Multi-objective optimization of a novel polygeneration concept integrating geothermal-solar hybrid thermodynamic cycle with PV-powered CO2 refrigeration for cleaner electricity, heat and cold production

The growing demand for sustainable energy solutions has increased interest in renewable-based multi-generation systems. This study proposes a hybrid tri-generation concept integrating geothermal, solar thermal, and photovoltaic technologies for simultaneous electricity, heat, and cooling production. The system couples a geothermal-solar hybrid Kalina cycle with a PV-powered CO2 refrigeration unit adapted to Kenitra's climatic conditions. A simulation and optimization framework was developed to evaluate thermodynamic and economic performance. Four solar collector technologies—Flat Plate, Evacuated Tube, Compound Parabolic, and Parabolic Trough (PTC)—were compared. The optimization considered energy and exergy efficiencies, Net Present Value (NPV), Levelized Cost of Electricity (LCOE), and Levelized Cost of Heat (LCOH). PTC achieved the best overall performance with 828.82 MWh of annual electricity generation, energy and exergy efficiencies of 33.56 % and 14.95 %, an NPV of 6948.3 k$, and an LCOE of 0.3017 $/kWh. Evacuated Tube Collectors delivered the highest thermal output (7148.4 MWh) and the lowest LCOH (0.0365 $/kWh). The yearly avoided GHG emissions reached up to 4563.74 tCO2eq for the ETC configuration. A multi-objective optimization framework combined to a geometrical decision-making method is implemented to optimize energy efficiency, exergy performance, and economic viability. The design space included 33,936 configurations, with 644 non-dominated solutions identified through Pareto front extraction. The final optimal design recommends PTC collectors with an area of 10,000 m2, a geothermal outlet temperature of 55 °C, and a PV capacity of 44 kWp as the most cost-effective and sustainable configuration.