Thermodynamic Analysis of Gravity Assisted Solar-Powered Reverse Osmosis Unit for Greenhouses Situated in a Depleted Zone with Performance Evaluation and Improvements Using Nanofluids

The Sabkha-Tah region of Western Sahara is a location where adverse weather conditions make it difficult for certain crops' conventional farming. However, the region is uniquely situated ina depleted zone 60 m below sea-level. An analysis of a novel multi-generation system that harnesses the surrounding geography to produce power, cooling, and freshwater for a greenhouse is performed. The system utilises the Atlantic Ocean's hydrostatic pressure to decrease the reverse osmosis (RO) unit's power consumption. The system demonstrates that 46.18 kW of energy can be saved when using the water's hydrostatic pressure. The energy required to produce 1 m³ of fresh water is 2.51 kWh, and the overall energy and exergy efficiencies are 59.2% and 29.6%, respectively. Then the parabolic trough collector in the multigeneration system is investigated for further improvements. Thermal performance comparison of various working fluids operating in a Parabolic Trough Collector (PTC) is conducted. Fluids such as gases (helium, carbon dioxide, and air), liquid sodium, and liquids(pressurised water, Therminol VP1, Syltherm 800) are evaluated. This study also examines the efficiency enhancement obtained from the dispersion of copper nanoparticles in base fluids. The study results demonstrate that the Cu/Syltherm 800 nanofluid showed the most enhancement in thermal efficiency with 0.141% while the highest energy efficiency among thermal oils achieved by Cu/Therminol VP1. Moreover, another part numerically investigates the impact of nanoparticles on a district cooling system's energy performance. For a fixed cooling capacity of280 kW, the corresponding system coefficient of performance (COP) increased by 3.9 %.Finally, two multigeneration systems configurations that use two different cooling cycles(absorption and HVAC) are compared. The overall energy efficiency of multigeneration system using the absorption cooling cycle is higher by 11.42% compared to the one that uses an HVAC system while it increases by 0.9% by replacing both chilled water in the HVAC system by Cu/water and Therminol VP1 in parabolic trough collector by Cu/Therminol VP1.