Design and analysis of a renewable energy driven greenhouse integrated with a solar still for arid climates

Closed or protected agriculture in arid climates requires a significant amount of energy to maintain optimum conditions due to the harsh external environment and unavailability of water for irrigation of crops. Therefore, this study proposes a novel greenhouse system integrated with a solar still that reduces the cooling load by absorbing a part of the incident solar irradiance. The greenhouse utilizes the humidification-dehumidification phenomena to supply cooling and water for the plants from the ambient air. The complete system consists of an evacuated tube collector, a greenhouse unit integrated with a solar still, an absorption cooling cycle, and thermal energy storage. A comprehensive thermodynamic model is developed and analyzed using the 1st and 2nd laws of thermodynamics. Moreover, the effect of solar irradiance, ambient temperature, and greenhouse operating parameters on the system's performance is evaluated, demonstrating that the system can operate in a continuous and stable mode. Results illustrate that the humidification-dehumidification system inside the greenhouse produces sufficient water and cooling in an environment-friendly manner while the solar still reduces the cooling load by almost 20%. Moreover, the greenhouse maintains optimum temperature and relative humidity throughout the year while providing a space cooling load of 1437.95 kW and 4.03–5.20 m³/day of water. The proposed system provides an opportunity for year-round agriculture in harsh climates with a scarcity of fresh water. In addition, the system is flexible depending on the crop requirement and geographical location of the site.