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Universidad de Córdoba (2019)

New theoretical developments in solar capture for static and mobile structures

Fernández de Ahumada, Luis Manuel

Titre : New theoretical developments in solar capture for static and mobile structures

Auteur : Fernández de Ahumada, Luis Manuel

Université de soutenance : Universidad de Córdoba

Grade : DOCTORADO EN INGENIERÍA AGRARIA, ALIMENTARIA, FORESTAL Y DEL DESARROLLO RURAL SOSTENIBLE 2019

Résumé partiel
Solar irradiance is a fundamental variable for the characterization of the solar resource as an energy source. The scarcity of data on this variable has encouraged the development of explanatory models (isotropic models, anisotropic models, etc.). However, the models of solar irradiance have not been exploited so far in the generation of knowledge of patterns relating to optimal capture. In particular, this lack of development is evident in the study of solar trackers of photovoltaic facilities and in the radiation incident on buildings in cities. Mathematically, equations governing irradiance models can be derived with respect to position variables and, in this way, generate movement results that optimise capture and, therefore, energy production. Likewise, the exploitation of these models enables to explain known results in the sustainable energy field. A good example is the case of solar trackers based on the maximization of solar capture which have greater energy generation rates than those based on astronomical tracking. This thesis presents the analytical deduction of generic and unified equations of the movement of solar tracking systems. As a novelty, these equations are more generic, thus allowing the optimization of the positioning of photovoltaic (PV) facilities where diffuse and reflected irradiance are usable as opposed to those usually published that just consider the position of the sun (astronomical motion equations). The analysis of the results obtained criticizes the axiomatic idea – widely considered by numerous authors – establishing that the ideal tracking system in PV facilities is that tracker providing the best possible alignment with direct sunbeams. In PV plants based on solar tracking, during low-elevation solar angle hours, shadows appear between the collectors causing a dramatic decrease in production. This thesis presents a novel optimal tracking strategy to prevent the creation of these shadows. The presented method determines whether or not there is shading between collectors. Thus, when the collectors are not shaded, a tracking trajectory for maximum irradiance on the collectors is suggested. When the collectors are shaded, backtracking is proposed. Therefore, energy production in plants with this novel tracking method can be 1.31 % higher than that in PV plants with astronomical tracking. Moreover, this method allows the study of PV facilities for which there have been no published approaches, such as plants with non-rectangular collectors or those located on topographically heterogeneous surfaces.

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