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Over the past decades, the penetration of renewable energy sources is growing at a significant pace on a global scale. In parallel, the utilization of renewables could possibly act as the basis for the transition to a Circular Economy, which aims to reduce the use of finite resources. Compared to other European countries, Greece has achieved a significant share of renewables in its' energy mix and in parallel promotes various policies aiming to accomplish zero-carbon emissions by 2050. An important element of this procedure is the broader acceptance of renewables by the public. This paper investigates this concept by capturing citizens' view on renewable energy sources along with the overall concept of Circular Economy in Greece. By implementing a questionnaire analysis, empirical findings capture the intention of citizens to further develop and invest on renewable energy. Besides, our analysis identifies that as education level increases, the willingness to pay more for renewables and their acceptance from the public increases, as well. Finally, empirical findings indicate that Greek citizens are aware of the concept and the benefits arising from Circular Economy, yet additional efforts need to be addressed for the growth of this concept in Greece. • The study captures citizens' view on RES and Circular Economy in Greece. • Participants are aware and sensitive on environmental and climate change issues. • Participants accepted the existence of RES and are willing to pay additional cost. • As the level of education increased, willingness to pay for RES also increased. • Additional efforts need to be addressed for the growth of Circular Economy in Greece. [ABSTRACT FROM AUTHOR]

The European Union targets for 27% renewable energy share by 2030. At the same time, all new buildings should be nearly zero energy buildings from 2020 onwards. A major obstacle to these objectives is a combination of current economic stagnation and limited investors' confidence, which leads to low investment proportion. Despite many renewable energy technologies are already at a competitive level, the implementation rate in buildings is still low. In this paper, we focus on advances in efficient mechanisms to overcome non-technical barriers to the increase of renewable energy applications in buildings, such as Energy Performance Contracting (EPC). Tertiary sector holds a huge untapped potential for such applications, especially in Southern Europe. The Trust-EPC-South European initiative, implemented in six southern EU countries with a mix of beginner and intermediate energy service markets, aims at encouraging the financing of sustainable energy solutions in the tertiary sector, by creating a framework for standardization, assessment and benchmarking, thus improving trust and confidence in the financing parties. This paper presents three case studies in Greece, a Mediterranean family resort hotel, a resort and spa hotel and an office building. The installation of renewable energy measures, including photovoltaic systems, solar thermal systems and heat pumps, was examined and their EPC potential was rated, by using the described standardization and benchmarking methodology. Their economic savings range from 3 to 23% on yearly energy costs, at a discounted payback of 3–6 years, depending on the measure. A sensitivity analysis shows the impact of the variation of technical and economic parameters on the EPC projects feasibility. The standardization practice applied is expected to support the project actors in securing appropriate financing and eventually proceed with the renewable energy installations through the EPC. [ABSTRACT FROM AUTHOR]

The present paper focuses on the determination of optimum layouts for linear arrays of heaving Wave Energy Converters (WECs) in front of a vertical wall. Optimum layouts maximize the annual averaged absorbed energy at a given marine site and satisfy spatial constraints. For achieving this goal, we developed an efficient optimization numerical framework, where a genetic algorithm solver is appropriately coupled with a frequency-domain hydrodynamic model, while, furthermore, a numerical wave model is utilized to determine the local wave climate conditions at the site of interest. The context is applied for an array of five semi-immersed, oblate spheroidal heaving WECs deployed at five near-shore sites of mild wave environments in the Aegean Sea, Greece. For each site, different optimization cases are solved, facilitating the investigation of different aspects of the examined problem. The largest annual energy absorption ability is observed for optimum layouts, characterized by the placement of the array close to the wall and the formation of clusters of closely-positioned WECs near the wall edges. Compared to arrays employed at sites in south-eastern Aegean, optimally-arranged arrays at central Aegean locations showed reduced energy absorption ability due to milder local wave conditions and/or the existence of quite limited water depths. • Optimum layouts for heaving WECs linear arrays in front of a wall are determined. • Evaluation includes maximizing annual energy and satisfying spatial constraints. • Optimum layouts are realized by placing the WECs close to the wall. • Optimum layouts with WECs clusters near the wall edges show the largest energy absorption. • Maximized energy depends strongly upon site's local wave and depth conditions. [ABSTRACT FROM AUTHOR]

