Field Quality Control of Spectral Solar Irradiance Measurements by Comparison with Broadband Measurements

Aitor Marzo,Joaquín Alonso-Montesinos,Javier Barbero,Jesús Polo,Jesús Ballestrín,Gabriel López,Pablo Ferrada

doi:10.3390/su131910585

Abstract

Measurement of solar spectral irradiance is required in an increasingly wide variety of technical applications, such as atmospheric studies, health, and solar energy, among others. The solar spectral irradiance at ground level has a strong dependence on many atmospheric parameters. In addition, spectroradiometer optics and detectors have high sensitivity. Because of this, it is necessary to compare with a reference instrumentation or light source to verify the quality of measurements. A simple and realistic test for validating solar spectral irradiance measurements is presented in this study. This methodology is applicable for a specific spectral range inside the broadband range from 280 to 4000 nm under cloudless sky conditions. The method compares solar spectral irradiance measurements with both predictions of clear-sky solar spectral irradiance and measurements of broadband instruments such as pyrheliometers. For the spectral estimation, a free atmospheric transmittance simulation code with the air mass calculation as the mean parameter was used. The spectral direct normal irradiance (Gbλ) measurements of two different spectroradiometers were tested at Plataforma Solar de Almería, Spain. The results are presented in this article. Although only Gbλ measurements were considered in this study, the same methodology can be applied to the other solar irradiance components.

Highlights

Ninety-seven percent of the radiation incident on the top of Earth’s atmosphere coming from the Sun is distributed between the wavelengths: 290 to 3000 nm [1]
Both results were due to using the original factory calibration (OFC) of the equipment, which did not consider the change in length of the fiberoptic cable that carries the light collected by the probe through itself to the spectroradiometer
This study addressed the quality control of spectral solar irradiance measurements by comparison with broadband measurements

Summary

Introduction

Ninety-seven percent of the radiation incident on the top of Earth’s atmosphere coming from the Sun is distributed between the wavelengths: 290 to 3000 nm [1]. The distribution of radiation within this wavelength range is known as the solar radiation. As solar radiation travels from the outer layers through the atmosphere to the ground, the solar spectrum is attenuated and shaped due to absorption and scattering processes. These extinction processes result from the interaction between the radiation and the atmosphere components, such as aerosols, water, and gas molecules, showing a strong spectral dependence. The shape of the solar spectrum depends on the length of the light path through the atmosphere and the concentration and nature of its components.

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Results

Discussion

Conclusion