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The present paper proves that the vast water supply infrastructure of Athens and the region of Attica could produce useful hydropower. The first aim of this paper is to present the unconventional small hydro philosophy of recovering the hydraulic energy wasted in the existing break pressure devices and energy dissipating structures of the Water Supply Network of Athens, the capital of Greece and of the whole Attica region. The paper discusses themes concerning the replacement, in this large drinking water infrastructure, of all the existing break pressure devices, by a series of small hydro plants and also the efficient ways by which such small unconventional hydro schemes could be realized. The second aim of the paper is to highlight some important CFD simulation features which however needs further investigations and to present preliminary some Flow-3D results concerning the hydrodynamic performances of this series of small hydro plants harnessing the important wasted hydraulic energy of the Attica Water Supply Network. [ABSTRACT FROM AUTHOR]

The use of renewable energy sources instead of conventional energy sources is at the core of policy actions to reduce dependency on fossil fuels worldwide. As a result, especially during the last decade, the cost of renewable energy has significantly decreased, enriching renewable energy cost-competitiveness. Due to the spatial nature of renewable energy sector-related decisions, the synergy of geographical information systems (GIS) and Multiple Criteria Decision Analysis (MCDA) models can enrich the quality of the related decisions given their ability to effectively support land management considerations. Moreover, their implementation significantly enriches the performance of the traditional capital projects evaluation methods (CPEM) by providing physical data to the sizing process in a quick and accurate manner. Thus, decision-making frameworks that combine GIS-based suitability analysis with traditional financial evaluation techniques can significantly enrich the planning phase to achieve efficient installations in terms of required area reduction, power generation maximization and local characteristics examination. With respect to the realization of wind energy exploitation projects, the paper at hand proposes a framework capable of expanding the use of the traditional GIS-based derived suitability index to establishing portfolios. Moreover, the proposed framework is enriched by robust analysis using Monte Carlo Simulation (MCS), which provides significant insights regarding the stability of the derived portfolios and the projects that they comprise. The proposed framework is illustrated through a case study in the Thrace region in northeastern Greece., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

This paper presents a short view of the first Archimedean Screw Turbines CFD modelling results, which were carried out within the recent research entitled "Rebirth of Archimedes in Greece: contribution to the study of hydraulic mechanics and hydrodynamic behavior of Archimedean cochlear waterwheels, for recovering the hydraulic potential of Greek natural and technical watercourses". This CFD analysis, based to the Flow-3D code, concerns typical Tubular Archimedean Screw Turbines (TASTs) and shows some promising performances for such small hydropower systems harnessing the important unexploited hydraulic potential of natural and technical watercourses of Greece, of the order of several TWh / year and of a total installed capacity in the range of thousands MWs. [ABSTRACT FROM AUTHOR]

The present paper describes the evaluation of the Greek Archimedean Small Hydro Resources, considering the basic data for the 14 water regions of the country, adopting a holistic assessment methodology of the total theoretical hydro potential of Greece, which could be exploited by using Archimedean Screw Turbines (ASTs). The total evaluation of the theoretical Archimedean hydropower potential of Greece, which may be produced with ASTs, is of the order of several TWh / year, with a theoretical installed capacity of screw turbines in the range of thousands MW, with important values of special capacity and special capacity density, demonstrating the major existing unexploited hydropower potential for a future true sustainable development with small hydro plants in Greece based on environmentally friendly screw turbines. [ABSTRACT FROM AUTHOR]

The European Union is committed to a 55% reduction in greenhouse gas emissions by 2030, as outlined in the Green Deal and Climate Law initiatives. In response to geopolitical events, the RePowerEU initiative aims to enhance energy self-sufficiency, reduce reliance on Russian natural gas, and promote hydrogen utilization. Hydrogen valleys, localized ecosystems integrating various hydrogen supply chain elements, play a key role in this transition, particularly benefiting isolated regions like islands. This manuscript focuses on optimizing a Centralized Green Hydrogen Production Facility (CGHPF) on the island of Crete. A mixed-integer linear programming framework is proposed to optimize the CGHPF, considering factors such as land area, wind and solar potential, costs, and efficiency. Additionally, an in-depth sensitivity analysis is conducted to explore the impact of key factors on the economic feasibility of hydrogen investments. The findings suggest that hydrogen can be sold in Crete at prices as low as 3.5 EUR/kg. Specifically, it was found in the base scenario that, selling hydrogen at 3.5 EUR/kg, the net profit of the investment could be as high as EUR 6.19 million, while the capacity of the solar and wind installation supplying the grid hydrogen facility would be 23.51 MW and 52.97 MW, respectively. It is noted that the high profitability is justified by the extraordinary renewable potential of Crete. Finally, based on our study, a policy recommendation to allow a maximum of 20% direct penetration of renewable sources of green hydrogen facilities into the grid is suggested to encourage and accelerate green hydrogen expansion. [ABSTRACT FROM AUTHOR]