The exploitation of RES and their combination with desalination may be the solution to water scarcity and volatility of the electricity grids in remote offshore areas around the world. This research work investigates an HRES of a 12 MW wind park, a 1.8 MW photovoltaic park and a 1000 m3/d desalination plant in Karpathos, Greece. Concerning the wind and solar power, 30% and 20% respectively is integrated to the grid and the remaining is obtainable for desalination and water pumping, which is used as energy storage. The surplus energy returns to the grid, reducing the deficit. The project's lifespan is 40 years, rendering the stochastic time series necessary and the paper culminates in the economic sustainability investigation of this HRES. Several results can be obtained, as follows: i) the HRES′ reliability is high, since the system is able to cover the entire drinking water needs of the island, 89.75% of irrigation and 50.63% of energy needs. ii) The wind and solar potential of Karpathos has a decisive role, possessing the 3.02% of the total produced energy. iii) The IRR of various selling prices of desalinated water and energy ranges from 10% to 17%, rendering the investment viable and even profitable. • The HRES meets the island's entire drinking water needs, 90% irrigation and 51% of its energy needs. • The PSH produces 36% of the energy, increasing the HRES′ efficiency by exploiting the energy excess. • The ARMA (1,1) stochastic model is implied to include the uncertainty of rainfall and temperature. • The Negra et al. method is implied to simulate the variability of wind speed, for the project's lifespan. • The cost-benefit analysis shows that the HRES is viable economically, with IRR ranging from 10 to 17%. [ABSTRACT FROM AUTHOR]

PHPS is a mature energy storage technology, leading to more efficient energy management and further integration of Renewable Energy Sources (RES). This paper investigates the implementation of such a system at Kastraki, Greece, combined with a second upstream reservoir with a total capacity of 10 hm3 and evaluates its efficiency. The position and the geometric characteristics of the second reservoir are determined with ArcGIS. When excess of energy exists, water is pumped from Kastraki reservoir and stored in the upper one. Otherwise, the stored water is used for energy production. The simulation is performed for 40 years with a monthly time step. Furthermore, another simulation for a typical day in July is conducted, when water and energy needs are increased. The system is evaluated in terms of covering the water supply and energy needs, as well as in terms of efficient energy management. Several results can be obtained, as follows: i) the reliability of the PHPS system for the coverage of monthly water supply and irrigation needs is 82.84 %. ii) The coverage of water supply needs for a typical day in July is 99.99 %. iii) The average monthly coverage of energy needs amounts to 83.86 %. [ABSTRACT FROM AUTHOR]

PHPS is a mature energy storage technology, leading to more efficient energy management and further integration of Renewable Energy Sources (RES). This paper investigates the implementation of such a system at Kastraki, Greece, combined with a second upstream reservoir with a total capacity of 10 hm3 and evaluates its efficiency. The position and the geometric characteristics of the second reservoir are determined with ArcGIS. When excess of energy exists, water is pumped from Kastraki reservoir and stored in the upper one. Otherwise, the stored water is used for energy production. The simulation is performed for 40 years with a monthly time step. Furthermore, another simulation for a typical day in July is conducted, when water and energy needs are increased. The system is evaluated in terms of covering the water supply and energy needs, as well as in terms of efficient energy management. Several results can be obtained, as follows: i) the reliability of the PHPS system for the coverage of monthly water supply and irrigation needs is 82.84 %. ii) The coverage of water supply needs for a typical day in July is 99.99 %. iii) The average monthly coverage of energy needs amounts to 83.86 %. [ABSTRACT FROM AUTHOR]

