## 1 Introduction  
Most minor islands are not interconnected to the main national electrical grids, and energy is provided by power generation systems consisting of thermal power plants [1]. This causes a financial dependency on the price of fossil fuels [2] and high electricity generation costs [3]. For this reason, island communities are facing numerous energy challenges regarding fuel import dependency and the transport of fuel supply [4]. Furthermore, small islands represent a typical example of such communities, for which the final users' energy consumption often depends on an electricity source provided by diesel and heavy-fuel oil power plants [5]. [PERSON] et al. [6] proposed a characterization of island energy load based on economic, demographic, and cultural criteria. They underlined how islands with the highest demand per capita are generally located in developed countries, while they have a considerable tourist vocation that strongly influences both the energy consumption and the load profile of the island itself. It would be consequently advantageous to increase the energy efficiency of the whole system via the use of local renewable energy sources (RES) at large scale or by implementing retrofit strategies at the end-user level (including building automation control, small RES plants, etc.) [7, 8]. As [PERSON] [9] affirmed, RES installation is a suitable action to decrease the dependency on fossil fuels and resulting environmental problems, because, in general, they are free from large emissions and locally available. Many studies are available on the use of renewable energy sources on islands. For example, [PERSON] et al. [10] studied a pathway for small islands to replace fossil fuels by renewable sources, applied to a case study in Jamaica. They found that renewable energy can be achieved in such a manner as to satisfy and be in line with the Intergovernmental Panel on Climate Change guidelines for limiting temperature rise to 1.5 \({}^{\circ}\)C. The aim of the study of [PERSON] et al. [11] was to analyze the impact of the interconnection of two Azores small islands in the path to 100% RES for the whole energy system. [PERSON] [12] focused his attention on Cobrador Island in the Philippines to study the impact of providing more affordable, reliable, and sustainable access to energy on consumption patterns, appliance uptake, and overall socio-economic development. To do this, similarly to this study, a survey was conducted to assess the impact of providing a continuous renewable-based power supply on local development and the sustainable development goals. [PERSON] et al. [13] proposed a general method to classify global islands with regard to RES installation potentiality, employing cluster analysis based on climatic, physical, and socio-economic parameters. The possibility to convert the existing thermal-power plant into combined heat and power (CHP), i.e., a degeneration system, including the construction of district heating/cooling networks, was investigated by [PERSON] et al. [14]. Nevertheless, this study conducted on six Italian small islands demonstrated that CHP technology is only moderately economically attractive when public support mechanisms are included in the analysis. Better results are achieved if hybrid renewable poly-generation systems are considered; however, once again, huge investments are needed. Indeed, the economic attractiveness of such systems is related to the linear density of the energy demand and to the fact that the majority of the energy available for heating and cooling purposes is currently used. [PERSON] et al. [15] studied an innovative poly-generation system powered by solar and geothermal sources on Pantelleria Island. The described plant is able to cover the electricity and the heat demands of a small community, as well as to simultaneously cover the freshwater demand of the island. In another work, [PERSON] et al.