# GIS-Based Solar Radiation Mapping, Site Evaluation, and Potential Assessment: A Review
## 5 Discussion and Conclusions  
In this paper, numerous published articles on GIS-based methods and applications for the planning and design of solar power systems were reviewed. For solar radiation mapping, site evaluation, and potential assessment of PV and CSP systems, GISs have been used for purposes ranging from simple to complex, such as (i) DB and visualization, (ii) rooftop extraction, (iii) shading analysis, (iv) solar radiation modeling, (v) spatial analysis, and (vi) MCDA. In addition, GIS-based methods can be applied differently according to the scale of study area, as well as the type of solar energy conversion technology. Based on the detailed literature review, the following conclusions were drawn. 1. Solar radiation maps can be useful spatial DBs in spatial and temporal analyses of solar resources. Interpolation methods can be employed for solar radiation mapping in areas with sufficient measured data. The results are presented as solar maps over large areas in pixels. In the absence of sufficient measured solar radiation data, other weather information can be used to predict solar radiation. This method is performed for a specific point, such as a station, by predicting the solar radiation relatively accurately based on various parameters. In recent years, machine learning techniques such as ANNs have been used. After accurately estimating the solar radiation for additional stations, more accurate solar radiation mapping can be achieved via interpolation. Solar radiation models using topography were also developed to predict solar radiation where there is no measured data. Various algorithms and shadow analysis based on GISs are mainly utilized in these models. The solar radiation maps produced using these methods can facilitate the identification of solar resources in specific areas and the determination of suitable areas for solar power plants. Validation using measured data is necessary to verify the accuracy of such maps. 2. GISs are useful for site evaluation when installing solar power plants for PV or CSP. While diffuse radiation is also an important factor in PV suitability analysis, only direct radiation is considered in CSP suitability analysis. In most site evaluation studies, solar radiation is the primary consideration and is obtained in various ways depending on the presence or absence of data. In particular, site evaluation by employing a GIS is useful for supporting decision making on the regional scale, and it is necessary to consider economic, environmental, technical, social, and risk factors in addition to solar radiation. These factors can be used to exclude unsuitable regions through Boolean overlay. They can also be employed in various MCDA methods to estimate suitability indices. Some researchers have performed suitability analysis for buildings, mines, and reservoirs. 3. The assessment of solar PV potential is critical in the development of planning policies and financing schemes for successful PV system deployment. Most of the reviewed literature focused on assessing the technical potential in the region of interest among the three types of solar potential. GISs are effective for assessing physical potential (total solar radiation on the surface/rooftop) and geographic potential (available surface/rooftop area considering the shadow), serving various purposes such as DB and visualization, rooftop extraction, radiation modeling, shading analysis, and spatial analysis tools. In addition, GISs can be utilized to visualize and interpret solar energy-based power output or economic values in the geospatial context in technical potential assessment. Despite the advances of PV and CSP technology, a lack of information regarding the feasibility of solar power systems among installers and consumers, financial groups that broker large installations, policymakers who enable the deployment of technology, and even scientists and engineers from other complementary disciplines, has become a formidable barrier to their extensive penetration.