## 4 Conclusions  
A techno-economic analysis was carried out to investigate the energy performance and the viability of an innovative CHP system, based on a transcritical geothermal-driven ORC unit and a heat exchanger (HEX) for the exploitation of a high-temperature geothermal source (230 \({}^{\circ}\)C). The sub-systems operate in parallel to satisfy the energy request of a commercial centre. Depending on the energy demand, the geofluid drives both the ORC and HEX sub-units: at full electric load, the geothermal water drives the sole ORC and no thermal production is present, whereas at partial load a fraction of the geofluid feeds the HEX system.  
A thermodynamic model was developed to predict the performance of the geothermal-driven integrated system at full and part loads. First of all, the influence of the maximum temperature on the ORC behaviour was evaluated through a parametric investigation for both simple and regenerative ORC arrangements and the proper system configuration was defined by adopting a multi-variable optimisation. To this purpose, electric power and efficiency were considered as objective parameters and the \"minimum distance\" method was used to find the most suitable apparatus. In particular, the optimised system consists of a regenerative 101.4 kW kWel ORC unit with 17.4% electric efficiency and a geothermal heat exchanger that guarantees 249.5 kWth.  
As a test case, the application of the integrated CHP system to a commercial centre located in Phlegreaan Fields (Southern Italy) was considered and the payback time was used to evaluate the economic viability. To this aim, the costs of the different components were estimated through the bare module cost methodology and three operating strategies were compared: electric- and thermal-driven and mixed strategies. For each operating mode, the yearly electric and thermal energy balances were evaluated on an hourly basis. The results highlight that mixed-mode represents the best solution according to both energy and economic points of view. Particularly, the integrated system provides an electric and thermal self-consumption higher than 90%, while thermal and electric strategies revealed lower performance (electric self-consumption lower than 50% for the thermal-driven mode and thermal self-consumption less than 70% for the electric strategy). Furthermore, the mixed strategy assures no heat dumping and the highest equivalent hours of operation--i.e., 8095--whereas thermal- and electric-driven strategies show 2977 and 6028 h, respectively. Finally, the payback time lower than five years confirms that the proposed system represents a viable technical solution for small-scale and combined energy production, able to give a contribution in the transition towards cleaner and more sustainable technologies. Specifically, the geothermal exploitation in the suggested integrated apparatus provides a yearly CO2 emission reduction of more than 250 tons and a greenhouse gas saving of more than 300 tons of CO2 equivalent per year.  
Conceptualization, A.A. and P.M.; methodology, A.A. and P.M.; software, A.A. and P.M.; validation, A.A. and P.M.; formal analysis, A.A. and P.M.; investigation, A.A. and P.M.; resources, A.A. and P.M.; data curation, A.A. and P.M.; writing--original draft preparation, A.A. and P.M.; visualization, A.A. and P.M.; supervision, A.A. and P.M. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
The authors declare no conflict of interest.