Abstract
The growing needs for fruit and vegetable production, together with the current climate change situation, make agriculture under plastic and greenhouse cooling indispensable. The most commonly used approaches are natural ventilation, shading and fan-pad systems. To foster a climate that allows forplant production under cover in extreme conditions, a novel fan-pad system has been devised that incorporates a pre-chamber and an air distribution system using air ducts running alongside the crop rows. The system has been tested in a greenhouse in Almeria (Spain) during the daytime in August, when the weather was hotter. Tests were also carried out in combination with natural ventilation and shading. The results indicate that the fan-pad system was efficient under extreme weather conditions and that it avoided creating horizontal thermal gradients. By determining the theoretical value of the air temperature leaving the pad, we were able to estimate the evaporative cooling potential of the fan-pad system as a function of the outdoor climate. Under extreme conditions, the fan-pad system’s efficiency decreased along with increased air temperature and, above all, the increased relative humidity of the outside air. When the outdoor climate is warm and humid, natural ventilation may be the most efficient temperature control method. If the outdoor climate is warm and dry, the evaporative pad is more effective, especially when combined with shading.
Highlights
Greenhouses are built to protect crops from inclement weather and to increase crop quality [1,2].In warm climates, greenhouses are specially adapted to agricultural production during the cold and mild periods of the year
To improve operational understanding of the new fan-pad system used in this work, we first analysed the effect of the fan-pad system on the greenhouse
A psychrometric assessment was performed, indicating that the treated air experienced evaporative cooling in the pad, and that heating occurred in the pre-chamber
Summary
Greenhouses are built to protect crops from inclement weather and to increase crop quality [1,2].In warm climates, greenhouses are specially adapted to agricultural production during the cold and mild periods of the year. In arid and semi-arid areas, summer is characterized by temperatures that can exceed 40 ◦ C and relative humidity levels below 30% during the day [4]. For this reason, strategies aimed at reducing the air temperature inside the greenhouse have been developed for the hottest times of the year. In the case of greenhouses in semi-arid climates, the most commonly used cooling systems are natural ventilation and shading, due to their low economic cost. Natural ventilation has the inconvenience of pests and/or vectors of disease entering the greenhouse, so the air vents need to be Agronomy 2020, 10, 752; doi:10.3390/agronomy10050752 www.mdpi.com/journal/agronomy
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
