Athanasios-Foivos Papathanasiou

Water scarcity and increasing energy demand are critical challenges that often characterize Mediterranean regions, especially islands such as Crete. A sustainable solution for a combined water and energy supply lies in the domain of hybrid renewable energy systems. This research study evaluates a large-scale wind-driven desalination system with pumped-hydro energy storage for the Regional Unit of Rethymno, Crete, focusing on climate-driven demand and air temperature variation. The proposed system integrates wind energy production, seawater desalination, pumped-hydro storage, and water supply both for domestic and for irrigation purposes. Four scenarios, each with increasing air temperature, are examined in order to assess their effect on water demand and system performance. The analysis evaluates electricity allocation, the production of desalinated water, domestic and irrigation coverage, as well as the economic performance of the system. The results indicate that domestic water demand is almost fully covered in all four scenarios, reaching nearly 99.9%, while irrigation water coverage decreases from 82% under present conditions to 67% under higher-temperature scenarios. Wind-generated electricity is mainly used for water-related processes, with a constant share supplied to the grid. The economic assessment indicates that the system can operate under break-even conditions using realistic water and electricity prices.

The accelerating impacts of climate change-including intensifying heatwaves, recurrent droughts, and growing water scarcity-are placing increasing pressure on urban infrastructure, including recreational facilities such as swimming pools. The review considers both public and private swimming pool facilities, with particular relevance to urban and tourism-oriented pools that face increasing resource pressures under climate stress. While pools provide important public-health benefits by offering spaces for exercise, social interaction, and thermal relief, they are also highly water-and energy-intensive. This paper develops a conceptual framework for sustainable swimming pool management under climate stress, integrating the water-energy nexus, climate-resilient infrastructure, and sustainability transitions. A structured review of peer-reviewed literature published primarily between 2017 and 2026 (Google Scholar, GreenFILE, and PubMed) synthesizes technical, environmental, and policy evidence on water use, energy demand, and mitigation options in pool operations. The review predominantly draws on European case studies and policy contexts, reflecting climatic, regulatory, and infrastructural conditions common in Southern and Central Europe. The analysis shows that energy use-dominated by pool heating-represents the largest source of environmental impact, making renewable heating technologies such as solar thermal systems, photovoltaic-thermal collectors, and ground-source heat pumps among the most effective climate-mitigation measures. On the water side, backwash water recovery and reuse systems emerge as the single most powerful intervention, capable of reducing freshwater demand by up to 96% in well-designed systems, while low-cost efficiency devices provide essential baseline savings. By reframing swimming pools as adaptive urban infrastructures rather than discretionary amenities, the paper demonstrates how recreational water facilities can function as testbeds for integrated water-energy solutions, contributing to climate adaptation, resource efficiency, and long-term public-health resilience.

Samothrace is a Greek island in the northern Aegean Sea. Though connected to the mainland grid and demonstrating strong wind potential, it is challenged by seasonal shortages in both electricity and potable water. This study assesses a Hybrid Renewable Energy System designed to meet local energy and water demands while maintaining economic viability. The system consists of 10 wind turbines (23.5 MW), a reverse osmosis desalination plant yielding 876,000 m³/year, and four alternative storage configurations: green hydrogen, pumped hydro, lithium-ion batteries, and a combined green hydrogen–pumped hydro option. Using identical climatic and demand data, system performance was simulated for the years 2011–2020. Wind generation reached 113,000 MWh annually, of which 81–84% was exported to the mainland. Potable water demand was met at a rate of 99% in all scenarios, with monthly production ranging from 17,500 m³ in February to almost 50,000 m³ in August, thus requiring 1.80% of wind output. Investment costs ranged from 34.4 M € to 39.8 M €; net present values remained around 75 M € for all scenarios. Results demonstrate that complete autonomy can be achieved; however, economic sustainability is maximized by leveraging the interconnection and sizing storage below full-autonomy levels.

This chapter is concentrated on the evaluation of a hybrid renewable energy system for meeting electricity and water needs in Mykonos, an island with strong seasonal demand driven by summer tourism. The system integrates 22 wind turbines of 2.3 MW each, four desalination units with a total capacity of 1,400 m³/h and pumped-hydro storage reservoirs of 3,900,000 m³. Two operational scenarios were examined, prioritizing electricity or water. Annual electricity and water demand were estimated at 264,062 MWh and 4,218,250 m³, respectively. Results show that in the electricity-priority scenario, energy coverage reached 79.16%, while water coverage was 62.95%; and in the water-priority scenario, water coverage achieved 99.99% with energy coverage at 72.58%. Hydroelectric production ranged from 194 MWh/year to 5,495 MWh/year, depending on the storage utilization. Overall, the findings highlight that prioritizing water demand, while maintaining sufficient electricity coverage, provides the most resilient strategy, demonstrating that integrated water–energy management can reduce fossil fuel dependence and strengthen sustainability on islands with high seasonal variability.

