A Pilot Study on the Microclimate of a Multi-span Solar Energy Greenhouse

Abstract

Abstract. Extreme low and high temperature is the main obstacle to grow plants in an ambient environment. Due to climate change, these problems are getting worse day by day. To resolve this dilemma a new type of energy-saving greenhouse structure, a multi-span solar energy greenhouse (SEG), was designed and constructed in the Yangtze valley region of China. Using a multi-span plastic greenhouse as a control greenhouse (CG), the microclimate characteristics of the SEG were studied in winter and summer. The results showed that, because the SEG adopted the cooling way of the combination of external shading and natural ventilation in summer, on a sunny day and cloudy day, the average air temperature of the SEG were 3.9°C and 0.9°C lower than CG, respectively, the average solar transmittance were 40% and 18% lower than CG, respectively, indoor microclimate distribution was more uniform. In an acute temperature condition, the effect of natural ventilation on cooling inside the SEG was better than CG during the daytime. Additionally, during the winter season, on a sunny day and cloudy day, compared with CG, the average solar transmittances of the SEG were 24% and 12% lower than CG, respectively, at the same time, the average air temperature of the SEG were 2.1°C and 2.3°C higher than CG, respectively. During the nighttime, the soil surface as well as the film temperature of the SEG, was higher than CG, whether it was on a sunny or a cloudy day, the daily effective accumulated temperature in SEG was more than CG. A north wall was built inside the SEG could effectively improve indoor nighttime temperature, and per unit volume of the SEG could save 0.63 L of diesel per day in winter, thereby saving $0.53, and reducing carbon emissions by 1.74 kg. Taken together, considering all aspect we concluded that the indoor environment of the SEG was more suitable for plant growth and cost-effective for crop cultivation as well. Keywords: Energy-saving, Greenhouse, Microclimate characteristics, Solar energy, Thermal environment.