Estimativas das radiações direta e difusa em superfícies inclinadas com base na razão de insolação

Abstract

RESUMOForam obtidas e avaliadas equações estatísticas com agrupamentos de dados anuais, sazonais e mensais, para estimativa das componentes direta e difusa da radiação solar com base na razão de insolação (razão entre brilho solar e fotoperíodo) incidente na horizontal e em superfícies inclinadas a 12,85, 22,85 e 32,85° voltadas para o Norte, em Botucatu, SP. Empregaram-se as razões entre as duas componentes e a radiação no topo da atmosfera, em uma base de dados cujas medidas nas três inclinações ocorreram em diferentes períodos (22,85°: 04/1998 a 07/2001; 12,85°: 08/2011 a 02/2003 e 32,85°: 03/2003 a 12/2007) e concomitantes com as medidas na horizontal e com a insolação. As correlações apresentaram comportamentos linear e polinomial de segundo grau para a direta e a difusa, com maiores coeficientes de determinação em períodos com baixa variação da nebulosidade. Os maiores valores da radiação direta e difusa foram encontrados no inverno e no verão, respectivamente. O aumento do ângulo de inclinação diminuiu o desempenho das equações de estimativa em todos os agrupamentos de dados com aumento do espalhamento e diminuição do ajustamento. As equações mensais apresentaram desempenhos superiores para as duas componentes.Palavras-chave: energia solar, indicativos estatísticos, modelo Angströn-Prescott, transmissividade atmosférica Estimates of direct and diffuse radiation incident on inclined surfaces based on ratio of sunshine duration ABSTRACTStatistical equations were obtained and evaluated with annual, seasonal and monthly data groupings for estimates of direct and diffuse components of solar radiation based on the sunshine duration (ratio of sunshine and photoperiod) incident on horizontal and inclined surfaces to 12.85, 22.85 and 32.85° with facing to North, in Botucatu, SP. The ratios between the two components and radiation at the top of the atmosphere were used, in a database whose inclinations were measured in three different periods (22.85°: 04/1998 to 07/2001; 12.85°: 08/2011 to 02/2003; and 32.85°: 03/2003 to 12/2007) and concomitant with horizontal measures and sunshine duration. The correlations showed a linear and second degree polynomial behavior for the direct and diffuse radiation, with higher coefficients of determination in periods of low variation in the coverage of the sky (cloudiness). The highest values of the direct and diffuse radiation were found in winter and summer, respectively for all surfaces evaluated. The increase in the inclination angle decreased the performance of equations in all groups of data with increase in scattering and decrease in index of the adjustment, however, the monthly equations allowed better performance for the two components.

Radiação global e difusa diária na região de transição Cerrado-Amazônia brasileira

“…However, since the radiation is transmitted, there is an inversion process of the diffuse radiation between the cloud and the surface, wherein scattering with isotropic characteristics is generated. In turn, in the dry season isotropic and anisotropic scattering occur together (CHWIEDUK, 2009;POSADILLO;LUQUE, 2009;SOUZA et al, 2012;ESCOBEDO, 2013;DAL PAI et al, 2016).…”

“…The solar radiation that reaches the Earth's surface on the horizontal plane is called global radiation and can be divided into direct and diffuse components. Solar radiation is subject to atmospheric attenuation by reflection, absorption, and diffusion due to the interaction of electromagnetic waves with the constituent gases of the atmosphere, clouds and aerosols, which makes it difficult to predict (SOUZA; ESCOBEDO, 2013;RELVA et al, 2019).…”

DIURNAL EVOLUTION OF FIRE BEHAVIOR AND MICROCLIMATE IN AREAS OF Eucalyptus urograndis (CLONE H13) IN THE CERRADO AMAZONIA TRANSITION ZONE

“…In general, the behavior of meteorological elements is dependent on the incidence of energy, which in turn causes instantaneous variations depending on the time of year, latitude (Liu et al, 2018;Séférian et al, 2018), and time of the day (Barry and Chorley, 2013). The zenith angle (Z) consists of the degree of scattering of solar energy in relation to a local zenith (Santos et al, 2015) and its behavior indicates that the smallest spreads occur when the zenith angle approaches zero (between 10:00 and 14:00 hours) (Souza and Escobedo, 2013); this moment is when the behavior of the local meteorological elements intensifies and consequently alters the behavior of the fire (Torres et al, 2010).…”