## 5 Conclusions  
This paper presents two energy studies: a study under real operating conditions and a theoretical study, of various photovoltaic module mounting systems (fixed tilt angle system, horizontal single-axis tracker). Fixed tilt angle systems are characterised by keeping the position of their photovoltaic field constant, from sunrise to sunset. The horizontal single-axis trackers that comprise photovoltaic power plants have three operating modes (Scenario 1) (backtracking mode, static mode (\(\beta_{\max}=\pm 60\)(\({}^{\circ}\))), normal tracking mode). If we consider a horizontal single-axis tracker, it is not necessary to consider the shadows between mounting systems. Therefore, the horizontal single-axis tracker can be in normal tracking mode from sunrise to sunset (Scenario 2). In this case, the limit movement has an angle of \(\pm 90\)(\({}^{\circ}\)). The fixed tilt angle system was used as a baseline for comparison. The experimental setup was installed at the Department of Electrical Engineering of the University of Oviedo (Gijon, Spain) (latitude \(43^{\circ}31^{\prime}22^{\prime\prime}\) N, longitude \(05^{\circ}43^{\prime}07^{\prime\prime}\) W, elevation \(28\) (m) above sea level). Gijon 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 Gijon under the Koppen climate classification is \(C_{fb}\). Three assessment indicators were analysed (annual energy gain (\(AEG\)), monthly energy gain (\(MEG\)), daily energy gain (\(DEG\))). In order to carry out the proposed studies, it was necessary to implement several specific codes to determine the components of the incident solar irradiance on the photovoltaic field of the mounting systems under study. The software used to implement the codes was _Mathematica_. The main conclusions obtained are summarised below:  
1. 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.
2. 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 (\(-24\)%).
3. In scenario 1, on days 70 to 277 the horizontal single-axis tracker performed better. 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  
Figure 14: Scatter diagram for the three mounting systems and fit curve.  
was considered under real operating conditions, the highest and lowest \(DEG\) values were 58% and \(-47\%\), respectively.  
One possible line of future work is the analysis and implementation of a PV module mounting system with several fixed positions.  
Conceptualization, A.B., J.M.-S. and L.B.; methodology, A.B. and L.B.; software, J.A.F.-R.; validation, A.B., J.A.F.-R. and L.B.; investigation, J.M.-S. and J.A.F.-R.; data curation, J.M.-S.; writing--original draft, J.M.-S.; writing--review and editing, J.A.F.-R. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The data presented in this study are available on request from the corresponding author.  
We wish to thank Gonvarri Solar Steel [19] for their contributions to this study.  
Author [PERSON] was employed by the company Energia y Calidad SL (INGEPEC). The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.