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This paper puts forward a generic methodological framework to holistically assess WtE technologies based on the PROMETHEE approach. In addition to environmental and economic aspects, the method focuses on large-scale applicability and social preference, thus adopting economic, environmental, social, and technological criteria. Three data sources are selected, namely the scientific literature, a public survey, and an experts' opinion survey, which is a novel combination with the aim to cover public consensus, technological applicability, and to provide alternative data sources for the economic and environmental criteria, thus enriching the methodology with the input of location specific data. The demonstration of the applicability of the proposed methodology is realized at a national level for the case of Greece. Anaerobic Digestion is shown to be the most preferable choice, recognized for its cost-effectiveness and lower environmental burden to other WtE technologies (i.e., gasification, pyrolysis, incineration). When all criteria are evaluated with equal weights, anaerobic digestion greatly outperforms incineration (net flow 0.833 versus 0.1667), while incineration only becomes the most preferred choice if the social criterion is in high focus (i.e., over 63% weight). [ABSTRACT FROM AUTHOR]

According to the European Energy Efficiency Directive for Buildings, member states are required to develop long-term strategies to adopt more sustainable, secure, and decarbonized energy systems in buildings by 2050. In this line of approach, an optional common regime has been established to define and calculate the smart readiness of buildings and assess their ability to adapt their operation to the needs of the occupants and the network. Thus, the smart readiness indicator (SRI) emerged, which assesses technological readiness by examining the presence and evaluation of the functionality level of various smart services, aiming at energy savings, the ability of the building to respond to users' needs, and energy flexibility. This paper focuses on examining the SRI calculation methodology's application to an office building, which is currently being deeply renovated. Initially, there is an analysis of the SRI, its calculation methodology, and its goals. This is followed by the practical calculation part of the SRI for a typical office building located in Greece and belonging to the climate zone of southern Europe. The results indicate that the SRIs application is not a straightforward issue since parameters that need to be considered are not regulated to the same degree. On the other hand, SRI can provide a stimulus for exploiting the renovation potential of buildings, precisely by integrating the various aspects and linking those to the use of innovative technologies. [ABSTRACT FROM AUTHOR]

This paper performs a comprehensive analysis of the wind energy potential of onshore regions in Greece with emphasis on quantifying the volume risk and the spatial covariance structure. Optimization techniques are employed to derive efficient wind capacity allocation plans (also known as generation portfolios) incorporating different yield aspirations. The generation profile of minimum variance and other optimal portfolios along the efficient frontier are subject to rigorous evaluation using a fusion of descriptive and statistical methods. In particular, principal component analysis is employed to estimate factor models and investigate the spatiotemporal properties of wind power generation, providing valuable insights into the persistence of volume risk. The overarching goal of the study is to employ a set of statistical and mathematical programming tools guiding investors, aggregators and policy makers in their selection of wind energy generating assets. The findings of this research challenge the effectiveness of current policies and industry practices, offering a new perspective on wind energy harvesting with a focus on the management of volume risk. [ABSTRACT FROM AUTHOR]

According to the latest energy efficiency European directive (EED 2023/1791/EU), the expected energy renovation rate of at least 3% of the buildings' floor area each year towards nearly zero-energy buildings (nZEBs) is extended to include public buildings not only of the central government (as per the first EED 2012/27/EU) but also of regional and local authorities. This poses a great challenge, especially for Municipalities that often manage large building stocks with high energy demands. In response to this challenge, this paper presents the application of the so-called "typology approach" for conducting public buildings' energy renovation plans at the local level. A computational survey is initially introduced to decide the optimal set of building-stock clustering criteria among all possible combinations, involving the minimization of the RMSE index regarding the primary energy consumption of each building. For a representative building from each identified typology, the key performance indicators (KPIs) are computed for alternative energy-upgrading scenarios. Exploiting the IMPULSE Interreg-MED project tools, the KPIs from each representative building are at first extrapolated to all buildings of the examined stock and, finally, a gradual energy renovation plan is automatically produced based on user-defined decision parameters including the required annual renovation rate. The methodology is applied for the case of the Municipality of Hersonissos in Greece. For the specific 44-buildings' stock it was found that the optimal clustering set included four criteria, building use, construction year, heating, and a cooling system, leading to 15 building typologies. Finally, assuming a 7% renovation rate per year, a 12-year gradual renovation (nZEB transformation) plan is obtained foreseeing an 85% CO2 emissions' reduction. [ABSTRACT FROM AUTHOR]

