Thermal Model Development for Solar Greenhouse Considering Climate Condition
Abstract
Water crisis in the Middle East, leads policy makers to consider development of greenhouses on large scale. Typical greenhouses usually use energy carriers like natural gas and gasoline to provide suitable microclimate for plants. The consequence of greenhouse development will be huge amount of fossil fuels consumption, producing CO2 and forcing loads to gas, gasoline and electricity networks. Considering excellent solar energy potential in the Middle East, solar greenhouses seems to be an innovative solution. In this research, after studying different solar greenhouse experiences around the world, a successful model has been chosen, redesigned and improved. Solar greenhouse is designed to utilize solar energy by its passive energy system and minimize external energy demand. In order to investigate its performance, a mathematical thermal model has been developed to predict inside air temperature, which is the most important parameter in greenhouse performance. Solar Greenhouse Thermal Model (SGTM) is based on solar collector analysis and trombe wall calculations in buildings, it receives hourly climate data (solar radiation, wind speed and ambient temperature) and calculate hourly solar greenhouse inside air temperature during the year. SGTM has been validated and can be used to predict solar greenhouse inside air temperature in any region. Results of using SGTM show that solar greenhouse is suitable for Tehran climate condition, and it works passively without auxiliary heating system in the winter, but it needs auxiliary cooling system in the summer. Sensitivity analysis indicates that the greenhouse size play a vital role in its thermal performance. So, there is an optimal size for solar greenhouse in each climate condition.