Ventilation Rates for a Naturally-Ventilated Greenhouse in Central Mexico

Contribution to the Sustainability of Agricultural Production in Greenhouses Built on Slope Soils: A Numerical Study of the Microclimatic Behavior of a Typical Colombian Structure

“…It was also found that for the period between 15:00 and 18:00 h, the value of the normalized velocity was higher than 100%, which means that the air flow velocity inside the structure was higher than the external wind flow. The values of the highest normalized velocity agreed with the time when the temperature of the outside environment started to decrease, therefore it can be mentioned that this acceleration of the air flow inside the greenhouse may be strongly associated with the thermal effect of natural ventilation by buoyancy; an effect that generally produces rapid changes in temperature and velocity inside a greenhouse [59]. This buoyancy phenomenon is caused by convective movements generated between the soil and the greenhouse cover, since at that time the soil is the surface of higher temperature due to energy storage throughout the day, while the cover usually cools rapidly to the level of the outside ambient temperature [34,60].…”

“…Greenhouse air exchange rates (GAERs) in volumes per minute (Vmin −1 ) were calculated for each of the simulated hours, with these values ranging between a minimum and maximum value of 0.28 Vmin −1 and 1.29 Vmin −1 (Figure 8). These data show that only for a period of 3 h (12:00-15:00) was the GAER value higher than the minimum recommended value for passive greenhouses, which should be at least 1 volume renewed per minute (Vmin −1 ) [59]. Therefore, it can be deduced that the greenhouse evaluated presents deficient ventilation rates for 69.7% of the hours of the day-time period, and so it is recommended that future studies address design alternatives in the structure to maximize this index, since its influence on the microclimate behavior of the structure is very relevant [63].…”