_applied_  
_sciences_  
_Editorial_  
Renewable Energy Systems 2020  
**[PERSON]**  
Department of Industrial Engineering, University of Naples Federico II, 80125 Naples, Italy;  
[EMAIL_ADDRESS]  
In the last few years, several states have experienced a significant growth of the global energy demand. The simultaneous increase of greenhouse gas emissions is also associated with an increase in meteorological catastrophic events in numerous areas of the world. In this framework, several countries have agreed to develop a novel sustainable energy pattern and to accomplish it with all the actions required to limit the rise of the average temperature of the Earth. This goal can be achieved through different strategies: developing novel efficient energy conversion systems, promoting energy efficiency and a more conscious use of energy, and promoting the use of novel and innovative renewable energy technologies. This effort has led to a number of positive effects, such as energy diversification, reduction of pollutant emissions, and the development of local green economies. On the other hand, the large non-programmable amount of renewable energy delivered to electric grids poses severe issues in terms of the management of excess energy and balance between demand and supply. This phenomenon is determining an increasing cost of the management of electric grids, which is typically transferred to the final consumer. In this context, the Special Issue \"Renewable Energy Systems 2020\" aims at collecting the most significant and recent studies dealing with the integration of renewable technologies into new or existing water, electricity, heating, and cooling networks. In this editorial, the collected papers analyzing the possible utilization of renewables for multiple purposes (power production, heating, cooling, water management, transport), aiming at increasing the diffusion of such sources, are summarized.  
**1. Introduction**  
In recent years, the future availability of non-renewable fuels (such as natural gas, coal, oil) and drinkable water scarcity, particularly in coastal/island and semi-arid areas, are becoming severe issues [1]. Therefore, sustainable energy plants, based on renewable energy technologies, such as geothermal, wind, solar, biomass, etc., should be taken into account, in order to achieve eco-friendly development. In this framework, EU (European Union) nations plan to cover by 2030 at least 32% of the total energy consumption by renewable energy sources and to reduce greenhouse gas emissions by 80-95%, when compared to 1990 levels, by means of a 100% renewable electric energy system [2].  
Considering this background, the studies collected in this Special Issue cover the following topics: (i) the analysis of plants based on photovoltaic (PV) panels and battery energy storages, investigating the use of electric vehicles [3], the coupling of these systems with a single hydropower plant for renewable energy communities [4], the assessment of the impacts of these plants on the effectiveness of electric distribution grids [5], their economic evaluation in residential applications for islands not electrically connected to the mainland [6], and the development of novel control strategies to address voltage disturbance in transmission systems connected with PV systems [7]; (ii) the economic analysis of a novel floating offshore wind structure, built with concrete [8]; (iii) the power to synthetic natural gas (PtSNG) plants to store intermittent renewable sources [9]; (iv) a low-cost secured distributed Internet of Things (IoT) system for monitoring and controlling appliances/devices connected in a polygeneration microgrid supplied by renewable technologies [10] as well as the optimization of both independent energy systems, ensured by the integration of the thermal/electric energy systems and renewable energy systems [11], and of building energy consumption by means load forecasting methodologies [12].