This paper presents a study on the optimal district integration of a distributed generation (DG) system for an energy community (EC) and the implementation of sharing electricity (SE) between users. In recent years, the scientific community has frequently discussed potential pathways to achieve a 100% renewable energy source (RES) scenario, mainly through increasing electrification in all sectors. However, cooling-, heat-, and power-related technologies are expected to play a crucial role in the transition to a 100% RES scenario. For this reason, a research gap has been identified when it comes to an optimal SE solution and its effects on the optimal district heating and cooling network (DHCN) allowing both electrical and thermal integration among users. The considered system includes several components for each EC user, with a central unit and a DHCN connecting them all. Moreover, the users inside the EC can exchange electricity with each other through the existing electric grid. Furthermore, the EC considers cooling storage as well as heat storage systems. This paper applies the Mixed Integer Linear Programming (MILP) methodology for the single-objective optimization of an EC, in Northeast Italy, considering the total annual cost for owning, operating, and maintaining the entire system as the economic objective function. After the optimization, the total annual CO2 emissions were calculated to evaluate the environmental effects of the different solutions. The energy system is optimized in different scenarios, considering the usage of renewable resources and different prices for the purchase of electricity and natural gas, as well as different prices for selling electricity. Results showed that, without changing utility prices, the implementation of SE allowed for a reduction of 85% in the total electricity bought from the grid by the EC. Moreover, the total annual EC costs and CO2 emissions were reduced by 80 k€ and 280 t, respectively.

Several literature works have highlighted that the expansion of electrification across all sectors is a crucial factor in promoting the transition of energy systems towards carbon neutrality by mid-century. However, polygeneration systems through the appropriate integration of different renewable energy sources are expected to play an important role in such transition by effectively reducing the total primary energy demand, as explored in the present work for an energy community (EC) case study. Therefore, this paper presents the optimal synthesis, design, and operation of an EC system working under three different scenarios and evaluates the trade-offs between the total annual costs and greenhouse gas (GHG) emissions (evaluated as CO2 equivalent emissions). The EC is a District Heating and Cooling Network (DHCN) composed of nine third sector buildings in the northeast of Italy. The DHCN superstructure includes several possible energy supply components for each EC member, a central unit, and heat and/or cooling connections between buildings. Moreover, peer-to-peer electricity sharing is allowed among EC members, through a local electricity grid, before buying/selling electricity from/to the main grid. The superstructure was optimised through a mixed integer linear programming (MILP) model considering a multi-objective optimisation for the total annual cost (for owning, operating, and maintaining the entire system) and the total annual CO2eq emissions as the objective functions. The three scenarios through which the EC system is optimized and evaluated consider the type of consumed gas (natural gas or biomethane) and the electricity consumption configuration (on-grid or off-grid). Results have shown that the cost (per ton of CO2eq) to reduce emissions is too high if the European Union's carbon market is considered. This was especially critic for the natural gas scenario, where the cost per ton of CO2eq (between two optimal solutions) was about four times higher than its cost on carbon market.