Abstract
This paper presents a Local Energy Market (LEM) model based on Walrasian Auctions for near real-time energy trading among peers in an Energy Community. The market operates with minimal information exchange, where peers only indicate trade decisions and quantities. The auctioneer updates prices iteratively to balance supply and demand. Two core algorithms support the LEM: (1) the Auctioneer Price Decision Algorithm, which adjusts prices based on past imbalances, and (2) a real-time bidding optimization algorithm, which optimizes peers' energy dispatch and local energy trading decisions based on expected demand, generation, storage, and opportunity costs of external trading. This work details the design and implementation of the bidding optimization algorithm and evaluates its performance through simulations. The results compare the LEM to a centralized pool-based market and individual optimizations, assessing its efficiency and imbalance control. The findings support the development of innovative and decentralized energy markets and smart grid applications.

Abstract
The rapid rise of Renewable Energy Communities (REC) offers unique opportunities for decentralizing and decarbonizing energy systems but also brings challenges in designing fair mechanisms for distributing the benefits of collective self-consumption. This paper evaluates three approaches for benefit-sharing based on the Shapley value, direct marginal contributions, and system marginal cost. A case study compares these methodologies in terms of practicality, fairness, and impact on financial returns. Additionally, this paper proves that settling local transactions using system marginal costs ensures that all REC participants incur equal or lower costs compared to operating independently.

Abstract
Renewable energy communities (REC) can involve final consumers into the energy system incentivizing investments in decentralized renewable energy sources and shaping their energy behaviour to improve the local balance of consumption and generation. However, RECs can also help alleviate energy poverty, which occurs when low incomes and inefficient buildings and appliances result in disproportionately high energy costs for households, by lowering energy expenses through the sharing of surplus electricity at reduced prices with vulnerable members. This work explores REC business models with the specific focus on incorporating and empowering vulnerable consumers. Based on the literature review, we propose indexes to assess the vulnerability and non-vulnerability of REC members. From these indexes, we propose two business models based on two different strategies for the operation and settlement of a REC with flexible assets and vulnerable members.

Abstract
Agriculture and energy use are increasingly linked, especially as farms' energy needs grow. Renewable Energy Communities (RECs) help farmers, particularly in remote areas, access affordable surplus energy from other producers, while sellers gain extra revenue. This study focuses on the creation of RECs as a sustainable and economically viable solution for small and medium-sized agribusinesses to address their energy challenges. We explore the complementarities and potential benefits of RECs from the experience learned in the Tools4AgriEnergy project, using RECreation digital platform for the management of RECs. A case study is used, based on the Alqueva region in Portugal with six members that develop different agri-food sector activities. Using tariffs compliant with Portuguese regulations, results indicate that the development of self-consumption activities can achieve significant energy cost savings annually.

Abstract
Energy community developers are relevant actors for the deployment of energy communities as they can overcome initial investment costs and better navigate complex licensing processes. Their strategy depends on the chosen business model, typically aimed at maximizing their profit while providing tangible benefits to the potential members of the energy communities to encourage their engagement. This works describes strategies for an energy management system adapted to energy community developers whose business model consists in installing, owning and managing energy assets (such as photovoltaic panels and batteries) in its own facilities and in the facilities of those energy community members able and willing to provide them, to sell the locally produced energy for self-consumption in the energy community.

Abstract
Deploying renewable energy communities, self-consumption and local energy markets are one of the ways to contribute to the energy system decarbonization by increasing the renewable energy share in the production mix and contributing to a better local balancing. However, how collective self-consumption structures are regulated has a direct impact on the flexibility of the energy sharing mechanisms and business models that can be set up. This paper compares and discusses how the European Union directives on self-consumption have been transposed to the national regulations of Portugal, Spain and France, providing a detailed regulatory discussion on the definition of basic concepts such as individual and collective self-consumption and renewable energy communities, proximity rules among members, energy sharing mechanisms and energy allocation coefficients, how the energy surplus is managed in each case, or how the grid access tariffs are modified to account for the self-consumed energy. The study highlights that dynamic allocation coefficients provide significant advantages for collective self-consumption by improving energy allocation efficiency, enabling advanced business models, and facilitating the integration of local energy markets, as it is the case in Portugal and France, while their absence in Spain limits these opportunities. The work also highlights the trade-off between flexible energy sharing and implementation complexity, and the role of digital tools to operationalize energy communities. Suggestions on potential regulatory improvements for all countries are also proposed. © 2025