Solar Energy Measurements

Solar radiation and daylight are essential for life on earth. Solar radiation affects the earth's weather processes that determine the natural environment. Its presence at the earth's surface is necessary for the provision of food for mankind. Thus, it is important to be able to understand the physics of solar radiation and daylight and also to measure the latter with precision and repeatability. The understanding of the climatological study of radiation and collection of relevant data is comparatively new. Until 1960, there were only three stations in North–West Europe with irradiation records exceeding a 25-year period. Similarly, daylight was not recorded on a continuous basis. Furthermore, until 1991, there were records of vertical irradiance and illuminance for very few locations around the world. However, in response to the call made by Commission Internationale de l'Eclairage (CIE), the year 1991 was declared the International Daylight Measurement Year, and this led to a worldwide effort to measure solar irradiance and illuminance. New calibration standards were thus revised, and quality control procedures for measured data were set in place.This chapter provides a historical review of the relevant research and development of solar metrology, instruments, their calibration and physical sensitivities, and quality control (QC) procedures and brings together all the recent modeling work related to solar irradiance that is much needed for the QC of large measured data sets. Keywords: ambient energy; diffuse irradiance; global irradiance; insulation measurement; pyranometers; renewable energy; solar energy; solar meteorology; solar radiation measurement; solar resource assessment