A new solar atmospheric water harvesting integrated system using CPV/T – Stirling engine – Absorption cooling cycle and vapor compression refrigeration cycle

Abstract

This research theoretically investigates the performance of a new integrated solar atmospheric water harvesting system. The system consists of a concentrated photovoltaic thermal unit (CPV/T) to capture solar radiation and produce electricity. The rejected heat is utilized to drive an alpha-type Stirling engine and a single effect LiBr/H2O absorption cooling cycle (ACC). The power output of the Stirling engine and the CPV/T is used to drive a vapor compression refrigeration cycle (VCRC), whereas the cooling capacity of the cooling cycles is used to cool and dehumidify ambient air and generate potable water. Moreover, a heat recovery heat exchanger is employed to pre-cool the supply air before entering the evaporator, thus increasing the water production rate. The model is validated and solved numerically. A parametric study is conducted to show the effect of a variety of ambient and operating conditions on the system's performance. The highest water production rate is found, as expected, to be in hot and humid climates where the solar radiation, the ambient temperature, and the relative humidity are high. The freshwater production exhibits a non-monotonic behavior with increasing the air mass flow rate, and the maximum potable water production was identified. At solar radiation values of 0.6, 0.8, and 1 (kW/m2), the maximum water production was generated at air mass flow rate values of 1.6, 2.8, and 3.8 (kg/s), and the corresponding maximum water production were 13.37, 20.12, and 26.28 (L/h), respectively. It is found that this integrated system can produce up to 30 L/h under hot and humid ambient conditions, and pre-cooling of the supplied air yields better performance under drier conditions. The proposed system is suitable for small-scale applications where water demand is less than 180 L/day. It is found that the amount of electrical energy consumed per liter of produced water by this system is between 225 and 315 Wh/L approximately.