# Visibility Assessment of New Photovoltaic Power Plants in Areas with Special Landscape Value
## 1 Introduction  
The integration of power plants based on renewable energies into the electrical grids has accelerated in recent years, primarily for environmental reasons, such as the effort to reduce greenhouse gas emissions from fossil fuels. Economic support from government authorities for these facilities, which are mainly wind and photovoltaic (PV) power generation plants, have led to their expansion throughout Europe [1]. For this expansion, finding the land available for building a new facility is the initial requirement. In the case of new wind farms or PV power plants, there are many factors involved in the decision to select the right location (wind or solar resources, distances to roads, distances to power lines, terrain orography, proximity to urban centres, visual impact, etc) [2; 3; 4; 5]. In areas where tourism is an important component of the local economy or in areas with a high landscape or cultural value, one of the most important factors in people accepting the installation of new power facilities is the visual impact. It is in the interest of local authorities and economic entities related to tourism that visitors or tourists perceive the landscape in its natural or original state [6] and as free from visual intrusions as possible. This dimension can cause projects to be suspended as a result of social rejection to the alteration or modification of the landscape [7]. In the field of power plants based on renewable energies, wind energy has the greatest negative impact on landscapes per unit of energy generation, followed by PV solar energy [8]. This has meant that the visual impactassessment of wind farms is more developed, although some of the proposed solutions can be applied to PV plants. [PERSON] et al. in [9] seek to develop a conceptual definition of social acceptance, identifying and synthesizing the factors of discontent at play in the acceptance of wind farms, transmission lines and pumping groups for energy storage. In wind farm projects, the assessment of visual impact acquires great importance because of their lack of aesthetic integration into the landscape [10]: the authors assess the magnitude of the aesthetic impact on the landscape by means of a proposed indicator. Measurements of visibility, colour, fractality and continuity are taken from photographs and combined with each other. The results of the indicator are contrasted with the impact perceived by a sample of the local population. This perceived impact is found through surveys. In [11], the variables that can affect the visual impact are analysed, such as the visual magnitude and the overall colour difference, according to the author. From the analysis of images of the wind farm under study, parameters such as the difference in clarity, the difference in colour saturation and the difference in hue are obtained, which factor into the calculation of the overall difference in the colour represented by the visibility of the wind farm. The author analysed images of the wind farm at different times of the day and, using atmospheric visibility data, determined the temporal distribution of visual impacts in the area being studied. Other works use a method that quantifies the degree of visibility of an offshore wind farm from various observation points along the coast [12]. In this assessment of the degree of visibility, the authors introduce three indicators: the horizon occupation indicator (surface occupied by the wind farm on the horizon and defined by the area delimited by the convex envelope joining the turbine hubs), the distinguishable turbine indicator (defined as the relationship between the number of distinguishable turbines and the total number of turbines), and the aesthetic indicator (based on the alignment of the turbines). PV power plants can bring about the transformation of a large area (land-use change, earthworks, vegetation removal), producing a significant alteration to the landscape.