# Energy Transition on Sifnos: An Approach to Economic and Social Transition and Development
## 1 Introduction
### Prior Literature Regarding Energy Transition in Insular Systems  
Energy transition refers to the process of moving towards the replacement of the currently used fossil fuels for energy production with RES, as well as the introduction of new energy systems with improved operation efficiency and low primary energy consumption, described with the term \"rational use of energy\" (RUE) [12; 13]. The necessity and the essential guidelines of energy transition were set by the European Commission in the Directives (EU) 2018/2001 [14] and (EU) 2018/844 [15]. In the technical and scientific literature, energy transition, particularly for islands, constitutes a popular and widely studied topic. The relevant articles can be distinguished into two main categories:  
* Articles studying the technical aspects of power production systems, including the layout, the operation algorithm, the introduction of new technologies or the combination of systems, etc. * Articles studying the social, environmental and developmental perspectives of energy transition. Energy transition on islands is mainly approached using electricity production technologies from RES, supported by storage plants, formulating in this way the so-called \"hybrid power plants\" (HPP). For large islands, with a power demand higher than 5 MW, the optimum storage technology has by far been proved to be the pumped hydro storage (PHS) systems [14; 15; 16; 17; 18; 19], due to their large storage capacity, their considerably long autonomy operation period and the low specific cost of set up, which, under favorable land morphology and appropriate placement, can be as low as EUR 30/kWh of storage capacity [10]. PHS systems can also contribute to the regulation of the electrical grid frequency, through both the fast and flexible operation of hydro turbines and the management of the pump loads [20]. Thus far, there are two integrated and operating wind parks--the PHS systems in the islands of El Hierro, Canary Islands, Spain [21; 22] and Ikaria, Eastern Aegean Sea, Greece [23]. For smaller islands, with peak demand lower than 5 MW, normally the high infrastructure set-up costs of PHS systems cannot be compensated by the relatively low electricity demand, although there can be cases with favorable land morphology and high existing electricity production specific cost where PHS systems can be feasible [24]. However, such cases should be considered as exceptions. Usually, small hybrid power plants are supported by electrochemical storage devices. The scientific literature on such small systems usually deals with their technical and economic feasibility, under alternative operation algorithms, involved technologies and insular conditions [25; 26; 27]. The essential feature of these technologies is their considerably high set-up cost, caused mainly by the high procurement cost of batteries (EUR 200-500/kWh, depending on the storage technology) and their low lifetime period, which further increases the project's set-up cost due to the required regular replacements [28; 29; 30]. For this reason, such systems are usually proposed with a small number of storage modules and, subsequently, low storage capacity. Aiming to overcome this drawback, sophisticated solutions with additional storage alternatives are often examined, with the most popular being hydrogen production via electrolysis units [31; 32; 33]. Finally, in case of islands with extensive agricultural and stock farming activities, the introduction of biomass-based systems has been proposed [34]. On Reunion Island, for example, the available biomass sources can cover more than 50% of the annual electricity demand [35; 36]. The second type of article deals with the environmental, social and economic extensions of energy transition, such as the public acceptance of energy transition projects and the maximization of their contribution to the social and economic growth of insular communities.