João Mello

Abstract
Energy Communities (ECS) and Self- consumption structures are receiving significant attention in Europe due to their potential contribution to a sustainable energy transition and the decarbonization process of the energy system. They are considered a powerful instrument to involve end-consumers in active participation in the energy system by becoming self-producers of renewable electricity and increasing their awareness of their potential contribution by adapting their energy behavior to the global or local power system needs. An EC can also contribute to alleviating energy poverty, which occurs when low incomes and poorly efficient buildings and appliances place a high proportion of energy costs on households. The main driver would be the reduction in energy costs obtained if some members agree to share their surplus electricity at a lower price with vulnerable members. Similarly, a renewable EC (REC) can facilitate access to energy assets by sharing the investments among the community members and exploiting existing complementarities. For example, vulnerable members could share their roofs with others to install solar panels in exchange for low-cost electricity. RECs can also help vulnerable members by reducing the barriers to accessing subsidies for building efficiency investments thanks to collective community initiatives, easing information dissemination and helping with bureaucratic processes.

Abstract
Extensive literature is available for modeling and simulating local electricity markets, often called P2P electricity markets, and for pricing local energy transactions in energy communities. Market models and pricing mechanisms provide simulation tools to better understand how these new markets behave, helping to design their main rules for real applications, and assessing the financial compensations of the internal energy transactions. As such, pricing mechanisms are often needed in energy management systems when centralized management approaches are preferred to market-based ones. First, this paper highlights the links between local electricity markets, pricing mechanisms for local electricity transactions, and other approaches to sharing the collective benefits of participating in transactive energy communities. Then, a standard nomenclature is defined to review some of the main pricing mechanisms for local energy transactions, an innovative pricing mechanism based on the economic principles of a post-delivery pool market is proposed, and other relevant approaches for local electricity market simulation such as Nash equilibrium or agent-based simulation are also revisited. The revision was based on systematic searches in common research databases and on the authors' experience in European and national projects, including local industrial applications for the past five years. A qualitative assessment of the reviewed methods is also provided, and the research challenges are highlighted. This review is intended to serve as a practical guide to pricing mechanisms and market simulation procedures for practical designs of internal financial compensation to share the collective benefits of energy communities.

Abstract

Abstract
This paper proposes a three-stage model for managing energy communities for local energy sharing and providing grid flexibility services to tackle local distribution grid constraints. The first stage addresses the minimization of each prosumer's individual energy bill by optimizing the schedules of their flexible resources. The second stage optimizes the energy bill of the whole energy community by sharing the prosumers' energy surplus internally and re-dispatching their batteries, while guaranteeing that each prosumer's new energy bill is always be equal to or less than the bill that results for this prosumer from stage one. This collective optimization is designed to ensure an additional collective benefit, without loss for any community member. The third stage, which can be performed by the distribution system operator (DSO), aims to solve the local grid constraints by re-dispatching the flexible resources and, if still necessary, by curtailing local generation or consumption. Stage three minimizes the impact on the schedule obtained at previous stages by minimizing the loss of profit or utility for all prosumers, which are furthermore financially compensated accordingly. This paper describes how the settlement should be performed, including the allocation coefficients to be sent to the DSO to determine the self-consumed and supplied energies of each peer. Finally, some case studies allow an assessment of the performance of the proposed methodology. Results show, among other things, the potential benefits of allowing the allocation coefficients to take negative values to increase the retail market competition; the importance of stage one or, alternatively, the need for a fair internal price to avoid unfair collective benefit sharing among the community members; or how stage three can effectively contribute to grid constraint solving, profiting first from the existing flexible resources.

Abstract
Prosumers can organize themselves in collective self-consumption (CSC) structures and renewable energy communities (RECs) to share energy they produce locally. In addition, through their contracted balancing responsible party (BRP), i.e., retailer and aggregator, they could become flexibility providers for system services to solve, for example, local grid constraints. Since CSC and REC structures are progressively being regulated in many countries, local energy markets (LEMs) and local flexibility markets (LFMs) to be developed with these structures should find the way to comply with existing CSC rules to settle energy transactions and flexibility activation, both, locally and with the wholesale markets (WSMs) settlement, and the existing barriers and regulatory improvements should be identified to allow future implementations. Indeed, the integration of local and WSMs is still a matter of development, demanding innovative solutions, one of the main issues being, for example, the impact of the flexibility activation by one BRP into another BRP's expected delivery commitment in the WSM. This work proposes innovative designs for LEM and LFM based on common CSC rules of existing regulations, and a conceptual approach to integrate them together and with the WSM balancing responsibilities of the BRPs involved, identifying existing regulatory barriers. While many LEMs in the literature operate as WSMs, with future markets and delivery commitments for prosumers, we propose the use of a post-delivery LEM that can be cleared even after the delivery of energy, which strongly simplifies prosumers participation avoiding the need of these a priori unrealistic commitments. The business model, the main roles involved, and the contractual framework to connect the BRPs while allowing prosumers to freely contract the BRP of their choice for both energy supply and flexibility provision are described and can serve as a guide for future regulatory improvement of the common regulatory frameworks.