# Visibility Assessment of New Photovoltaic Power Plants in Areas with Special Landscape Value
## 1 Introduction
It takes into account all possible observers in motion (by roads) or in situ (urban centres), the orography of the terrain, the height of the observer and the size of the PV plant (height of panels, surface occupied). In urban areas, there is an increase in the use of solar PV technologies, which are mainly attached to building envelopes (roofs and facades). [PERSON] et al. presents in [24] a methodology for assessing the visibility of building envelope surfaces exposed to solar radiation, which could host solar modules (thermal or photovoltaic) in urban areas and where public perception of this type of facility is not affected. The viewshed is determined on the cumulative viewing time from observation points, equidistantly arranged along urban roads, taking into account the height of the observer. The maximum visibility distance limit for calculations is 500 m, imposed by computational constraints. As a consequence of population growth and industrial and socio-economic development, the need to build new infrastructure arises, which may have a direct impact on cultural and landscape heritage, the components of which may be seriously affected [25]. Therefore, the conflict between development policies and heritage conservation policies makes it necessary to propose and make use of tools that evaluate the effects produced by such infrastructures on cultural and landscape heritage, in order to maintain a balance between the two conflicting interests [26]. The methodology proposed in this work can help the agents involved to make decisions regarding the most suitable sites for the installation of new PV plants under an objective visibility criterion, keeping landscapes of special interest or unique cultural sites safe from the intrusion of these facilities, which could create a significant visual impact. The methodology helps to identify the most suitable sites for the construction of new PV plants using GIS tools on a digital surface model (DSM) and taking into account the possible observers who move through the paths of geographical areas that are especially protected by interest in their cultural and landscape value. These tools are integrated in the open-source software QGIS [27]. The proposed method considers the global visibility of future PV power plant elements, that is, the method evaluates what portion of the elements can be seen by the observers and also what part of the elements can be seen above the skyline. Facilities with the sky in the background have higher colour contrast and therefore greater visibility than facilities with the terrain in the background [28]. Variations in the visibility of PV facilities, caused by changes in colour contrasts during the day or by the weather, have not been considered in this work. In the scientific literature, the issue of visual impact caused by PV facilities has generally been approached under subjective criteria, evaluating the visual perception people have of these types of facilities by means of surveys, photographs, 3D computer simulations, etc. To our knowledge, no published work proposes an objective method, based on visibility (total or partial), to identify locations where the construction of new PV facilities would produce a lower visual impact than elsewhere. Furthermore, there are not any published works related to site selection for new facilities in areas of special landscape and cultural protection, where the potential observers are visitors or tourists travelling in such environment. The methodology proposed in this paper aims to fill these gaps. We define a variable called Global Accumulated Perception Time (_GAPT_), for the evaluation of the visibility of new PV facilities. This variable, which will be defined in detail in Section 2, is related to the cumulative total hours in a year in which a proposed PV plant can be seen by observers moving along the roads or paths in the area under study.