Identification and Modeling of Environmental Climates Inside Naturally Ventilated Tropical Greenhouse Saiful Farhan M. Samsuri, Robiah Ahmad, Mohamed Hussein, Abd Rahman Abd Rahim Department of Applied Mechanics, Faculty of Mechanical Engineering Universiti Teknologi Malaysia Johor, Malaysia saifulfarhan@gmail.com, robiah@fkm.utm.my, mohamed@fkm.utm.my, rahmanar@fkm.utm.my Abstract— This paper focuses on modeling and identification of environmental climates inside naturally ventilated tropical greenhouse (NVTG). The NVTG climate model is an essential tool for developing the climate control system. A real-time wireless monitoring system for measuring prototyped NVTG environmental climates for chili plantation was developed. The variables to estimate the NVTG outputs variables namely internal relative humidity and internal temperature are external temperature, external humidity, irradiance, and wind speed. Modeling based on mathematical equation as well as using system identification (SI) technique is outlined. The paper also highlights on SI procedure namely data acquisition, identified model structure that represents NVTG using NARX and ARX model structures, parameter estimation technique, and model validation. Simulation studies reveal that linear and nonlinear polynomial models are able to model and simulate the NVTG performance. Keywords-Naturally ventilated tropical greenhouse, environmental climates, modeling, identification I. INTRODUCTION Naturally ventilated tropical greenhouses (NVTG) are building structures that allow the creation of an indoor microclimate for crop development, protect plants from adverse outdoor conditions that are usually faced in conventional open field crop such as soil infertility, heavy rain, weedicides and crucial insects and diseases [1]. The developed experimental NVTG prototype was adapted from the greenhouse concept without climate control inputs (such heating, fog system and etc) involved. Protecting plants from any unneeded conditions is important in order for plants to grow in a healthy way. Besides environmental control system, the NVTG also incorporates with fertigation system for nutrient solution supply system. The greenhouse climate parameters can be modified and controlled by artificial actuation such as heating and ventilation input, air temperature and humidity in order to provide the best environmental conditions for the plants. The modern NVTG nowadays aims to be a sustainable crop production system with reduced energy consumption and biocide use while maintaining a high crop quality and yield [2]. In the recent years, many researches related to various dynamic climate control regimes were developed dealing with temperature, humidity, ventilation and etc [3]. All the researches that have been carried out are based on one main objective which is to monitor and control the variables inside the greenhouse to be within suitable ranges. Most of studies that have been carried out for insect screens attributed to windows or vents whereas not much on full insect screened net-houses for tropical climates. The NVTG covering material is important to suit the insect protection requirement of the crops inside. However, it also affects the greenhouse microclimatic condition by influencing temperature and humidity distribution within the greenhouse. Tropical regions are susceptible to heavy rain, which is unevenly distributed throughout the year. Therefore, it is general practice to use insect screens around sidewalls of a greenhouse and the roof is covered with plastic sheet. In the present study, clear polyethylene sheet roofing and polyethylene insect-screen sidewalls were used to clad greenhouses for growing the chili crop. The effects of cladding materials on the temperature and humidity distribution patterns were monitored and studied. The NVTG climate model is a significant tool for greenhouse climate simulation and analysis [4]. The NVTG climate model is considered as a complex non linear process. It involves multivariable inputs and outputs in the system [5]. The model should be able to describe the responses of the NVTG climate to the external influences such as solar radiation, outside air temperature, wind speed and outside humidity as well as the control action performed over the actuators used in the NVTG such as ventilators, heating system and etc. For the simulation and modeling of the greenhouse control system, several methods have been studied by other researchers. The application varies for different types of plantation namely for tomato, roses and etc [6,7]. This research was aimed to provide the best environmental conditions for the plants by maintaining the variables inside the greenhouse environment to be within suitable range. This is essential in order to maintain high crop quality and yield. A research that deals with the problem of modeling and control of climate inside greenhouse has been studied to ensure a favorable inside microclimate for the culture development and to minimize the production cost. Evaluation of control performance is achieved through a benchmark physical model derived from energy balance for the temperature and water mass balance for the hygrometry [3]. 2010 Fourth Asia International Conference on Mathematical/Analytical Modelling and Computer Simulation 978-0-7695-4062-7/10 $26.00 © 2010 IEEE DOI 10.1109/AMS.2010.86 402