Development of a single energy balance model for prediction of temperatures inside a naturally ventilated greenhouse with polypropylene soil mulch

In this study, a semi-empirical dynamic model of energy balance was developed to predict temperatures (air, plants, greenhouse cover and soil) in a naturally ventilated greenhouse with a polypropylene mulch covering the soil in a Mediterranean climate. The model was validated using experimental data of 5 non-successive periods of 5 days throughout the crop season in the province of Almería (Spain). During the evaluation period, the transmissivity of the cover ranged between 0.44 and 0.80 depending on whitening, and the leaf area index of the tomato crops growing inside the greenhouse varied from LAI = 0.74 to 1.30 m2 m−2. The model mainly consists of a system of 6 non-linear differential equations of energy conservation at inside air, greenhouse plastic cover, polypropylene mulch and three layers of soil. We used multiple linear regressions to estimate the crop temperature in a simple way that allows a reduction in the number of parameters required as input. The main components of the energy balance in warm climate conditions are the solar radiation, the heat exchanged by natural ventilation and the heat stored in the soil. To improve the estimation of the heat exchanged by ventilation, different discharge coefficients were used for roof CdVR and side openings CdVS. Both coefficients changed throughout the time as a function of the height and opening angle of the windows and of the air velocity across the insect-proof screens. The model also used different wind effect coefficients Cw for Northeast or Southwest winds, to take into account the different obstacles (a neighbouring greenhouse at the south and a warehouse at the north). A linear regression of the wind direction angle θw was used as correction function for the volumetric ventilation flux G. The results showed that the accuracy of the model is affected mainly by errors in the cover transmissivity on cloudy days (when diffuse radiation prevails) and errors in the temperature of air exiting the greenhouse on windy days (when hot air stagnated near roof openings, that were closed by the climate controller to avoid wind damage). In general, the results of validation comparing calculated values with those measured on 25 days (with relative root mean square errors below 10%), show sufficient accuracy for the model to be used to estimate air, crop, plastic cover, polypropylene mulch and soil temperatures inside the greenhouse, and as a design tool to optimise the ventilation system characteristics and control settings

Effects of grennhouse lime shading on filtering the solar radiation

Protecting crops under a greenhouse allows their optimal management all over the year. Mostly during summer, in order to limit the indoor temperature and create suitable internal growing conditions, a common traditional solution is whitening the external side of the cladding material with slaked lime (calcium hydroxide– Ca(OH)2). The benefits of whitewashing reported in the literature confirm that it has positive effects both on the microclimate and on the development of crops. This paper shows the results of a research, performed by using spectrophotometers in the Laboratory for Testing Materials of the University of Basilicata (Italy), aimed to analyse different types of calcium hydroxide solutions. The analysis verified the variation of radiometric properties and shading effect. The whitening concentration was a fixed dose of simple calcium hydroxide, diluted in two different water concentrations, then painted on an EVAC plastic film. Moreover, an un-painted transparent EVAC plastic film was considered as a reference. The radiometric measurements on the samples were carried out to measure transmittance, reflectance and absorbance on all wavelengths of the Photosynthetically Active Radiation (PAR). The results have given information on the effect of different dilutions of slaked lime on the selective filtering of the solar radiation. These conclusions may be useful to compare similar results with more recent solutions for greenhouse shading, such as the use of plastic nets

Application of Artificial Intelligence for Modeling the Internal Environment Condition of Polyethylene Greenhouses

Accurate temperature prediction and modeling are critical for effective management of agricultural greenhouses. By optimizing control and minimizing energy waste, farmers can maintain optimal environmental conditions, leading to improved crop yields and reduced financial losses. In this study, multiple models, including Multiple Linear Regression (MLR), Radial Basis Function (RBF), and Support Vector Machine (SVM), were compared to predict greenhouse air temperature. External parameters, such as air temperature (Tout), relative humidity (Hout), wind speed (W), and solar radiation (S), were used as inputs for these models, and the output was the inside temperature. The results showed that the RBF model with the LM (Levenberg–Marquardt) learning algorithm outperformed the other models, achieving the lowest error and the highest coefficient of determination (R2) value. The RBF model produced RMSE, MAPE, and R2 values of 1.32 °C, 3.23%, and 0.931, respectively. These results demonstrate that the RBF model with the LM learning algorithm can reliably predict greenhouse air temperatures for the next two hours. The ANN model can be applied to optimize time management and reduce energy losses, improving the overall efficiency of greenhouse operations

Energy performance and climate control in mechanically ventilated greenhouses: A dynamic modelling-based assessment and investigation

Controlled environment agriculture in greenhouse is a promising solution for meeting the increasing food demand of world population. The accurate control of the indoor environmental conditions proper of greenhouses enhances high crop productivity but, contemporarily, it entails considerable energy consumption due to the adoption of mechanical systems. This work presents a new modelling approach for estimating the energy consumption for climate control of mechanically ventilated greenhouses. The novelty of the proposed energy model lies in its integrated approach in simulating the greenhouse dynamics, considering the dynamic thermal and hygric behaviour of the building and the dynamic response of the cultivated crops to the variation of the solar radiation. The presented model simulates the operation of the systems and the energy performance, considering also the variable angular speed fans that are a new promising energy-efficient technology for this productive sector. The main outputs of the model are the hourly thermal and electrical energy use for climate control and the main indoor environmental conditions. The presented modelling approach was validated against a dataset acquired in a case study of a new fully mechanically controlled greenhouse during a long-term monitoring campaign. The present work contributes to increase the knowledge about the dynamics and the energy consumption of greenhouses, and it can be a valuable decision support tool for industry, farmers, and researchers to properly address an energy efficiency optimisation in mechanically ventilated greenhouses to reach the overall objective of decreasing the rising energy consumption of the agricultural sector

