Original papersControl of greenhouse-air energy and vapor pressure deficit with heating, variable fogging rates and variable vent configurations: Simulated effectiveness under varied outside climates
Introduction
Outside conditions are always variable, especially in locations with extreme environments. Climate in greenhouses is continuously influenced by the outside conditions. Thus greenhouse climate control is needed to maintain desired setpoints. Under non-extreme conditions, natural ventilation (NV), the most common method used worldwide aiding to maintain suitable climate conditions for plant production (Kittas et al., 1997, Katsoulas et al., 2006), together with on–off control logics, may be sufficient to effectively maintain appropriate climate conditions for plant growth. However, when the outside climate is extreme, as it is in arid and semiarid regions, other control systems such as cooling (Sethi and Sharma, 2007), heating (van Beveren et al., 2019), and flexible controllers (Pahuja et al., 2015), such as variable frequency drives (VFD) (Teitel et al., 2004), may be used to enhance the capabilities of the greenhouse climate control systems. Hybrid systems, such as the aforementioned, must be accompanied with effective control strategies and should be aligned with local climates to ensure appropriate greenhouse environmental conditions (Ghoulem et al., 2019).
In the case of greenhouse cooling, previous experimentation with fogging has proven good results (Sase et al., 2006, Villarreal-Guerrero et al., 2013). Fogging systems operate with a lower water use (López et al., 2012) and a higher environmental uniformity than pad-fan (Toida et al., 2006), improving plant productivity (Leyva et al., 2013, Lu et al., 2015). Evaporative cooling, such as fogging systems, simultaneously used with NV and shading could potentially reduce greenhouse energy requirements (Ghoulem et al., 2019), and operation costs, instead of coupling it with mechanical ventilation. Furthermore, fogging systems could also be used for applying crop-protection products (Sánchez-Hermosilla et al., 2013).
Several climate control strategies employing fogging systems coupled with NV have been developed and experimented (Baille et al., 2006, Sase et al., 2006, Handarto et al., 2007, Li, 2007, Perdigones et al., 2008, Garcia et al., 2011, Villarreal-Guerrero et al., 2012a, Lu et al., 2015). However, the control of cooling with fog and NV is complex due to the interaction of various environmental factors (Merril et al., 2016). In addition, when the outside climate gets too cold and cooling control is not needed, the use of heating may be required to be psychrometrically able to reach appropriate set points for plant growth. Thus, there is still a need for more research on how to effectively control the climate of greenhouses under varied outside conditions.
In the past years, a strategy for NV coupled with fogging systems and its control algorithm was developed (Villarreal-Guerrero et al., 2012a) and validated (Villarreal-Guerrero et al., 2013) for a semiarid greenhouse. During validation, the strategy performed satisfactorily. Moreover, the capabilities of the strategy to maintain a desired greenhouse climate under different outside climatic conditions were tested afterwards (Villarreal-Guerrero et al., 2014). The strategy showed a good performance when cooling was needed in the greenhouse. However, since the strategy was primarily developed for cooling, a tight control on the set points was not possible during night and early in the morning when increasing the greenhouse internal energy was required.
Therefore, the original strategy was improved and the algorithm modified by including a heating component with the same principle originally used for cooling. The present study presents results from computer simulations of the strategy under two locations with varied outside climates. An analysis was made on the capabilities of the strategy on maintaining desired climate conditions. In addition, recommendations for further improvements on the algorithm are stated.
Section snippets
The climate control strategy
In this study, we evaluated the capabilities of a greenhouse climate control strategy, which considers the cooling and humidification effects from crop transpiration. The strategy operates with variable vent configurations, a fogging system operated on a VFD basis and proportional heating (100 and 200 W m−2). The strategy uses set points of air enthalpy to take actions on the vent configurations and the heating system. Likewise, it uses set points of air VPD to control the fogging rate. These
Results and discussion
To find out about the capabilities of the new strategy to maintain the greenhouse climate around the set points, seven days were simulated. Four days corresponded to the first location while three were measured at the second one. Table 1 shows some descriptive values prevailing during such days. In general, SLP has a hotter and a drier climate than Chapingo. Thus, the strategy would normally have to perform more cooling in SLP than in Chapingo while more heating may be needed in Chapingo than
Conclusions
The performance of a strategy to control the greenhouse climate was tested for two locations with different climates using numerical simulations. The strategy equipped with cooling showed a good performance whenever cooling requirements were present. When conditions were cold and humid, the addition of a heating component to the strategy allowed achieving the desired set points. However, when the water vapor present in the air was excessive, the heating component of the strategy was not capable
CRediT authorship contribution statement
Federico Villarreal-Guerrero: Conceptualization, Methodology, Software, Writing - original draft. Alfredo Pinedo-Alvarez: Data curation, Writing - review & editing. Jorge Flores-Velázquez: Investigation, Visualization, Supervision, Writing - review & editing.
