Worldwide multi-model intercomparison of clear-sky solar irradiance predictions

Abstract

Abstract. Accurate modeling of solar radiation in the absence of clouds is highly important because solar power production peaks during cloud-free situations. The conventional validation approach of clear-sky solar radiation models relies on the comparison between model predictions and ground observations. Therefore, this approach is limited to locations with availability of high-quality ground observations, which are scarce worldwide. As a consequence, many areas of interest for, e.g., solar energy development, still remain sub-validated. Here, a worldwide inter-comparison of the global horizontal irradiance (GHI) and direct normal irradiance (DNI) calculated by a number of appropriate clear-sky solar radiation models is proposed, without direct intervention of any weather or solar radiation ground-based observations. The model inputs are all gathered from atmospheric reanalyses covering the globe. The model predictions are compared to each other and only their relative disagreements are quantified. The largest differences between model predictions are found over central and northern Africa, the Middle East, and all over Asia. This coincides with areas of high aerosol optical depth and highly varying aerosol distribution size. Overall, the differences in modeled DNI are found about twice larger than for GHI. It is argued that the prevailing weather regimes (most importantly, aerosol conditions) over regions exhibiting substantial divergences are not adequately parameterized by all models. Further validation and scrutiny using conventional methods based on ground observations should be pursued in priority over those specific regions to correctly evaluate the performance of clear-sky models, and select those that can be recommended for solar concentrating applications in particular.

Calibration and Validation of Global Horizontal Irradiance Clear Sky Models against McClear Clear Sky Model in Morocco

“…Empirically based irradiance models need geometric parameters, such as solar zenith angle position, and/or key climatological parameters, such as sunshine duration, relative humidity, surface pressure, clearness of the atmosphere, and air temperature as input parameters [17,18], whereas broadband models need inputs that fully define the atmospheric state in detail, such as aerosol optical depth, amount of precipitable water, and ozone column [4,[19][20][21]. Specific atmospheric or meteorological characteristics are not always available or are of low quality, limiting the model outputs' accuracy [21,22]. GHI at the ground surface can also be accurately estimated using satellite images [23][24][25][26][27].…”

Μελέτη Της Επίδρασης Των Αιωρούμενων Σωματιδίων Και Των Νεφών Στην Ηλιακή Ακτινοβολία

“…Όμως, η απουσία πυκνών ακτινομετρικών δικτύων παγκοσμίως και τα χρονικά κενά στις χρονοσειρές της SSI δείχνoυν ότι, η μέτρηση των συνιστωσών της από επίγειους σταθμούς(μέθοδοςand Hansen, 1974;Laaroussi et al, 2016). Οι επίγειες μετρήσεις και οι δορυφορικές χρονοσειρές ή τα δεδομένα επανάλυσης θεωρούνται ως οι πιθανές επιλογές δεδομένων εισόδου, οι οποίες μπορούν να εισαχθούν στα εμπειρικά μοντέλα για τις εκτιμήσεις της GHI υπό ανέφελες συνθήκες(Janjai et al, 2011;Javadnia et al, 2017;Ruiz-Arias et al, 2017). Ειδικότερα, στην εργασία των, πραγματοποιήθηκαν εκτιμήσεις της GHI στην Καλιφόρνια, χρησιμοποιώντας τέτοιου τύπου μοντέλα, όπως το REST2 και δορυφορικά ατμοσφαιρικά δεδομένα εισόδου από το MODIS.…”