Abstract
Natural ventilation systems are the main climatic control method used in mediterranean greenhouses. The objective of these sistems is to set good climatic conditions for the crop. It is important to investigate wich factors affect the natural ventilation process and to develop tecnics to enhace the air exchange between the exterior and interior of the greenhouse. In one hand, it has been studied how different vents configurations (side and roof vents) affect the natural ventilation capacityof the greenhouse. Moreover, novel tecnics have been developed to study features of insect proof-screens installed in the greenhouse vents. In order to study the natural ventilation process in greenhouses, this work is divided in three parts: In the first part, different vents (side and roof vents) configurations have been evaluated. By using sonic anemometry, air flow pattern in the vents of a multi-tunnel greenhouse was studied. Natural ventilation capacity (air exchange or ventilation rate) and climatic conditions (wind direction and intensity) was measured for different ventilator configuartions. It was observed that the airflow pattern in the greenhouse and the ventilation capacity depends of the number of vents and the vents orientation relative to wind.
The second part is about a control system and algorithm that was developed for a low-speed wind tunnel used tu study aerodynamic properties of insect proof screens and evaporative cooling pads, amoung others. The sensors and actuators signals were managed by an electronic interface controlled with an Arduino board. The novel algorithm allows to control the fan speed to set a specific airflow velocity or pressure drop in the test section. The control algorithm automatically identifies the system model of the experimental medium, then it calculates a proportional and intergal controller and finally the controller is implemented. The control system was evaluated with different insect-proof screens and a evaporative cooling pad. Results shows a high precision in the measurements and a fast response of the control system. Finally, in order to evaluate the influence of the insect-proof screens in insect population dynamic in the greenhouse, an algorithm to automatically identify and count whitefly (Bemisia tabaci ) and thrip (Frankliniella occidentalis) in sticky traps installed in greenhouses was developed. The algorithm combines digital image processing and artificial neural networks. The algorithm detects objects in the trap image and obtain a sample image from each detected object, then the sample image is segemented and teh morphological and color features are calculated for the region of pixel segmented, finally, the object is classified as target insect (whitefly or thrip) or non-target object by using a artificial neural network. A high precision to identify and count the target insects was obtained with this algorithm.
Scientific publications presented in this work contributed to knowledge of the natural ventilation process in the mediterranean greenhouse. Moreover, this work propouses a novel tools to study the influence of insect-proof screens in natural ventilation capacity of mediterranean greenhouses (a control system for a wind tunnel), and the insect (whitefly and thrip) population dynamic in the greenhouse (insect identificacion algorithm).