers. However, the β value can be estimated if the global and diffuse (or direct) radiations are known. This paper presents preliminary values of β to Natal city through of mathematical methodology. This methodology is based on Direct Normal Irradiation (DNI), which was calculated from global and diffuse radiation, and the cosine of the zenith angle. It is expressed in terms of individual transmittances of the various atmospheric attenuations, such as ozone layer thickness, precipitable water steam thickness and evenly mixed gases.
Keywords
Angstrom's turbidity coefficient, Solar irradiance, Direct Normal Irradiance, Natal
