A Model of Humidity within A Semi-closed Greenhouse

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Semi-closed greenhouses are more efficient in water and energy use than conventional ones. However, one of the challenges is the humidity control. This paper is based on experimental data generated during the 2012 tomato production cycle in a semi-closed greenhouse located at the Humboldt University of Berlin. The aim was to generate two models for simulation of the humidity behavior. In the first model, the greenhouse was completely closed and only transpiration and condensation processes were taking place. In this model, after calibration, a mean absolute error (MAE) of 1.94 and a correlation coefficient (r) of 0.87 were obtained, with the boundary layer resistance and the radiation extinction coefficient being the most varying parameters. The second model, in addition to the processes considered in the first, had natural ventilation, so a sensitivity analysis was performed before calibration, resulting in a MAE = 2.17 and r = 0.85, with the latent heat of vaporization and the radiation extinction coefficient being the most sensitive parameters. The developed models allow for a quantitative comparison of the processes involved in the water balance in the open and closed system, and will thus enable us to improve control over this factor. Both models were implemented using Simulink in Matlab

Raquel Salazar-Moreno
Azucelli Maythe Mauricio-Pérez
Irineo Lorenzo López-Cruz
Abraham Rojano-Aguilar
Revista Chapingo Serie Horticultura