Wind energy presents a high growth potential in the EU as an emission reduction strategy and to achieve the climate neutrality goal by 2050. Wind farms suitability analysis is one of the primary goals in the spatial planning of wind energy developments. This research paper introduces a hybrid spatial multicriteria GIS-based framework that combines Analytic Hierarchy Process (AHP), PROMETHEE II and Machine Learning algorithms to determine and predict the most efficient onshore wind farm locations by generating suitability index mappings. The methodology allows to overcome PROMETHEE II limitations in raster driven suitability analysis, utilizing machine learning regression methods as the k Nearest Neighbor and Support Vector Machines to predict a graduating mapping of suitability index for wind farm locations in northeastern Greece. The best configured models presented a RMSE of 0.0344 and 0.0154 respectively, indicating a quite high predictive performance. Suitability results indicate that 56.10 % of the feasible locations in the Thrace area present a positive outranking character for the kNN model and 56.79 % for the SVR model. The proposed framework, enriched by PROMETHEE II capabilities, assists energy and spatial planners in identifying suitable sites for wind farm siting and enables rational decision making that enhances efficient wind energy investments. [ABSTRACT FROM AUTHOR]

The present paper proposes and implements an integrated evaluation framework for selecting the most appropriate sites for wind-farm development projects. This framework focuses on the combined use of geographic information systems (GIS) and spatial multi-criteria decision analysis, aiming to provide a decision tool for wind-farm planning at the regional level. This procedure has been developed by means of various technological, economic, social, and environmental criteria (known as siting criteria), which were used either as constraints and/or as evaluation factors in order to identify first the potential/appropriate sites for wind farm installation and then to evaluate these sites using a composite Suitability Index (SI). The proposed decision tool is thus able to get the optimal locations for future projects, as well as the suitability score of the already licensed projects. The results of this paper support the potential role of planners in designating areas for wind farm development. [ABSTRACT FROM AUTHOR]

The current paper reflects on the challenges faced by European islands with regards to electricity supply, focusing on an island area of major interest, i.e. the Aegean Sea region. In this context, the main problems related to the use of imported oil and the associated high electricity production costs are discussed, together with the prospects of increased exploitation of Renewable Energy Sources (RES). For the latter accomplishment, the main elements of an integrated energy solution are presented, comprising mature RES technologies and more novel aspects, corresponding to energy storage, Demand Side Management and intelligent Energy Management on the basis of advanced forecasting techniques. Moreover, insight and preliminary operational evidence are provided with regards to the application of such an integrated solution on the island of Tilos, in Greece, where the development and test-operation of a pilot smart microgrid and Hybrid Power Station were recently completed, in the context of the TILOS Horizon 2020 Program. • A short review of the electricity production status in Aegean islands is undertaken. • Challenges and prospects of RES in the Aegean islands' region are discussed. • We present novel elements that can support increased RES shares for Aegean islands. • We focus on the development and pilot operation of Tilos island smart microgrid. [ABSTRACT FROM AUTHOR]

Solar heating and cooling (SHC) systems can be relevant in the achievement of energy and climate European goals. The benefits of these technologies should be evaluated taking into account their life-cycle energy and environmental impacts, calculated by applying the Life Cycle Assessment (LCA). The development of a complete LCA can be difficult and time-consuming particularly for non-experts in LCA, discouraging them in developing the life-cycle assessments. To overcome this issue, the paper presents "ELISA - Environmental Lifecycle Impacts of Solar Air-conditioning systems", a user-friendly simplified tool for estimating the life-cycle energy and environmental benefits/impacts of solar technologies for heating and cooling in different geographic contexts and comparing them to conventional systems. The tool was applied to analyse three systems (thermal SHC, conventional and PV assisted system) in Greece and to identify the one characterized by the best life-cycle performances. The results revealed that the impacts of PV assisted system are about 60% lower than those of the others, highlighting the advantage of using renewable electricity for building air-conditioning in locations with high solar radiation availability. ELISA can be used by researchers, designers and decision-makers to introduce the life-cycle thinking in the early design phase of heating and cooling systems. • ELISA is a tool for developing a simplified LCA of solar heating and cooling technologies. • ELISA calculates the impacts of heating and cooling systems in a specific geographic context. • Three systems installed in Athens (Greece) are examined by combining ELISA with a simulation tool. • The PV assisted system is the best one in terms of life-cycle energy and environmental performance. [ABSTRACT FROM AUTHOR]

