Quality Assurance Procedure for Solar Radiation at Minute Resolution

Abstract

This article proposes a quality assurance (QA) procedure for evaluating measurements of global horizontal, diffuse horizontal and direct normal irradiances. The QA is divided into physical, comparative and refining tests, including Baseline Surface Radiation Network (BSRN) recommended quality tests. The comparative tests (tracker off and coherence tests) evaluate the connection among the three main radiation components. The coherence test as proposed by BSRN is complemented with a comparison between the measured radiation series with a validated clear sky model to define which of the three radiation components is presenting problems. Three stations in Pernambuco, Brazil and one in Gobabeb, Namib have been qualified using the proposed QA, with two of these stations belonging to BSRN (Petrolina and Gobabeb). The results show that the direct normal irradiance series can present considerable outliers due to soiling in pyrheliometers. For solar stations without periodic maintenance, the series of direct normal radiation measured by pyrheliometers can have more soiling problems than other radiation components measured by pyranometers.