Medição da Radiação Solar Global e Difusa Utilizando Piranômetros com Sensores Fotoelétricos

• Ano de defesa: 2008
• Autor(a) principal: Victoria, Idilio Manoel Brea
• Orientador(a): Vianna, João Carlos Torres
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Pelotas
• Programa de Pós-Graduação: Programa de Pós-Graduação em Meteorologia
• Departamento: Meteorologia
• País: BR
• Palavras-chave em Português: Medição de radiação solar; Radiação difusa; Anel de sombra
• Palavras-chave em Inglês: Solar radiation measurement; Diffuse radiation; Shadow band
• Área do conhecimento CNPq: CNPQ::CIENCIAS EXATAS E DA TERRA::GEOCIENCIAS::METEOROLOGIA
• Link de acesso: http://repositorio.ufpel.edu.br/handle/ri/2187

In Brazil, most of the Institutions that measure solar radiation and the display only the global radiation incide on a horizontal surface. In the region of Pelotas - RS, the Estação Agroclimatológica de Pelotas, linked to Embrapa, has had the data of global solar radiation daily estimated from 1971 to 1992 and measurements starting in 1993. Considering that the solar systems should be installed so that a larger amount of energy is collected, the element collectors should be installed with a certain inclination related to horizontal surface and oriented to towards the Equator. That means that the radiation data made available by the Institutions that measure global solar radiation should be worked in a way that it is possible to obtain an estimation of the solar radiation incident on a sloping surface. The existing procedures used by solar system designers in Brazil to estimate the global solar radiation incident on a sloping surface, use statist methods originating from the diffuse measurement incident in other countries. With the objective of better estimating the solar radiation incident on a sloping surface and spreading the diffuse solar radiation measurement through the use of pyranometers which use photoelectric sensors, of low cost, in substitution to the thermoelectric sensors, this work describes and validates the procedures of measurement of global and diffuse solar radiation so as for these to be considered of good quality. For this experience three metallic bases were used. Two of them set up under the inspiration of the Robinson and Stoch model, attached to a radiometric platform, at CEFET RS, at a height of 19m. They received shadow bands on the measurement of diffuse radiation with the band axis in the N-S direction. Pyranometers with photoelectric sensors and thermobattery were used. The termobattery considered a secondary pattern, as reference in measurements with global and diffuse solar radiations. These, linked to the data acquisition system and to the microcomputer had the data measured interpreted in the calibrating of the pyranometers study and the measurements of the radiations mentioned before. Considering the work with solar radiation data, the recommended statistic tests were applied: medium deviation error (MBE), medium quadratic error (RMSE) and the correlational coefficient (CC). It is possible to conclude that the use of Licor LI 200 pyranometer, with the photoelectric sensor, for measurement of the global and diffuse solar radiation must be preceded by a good calibration, performed periodically. The global solar radiation data obtained presented good quality, coinciding with the values measured with the standard Eppley PSP pyranometer, observing the uncertainty of the equipments. Regarding the diffuse solar radiation measurements, although the Licor pyranometer operated under less proper conditions of performance, in other words, in very cloudy days, after the corrections due to shadowing, at atmospheric and temperature conditions, it was possible to obtain better quality results, reducing significantly the error values of MBE and RMSE.