Georgios-Fivos Sargentis

Decarbonization has been set as the ultimate target of the European energy policy, and, under this frame, Greece has substantially reformed its electricity mix over the last two decades. Yet, the rapid transition of the country’s electricity production system towards a model that strongly relies on non-controllable renewables, without improving its energy storage means, has caused several adverse impacts that reasonably raise serious concerns about its sustainability. Further questions arise when accounting for the projections and underlying assumptions reported in the National Energy and Climate Plan. In this vein, key policy, societal, technical, sustainability and science issues are discussed, involving the challenges, perspectives and potential drawbacks of Greece’s long-term energy planning. To reveal the critical role of storage, a toy simulation-optimization model is applied at the national scale to evaluate several scenarios of wind and solar P/V development under the premise of a theoretically fully decarbonized mix. This allows the exploration of trade-offs between energy storage and power capacity needs against key performance metrics (frequency and quantity of deficits and percentage of rejected renewable energy). Preliminary feasibility issues are also highlighted by considering alternative configurations of pumped hydropower storage units and associating their approximative investment costs with scale and geometry.

Monastic communities established in isolated and environmentally demanding landscapes historically developed sophisticated hydraulic infrastructures to ensure long-term self-sufficiency and resilience. This study investigates the historical water management system of the Holy Monastery of Dochiariou on Mount Athos, Greece, a Byzantine monastic complex founded in the late 10th century. Combining in situ field observations with historical and architectural analysis, the study reconstructs an integrated gravity-driven hydraulic network consisting of subterranean qanat-type galleries, open channels, watermills, cascading reservoirs, concealed conduits, and inverted siphons. The analysis positions the system comparatively within Ancient Greek, Roman, Ancient Persian, and Byzantine hydraulic traditions using criteria related to water capture, conveyance, storage, energy use, and organizational logic. An approximate water balance assessment based on the identified storage infrastructure is also introduced to evaluate the functional capacity and self-sufficiency potential of the monastic complex. The results indicate that the system combined source diversification, distributed storage, passive operation, and adaptation to topographic constraints to sustain monastic activities over long periods. Rather than proposing direct technological replication, the study identifies transferable principles relevant to contemporary discussions on decentralized, resilient, and resource-efficient water infrastructure.

We propose a quantitative, spatially explicit framework for assessing local self-sufficiency and resilience within the Water–Energy–Food (WEF) Nexus. The methodology introduces normalized, per capita indicators that quantify the degree of dependence on local versus external resources, explicitly incorporating physical availability, renewability, energy requirements, infrastructure, and land-use constraints. In contrast to conventional composite indices, the proposed framework adopts a non-compensatory structure, whereby deficiencies in one sector cannot be offset by surpluses in another, reflecting the physical constraints of the nexus. Indicator values range from 0 (complete dependence on external resources) to 1 (full local self-sufficiency) and are formulated dynamically, enabling comparison across existing conditions and alternative infrastructural or policy scenarios. The framework is applied as a proof of concept to a small rural settlement in North Euboea, Greece. The results indicate substantial potential for food and renewable energy self-sufficiency under optimized infrastructure configurations, while also revealing critical vulnerabilities associated with groundwater-dependent water supply and seasonal energy imbalances. The analysis further demonstrates how spatial proximity, energy–water coupling, and land-use competition jointly constrain achievable self-sufficiency levels, highlighting trade-offs that are often overlooked in sectoral or purely volumetric assessments. By explicitly linking resource flows with spatial proximity and infrastructural choices, the proposed indicators provide a robust and transparent tool for resilience-oriented planning under conditions of climatic, environmental, and systemic uncertainty.

The prehistoric and historic Greek populations have a long and glorious history and could teach us significant lessons relevant to water resources and their management. Most Greek civilizations lived in harmony with the environment, with a profound understanding of environmental sustainability. The Minoan era, considered as Pax Minoica (or Minoan peace), was a time when palaces and other living places did not have defensive walls; in that time, human rights and power without a military aristocracy developed. During that time, hydro-structures with a high degree of security, which remained in operation for millennia, were developed, most of them established in predominantly arid areas for reasons of security, protection, and public health. The study presents important elements of the development and progress of these technological achievements provided by ancient civilizations throughout the prehistoric to modern period, in the context of revealing and highlighting potential lessons to understand and address current critical issues in the management of water resources. Furthermore, the methodology used and the technological structural advancement of water works, their infrastructure durability, and early water law principles are considered. Many modern systems are designed for operational lifespans of 50–100 years, whereas several ancient Greek hydraulic structures remained functional for centuries by relying on renewable natural resources—reflecting a fundamentally different design philosophy centered on longevity and robustness. Thus, terms such as “sustainability” and “water security/safety”, first taught by ancient civilizations, need to be reconsidered and adopted again nowadays to inspire policies, strategies, and actions against the increasing challenges.

