Validation of model chains for global tilted irradiance on East-West vertical bifacial photovoltaics at high latitudes

Abstract

In this paper, a methodology is introduced to identify and validate the most effective model chain to estimate solar irradiance on East-West vertical bifacial photovoltaics (E-W VBPV) at high latitudes. While previous studies mainly focused on the validation of a specific step of the model chain (i.e., decomposition or transposition stage), this work investigates the whole model chain and how the combination of different models influences the results’ accuracy. After a comprehensive review, the 29 decomposition models, which perform the best in the Nordics, and the 25 most common physical and empirical transposition models are selected and combined into 725 model chains. Each model chain is experimentally validated against 1-min data about global tilted irradiance on the front and the rear of E-W VBPV in Turku (Finland). Nine different statistical metrics are calculated to rank the model chains while describing various aspects of the model chain performance (e.g., error magnitude, bias direction, reference data fitting). The main research outcomes indicate that the accuracy and bias of the model chains differ between the East and West sides of the VBPV. Therefore, using a specific model chain for each VBPV side is recommended. In this regard, the Erbs/Steven1 (decomposition model/transposition model) model chain is the top-ranked for the East side, while the Yang2/Hay1 model chain results the best for the West side. Following this, recommendations to select appropriate solar irradiance model chains for future E-W VBPV applications at high latitudes are outlined.