According to the recent revision of the Greek National Energy and Climate Plan, the country sets out to accomplish an ambitious target concerning the integration of renewables in the local electricity mix during the ongoing decade, at the levels of 80% by 2030. This implies the need to more than double the existing wind and PV capacity at the national level, which in turn introduces numerous challenges. Amongst them, spatial planning for new RES installations seems to be the most demanding, with the adoption of novel technological solutions in the field of RES potentially holding a key role. New technologies, like offshore wind and floating solar, are gradually gaining maturity and may offer such an alternative, challenged at the same time however by the need to entail minimum disruption for local ecosystems. To that end, we currently assess the theoretical potential of floating PVs for lentic water systems of the Greek mainland. We do so by looking into 53 different lentic water systems across the Greek territory that meet the constraint of 1 km2 minimum surface area, and we proceed with the estimation of the relevant floating PV capacity per system under the application of a minimal intervention approach, assuming PV coverage of 1% over the total lentic water system area. In this context, our findings indicate a maximum, aggregate theoretical capacity that could exceed 2 GWp at the national level, with the respective annual energy yield reaching approximately 4 TWh or, equivalently, >6% of the country's anticipated annual electricity consumption in 2030. Finally, our results extend further, offering a regional level analysis and a set of policy directions and considerations on the development of floating solar in Greece, while also designating the energy merits of floating PVs against similar, land-based installations. [ABSTRACT FROM AUTHOR]

Nearly zero-emission buildings (nZEBs) are increasingly being constructed in Europe. There are also incentives to refurbish older buildings and transform them into nZEBs. However, permission is not always granted for their connection to the grid to infuse surplus photovoltaic electricity due to the grid being overloaded with a large number of renewables. In this study, the case of a refurbished school building in Central Greece is examined. After refurbishing it, a significant amount of photovoltaic electricity surplus is observed during the summer and neutral months, which cannot be exported to the grid. The absence of an adequate battery storage capacity resulted in the rejection of an application for exporting the school's surplus to the network and the photovoltaic installation staying idle. An alternative approach is proposed in this work, involving a shift in the export of the photovoltaic electricity surplus to the evening hours, in order for the school to be granted permission to export it to the network. To this end, an optimal battery storage size is sought by employing a building energy system simulation. The mode of operation of the battery designed for this application is set to discharge daily, in order to export the electricity surplus in the afternoon hours to the evening hours, when it is favorable for the network. Additionally, the optimal size of the thermal energy storage of the heating system is studied to further improve its energy efficiency. Our battery and storage tank size optimization study shows that a significant battery capacity is required, with 12 kWh/kWp photovoltaic panels being recommended for installation. The ever-decreasing cost of battery installations results in the net present value (NPV) of the additional investment for the battery installation becoming positive. The solution proposed forms an alternative path to further increase the penetration of renewables in saturated networks in Greece by optimizing battery storage capacity. [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]