Modern digital technologies and geoinformatics have experienced rapid growth, offering powerful tools to bridge the gap between scientific communities and society in landscape assessment and mapping. This research details the application of a crowdsourcing scheme that utilizes a dedicated mobile application to facilitate direct public participation in quantifying perceptions of urban landscapes and architecture. Initially developed as an educational tool, the methodology has been tested by university students across Italy, Greece, and France, providing a foundational phase for assessing landscape quality and urban typologies. Building upon these educational pilot studies, the work explores the evolution of this methodology into a broader, multicultural citizen science initiative designed to improve the quality and quantity of available landscape perception data.A significant technical advancement in this research involves the integration of automated image analysis to process the novel data generated by participants from any location. The photographic material was examined using stochastic image analysis based on climacograms, in which images are treated as two-dimensional grayscale intensity fields and analyzed across multiple spatial scales. The method enables the comparison of image patterns based on the visual complexity of the uploaded photographs. A primary challenge addressed was the algorithm's performance when processing real-world, non-curated smartphone images. The analysis began an assessment on how the methodology handles environmental noise, such as sky, trees, and unconventional capture angles, which are inherent to bottom-up crowdsourcing schemes.The early results indicate that the method can reveal group-level tendencies associated with differing architectural characteristics, particularly in relation to visual complexity, while not supporting reliable classification at the level of individual image. In detail, the findings indicate a trend towards two categorizations: firstly, between modernist-type movements, characterized by minimal elements, and secondly between eclectic or decorative movements, which exhibited higher measured complexity; however, this this behaviour was not observed universally on all analyzed movements The stochastic analysis also indicated theoretical overlaps between certain movements, such as Postmodernism and Eclecticism, based on shared decorative patterns. While the results highlight that environmental factors can influence the analysis of individual photographs, the method utilized presents potential for distinguishing movement trends with logical consistency even from unfiltered data.Scientifically, this yield of quantitative data sets the groundwork for improved research in the humanities and culture, showing a strong correlation with established landscape quality indices. Socially, the project provides a scalable model for participatory mapping that fosters critical thinking about urban quality, creating new conditions for communication between universities and the broader public. Overall, the presented work reports on the early-stage results of this methodological exploration and aims to evaluate the combined use of participatory mobile data collection and exploratory image-based analysis for landscape and architectural studies, while identifying key challenges related to data quality, interpretation, and future methodological refinement.

The Water-Energy-Food (WEF) Nexus represents a critical framework for sustainable resource management, particularly in water-scarce Mediterranean islands like Naxos, Greece. This research examines the interdependence of water, energy, and food systems on Naxos, a Cycladic island facing challenges from climate variability, tourism pressures, and agricultural demands. We assess the island's natural resources and evaluate current needs for residents and primary production sectors, highlighting inefficiencies in existing infrastructure such as desalination units and energy mixes reliant on fossil fuels. Using geospatial analysis via QGIS, the island was divided into 28 grid cells to quantify rainwater harvesting potential from rooftops, courtyards, and road networks. Annual precipitation data were integrated with land use patterns to estimate harvestable volumes, ranging from 5,800 m³/yr in coastal cells to over 200,000 m³/yr in mountainous areas. Prioritization of water needs focuses on domestic supply for permanent residents and irrigation for crops like potatoes, olives, and vineyards, while incorporating animal manure as a nutrient source to reduce fertilizer dependency and embedded energy costs. Traditional techniques, such as cisterns for rooftop collection and roadside swales/bioretention systems for runoff management, are proposed as low-energy, resilient solutions. Results indicate that optimized harvesting could cover a significant part of irrigation needs and alleviate desalination reliance, enhancing self-sufficiency.

