IMPROVEMENT OF DIFFUSE SOLAR IRRADIANCE MEASUREMENTS WITH NONCOSINE INSTRUMENTS

摘要

As a result of sky radiance anisotropy, significant errors spoil diffuse solar irradiance data obtained by means of noncosine-true instruments, which happens in spite of knowledge of the relative cosine response. To reduce these errors we recommend a method that involves an additional measurement of diffuse irradiance from a horizon band. The efficiency of the so-called double-measurement method is found to be optimum for a 25 degrees horizon band elevation. We confirm the feasibility of the method with relevance tests that use diffuse solar spectral measurements carried out on cloudless skies by means of an UV spectroradiometer. (C) 1996 Optical Society of America [References: 11]