17 th International Conference on Environmental Science and Technology Athens, Greece, 1 to 4 September 2021 CEST2021_00025 Support Structure Suitability for Offshore Wind Farms Development in Greece based on a Sustainable Site-Selection Framework Spyridonidou S. 1,* and Vagiona D. 1 1 Department of Spatial Planning and Development, Faculty of Engineering, Aristotle University of Thessaloniki, 54124 Greece *corresponding author e-mail: sspyrido@plandevel.auth.gr Abstract. Site-selection and spatial planning form a crucial step toward the successful development of Offshore Wind Farms (OWFs). Deployment of wind turbines in different water depths has raised the issue of selection of the most suitable support structures. In this work, a well-structured site-selection framework is proposed for the appropriate OWF development in Greece. The methodology includes two successive phases: (Phs.1: Siting Phase) the identification of suitable sites for OWF insta lla tion using Geogra phic Information Systems (GIS) based on sixteen exclusion criteria (e.g., water depth and wind power density); and (Phs.2: Support Structure Suitability Phase) the determination of most appropriate and commercially available support structure(s) for each suitable site. The proposed exclusion limits are retrieved from the authors’ systematic review in offshore wind energy research and based on the maximization of environmental sustainability, and the technical and economic viability of OWFs. Twenty sustainable site solutions of either fixed (e.g., jacket) or floating (e.g., Hywind) support structures are proposed. The suggested methodology could support policy makers towards the global and national proper development of such wind energy projects. Keywords: site-selection; spatial energy planning; offshore wind; support structure; GIS 1. Introduction Wind energy has a key role to the accomplishment of energy interdependency of European Union (EU), since it covers 16.4% (13.4% coming from onshore and 3% from offshore wind) of EU electricity demand (including United Kingdom) in 2020 (WindEurope Business Intelligence et al., 2021). The aforementioned portion corresponds to 458 TWh of electricity produced. Offshore wind installations are constantly growing, due to the multiple benefits they present in siting issues (e.g. space availability, power generation, landscape disturbances minimization). Offshore wind farm (OWF) installations form currently a great portion of wind energy market, since it corresponds to 11.40% (i.e., 25 GW) of Europe’s cumulative wind power capacity (i.e., 219.5 GW) at the end of 2020 (WindEurope Business Intelligence et al., 2021). In Greece, wind energy market development focuses only on onshore installations, since OWFs have not been planned and deployed yet. Site-selection and spatial planning have a crucial role toward the successful deployment of OWFs, since inappropriate siting may lead to uneconomic viability and social opposition of wind projects. Aiming to solve and avoid the above essential siting issues, Geographic Information Systems (GIS) have been utilized within a large number of studies in OWF siting applications (Castro-Santos et al., 2020; Christoforaki and Tsoutsos, 2017; Saleous et al., 2016; Spyridonidou et al., 2020). An additional and important issue in the OWF site-selection processes, is the selection of the most suitable support structure of wind turbines in different water depths, since this issue is directly linked with the economic viability of the project and the engineering limitations of each support structure in specific water depth ranges (Myhr et al., 2014). In the present work, a site-selection framework is developed for the identification of sustainable OWF sites in Greece, considering essential siting constraints (e.g., territorial waters, wind power density), and for the suitability of each support structure within the sustainable sites, considering Levelized Cost Of Energy (LCOE) of each system in different water depths and other important parameters. The remainder of the paper is structured as follows. Section 2 presents the Siting and Support Structure Suitability Phases of the proposed framework in detail. The results of this work are presented and discussed in Section 3, while the concluding remarks of this investigation are cited in Section 4. 2. Materials and Methods The site-selection framework is applied on national spatial planning scale. In particular, the study area includes the territorial waters of Greece and therefore any marine area further away of six (6) nautical miles from the coastline is excluded. The methodology is shown in Figure 1 and includes two successive phases. In the Siting Phase (Phs 1.), exclusion criteria and incompatibility zones are defined (Table 1) based on: (a) authors’ previous research (Spyridonidou and Vagiona, 2020); (b) the special characteristics of the study area; (c) the respective provisions and policies of the Greek Specific Framework for the Spatial Planning and Sustainable Development for the Renewable Energy Sources (SFSPSD-RES) (SFSPSD-RES, 2008); (d) the interna tional guidelines for proper WF siting (i.e., Na tional Renewable Energy Laboratory (NREL)) (Na tional Renewable Energy Laboratory, 2015); and (e) the special siting requirements of offshore support structures. The