Study of the application of solar chimneys combined with earth-air heat exchangers ventilation system (SEVS) in a solar greenhouse

Opening the top vent for natural ventilation is often used in traditional solar greenhouses in winter. However, the temperature adjustment in greenhouses often cannot meet expectations. In this study, the SEVS was applied in the experimental solar greenhouse. Effects of the SEVS on the air velocity and temperature distribution in the greenhouse were investigated using experimental and numerical methods. The results showed that the SEVS enhanced the natural ventilation of the greenhouse. When the distances among solar chimneys and among earth-air heat exchangers were all 4.6–6 m, the air distribution was relatively uniform with an average air velocity of 0.259–0.481 m/s and an indoor temperature of 24–24.9 °C, which met the growth requirements of tomatoes. However, the air velocity at the vents of earth-air heat exchangers was large, ranged from 1.86 m/s to 1.93 m/s, which had negative impact on crop growth near the vents. The vents of earth-air heat exchangers were improved. The results showed that when the width of the vent was 0.5 m and the length was 3∼4 m, the air velocity in the crop areas near the vents could be maintained below 0.5 m/s, and the indoor air distribution could also be improved. Field tests demonstrate that the soil temperature stabilizes at approximately 16 °C at a depth of 1.2 m below the ground, enabling the SEVS to maintain the temperature environment required for the growth of crops such as tomatoes when outdoor temperatures exceed 2 °C.