The main aim of this paper is to prove, according to our inventory that, beyond the horizon of the era of transition and economic crisis of nowadays, Greece is a real "Archimedean Screw Hydropower Development Terra Incognita", a country generously blessed with water, having an important hydropower potential. This inventory shows that the unexploited small hydropower capacity of Greece, including Archimedean possibilities, is approximately 3.500MW. The significant untapped small hydrodynamic potential demonstrates the important role of Pindos Mountain Range, controlling the annual rainfall difference between the North-Western and the Eastern Greece. The climatic and topographic conditions in Greece favor the development of many small Archimedean screw hydropower stations, harnessing the potential of a large number of small and big watercourses crossing mainland of the country. Pleiades of very promising Archimedean small hydro screw plants, having inclined and horizontal axis hydrodynamic rotors, could be installed following two hydro development axis (spears). [ABSTRACT FROM AUTHOR]

The present study is in line with the United Nations Sustainable Development Goals (UN-SDGs) that address pertinent global issues. This study focuses on the need for access to clean and affordable energy consumption, responsible energy consumption, sustainable economic growth, and climate change mitigation. To this end, this paper evaluates the relevance of the renewable energy sector on the environmental Kuznets curve (EKC) framework in Portugal, Italy, Greece, and Spain for the period 1995–2015. As an econometric strategy, we adopt the use of panel data over the highlighted countries. In the first step, we apply the unit root test recommended by Levin, Lin, and Chu in conjunction with ADF-Fisher, and Phillips-Perron for robustness and consistency. We found that the variables used in this study are integrated I (1) in the first difference. In the second step, we apply the Pedroni cointegration test, and Kao Residual cointegration test, and we observe that the variables are cointegrated in the long run. The generalized least squares (GLS), the panel fully modified least squares (FMOLS), ordinary least squares robust (OLS), and panel quantile regression are considered in this research. The econometric results validate the assumption of the environmental Kuznets curve, i.e., and there is a positive correlation between income per capita and a negative effect of squared income per capita on carbon dioxide emissions. In contrast, we observe that renewable energy reduces CO2 emissions. Finally, we also find a direct connection between the urban population and the environmental degradation in the examined blocs. These results show that in Portugal, Italy, Greece, and Spain, more is required to achieve environmental sustainability in the respective countries growth trajectory. Further policy prescriptions are appended in the concluding section of this study. [ABSTRACT FROM AUTHOR]

This article presents an integrated approach for solving the optimization of economic dispatch and commitment EDC problems of hybrid thermosolar concentrating power generating systems using matrix mathematics. The model uses matrices, and is solved by matlab programming. The study case of a hybrid thermosolar system in the north-west of Greece shows the impact of concentrating solar power (CSP) generation on the optimal cost of energy produced: the CSP system increases the operational costs as compared to the fossil fuel thermal systems. To acquire the benefits of cleaner electric energy with diminished emissions versus the minimal cost of electrical energy generation belongs to multicriteria managerial decisions. This approach can be applied to hybrid energy systems with large numbers of thermal and CSP generators. It offers an accurate instrument to energy engineers and researchers, for critical managerial decisions regarding electrical energy economics. [ABSTRACT FROM AUTHOR]

Research activity in the field of combined cooling heating power (or trigeneration) systems with high renewable energy source (RES) contributions has increased rapidly over the last few years, in line with the European Union legislation about energy communities. However, technical challenges arise regarding the synergetic, sustainable and optimal integration of RES in local energy systems. In the present study, the operation of a trigeneration system located in the student residences of Democritus University of Thrace in Greece is examined. The system involves a combination of highly promising renewable and storage technologies, including solar thermal energy and biomass for heat generation, hot water tanks for thermal energy storage, absorption refrigeration for cooling, along with Organic Rankine Cycle and photovoltaic systems for electricity generation. System modeling and simulation have been implemented in Dymola environment with the use of Modelica equation-based modeling language. The accuracy of the model response has been validated against available measurements. Specific design and control measures have been proposed, simulated in a transient fashion and evaluated in terms of (i) RES generation, (ii) solar fraction and (iii) temporal flexibility. The measures examined, including the placement of a Li-ion battery, resulted in an increase of 24.6% in the heating demand solar contribution and of 7.9% in the renewable energy generated for the electricity demand, over the examined periods. [ABSTRACT FROM AUTHOR]

This paper describes the installation, technical characteristics, operation and economic evaluation of a grid-connected building-integrated photovoltaic system (BIPV) installed in Northern Greece, and in particular in the city of Kastoria. The technical and economical factors are examined using a computerized renewable energy technologies (RETs) assessment tool. A number of different economic and financial feasibility indices are calculated for different financing scenarios in order to assess the gross return of the investment. Useful conclusions were drawn regarding the feasibility of BIPV systems and their potential for increased energy market penetration. [Copyright &y& Elsevier]

