Thermodynamic and Environmental Assessment of Solar-Assisted sCO2 Waste Heat Recovery Systems Under Variable Cooling Demand from Building Materials

The residential sector accounts for a significant portion of global energy demand, which can be met through sustainable alternatives such as solar energy. This study evaluated the energy, exergy, environmental, and exergy-sustainability performance of three waste heat recovery configurations (double-loop organic Rankine cycle—DORC, Kalina cycle—KC, and organic Rankine cycle—ORC) coupled to a supercritical CO2 Brayton cycle with intercooling and reheating, designed to meet the demand of a residential complex of 120 homes in the Colombian Caribbean region, built with four different materials, using a concentrated solar power tower as the heat source. Mass, energy, and exergy balances were performed, along with a life cycle analysis, sizing the systems to supply a cooling load of 133 kW. The results show that the three configurations meet the required demand, with energy efficiencies above 50%: sCO2-DORC (51.7%), sCO2-ORC (51.61%), and sCO2-KC (51.32%), with a maximum exergy efficiency for sCO2-DORC (24.3%). The environmental analysis indicates that the construction phase accounts for more than 95% of total emissions. Overall, the results confirm the viability of these configurations for residential applications, promoting the integration of renewable energies and supporting the regional energy transition.