Environmental Control of a Greenhouse System Using NI Embedded Systems Technology Christakis Papageorgiou, Ahmed Sadriwala, Mohammed Almoalem, and Conor Sheedy School of Engineering, Bahrain Polytechnic, Kingdom of Bahrain Email: c.papageorgiou@polytechnic.bh Andre Hajjar National Instruments (NI) Email: Andre.Hajjar@ni.com Abstract—This paper presents the application of an automated environmental control system for a prototype greenhouse system using commercial embedded systems technology. The prototype greenhouse system was developed and instrumented with appropriate sensors to measure various environmental variables like the temperature, the light intensity, the soil moisture, the air humidity and CO 2 concentration. These measurements are provided to the control algorithm which is implemented on a commercial embedded system and manipulates various actuators like, a heating and cooling actuator, fans, lights, irrigation system, and louvers in order to achieve the desired set-points, as specified by the user through a Human-Machine Interface implemented in LabView software. Certain aspects of the greenhouse dynamics have been modeled in Matlab/Simulink using nonlinear differential equations and the simulation model has been validated against experimental data, showing good agreement between the simulation and the experimental data. The purpose of this work is to enhance research related to the accurate environmental control of greenhouse systems in order to minimize energy and water consumption and to develop a robust educational platform for teaching control system design, analysis, instrumentation and embedded systems development at the Engineering School of Bahrain Polytechnic. Index Terms—environmental control, automated greenhouse system, embedded system, temperature regulation I. INTRODUCTION A. Environmental Control of Greenhouse Systems The environmental control of a greenhouse implies the regulation of day and night air temperatures, the relative humidity and the carbon dioxide levels to ensure optimal plant growth. Heat, water vapor and carbon dioxide are transferred in and out of the greenhouse space in order to maintain the required set-points of temperature, relative humidity and carbon dioxide concentration. Heat is transferred by conduction, convection and radiation and various mass transfer processes are also occurring utilizing fans and louvers resulting in complex flows that Manuscript received July 22, 2015; revised November 2, 2015. involve both heat and mass transfer. A good introductory reference detailing the basic functions of a greenhouse system is found in [1]. A more detailed account of the functionality of an automated greenhouse system is presented in [2]. The authors discuss the various functionalities of a greenhouse such as light intensity control, heating control, cooling control, air circulation control and humidity control. Various active and passive actuation devices are presented in order to achieve the desired regulation effect. A brief discussion on closed- loop (feedback) control is given, detailing some requirements on sensing environmental variables and on control algorithm implementation. Interestingly, the authors present their analysis based on the application of a greenhouse automated system for the extreme Alaskan weather. They quote: ``By optimizing light, temperature and humidity, in conjunction with the proper fertilization, watering and selection of adapted varieties, an endless array of growing opportunities await the Alaska greenhouse gardener and commercial producer’’. Moving towards the more moderate Mediterranean climate, the authors in [3] present an analysis of the most important functionalities of an automated greenhouse system, namely the temperature and relative humidity control. The authors provide indicative set-point values for these variables that favor plant growth and based on the climograph information for a given location, they determine the levels of cooling or heating required to maintain these set-point values. The climograph contains information regarding the mean solar radiation and mean air temperature for a given location all around the year. It constitutes the starting point in identifying the actuation requirements for an automated greenhouse system. Special attention is given to energy efficiency and sustainability. The authors focus on providing favorable conditions for plant growth during the hot periods of the Mediterranean climate while using energy efficient processes like ventilation, shading, evaporative cooling and effective insulation. Similar design requirements are addressed in [4], where the authors present the application of an automated greenhouse system for the production of tomatoes. 331 ©2016 Journal of Automation and Control Engineering Journal of Automation and Control Engineering Vol. 4, No. 5, October 2016 doi: 10.18178/joace.4.5.331-339