This research study examines a renewable energy system that has been designed to meet the water needs of Mykonos, a tourism-dependent island in Greece with high seasonal demand. The proposed system consists of 22 wind turbines of 2.3 MW each, 4 desalination units with a total capacity of 1400 m³/h and multiple pumped-hydro storage reservoirs with a total volume of 3,900,000 m³. Two operational scenarios were analyzed. Water production through desalination was prioritized in both scenarios; however, their difference lies in the way excess renewable energy has been allocated: that is either to storage or to electricity generation. The results indicate that water demand in Mykonos is almost fully met in both scenarios, reaching a coverage of 99.9%. However, there is a significant difference between the two scenarios regarding energy coverage, which corresponds to coverage rates of 73% and 79%, respectively. From an economic perspective, the marginal selling price of electricity is EUR/MWh 100 and the cost of desalinated water ranges from EUR/m³ 0.48 to 0.91 depending on the operating scenario. Overall, the results demonstrate nearly complete water autonomy in both scenarios, whereas the second scenario is proven optimal in terms of energy coverage. This approach proves that integrated water and energy management can lower fossil fuel use and improve sustainability on islands with strong seasonal variations.

The aim of this study is to evaluate the technical performance and resilience of a Hybrid Renewable Energy System (HRES), designed to achieve water and energy autonomy on a Skyros Island, Greece. The system integrates renewable energy sources with multiple storage technologies. A high-resolution, 30-min simulation was developed, incorporating 10 years of historical weather data to model the operation of an HRES, which consists of wind turbines, photovoltaics, pumped hydro storage, and green hydrogen production. Reverse osmosis was used for desalination, and extended low-wind conditions were simulated to assess system resilience. Results indicate that the proposed system is, in fact, capable of meeting 89% of the annual energy demand and 99.99% of freshwater requirements by means of desalination. Wind power accounted for 53% of the total energy production, photovoltaics 2%, while pumped hydro and hydrogen storage contributed 17% and 6%, respectively. During artificially imposed windless periods, short-term deficits were addressed by the use of pumped hydro, while hydrogen ensured supply continuity in the final days, thereby demonstrating their complementary function. In this resilience stress-test, the system remained operational for 10 days during an artificial windless period, demonstrating the critical role of hybrid storage. The findings indicate that a combination of renewable energy with diversified storage and water management strategies can provide a reliable and self-sufficient water–energy nexus for remote islands. Finally, the novelty of this research work lies in the statistical analysis of calm-wind events and the development of the corresponding power-law relationship, conducted under the framework of the 30-min simulation.

This study explores the challenge of achieving water and energy self-sufficiency in isolated regions through the design a hybrid renewable energy system (HRES) for Skyros, a Greek island not connected to the mainland grid. The proposed system integrates wind turbines, photovoltaics, pumped hydro, and hydrogen storage to ensure a stable supply, particularly during peak summer demand. Using advanced R simulations, three scenarios were analyzed on a 30 min basis. A combined storage system meets 99.99% of water demand and 83% of electricity needs. A pumped hydro-only system covers 99.99% of water demand and 74% of electricity needs. A hydrogen-only system supplies 99.99% of water demand but just 67% of electricity needs. The findings indicate annual CO₂ emission reductions exceeding 9600 tons. Economic analysis confirms the system’s feasibility, with a projected 10-year payback period. The cost of desalinated water is estimated at EUR 1/m³, while energy costs range from EUR 0.083/kWh for pumped hydro to EUR 0.093/kWh for hydrogen storage and EUR 0.101/kWh for the combined system. Overall, the results highlight the potential of hydrogen storage to enhance system flexibility and complement pumped hydro, offering sustainable water and energy solutions for isolated regions while addressing both environmental and economic challenges.

The study aims to address the challenges of water scarcity and energy instability faced by small Mediterranean islands, exacerbated by tourism and population fluctuations. A Hybrid Renewable Energy System (HRES) is proposed to provide sustainable solutions by integrating wind turbines, pumped hydro storage, hydrogen storage, and desalination. The methodology involves simulating the system’s operation in two islands using historical data, wind energy calculations, and energy storage dimensioning. Three scenarios are evaluated: pumped hydro storage, hydrogen storage, and a combination of both, with a focus on covering water and energy demand, while minimizing costs. Results indicate that the combined storage scenario achieves 87% electrical demand satisfaction, surpassing single storage scenarios. Desalination ensures 99.99% water demand coverage across all scenarios, with marginal costs for potable water and energy calculated at 3 €/m³ and 0.016–0.131 €/kWh, respectively. The pumped hydro storage method proves more efficient, while hydrogen storage adds flexibility to the system. The findings highlight the adaptability of the proposed HRES for small islands globally, offering a replicable model for addressing the water-energy nexus. The study provides practical insights into integrating renewable energy, innovative storage solutions, and desalination for sustainable development in isolated regions.

The majority of the Greek islands have autonomous energy stations, which use fossil fuels to produce electricity in order to meet electricity demand. Also, the water in the network is not fit for consumption. In this paper, the potential development of a hybrid renewable energy system is examined to address the issue of generating drinking water (desalination) and electricity while releasing zero pollutants into the atmosphere. Wind turbines supply wind energy, while an additional amount of energy is stored using pumped-storage hydropower and green hydrogen tanks. These two storage options are investigated for the purpose of storing and distributing clean wind energy in a controlled manner. Three scenarios are investigated. The first scenario only relies on the pumped-storage hydroelectricity technology (88% of the total annual power demand is covered), the second scenario investigates hydrogen storage technology (83% of the total annual electricity demand is covered), and the third scenario uses a hybrid storage solution consisting of pumped-storage hydropower and green hydrogen tanks (95% coverage).