Experimental and Theoretical Evaluation of Incident Solar Irradiance on Photovoltaic Power Plants Under Real Operating Conditions: Fixed Tilt Angle System vs. Horizontal Single-Axis Tracker

The aim of this paper was to delve deeper into the nuances of incident solar irradiance on the photovoltaic field of a fixed tilt angle system versus a horizontal single-axis tracker. The fixed tilt angle system was used as a baseline for comparison. Three assessment indicators were analysed (annual energy gain (AEG), monthly energy gain (MEG), daily energy gain (DEG)). The procedure used comprised the following steps: (i) choice of solar irradiance estimation model; (ii) theoretical study; (iii) study under real operating conditions—for this purpose, an experimental setup was used; and (iv) comparison of these studies. The experimental setup was installed at the Department of Electrical Engineering of the University of Oviedo (Gijón, Spain) (latitude 43°31′22″ N, longitude 05°43′07″ W, elevation 28 (m) above sea level). Gijón is characterised by a temperate oceanic climate typical of Spain’s Atlantic coast, with cool summers and wet and mostly mild winters. The code assigned to Gijón under the Köppen climate classification is Cfb. The horizontal single-axis trackers that comprise photovoltaic power plants have three operating modes (Scenario 1). Some studies consider a unique mode of operation from sunrise to sunset (Scenario 2). The following conclusions can be drawn from the results obtained: (i) although the results obtained in the theoretical study and in the study under real operating conditions were different, a trend can be seen in the results; for example, the AEG obtained was approximately 13% and 8.5% in the theoretical study and in the real study, respectively, in Scenario 1 and approximately 18% and 10.5%, respectively, in Scenario 2; Scenario 2 obtained higher results than Scenario 1 in all the assessment indicators; but it must be considered that Scenario 1 is the real mode of operation; (ii) from March to September, the horizontal single-axis tracker generates more electrical energy; as this period contains the months of greatest solar irradiance, the horizontal single-axis tracker performs better annually; considering the theoretical study and Scenario 1, the highest value of MEG was in June (43%) and the lowest was in December (−29%); when the study was considered under real operating conditions, the highest result was in July (30%) and the lowest was in December (−24%); (iii) on the days between 70 and 277 in Scenario 1, the horizontal single-axis tracker generated more electrical energy; on the other days the opposite occurred; taking into account the theoretical study, the highest and lowest DEG values were 43% and −30%, respectively; when the study was considered under real operating conditions, the highest and lowest DEG values were 58% and −47%, respectively.