Abstract. In a commercial greenhouse, variables, such as temperature and humidity, should be controlled with minimal human intervention. A systematically designed climate control system can enhance the yield of commercial greenhouses. This study aims to formulate a nonlinear multivariable transfer function model of the greenhouse model using thermodynamic laws by taking into account the variables that affect the Greenhouse Climate Control System. To control its parameters, Mamdani model-based Fuzzy PID is designed which is compared with the performance of proportional-integral (PI) and proportional-integral-derivative (PID) controllers to achieve a smooth control action. The Fuzzy logic based PID provides robust control actions eliminating the need for conventional tuning methods. The robustness analysis is performed using values obtained from real-time implementation for the greenhouse model for Fuzzy based PID, PI and PID controllers by minimizing the Integral Absolute Error (IAE) and Integral Square Error (ISE). The greenhouse model has strong interactions between its parameters, which are removed by Relative Gain Array (RGA) analysis, thereby providing an effective control strategy for complex greenhouse production. Further, the stability analysis of non-linear greenhouse model is conducted with the help of the bode plot and Nyquist plot. Results show that good control performance can be achieved by tuning the gain parameters of controllers via step responses such as small overshoot, fast settling time, less rise time, and steady-state error. Also, smoother control action was obtained with Fuzzy based PID making the Greenhouse Climate Control System stable.
Greenhouse farming is considered as one of the most scientific approaches in agriculture, which are suitable for all climatic conditions, especially in Middle East, North America, and Europe. Sustainable greenhouses are innovative farming facilities for healthy vegetables and fruits in a controlled, conditioned indoor space. This article presents a literature review on the upgradation of a conventional to a sustainable greenhouse using modern engineering concept. This includes maintaining fully controlled indoor conditions such as temperature, relative humidity, and air velocity for specific agronomical parameters. The influence and improvements in upgradation of various heating, ventilation, and air-conditioning (HVAC) with the associated control systems and covering materials to reduce the energy consumption have been reviewed. Financial viability of conventional as well as upgraded greenhouses is highlighted. In Middle East climatic conditions, the major challenge is to control the optimal range of temperature (18–21°C), relative humidity (55 to 75%), and air velocity (0–1.3 m/s). It is found that the upgraded HVAC systems with climate control modules can increase the crop yield by 30%. Scientifically selected polycarbonate sheet covering materials are also found to increase the crop yield by up to 15% more than the conventional commercial greenhouses.
Controlled crop growth parameters, such as average air velocity, air temperature, and relative humidity (RH), inside the greenhouse are necessary prerequisites for commercial greenhouse operation. Frequent overshoots of such parameters are noticed in the Middle East. Traditional heating ventilation and air-conditioning (HVAC) systems in such greenhouses use axial fans and evaporative cooling pads to control the temperature. Such systems fail to respond to the extreme heat load variations during the day. In this study, we present the design and implementation of a single span, commercial greenhouse using box type evaporative coolers (BTEC) as the backbone of the HVAC system. The HVAC system is run by a fully-automated real time feedback-based climate management system (CMS). A full-scale, steady state computational fluid dynamics (CFD) simulation of the greenhouse is carried out assuming peak summer outdoor conditions. A pilot study is conducted to experimentally monitor the environmental parameters in the greenhouse over a 20-h period. The recorded data confirm that the crop growth parameters lie within their required ranges, indicating a successful design and implementation phase of the commercial greenhouse on a pilot scale.