Abstract: This paper aims at estimating the potential of PV systems applied on buildings (BAPVs) within a typical Greek building block. For the purpose of the study a block located in the municipality of Thessaloniki in northern Greece was chosen. The block consists of multistory residential buildings of various heights and represents the typical Greek building block. A detailed shading study of photovoltaic (PV) systems in the residential building block was carried out and is presented in the paper. The shading study was carried out using the Google Sketchup and PVsyst software tools, leading to significant conclusions firstly about shading losses of PVs in multistory building topologies and secondly about the actual available areas for PVs in a typical urban building block. Finally, an economic assessment of the PV systems examined was carried out, focusing on their feasibility and based on the feed-in tariff terms which have been enacted exclusively for residential PV installations since 2009. It was found that the majority of installations have a maximum six-year payback period. [Copyright &y& Elsevier]

The growth of renewable energy and especially photovoltaic energy in Greece is remarkable. There exist many grid-connected systems in Greek territory which have completed ten years operation. A challenging task for these systems is performance analysis, investigation of possible degradation in systems efficiency and formulation of a detailed solar potential record for each region. This paper focuses in the performance of a grid-connected PV system in central Greece which has completed six years' operation. The analysis methodology is based on three axes. The first is a calculation of the daily PR and yearly PR and their comparison for the 6 years of operation. The daily PR is further correlated with the averaged clearness index in order to assess the atmospheric effect on the PV performance. The second axis involves the application of a mathematic model, which describes PV power, to the available data. Computed values act as the reference values and deviation of the measured values thereof hint to probable changes in PV system performance. The third axis involves the computation of normalized efficiency to STC conditions. This includes (i) the computation of DC power from available AC data and inverters' efficiency, (ii) temperature normalization according to the temperature coefficients of manufacturer and (iii) comparison of efficiency at various weather conditions and computation of yearly average values, respectively, with Airmass. The analysis results hint to a small performance deterioration over the years, with degradation rates ranging from 1 to 4%. • The performance of a grid-connected Photovoltaic park after six years' operation is presented. • The processing of data is aided by the application of the most wide spread performance models. • An assessment methodology for PV parks efficiency calculation is formulated and applied. • The results hint to a performance deterioration, with degradation rates ranging from 1 to 4%. [ABSTRACT FROM AUTHOR]

Abstract The purpose of this paper is to present an integrated life cycle assessment of the electricity grid of Greece, considering the different power generation technologies currently operating in the country and the interconnected electricity transmission system. The energy and environmental assessment of both the generation and transmission systems is carried out employing SimaPro 7.1 Life Cycle Assessment software. The present work shows that the main, environmentally adverse, impacts (>60%) are associated with the electricity generation sector; in particular, with the system of mainland Greece, which is dominated by centralized fossil-fuelled power plants. Transmission of electricity was found to have 70%–90% lower life cycle impacts compared to generation. Transmission power losses are the most important contributor to GHG emissions, whereas transmission lines infrastructure and transformers are associated with much lower life cycle impacts. Findings concerning the primary energy demand exhibit analogous behaviour. Future electricity supply mixes with high shares of renewables could lead to substantially lower GHG emissions, whilst primary energy demand is expected to increase, due to the electricity intensive construction stage of renewables. Results concerning the contribution of electricity generation and transmission to environmental impacts related to human toxicity, ecosystem quality, resources depletion, etc., are also reported and discussed. Graphical abstract Image 1 Highlights • LCA is used to assess the environmental performance of Greek electricity system. • Power generation stage is the most important contributor to GHG emissions. • Electricity transmission has 70–90% lower life-cycle impacts than generation stage. • Significant sources of GHG emissions and PER are power transmission lines losses. • Future RES electricity generation will reduce GHG emissions but increase PER. [ABSTRACT FROM AUTHOR]

The standard efficiency of photovoltaics (PV) often deviates from the one achieved under real outdoor conditions. This paper presents relevant data collected using a small multi-crystalline photovoltaic array at an outdoor experimental facility located north of Athens. Measurements during summer and winter periods were used to quantify the PV performance and operating characteristics. Several correlations are provided in order to facilitate the estimation of the actual PV performance with readily available local parameters (e.g. ambient air temperature, wind speed). The PV efficiency was found to be about 18% lower than that under laboratory standard test conditions, under similar operating conditions. The mean annual PV efficiency was 8.7%. [ABSTRACT FROM AUTHOR]

