Photovoltaic Greenhouses in Hot and Arid Regions: Modeling for Optimal Micro-Climate Control and Energy Savings

Hot and arid climate regions are facing challenging water scarcity, harsh weather conditions and growing demand for food. Protected cultivation systems were developed to both adapt above challenges and address underlying sustainability issues (carbon footprint and water resources depletion). The present work aims the analysis of a pilot greenhouse combining solar-powered RO desalination, fan-pad cooling and hydroponic systems for optimal water/energy savings. The pilot system is mono-pitched greenhouse (8 m × 15m) 2 m gutter height and 20° south-tilted rooftop. Side and rooftop are covered with 8 mm polycarbonate multiwall-sheets. PV-panels were disposed in the greenhouse rooftop to provide partial shading during hot season. The site is located in northern Saudi Arabia (Latitude: 30.8541 Longitude: 41.1758 Elevation: 534.55 m). A weather data series (12/31/1981–12/30/2019) was analyzed to inform the simulation of the greenhouse micro-climate response. The simulation using COMSOL Multiphysics^© was performed for cooling and healing cycles. The greenhouse micro-climate model was constructed using coupled equations for convective and radiative heat and mass transfers. The thermo-physical properties of the system components and boundary conditions were introduced. Control variables were varied to determine the optimal conditions for plants growth inside the greenhouse. Results includes temperature space–time variations inside the greenhouse. It was found that fans arrangement affects the distribution of temperature and humidity in the greenhouse. Furthermore, temperature distribution efficiency factor of 95% (depicting the distribution homogeneity inside the greenhouse) can be achieved.