The Water–Energy–Food (WEF) Nexus constitutes the foundational framework for human well-being, as access to these interconnected resources underpins societal prosperity and resilience. In an era of increasing resource pressures driven by population dynamics and geopolitical tensions, assessing the degree of local self-sufficiency within the WEF Nexus becomes essential for sustainable planning and vulnerability reduction. This study introduces a novel methodology for the quantitative and spatial evaluation of WEF self-sufficiency. We develop composite indicators that integrate key elements of the nexus—local availability and management of water resources, renewable energy potential, agricultural productivity, and land use patterns. Beginning from one capita, these indicators are normalized on a scale from 0 (complete dependence on external, distant resources) to 1 (full local self-sufficiency), providing a clear, comparable metric for dynamic assessment at different scales. As a proof-of-concept case study, the methodology is applied to a small rural village in North Euboea, Greece, a region characterized by post-wildfire recovery challenges, traditional agriculture (e.g., olive groves), limited infrastructure, and strong reliance on local hydrological and biomass resources. Spatial analysis, incorporating GIS-derived data on precipitation, soil fertility, solar/wind potential, crop yields, and energy consumption patterns, reveals the village's current self-sufficiency levels across the nexus components. Results highlight strengths in local food production and renewable energy opportunities, while identifying vulnerabilities in water storage and seasonal energy needs. The proposed indicators offer a practical tool for policymakers, enabling targeted interventions to enhance resilience and promote circular practices in order to safeguard prosperity in unrest periods. Future extensions aim to scale the indicators to urban systems and larger regions, exposing structural weaknesses in modern, highly interconnected settlements.

Although extensive information exists on the chronological evolution of the fortified monastic complexes on Mount Athos, data regarding the construction dates of their hydraulic infrastructure remain comparatively limited. Since water constitutes a fundamental prerequisite for sustained settlement and construction, the development of a monastery presupposes access to reliable and sufficient natural resources essential for its establishment and long-term survival. This study applies a quantitative reverse-engineering approach to estimate the water demands associated with the construction of Dochiariou Monastery's principal fortified elements, namely the katholikon, the tower , and the perimeter walls. By approximating the number of monks, draught animals , and construction workforce, as well as the volumes of building materials (brick, stone , and lime mortar), we quantify minimum water requirements for mortar production, brick making, human and animal consumption, and material transport along the steep kalderimi (stone-paved path) from the Αrsanas (dock). Order-of-magnitude calculations indicate that the annual water yield of local springs provides only a marginal surplus, insufficient to sustain intensive, multi-year construction phases in the absence of engineered storage or supplementary water sources. The central aqueduct—terminating directly into the tower—exhibits a high potential discharge capacity and a strategically integrated layout, suggesting that it may have predated the major building campaigns. This analysis indicates that the aqueduct and associated hydraulic works were likely among the earliest infrastructural interventions, enabling subsequent expansion in an isolated, topographically constrained environment. The findings demonstrate the value of reverse engineering as a methodological tool for inferring the relative chronology and functional role of medieval hydraulic systems, particularly where direct archaeological or archival evidence is scarce. These insights further underscore adaptive water-management strategies that underpin long-term settlement resilience in resource-limited environments.

Snow plays a crucial role in Europe’s hydrological cycle, influencing water availability,river runoff, and seasonal storage in mountain and northern regions that support bothnational and transboundary water systems. This study examines key snow-relatedprocesses including snowfall, snow cover fraction, and snow water equivalent acrossEurope. Stochastic approaches are applied to quantify long-term persistencecharacteristics in snow and hydrological processes. Synthetic scenarios are furthergenerated to assess potential responses of snow under regional warming. Theresults are expected to provide insights into European snow dynamics and their rolein shaping seasonal streamflow and water availability. This study offers a Europe-wide stochastic perspective on cryosphere–hydrosphere interactions under climatevariability, where changes in snow storage and melt dynamics can affect hydropowerproduction, agricultural water demand, and drinking water supply.

In a context where energy efficiency is a major concern, studying linear and local head-losses in hydraulic networks is essential. These losses are mainly caused by internal fluid friction and network singularities (such as bends, section changes, valves, etc.), have a direct impact on water transport efficiency and management. In this study, we focus on a laboratory-scale hydraulic network combining both experimental measurements and model simulations using theoretical arguments and the EPANET software. The main objective is to identify, quantify, and interpret the uncertainty in both linear and typical local head-losses through key parameters, such as the friction factor and the local-loss coefficient, for various flow conditions.