This paper uses monthly data from Aug. 2004 to Feb. 2014 and employs the Autoregressive Distributed Lag bounds test approach to study the short and long-run relationship of renewable and non-renewable electricity with economic growth in Greece. Dummies reveal most of the major energy policy adaptations taking place in Greece to overcome the economic crisis and reach stipulated renewable energy targets. Results show that in the short-run, fossil sources play the baseload role in electricity production and there is a clear substitution effect between sources, while in the long-run, fossil sources contribute to the development of renewable energy sources as backup energy. [ABSTRACT FROM AUTHOR]

Need for food and energy challenge humanity. Producing biofuels from energy crops leads to the dilemma: “energy crops for biofuel or for food?” This paper aims to answer this dilemma through the SWOT analysis, for the first time for Greece. Results of the first alternative show strengths including creation of direct and indirect jobs (Biofuel production industry), diversity of energy supply, and positive contribution of the greenhouse effect. Weaknesses include environmental impact, and dependence on land availability (additional need of arable land other than that required to grow food). Energy and climate change priority on policy agenda, EU directives promoting the use of biofuels, and economic competitiveness with fossil fuels, could create the external environment to promote bioenergy production. Conversely, results of the second option show strengths including food security, and non-risk of deforestation in order to find new land. Weaknesses include failure to increase employment opportunities by not creation of indirect jobs, and non exploitation of marginal lands. Respective external environmental factors include solution to food crisis, use of second generation biofuels, and development of new and non-edible varieties. Dependence on fossil fuels and failure to comply with the world agenda regarding climate change, constitute threats for this option. [ABSTRACT FROM AUTHOR]

This paper deals with the technical feasibility and economic viability of a solar thermal power plant using parabolic trough collectors in Greece. The power plant is to be installed in the island of Rhodes and its power output will be 8.55 MW. Power plant simulation is carried out using TRNSYS software (STEC library) and economic issues of the project such as initial cost of investment, operation and maintenance (O&M) and energy costs will be analyzed. It was found that for the particular investment, considering a 75% of initial investment cost loan (with a 10-year period), the payback period will be approximately 13 years. [ABSTRACT FROM AUTHOR]

Abstract: This paper attempts an integrated environmental assessment of certain crops, their products and by-products, which are promoted in Greece, as potential raw materials for liquid biofuel and low carbon energy production. The analysis is based on the experimental results of a Greek state funded research project (Hi-Bred fuels), which investigated the integrated management of energy crops for both biofuel and energy production. Four crops, some new for Greek agriculture and other indigenous, namely rapeseed, soya, sunflower and cotton, were cultivated under “real farming” conditions, keeping detailed data of all important aspects affecting their environmental profile. The main industrial processes employed in Greece for extracting, processing and esterifying vegetable oil from the oleiferous seeds were also identified and studied in detail. The data collected during the various production steps were introduced in Global Emission Model for Integrated Systems (GEMIS) software in order to create production cycle models of both non-esterified (straight vegetable oil) and esterified (biodiesel) biofuel models. Dedicated experiments were performed on a diesel passenger car in order to investigate the applicability of the final products. Results indicate that sunflower has the optimal environmental characteristics with respect to biofuel production with potential GHG savings of 58–71% depending on the end product. Rapeseed followed with GHG savings potential of 48%–62%, soyabean oil (47%–60%) and cottonseed oil (35%–47%). For the different products, and production steps, the results of the analysis for energy, CO2 equivalent emissions and other pollutant emissions are presented. Results concerning energy crops adaptability in Greek climate conditions and their product yields were quite promising, with the exception of the watering demands, which in some cases were not sustainable (GHG savings below 35%). Vehicle application results indicate that on a low level concentration (up to 10%v/v) all biofuels may be employed without important effects on vehicle emissions. Finally it is concluded that the use of residual waste biomass is a key aspect for achieving sustainable and environmentally efficient biofuels. [Copyright &y& Elsevier]

Abstract: This paper deals with the feasibility of RES-based systems for electricity supply in four different Greek Islands. Three specific typical loads were selected to be covered, where the grid connection was considered as optional. An optimization procedure in terms of energy efficiency and economical feasibility has also been applied, using the HOMER software for the energy part and a hand-made calculation procedure for the financial aspects. It is found that an off-grid project is not economically feasible and the grid connection is necessary only for the sale of excess electricity (not as a backup source). Finally, the relationship between environmental potential and produced energy is found to be linear, with almost constant behaviour for solar systems. [Copyright &y& Elsevier]