During the past few years, hydrogen use has come to be considered as an alternative energy carrier in a future decarbonized world. Many developed nations are undergoing a shift towards low-carbon energy sources, driven by the excessive reliance on fossil fuels and the detrimental effects of climate change. This study aims to investigate the potential for hydrogen deployment in the Greek energy market during the next few decades. In this context, green hydrogen's potential application in the Greek market is being assessed, employing an integrated techno-economic model grounded in worldwide trends and localized expenses. The forthcoming years will see an analysis of both the challenges and opportunities surrounding the integration and implementation of hydrogen in new and existing processes within Greece. Many alternative ways to produce hydrogen in Greece are investigated, contemplating different production paths. We evaluate how fluctuations in hydrogen, oil, and carbon prices affect the economics of green hydrogen adoption in oil refining, as is detailed in the draft of the European Union delegated act published in May 2022. The Levelized Cost of Hydrogen (LCOH) for different scenarios is calculated for the time frame up until 2050. A sensitivity analysis reveals that investment costs, electricity prices, electrolyzer efficiency, and carbon taxes significantly influence the LCOH, ultimately impacting the economic competitiveness of hydrogen production. These findings underscore the importance of aligning public–private partnership agendas in hydrogen production to create optimal conditions for investment attraction and development. [ABSTRACT FROM AUTHOR]

Energy poverty (EP) has emerged as a significant and multifaceted social challenge, both in Europe and globally, in recent years. Given the constraints of limited public resources, it is imperative that policies addressing EP focus on the most socially vulnerable households. To this end, effective policies necessitate a thorough understanding of the key characteristics defining households affected by this phenomenon. This research aims to contribute to the identification of energy-poor households by examining both established and novel EP indicators, utilizing the Athens urban area as a case study. The study employs the official EP indicator utilized in Greece, alongside three newly developed indicators. These indicators constitute essential components in the formulation of multivariate binary logistic regression models. The models incorporate predictors derived from existing government databases, encompassing household and building characteristics. From a policy perspective, this research introduces novel approaches for addressing EP, as the models and two of the newly introduced indicators demonstrate promising results in identifying energy-poor households. Importantly, this identification can be achieved without the need for primary questionnaire surveys or the compilation of complex information. [ABSTRACT FROM AUTHOR]

Combined concentrated solar power with photovoltaics can provide electricity and heat at the same system while maximizing the power output with reduced losses. Spectral splitting is required in such systems to separate the infrared part of the solar spectrum towards the thermal system, while the visible and near-infrared radiation can be converted by the photovoltaic solar cell. The performance of concentrated solar power plants comprising reflective beam splitters for combined generation of electricity and heat is presented in this work. A 50 MW power plant is considered in this work as a case of study in Southern Crete, Greece. The solar power plant consists of parabolic trough collectors and utilizes beam splitters with varying reflectivity. The dynamic performance of the power plant is modeled, and the annual energy yield can be calculated. Up to 350 MWt of thermal power can be delivered to the photovoltaic system utilizing a 50% reflecting splitter. The penalty to the high-reflectivity system is limited to 16.9% and the annual energy yield is calculated as 53.32 GWh. During summer months, a higher energy yield by up to 84.8 MWh/month is produced at 80% reflectivity compared to 90% as a result of the number of parabolic troughs. The reported energy yields with reflectivity by dynamic modeling can highlight discrete points for improvement of the performance in concentrated solar power photovoltaics. [ABSTRACT FROM AUTHOR]

Understanding the determinants of energy poverty among the elderly is crucial for shaping energy policies with significant economic and social implications. This research provides valuable insights into the factors influencing energy poverty among the elderly in Greece. To achieve the study's objectives, household survey data from 3651 elderly individuals for the year 2022 were utilized. The empirical findings, based on statistical and econometric analysis, affirm the influence of socioeconomic factors on the ability of the elderly to meet their energy needs and address energy poverty challenges. The analysis suggests that both household size and work-related pensions positively impact their ability to address their heating requirements. Elderly individuals with a higher level of education are less likely to experience energy poverty. Additionally, it is found that as perceived health status declines, elderly individuals are more likely to encounter difficulties in covering utility payments. These results underscore the importance of tailoring strategies to promote the adoption of energy poverty measures that cater to diverse demographic and income groups. This information is vital for ensuring that the elderly can afford to maintain a comfortable living environment without sacrificing other essential needs. [ABSTRACT FROM AUTHOR]