Energy, exergy, economic and environmental (4E) assessment of hybrid solar system powering adsorption-parallel/series ORC multigeneration system

Energy, exergy, economic and environmental assessment is performed for an integrated hybrid solar system powering a multigeneration system. The proposed multigeneration system is integrated parallel/series configurations of organic Rankine cycle (ORC) unit and adsorption chiller under weather conditions of Alexandria-Egypt. The solar subsystem comprises photovoltaic/thermal collectors (PVT) connected in parallel arrangement with evacuated tube solar collectors (ET). The system output aims to provide annual electricity requirements via PVT collectors and the ORC unit and supply cooling requirements during summer via an adsorption chiller for a small building. The hot water output of the solar system is used to drive the ORC unit and adsorption chiller in four configurations; (Conf-1) hot water drives the adsorption chiller, then its output hot water runs the ORC unit (series), (Conf-2) it drives the ORC first, then the adsorption chiller (series), (Conf-3) hot water is divided between adsorption and ORC (parallel), and (Conf-4) hot water drives only adsorption without using ORC unit. Moreover, the impact of the area ratio of the PVT to ET collector and the ORC working fluid and its flow rate on the system performance is investigated. A complete mathematical model is developed for the system components and solved using MATLAB software. The results show that Conf-4 has the best cooling production performance with an average value of 9.6 kW during the summer months and energy efficiency with an average value of 0.3 during August. Conf-1 is the best performing configuration in cooling production of about 5.6 kW average cooling capacity compared to Conf-2 and Conf-3. In contrast, Conf-2 has the best ORC unit performance with a maximum output of 1.2 kW on a typical day in July. Increasing the PVT collector area in the solar configuration negatively affects cooling production but increases electricity production, which augments the system's overall exergy and energy efficiencies. R600 is the best ORC working fluid compared to R290 and R134a in terms of average ORC power production of about 0.72 kW compared to 0.63 kW for R290 and 0.39 kW for R134a. Conf-1 is found to have the best energy savings of about 50.8 MWh/year and thus the best emissions of approximately 10.06 equivalent ton_CO2 per year. The system Payback period is about 9.8, 9.95, 9.9, and 8.45 years for Conf-1 to Conf-4, respectively, proving the system's economic feasibility.