Comparative life cycle cost analysis of various solar energy-based integrated systems for self-sufficient greenhouses

Abstract

Abstract This study provides a life cycle cost comparison of four different integrated systems powered by solar energy to provide electricity, water, and cooling for a self-sufficient greenhouse complex. System-1 and System-2 have a vapor absorption cooling system, while System-3 and System-4 have a vapor compression cooling system to provide the required cooling. All the systems have a multi-stage flash desalination unit driven by solar thermal energy to provide freshwater. PV or PV/T modules are installed to meet the electricity demands of the greenhouses. A new greenhouse roof concept is introduced in System-2 and System-4, where there are spectrum selective nanofluids as the working fluid of the PV/T units. This spectrum selective nanofluid absorbs solar radiations having wavelength greater than 1400 nm while flowing through the roof of the greenhouse, and thus reducing the cooling load of greenhouses. The thermal energy of PV/T is utilized to pre-heat the sea water entering the desalination unit for improved process efficiencies. The life cycle cost analysis indicates that the systems employing nanofluid are less costly than the regular systems due to better efficiency and lower energy requirements, especially in cooling. The reductions in life cycle cost of 22.3% and 12.8% are obtained for System-2 and System-4 as compared to System-1 and System-3, respectively. The evacuated tube collectors constitute more than 60% share of the life cycle cost of System-1 and System-3, while PV and PV/T modules have more than 50% share in the life cycle cost for System-2 and System-4. The ambient temperature and solar irradiance have a significant impact on the life cycle cost of all systems. The minimum values for the levelized cost of electricity and cooling are found to be 0.033 $/kWh and 0.015 $/kWh, respectively, for the System-3. System-2 has a minimum cost value of 1.45 $/m3 for the levelized cost of freshwater.