Despite the massive increase of renewable energy generation in Greece, large-scale battery energy storage systems (BESS) are yet to be integrated in the Greek electricity market. This paper analyzes the profitability of BESS in Greece, focusing on the Day-Ahead Market (DAM) and the Frequency Containment Reserve (FCR) market. To this end, we examine and compare the following three instances of BESS market participation with respect to the short-term uncertainty BESS participants face in terms of market prices and FCR utilization factors: (a) a theoretical perfect information instance, (b) a deterministic instance based on average historical values of the uncertain parameters, and (c) a stochastic instance based on alternative scenarios stemming from historical data. The last two instances are complemented by an out-of-sample validation representing BESS operation after uncertainty is materialized. Furthermore, for each of these three instances, we explore three cases involving participation only in the DAM, only in the FCR market, and in a combination of the DAM and FCR market, accounting for the different pricing mechanisms of these markets. The case studies employ real market and frequency data from Greece and compare the three instances and three market participation cases in terms of achieved profit and energy violation rate.

Energy Communities have emerged as a key mechanism for promoting citizen participation in the energy transition. In Greece, recent legislation replaced the virtual net-metering scheme with a virtual net-billing framework, introducing new economic and regulatory conditions for shared renewable energy investments. This study develops an optimization tool for determining the optimal PV system size and Demand Response actions for individual EC members under this new framework. The model is constructed to align closely with the current regulatory and legal context, incorporating technical, economic, and policy-related constraints. It uses real electricity production and consumption data from existing Greek ECs, as well as 2024 Day Ahead Market prices, grid fees, and surcharges. The results emphasize the importance of customized sizing strategies and suggest that policy refinements may be needed to ensure equitable participation and maximize community-level benefits.

Zonal day-ahead (DA) electricity markets followed by redispatch (RD) markets for congestion management are vulnerable to the strategic bidding behavior known as Inc-Dec gaming. Although previous literature has demonstrated the effects of Inc-Dec gaming, it has neglected the participation of flexible demand in RD markets. This paper addresses this gap by developing a novel multi-period bi-level optimization model of a strategic producer participating in DA and RD markets, accounting for the inherent time-coupling operating characteristics of demand flexibility (DF) in the RD market. This model includes an upper level problem determining the optimal bidding decisions of the strategic producer in the DA and RD markets, and two lower level problems representing the clearing process of the two markets. The role of DF in addressing Inc-Dec gaming is demonstrated through a small-scale case study involving a 2-node system and a 2-period market horizon (showing peak/off-peak dynamics), as well as a large-scale case study involving a modified IEEE RTS 24-node system and a daily (24-h) market horizon.

The European Green Deal requires coal-dependent regions to undergo a rapid yet socially balanced transition toward climate neutrality. In countries such as Greece, Poland, and Germany, the phase-out of lignite has created pressing challenges related to energy security, economic restructuring, and social cohesion. At the same time, these regions host extensive legacy energy infrastructures and strong institutional experience, offering unique opportunities for sustainable redevelopment through decentralised and digitally enabled energy systems.This paper explores how digitally supported energy communities can act as a key mechanism for supporting the just transition of former coal regions, bridging policy frameworks with advanced digital solutions. Based on the FlexBIT project, this study combines a comparative regulatory analysis of selected EU Member States with a focus on interoperability, data governance, and cybersecurity requirements for energy communities, alongside the design of digital platforms that enable flexibility services, energy sharing, and local energy market participation.The analysis highlights that while EU legislation, particularly RED II/III, the Electricity Market Directive, the Data Act, and NIS2, provides a strong enabling framework, national implementation gaps and fragmented digital infrastructures remain critical barriers. In Greece, regulatory complexity, uneven digital readiness, and limited access to interoperable platforms constrain the ability of communities to fully exploit local renewable generation, storage, and flexibility potential.The paper demonstrates how interoperable digital platforms, combining real-time data exchange, AI-based flexibility optimisation, and secure governance models, can repurpose existing energy infrastructures and empower local actors, including municipalities, SMEs, and citizens. By aligning regulatory compliance with digital innovation, energy communities can contribute to grid resilience, energy affordability, and social inclusion, transforming former lignite regions into hubs of clean energy innovation.Overall, the study positions digitally enabled energy communities as a scalable and replicable pathway for integrating policy objectives, technological solutions, and social equity within the just transition of coal regions in Greece and across Europe.

Zonal day-ahead (DA) electricity markets followed by redispatch (RD) markets for congestion management are vulnerable to the strategic bidding behavior known as Inc-Dec gaming. Although previous literature has demonstrated the effects of Inc-Dec gaming, it has neglected the participation of flexible demand in RD markets. This paper addresses this gap by developing a novel multi-period bi-level optimization model of a strategic producer participating in DA and RD markets, accounting for the inherent time-coupling operating characteristics of demand flexibility (DF) in the RD market. This model includes an upper level problem determining the optimal bidding decisions of the strategic producer in the DA and RD markets, and two lower level problems representing the clearing process of the two markets. The impacts of DF in mitigating Inc-Dec gaming are demonstrated through a small-scale case study involving a 2-node system and a 2-period market horizon, as well as a large-scale case study involving a modified IEEE RTS 24-node system and a daily (24-hour) market horizon.