Greenhouses are known to be the modern outlook for the agronomical industry in terms of high-end yield especially in the regions where climatic conditions are not stable like in the Middle East, Europe, and United States. Crop optimization is one of the major challenges facing the farmers and the controlled production centers can dictate this difficulty in the upcoming market. Greenhouses are considered as the high -tech production centers which can support the food industry to have a green revolution through the mass production of the vegetables and spices. Properly designed commercial greenhouses can increase the yield by minimizing the operational cost especially in terms of reducing the energy consumption. In order to have a properly designed greenhouse, the selection or up gradation of the shade structures can play a vital role. Conventional greenhouses are made of polycarbonate sheets and in some cases the polyhouses by using simple polyethylene sheets. In this scenario, the main drawbacks were the energy consumption, operational expenses and the effectiveness of the indoor temperature control. Custom designed shades based on the crop requirements can provide high production rate by reducing the energy consumption. The detailed microstructural analysis in conjunction with the photosynthesis demand can provide a better selection of the shade-net or curtains. Greenhouse shade structure can be upgraded using the motorized specially designed nets or by using thermal-reflective screens. This up gradation can provide four stage advantages. In stage one this can decrease the 50% of heat energy and which will save the HVAC operational cost. During the stage, two better temperature control during the day and night will provide a good environment to provide proper PAR (Photosynthetically Active Radiation)[5] for photosynthesis, in the wavelength range of 400 to 700 nanometer. Third and fourth stages are the protection from the frost as well heat stress during the different climatic conditions. In the present market condition, the commercial greenhouses are being built in large scale by neglecting the energy saving options in shade structures. The commercial greenhouses using the upgraded shade structures can save the operational cost by 25 to 30%. Selection of this shade-nets or curtains can be done using the detailed microstructural analysis of the material. Shade-nets/curtains can be controlled manually, mechanically or can be automated in large-scale greenhouses. Flowering dates in the plants can be accelerated using the shading materials and delayed by the use of control treatment, which coincides with the results obtained in the previous studies [1]. This has proven with high land experiments [2]. Greenhouse shade nets are used in order to protect crops and plants from adverse weather conditions, animals and pests, besides providing suitable conditions for plant growth. The essential performance properties required for greenhouse shade nets are the resistance to solar radiation and weathering. The intensity of the Photo Synthetically Active Radiation (PAR) directly influences plant growth. Other nonvisible radiations are ultraviolet (UV), infrared (IR) and far infrared (FIR)[16]. Polypropylene and polyester are more resistant to UV radiation than polyethylene, which is resistant to radiations in the visible region. The use of greenhouse shade nets in outdoor conditions also requires them to be resistant to abrasion[3]. The objective of the present work is to examine the effectiveness of the properly selected shade-net/curtain in commercial greenhouses in terms of high yield energy savings. This study was conducted to compare the traditional polycarbonate sheet with the innovation of properly designed shade curtain made-up from high-density polyethylene (HDPE) fiber reinforced material discover the best shading method for plant growth in an ideal energy conservation scenario. The study was conducted in the two identical greenhouses (planted with lettuce crop) located in Al Khawaneej farm in the Emirate of Dubai in the United Arab Emirates. Yield versus the energy consumption has been observed in a period of time and obtained the reduction in energy consummation of almost 20 to 30 %.
Commercial green houses are the back bone of farming industry in world where the climatic conditions are not stable especially in Middle East, Europe and United states. The commercial greenhouses are often high tech production facilities for vegetables or flowers. The glass greenhouses are filled with equipment like screening installations, heating, cooling, and lighting and also may be automatically controlled by a computer to maximize potential growth. Greenhouse concept will provide the stable indoor plant growth environment throughout the year irrespective of the outside climate variance. The indoor climate conditions can be maintained using the properly designed HAVC systems. The conventional commercial green houses are equipped with axial fans and the cooling pads to control the indoor climate conditions without central control of the equipment’s. Financial conditions of the commercial green houses are very important since the cost per plant will be determined by the overall contribution of the capital and operational expenses. In the present scenario the almost 30% of the net profit is eating by the HVAC systems operational cost. The major operation cost is due to the cooling pads work force and the electricity operational cost for the axial fans equipped with metal blade. The up gradation involves mainly the involvement of individual evaporative air-conditioned system instead of conventional systems. The green houses are equipped with individual evaporative cooling units, circulating fans, top mounted air louvers and the control systems to control the entire set up. The initial heat load calculations will give us an idea about the total heat load required to maintain the ambient conditions for indoor plant cultivation. CFD analysis will provide the exact equipment orientation and the load requirement. In conventional greenhouses the conventional equipment’s are equipped to get the results but the same will consume more electrical power and which is not effective in all weather conditions. Heat load calculations will provide us the system demand in a conditioned space based on the available material properties. Based on the heat load results we can do the proper equipment selection and set the airflow based on the demand. CFD analysis will help the modeling of the system in the actual condition. The aim of the study was to analysis the performance study of the individual evaporative cooling units in the greenhouse conditioned space. The results obtained from the heat loads and CFD analysis can be compared. The objective of the present work is to examine the designed Air conditioning system effectiveness in peak summer heat load conditions to check the design parameters (25 °C temperature and 50%RH) inside the greenhouse using Computational Fluid Dynamics (CFD) Analysis.
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