Solar irradiation is a major contributor to renewable energy sources and its utilization is vital for designing a sustainable and green energy network. Greece is a country with high solar potential and thus the exploitation of solar irradiation in this country is an urgent need in order to reduce fossil fuel utilization. Moreover, the increase in solar energy exploitation will lead to the mitigation of environmental policy goals for cleaner energy production processes. To date, Greece exploits solar irradiation mainly with flat plate collectors for low-temperature heating applications and with photovoltaics, while there are no installations including concentrating solar systems although they are attractive technologies. The objective of the present review paper is to demonstrate and to discuss the present steps in the domain of solar concentrating systems in Greece, as well as to suggest future steps aiming to increase the solar energy contribution in this country. More specifically, this work includes studies about parabolic trough collectors, linear Fresnel reflectors, compound parabolic concentrators, solar dishes, solar tower and concentrating thermal photovoltaics. The existing situation regarding solar energy utilization in Greece is collaborated and predictions about future perspectives are provided. It is concluded that although much research interest has been devoted to installations in Greece, no real solar concentration systems are currently in operation. Moreover, the existing studies indicate that solar concentrating systems lead to sustainable and viable investments with acceptable payback period time in the range of 5–7 years. As a result, it is suggested that this is the time to proceed in the next step of the development of real solar concentrating installation in Greece. • All the solar concentrating systems for the Greek climate are included in this review. • Applications for power, refrigeration, heating and polygeneration are presented. • Up today, many theoretical studies have been conducted for Greek solar systems. • In the future, there is a need for real applications and experimental studies. • The examined cases are found to be viable for the climate conditions of Greece. [ABSTRACT FROM AUTHOR]

This editorial is prepared for the Applied Energy Journal as a Virtual Special Issue (VSI) and it overviews the research work presented at the NAXOS 2018 6th International Conference on Sustainable Solid Waste Management, held from 13th to 16th June 2018 in Naxos Island, Greece. The research articles presented in VSI highlight the recent developments in waste valorisation for the recovery of energy, fuels and value-added products. They also cover the primary hurdles and potential solutions moving towards more sustainable society. This editorial not only presents the overall summary of the extended research papers from NAXOS 2018, but also provides an overview of the current trends and developments in the fields of waste management, waste valorization, and energy production systems. The articles published in this VSI cover a wide range of topics, including energy recovery from waste, waste to energy technologies, sustainable energy systems, anaerobic digestion, thermal arc plasma gasification, microalgal-based biorefinery, waste management, modelling of advanced gasification systems, waste valorization, and microbial fuel cell technology. 10 manuscripts, out of total 21 extended mansucripts invited, were accepted for publication in the Applied Energy Journal through peer review process conducted by the expert reviewers in the relevant fields with the aid of the guest editors. [ABSTRACT FROM AUTHOR]

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Climate and energy crises are increasing worldwide. Community-led humanitarian engineering interventions for localized sustainable development and disaster resilience could support populations at risk. This article presents findings from a study that investigated flood response and energy needs of two riparian communities in Greece and Nepal. The findings indicate that the co-development of a hybrid unit for hydropower generation and flood warning is most preferred. This prototype could find applications in different riparian areas as either a main or supplementary system. [ABSTRACT FROM AUTHOR]

Corruption reflects a set of illegal activities that jeopardize the smooth functioning of economies, society, and climate and environmental issues. This article tests the relationships between economic growth, corruption, renewable energies, international trade, and carbon dioxide emissions using panel data for European countries, namely Portugal, Spain, Italy, Ireland, and Greece, from 1995–2015. As an econometric strategy, this research uses the panel fully modified least squares (FMOLS), panel dynamic least squares (DOLS), and panel two-stage least squares estimator (TSLS). Considering the variables utilized in the research and the panel unit root test, we observed that the variables are integrated I (1) in the first difference. The variables of corruption, economic growth, renewable energies, international trade, and carbon dioxide emissions are cointegrated in the long run, using the Pedroni and Kao residual cointegration test arguments. The methodology of Dumitrescu–Hurlin to test the causality between carbon dioxide emissions, corruption, economic growth, and renewable energy shows that there is unidirectional causality between carbon dioxide emissions and corruption and economic growth and corruption. The results suggest that the corruption index and economic growth have a statistically significant positive impact on carbon dioxide emissions. However, renewable energies and international trade reduce climate change and improve the environmental quality. [ABSTRACT FROM AUTHOR]

Population growth, increasing droughts, and high irrigation needs are all factors that create freshwater shortage problems on islands. The pressing needs of remote islands usually call for water transport from the mainland or other neighboring islands, at a high cost. This study evaluates the design and economic viability of an alternative, sustainable water supply network on the Mediterranean island of Skyros in Greece. The proposed water supply system provides the island with potable water from desalination units, as well as water for agricultural use from a wastewater treatment plant. The total investment cost of the project is found to be €9.8 million, accounting for the cost of transportation of the water between the different settlements (installation, operations, and maintenance), as well as for the required energy of the involved methods. It is found that 44% of the expenses are related to the transport of potable and residual water, and 52% of the cost corresponds to the production of the required desalinated water. As part of a sustainable water and energy network, all energy needs of water generation are assumed to be covered by a renewable power plant. The total cost of water generation on the island with the proposed system is estimated at 2.49 €/m3, constituting a competitive and more sustainable solution, when compared to current practices. [ABSTRACT FROM AUTHOR]