Energy analysis of a geothermal-based energy community equipped with heating and cooling network coupled to an ORC plant

The Renewable Energy Directive of 2018 pushes for the diffusion of renewable energy communities, introducing the possibility of thermal and electric energy sharing. Despite that the large number of developed energy communities and countries transposition are focus only on electricity. One of the most energydemanding sector in Italy is the civil sector which includes the residential and tertiary sectors (for commercial or office use). In this sector the energy communities can be defined by using the district heating and cooling (DHC) technology for thermal energy sharing, that is one of the pioneers towards carbon neutrality as it allows to increase energy efficiency and decrease primary energy supply. Innovative technological concepts such as renewable integration in heating and cooling supply grids, sector coupling, and waste heat utilization allow reaching new goals towards the complete phase out of fossil fuels. Recent studies showed that geothermal energy is a renewable energy source that must be used and preferred to other forms of renewable energies due to its low environmental impacts. Campania Region has a high geothermal energy potential. As part of the GEOGRID research project, funded by the European Community through the Campania Region, the site in the Agnano district was chosen for the design of a four-pipe district heating and cooling network coupled with an Organic Rankine Cycle (ORC) plant: The GeoGRID system. The system supplies the electric, cooling and thermal energy demands of a small community consisting of eight multi-user buildings, using the geothermal energy source in the Solfatara area. The geothermal fluid is firstly used to supply the ORC evaporator and then thermal network. The configuration of the system allows direct space heating and Domestic Hot Water (DHW) production during the winter. During the summer the system guarantees the air conditioning of buildings by using an absorption chiller feed by the DHC network. The system is modelled through different energy tools that allow the dynamic simulation of the chosen configuration. Buildings and plants are modelled and simulated by means of TRNSYS 17 simulation software; while ASPEN model was used to estimate the parameters of the ORC plant. A techno-economic analysis has allowed to evaluate the energy potential extractable from the geothermal fluid, the ORC electric energy production, the pressure and dissipated heat losses of the network layout. The analysis has concerned calculation of community efficiency indexes achieved in renewable energy community configuration and from individual buildings in terms of quantity of electricity imported, exported from/to power grid and consumed on-site. Also, the advantages of thermal sharing have been defined.