Abstract: A detailed and integrated presentation of the green roof systems is provided in the present paper. Aiming to analyse a specific urban case study, we describe the basic architectural and scientific principles that characterize its performance and efficiency. Furthermore, a state of the art presentation of the system is provided, including the presentation of several case studies as well as a selection and description of plants that usually are extensively used in the green roof system all over the world. Energy and environmental investigation data of the green roof system performance in an office building located in the greater Athens area are provided. The energy efficiency was examined by calculating the energy savings through an accurate dynamic mathematical model. The thermal performance investigation showed a significant reduction of the building''s cooling load during the summer period arriving at approximately 40%. Moreover, the influence of the green roof system in the building''s heating load was fount insignificant, and this can be regarded as a great advantage of the system as any interference in the building shell for the reduction of cooling load leads usually to an increase of its heating load. [Copyright &y& Elsevier]

Abstract: The utilisation of renewable energy sources, and wind energy in particular, can be described in Greece as a story of high expectations, intense initial entrepreneurial interest, delays in the start-up phase of projects and, some times, disappointments during the implementation procedure. Still, the current situation gives reasons for some optimism. This paper provides a review of the present technological background in wind generators, as found in the Greek market, as well as a detailed analysis of the legislative framework. Moreover, it aims to analyse the development of the process of granting investment and production permissions and their implementation since 1999. Thus, it is possible to identify the main reasons for the problems that occurred since the liberalisation of the electricity market and to account for the interest in wind energy. Finally, comments and proposals are formulated concerning the hidden barriers, the pertinent problems and the promising perspectives of the use of wind energy in Greece. [Copyright &y& Elsevier]

The current interest in energy efficient design has led to a demand for methods of predicting daylight availability in buildings. However, basic daylight data, which are the basis of these prediction methods, are not available for most regions of Greece, as well as for many areas worldwide. For that purpose luminous efficacy can be used in order to generate daylight illuminance from solar radiation data, which are much more widely recorded.This paper concentrates on the analysis of global luminous efficacy in Greece under clear sky conditions. The study involves the evaluation of existing models with respect to daylight data recorded in Athens, Greece, as well as the development of new luminous efficacy models for global radiation.The study was based on climatic data provided by the National Observatory of Athens during the years 1996–2000 and tested according to CIE. recommendations. The proposed luminous efficacy models were derived by the analysis, correlation and linear regression of the accepted values of measured data. Statistical analysis techniques were used for the assessment of their performance, as well as for the evaluation of the accuracy in predicting global illumination provided by the proposed and the existing models.The new proposed models can offer engineers and researchers a more reliable and accurate approach for estimating the global illumination levels under clear skies. Nowadays, the knowledge of daylight levels is considered highly important in local architecture, the energy conservation and environmental policies in general, particularly in the case of Mediterranean regions, where clear sky conditions dominate. [Copyright &y& Elsevier]

The main object of this paper is the documentation and study of the main factors behind the spectacular diffusion of solar energy use for domestic hot water production in Greece. The time pattern of the diffusion of flat-plate solar collectors since its ‘out of the blue’ first appearance in 1974, shows that the diffusion rate grew exponentially at first, with the annual sales figure reaching 91,000 m2 by 1980. A rate slow down in the early 1980s was followed by a brief period of explosive growth, with the annual sales figure reaching its peak value of more than 185,000 m2 in mid-1980s. A rapid decline of the growth rate down to the present annual sales level followed. The installed solar collectors pattern has the characteristic form of an S-shape curve, representing the overall penetration of the flat-plate solar collector use for domestic hot water production in the Greek economy and society. This evolution has gone through an inflection point around 1987, i.e. at a time when about 1,000,000 m2 of collectors had been already installed. By the year 2000, about 2,070,000 m2 of collectors had been installed, with a tendency to level off by 2010, unless some of the present conditions determining this phenomenon change. [Copyright &y& Elsevier]