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
The authors deeply thank the ‘Universidad Autónoma Chapingo’ (UACh), for the help and the opportunity provided to access the data collected from the weather station installed at its facilities. Likewise, the authors thank the personnel at the 'Facultad de Agronomía y Veterinaria, UASLP', for allowing us to collect the weather data needed to perform the simulations for this location.
References (31)
- et al.
Dynamic modeling and simulation of greenhouse environments under several acenarios: a web based application
Comput. Electron. Agric.
(2010) - et al.
Climatic effects of two cooling systems in greenhouses in the Mediterranean area: external mobile shading and fog system
Biosyst. Eng.
(2011) - et al.
Greenhouse design and cooling technologies for sustainable food cultivation in hot climates: review of current practice and future status
Biosyst. Eng.
(2019) - et al.
Effect of vent openings and insect screens on greenhouse ventilation
Biosyst. Eng.
(2006) - et al.
Sonic anemometry to evaluate airflow characteristics and temperature distribution in empty Mediterranean greenhouses equipped with pad-fan and fog systems
Biosyst. Eng.
(2012) - et al.
Control of vapor pressure deficit (VPD) in greenhouse enhanced tomato growth and productivity during the winter season
Sci. Hort.
(2015) - et al.
A study of natural ventilation in an Almería-type greenhouse with insect screens by means of tri-sonic anemometry
Biosyst. Eng.
(2009) - et al.
Implementation of greenhouse climate control simulator based on dynamic model and vapor pressure deficit controller
Eng. Agric. Environ. Food
(2015) - et al.
Cooling strategies for greenhouses in summer: control of fogging by pulse width modulation
Biosyst. Eng.
(2008) - et al.
Evaluation of a fog cooling system for applying plant-protection products in a greenhouse tomato crop
Crop Prot.
(2013)
The Penman-Monteith evapotranspiration equation as an element in greenhouse ventilation design
Biosyst. Eng.
Survey of cooling technologies for worldwide agricultural greenhouse applications
Sol. Energy
Effect on energy use and greenhouse microclimate through fan motor control by variable frequency drives
Energy Convers. Manage.
Enhancing fog evaporation rate using an upward air stream to improve greenhouse cooling performance
Biosyst. Eng.
Optimal utilization of a boiler, combined heat and power installation, and heat buffers in horticultural greenhouses
Comput. Electron. Agric.
Cited by (15)
Enhancing crop yield in hydroponic greenhouses: Integrating latent heat storage and forced ventilation systems for improved thermal stratification
2023, Thermal Science and Engineering ProgressEffects of vent opening, wind speed, and crop height on microenvironment in three-span arched greenhouse under natural ventilation
2022, Computers and Electronics in AgricultureCitation Excerpt :Natural ventilation is an important factor affecting greenhouse production, which is greatly influenced by ventilation configuration. Appropriate ventilation mode is conducive to guiding external air flow into the room, forming a better airflow field, and improving the cooling and dehumidification effect of the greenhouse (Bournet et al., 2007; He et al., 2015b; McCartney et al., 2018; Villarreal-Guerrero et al., 2020). There are three main factors that impact natural ventilation: greenhouse factors (greenhouse type, size and internal crops), external factors (wind cases, solar radiation and local environment), and human factors (ventilation configuration, wet curtain and sunshade).
Feasibility study of wind turbine system integrated with insulated Greenhouse: Case study in Tunisia
2021, Sustainable Energy Technologies and AssessmentsCitation Excerpt :Besides, the energy optimization efficiency of greenhouses is significantly enhanced thanks to the control strategy, including PID, Fuzzy Logic Controller FLC, predictive, and optimal controls, etc. Villarreal-Guerrero [4] tested by simulations the performance of a variable frequency drive control, which is applied to the vents, heaters, and fogging systems to control the air energy and vapor pressure of greenhouse under different climates. The disadvantage of this command is that the set-points cannot be attained with a high level of ambient humidity.
Design and implementation of a power supervisory of a controlled greenhouse in the north of Tunisia
2021, Recent Advances in Renewable Energy Technologies: Volume 1Design and construction of bioclimatic wooden greenhouses 4: Architectural integration and quantitative analyses
2023, Design and Construction of Bioclimatic Wooden Greenhouses 4: Architectural Integration and Quantitative Analyses