## 1 Introduction
The operating time of the solar tracker in backtracking mode is (\(T_{R}\), \(T_{b1}\)) and (\(T_{b2}\), \(T_{S}\)) (see Figure 1). Due to wind loads, the tilt angle (\(\beta\)) of the \(PV\) field of a horizontal single-axis tracker cannot exceed a certain maximum tilt angle (\(\pm\beta_{\max}\)). This maximum tilt angle is usually 60(\({}^{\circ}\)) [19]. Therefore, although the position of the Sun may suggest that the \(PV\) field has a tilt angle greater than the maximum tilt angle, the solar tracker will remain at \(\beta_{\max}\). In other words, it will remain in static mode. The operating time of the solar tracker in static mode is (\(T_{b1}\), \(T_{b1}\)) and (\(T_{b2}\), \(T_{b2}\)) (see Figure 1). The choice of the \(\beta_{\max}\) angle has a great influence on the incident solar irradiance on the \(PV\) field [24]. And, as will be shown in the Results section, it also had a great influence on the conclusions of this study. The normal tracking mode is characterised by maximising the incident beam solar irradiance on the \(PV\) field. To do this, the solar tracking algorithm minimises the solar incidence angle with respect to the normal \(PV\) field [23]. This mode of operation is the longest operating period, as it covers from \(T_{\beta 1}\) to \(T_{\beta 2}\) (see Figure 1):  
To carry out a rigorous study of the incident solar irradiance on the \(PV\) field in \(PV\) power plants under real operating conditions considering a fixed tilt angle system and a horizontal single-axis tracker, the three modes of operation of this last mounting system must be taken into account. Some of the publications on horizontal single-axis trackers that do not take into account their three modes of operation are discussed below:  
1. [PERSON] et al. [25] presented several solar tracking algorithms for a horizontal single-axis tracker. The astronomical solar tracking algorithm obtained 25.2% more energy than the fixed tilt angle system. In this study, \(\beta_{\max}\) was not used. 2. A comparative study of different \(PV\) module mounting systems was the focus of the paper presented by [18]. In this work, 39 locations in the northern hemisphere with latitudes between 6(\({}^{\circ}\)) and 60(\({}^{\circ}\)) were analysed, as well as different mounting systems, including the horizontal single-axis tracker and the fixed tilt angle system. The horizontal single-axis tracker obtained better results than the fixed tilt angle system (between 10% and 17%), considering normal tracking mode from sunrise to sunset. Therefore, backtracking mode and static mode were not taken into account. Figure 1: Representation of the horizontal single-axis tracker periods of operation. * [PERSON] et al. [26] presented a tool that integrates crop modelling with horizontal single-axis trackers. In this tool, the solar tracker is considered to operate all day in normal tracking mode. Therefore, by not considering backtracking mode, the solar trackers shade each other. Furthermore, only horizontal single-axis trackers are analysed, without considering fixed tilt angle systems. * [PERSON] et al. [27] presented a technical and economic study of photovoltaic systems that used different photovoltaic tracking systems in six regions of different latitudes in China. This study included horizontal single-axis trackers and fixed tilt angle systems. The horizontal single-axis tracker obtained 41.40% more energy than the fixed tilt angle system. This study did not take into account backtracking mode or \(\beta_{\max}\). Other studies that did not take into account the movement limit (\(\beta_{\max}\)) include [PERSON] and [PERSON] [28], [PERSON] et al. [29], and [PERSON] et al. [30]. There have been several studies that take into account the three modes of operation of the horizontal single-axis tracker, such as [PERSON] et al. [31], [PERSON] et al. [32], etc. But these studies did not carry out a comparative study with fixed tilt angle systems.