One of the most crucial factors for energy transition and the incorporation of renewable energy sources into the existing energy map is citizen engagement. Local energy communities (LECs), which are cooperative-based coalitions aimed at reducing the carbon footprint of the residential building sector, have received increasing attention in the past decade. This is because residential buildings account for almost half of the total energy consumed worldwide. A resounding 75% of it is used for thermal energy consumption, heating and cooling, cooking and bathing. However, the main focus of the literature worldwide is explicitly on electrical LECs, despite the fact that the significant increase in natural gas and oil prices, creates instability in the heating and cooling prices. The scope of this study is to provide an overview of the research field regarding Thermal LECs, using both a thorough literature review as well as bibliometric analysis (VOSviewer software), in order to validate the findings of the review. The results indicate a collective scarcity of literature in the field of thermal/cooling energy communities, despite their proven value to the energy transition. A significant lack of directives, research background and state initiatives in the context of LECs incorporating thermal/cooling energy production, storage and distribution systems, was also observed. Case studies and the applications of such systems are scarce in the available literature, while published studies need further feasibility assessments.

Democritus University of Thrace (DUTh) has formed, under the European Project Renaissance (Renewable Integration & Sustainability in Energy Communities, HORIZON 2020, GA 824342), a virtual Renewable Energy Community (REC) in Greece located nearby Kimmeria at the northeast of the city of Xanthi, at the North-eastern Greece. The REC formed is the first energy community designed in a public housing settlement in Greece and its members are: (a) the Democritus University of Thrace, (b) the Municipality of Xanthi and (c) a local industry. DUTh’s main objective is to explore, leverage and mobilize stakeholders to apply schemes for a social group of end users (i.e., students from low-income families) in order to participate in the operation and management of a local renewable energy community, gaining also non-financial benefits. This paper presents the business case scenario and the market players evolving at an Energy Community which includes a public establishment of student residences in Greece.

Refrigeration systems claim increasing research attention as the climate crisis intensifies. One of the most well-established viable and feasible solutions is solar cooling, as the necessary cooling energy is produced by exploiting the available solar irradiance. The utilization of solar thermal energy to produce cooling energy by absorption chillers fed by a driving heat source (such as solar energy) to produce cooling power. Existing works in the literature present mainly case studies and simulations for small-scale systems (less than 50 kW_c). The case study presented investigates the performance of a single-effect 316 kW_c absorption chiller under different renewable-only driving heat source scenarios (solar-driven, biomass-driven, and a hybrid approach). The results indicate a significantly advantageous performance in combined heat generation (solar field and biomass boiler connected in series) compared to the scenarios of biomass or solar energy as a sole heat source. Moreover, an absorption chiller’s economic indicators appear more fetching than a centrifugal electric chiller of the same capacity, as the payback period is significantly reduced. The Net Present Value (N.P.V. – over 75% greater in the case of absorption chiller compared to the centrifugal electrical chiller) and Return on Investment (R.O.I.) values are increased in the case of the absorption chiller option (18.03% against 15.24% of the centrifugal electrical chiller). The system described in this paper operates in Eastern Macedonia and Thrace, Greece, and is part of one of the largest self-sufficient energy communities. The case study presented is the first attempt at performance evaluation of a large-scale (more than 250 kW_c) cooling system operating in a local energy community.

Distributed energy systems (DES) are currently at the forefront of the energy transition. Their placement brings production closer to the demand side of urban and sub-urban environments, making optimal design a necessity. However, the complexity of accurately addressing the energy demands via DES has received increasing research attention. This is mainly due to the impact they have on the energy transition’s socioeconomic aspect, as these systems are far from viable in most cases, especially when cutting-edge renewable technologies are involved. The current study aims to provide a practical and non-repetitive approach to DES design, explicitly referring to thermal distributed supply systems (TDESS). The authors present the last two of their three-layer Hierarchically Dependent Layering Methodology (HDLM) approach in designing a thermal local energy community (TLEC) from the ground up. The 2nd layer is the superstructure design of the TLEC, where a map approach is introduced and explores several combinations of the selected equipment, how they will interact to meet the heating and cooling loads and how they will form the superstructure. The 3rd is the economic assessment of the proposed scenario. The study results indicate relative ease of use of the model, as a non a priori approach is needed. Additionally, the proposed solution is economically viable as the respective performance indicators suggest.

The transition to a carbon-reduced future for one of the most energy-intensive actors, the building sector, requires the development of appropriate tools and methods. One such approach is local energy communities (LECs), especially thermal LECs (TLECs), which provide a promising vector towards that transition. LECs exploit energy users as key actors in the energy production process. However, their formation, creation, and continuation are still an ongoing endeavor. Many research efforts focus on creating and continuing LECs in an economic, legal, and incentivized manner, sparsely addressing the formation process. In this Part A, a collective tool for decision-making for potential TLECs is presented. The current study proposes a unified approach to classify the prosumers of energy (consumers who both produce and consume energy) using conventional methodologies (RenewIslands, Kaya Identity). A case study is presented in a fully operating LEC in Kimmeria, Greece, in which both the traditional methods of classifying users are applied as well as the proposed methodology, in comparison. The results indicate a significant improvement to the conventional solutions, which tend to overestimate the needed equipment, leading to extensive installation and operational costs.