## 4 Conclusions  
In this paper, the solar capture on horizontal one-axis trackers was mathematically modelled, thus establishing the rotation axis orientation for any irradiance model. Backtracking was used to avoid the shading of some panels on adjacent ones, modifying their orientation. The results obtained, combined with those in the literature, amount to an advance in the knowledge on photovoltaic trackers  
Figure 11: Losses with \(0^{\circ}\) axis azimuth and \(20^{\circ}\) inclination. Figure 12: Irradiance by varying the ratio d/h (h = 3 m). with axes parallel to the terrain, allowing an optimal design for terrains without the horizontality described in previous works. A program and a subroutine were implemented in VBA to automatically calculate the radiation affecting a solar tracker for different terrain configurations and for which it was possible to vary the characteristics of the installation, namely the rotation axis orientation and the ratio dimension of the panels \(h\) and the separation \(d\) between adjacent rows. Simultaneously, the program and subroutine provided the optimal azimuth \(\gamma\) value for the rotation axis to be suitably directed and the loss values for each possible maximum radiation value for each inclination \(\beta\) of the terrain. The calculations of the amounts of radiation affecting solar panels, assuming fixed width and distance between lines of panels and varying terrain inclinations \(\beta\) and azimuth \(\chi\), were made in Cordoba, Spain. For any given value regarding the terrain inclination \(\beta\), it was verified that a higher value of radiation was obtained for terrain that was oriented south (\(\chi=0^{\circ}\)). The optimum direction for the rotation axis collector \(\gamma\) should also be southwards. An important contribution of this research is the relationship established between the azimuth \(\gamma\) of the collector axis and the inclination \(\beta\) and azimuth of the terrain. For terrain that is not south facing, the rotation axis azimuth \(\gamma\) of the solar trackers should be different from zero and varies in the same direction as the land azimuth \(\chi\). If the axis of rotation is positioned in a different direction to the optimum, losses in potential energy production arise. These losses vary according to the terrain inclination \(\beta\). The greater the difference between the optimum azimuth \(\gamma\) and the terrain inclination \(\beta\), the greater the production losses will be. Another important conclusion drawn from this research concerns the collector layout on the power plant surface. As the distance \(d\) between rows of collectors increases, a greater amount of radiation is generated. Such growth is asymptotic. Overall, some progress has been achieved towards the objective of deepening knowledge concerning photovoltaic trackers. Consequently, guidelines were proposed for solar capture optimisation in photovoltaic plants. This work opens up further lines of research into the geometric layout optimisation of solar trackers involving more complex models, such as those of [PERSON] [34] and [PERSON] [33], and real databases. As a result of the aforementioned conclusions, it is considered that this study can be the basis for further work, such as the study of one-axis solar trackers located on terrains with irregular topographies or of the collector distribution system, considering potential uses of the land. Conceptualization, F.J.G.-U., I.M.M.-G. and R.L.-L.; methodology, I.M.M.-G. and L.M.F.-A. ; software, [PERSON]-M.; validation, I.M.M.-G. and L.M.F.-A. ; formal analysis, L.M.F.-A., I.M.M.-G. and R.L.-L.; bibliographic search, F.J.G.-U. and L.M.F.-A. ; data curation, J.M.J.-M. and R.L.-L.; writing--original draft preparation, L.M.F.-A., F.J.G.-U. and I.M.M.-G.; writing--review & editing, F.J.G.-U., I.M.M.-G., R.L.-L. and L.M.F.-A. ; supervision, I.M.M.-G., R.L.-L. and L.M.F.-A. All authors have read and agreed to the published version of the manuscript. This research received no external funding.