One minute Kt probability density distributions conditioned to the optical air mass and hourly Kt
Résumé
Present needs in concentrating solar power systems require knowledge of the solar irradiation temporal evolution. Daily or hourly generation of irradiation synthetic series is normally used in the estimation of solar resource, as measured series of radiation are only available for a reduced number of locations. Notwithstanding, the flickering nature of instantaneous solar irradiance is lost in hourly series, and it has a considerable impact on the non-linear behaviour of solar energy conversion systems. The study of the statistical behaviour of short term values of solar irradiation will facilitate more precise one minute synthetic generation of solar irradiation series, and consequently will facilitate more accurate estimations of concentrating solar power systems performance characterized by a fast and non-linear response to the incoming solar radiation. In this work, the probability density function of one minute values of clearness index kt (solar global horizontal irradiance to extraterrestrial horizontal irradiance ratio) conditioned to the optical air mass m (relative thickness of the air path traversed by a sun's ray when it reaches the earth's surface) and hourly kt in Carpentras (France) has been investigated. These distributions present a unimodal character, in contrast with bimodal character founded in distributions conditioned only to m. Distributions at kt equal to 0.75 markedly decrease with higher values of m. Otherwise, distributions of one-minute kt values at kt equal to 0.15 are almost independent of m, indicating a strong dependence of them on cloud conditions. Distributions at kt between 0.3 and 0.45 show a mixed behaviour, presenting similar peaks and dispersion, and different dependence on m.
Origine : Fichiers produits par l'(les) auteur(s)
Loading...