Effects of Cover Whitening Concentrations on the Microclimate and on the Development and Yield of Tomato (Lycopersicon esculentum Mill.) Inside Mediterranean Greenhouses

This work analyzes the influence of whitening a greenhouse roof on the microclimate and yield of a tomato crop. In the west sectors of two multi-span greenhouses, a whitening concentration of 0.250 kg L−1 was used as a control. In an autumn–winter cycle, a lower (0.125 kg L−1) and an increased (0.500 kg L−1) concentration were used in the east sectors of greenhouses 1 and 2. In a spring–summer cycle, the whitening concentrations in the east were varied depending on outside temperature. The effect of whitening on photosynthetic activity, production, plants’ morphological parameters, and the quality of the fruits were also analyzed. To evaluate the effect on microclimate, solar and photosynthetically active (PAR) radiations, air and soil temperatures, and heat flux in the soil were measured in greenhouse 1. Results show that excessive whitening leads to reductions of inside PAR radiation that decreases photosynthesis and crop yield. A whitening concentration of 0.500 kg L−1 is proposed at the beginning of the autumn–winter crop cycle, washing the cover when inside temperature drops to 35 °C. At the end of the spring–summer cycle, a concentration of 0.125 kg L−1 is recommended when inside temperature increases to 35 °C

Feasibility of a solar panel-powered liquid desiccant cooling system for greenhouses

To investigate the technical feasibility of a novel cooling system for commercial greenhouses, knowledge of the state of the art in greenhouse cooling is required. An extensive literature review was carried out that highlighted the physical processes of greenhouse cooling and showed the limitations of the conventional technology. The proposed cooling system utilises liquid desiccant technology; hence knowledge of liquid desiccant cooling is also a prerequisite before designing such a system. Extensive literature reviews on solar liquid desiccant regenerators and desiccators, which are essential parts of liquid desiccant cooling systems, were carried out to identify their advantages and disadvantages. In response to the findings, a regenerator and a desiccator were designed and constructed in lab. An important factor of liquid desiccant cooling is the choice of liquid desiccant itself. The hygroscopicity of the liquid desiccant affects the performance of the system. Bitterns, which are magnesium-rich brines derived from seawater, are proposed as an alternative liquid desiccant for cooling greenhouses. A thorough experimental and theoretical study was carried out in order to determine the properties of concentrated bitterns. It was concluded that their properties resemble pure magnesium chloride solutions. Therefore, magnesium chloride solution was used in laboratory experiments to assess the performance of the regenerator and the desiccator. To predict the whole system performance, the physical processes of heat and mass transfer were modelled using gPROMS® advanced process modelling software. The model was validated against the experimental results. Consequently it was used to model a commercials-scale greenhouse in several hot coastal areas in the tropics and sub-tropics. These case studies show that the system, when compared to evaporative cooling, achieves 3oC-5.6oC temperature drop inside the greenhouse in hot and humid places (RH>70%) and 2oC-4oC temperature drop in hot and dry places (50%<RH< 65%)

Research Trends on Greenhouse Engineering Using a Science Mapping Approach

Horticultural protected cultivation has spread throughout the world as it has proven to be extremely effective. In recent years, the greenhouse engineering research field has become one of the main research topics within greenhouse farming. The main objectives of the current study were to identify the major research topics and their trends during the last four decades by analyzing the co-occurrence network of keywords associated with greenhouse engineering publications. A total of 3804 pertinent documents published, in 1981-2021, were analyzed and discussed. China, the United States, Spain, Italy and the Netherlands have been the most active countries with more than 36% of the relevant literature. The keyword cluster analysis suggested the presence of five principal research topics: energy management and storage; monitoring and control of greenhouse climate parameters; automation of greenhouse operations through the internet of things (IoT) and wireless sensor network (WSN) applications; greenhouse covering materials and microclimate optimization in relation to plant growth; structural and functional design for improving greenhouse stability, ventilation and microclimate. Recent research trends are focused on real-time monitoring and automatic control systems based on the IoT and WSN technologies, multi-objective optimization approaches for greenhouse climate control, efficient artificial lighting and sustainable greenhouse crop cultivation using renewable energy

Proceedings of the European Conference on Agricultural Engineering AgEng2021

This proceedings book results from the AgEng2021 Agricultural Engineering Conference under auspices of the European Society of Agricultural Engineers, held in an online format based on the University of Évora, Portugal, from 4 to 8 July 2021. This book contains the full papers of a selection of abstracts that were the base for the oral presentations and posters presented at the conference. Presentations were distributed in eleven thematic areas: Artificial Intelligence, data processing and management; Automation, robotics and sensor technology; Circular Economy; Education and Rural development; Energy and bioenergy; Integrated and sustainable Farming systems; New application technologies and mechanisation; Post-harvest technologies; Smart farming / Precision agriculture; Soil, land and water engineering; Sustainable production in Farm buildings

Análisis sobre la actividad científica referente a las estrategias de climatización pasiva usada en invernaderos: Parte 2: análisis técnico

Agricultural production of greenhouse crops is becoming increasingly important worldwide, and this is no exception in Latin America and the Caribbean, where every year the areas under this cultivation system grow in surface area and crop diversity. Likewise, the effects of climate change or of some climate variability phenomena, cause that in the interior of the main greenhouse structures implemented in some occasions, inadequate microclimate conditions are generated for the growth and development of plants, affecting crop yields and therefore the sustainability of this type of food production systems. It is also important to mention that in some underdeveloped countries, due to local economic conditions, it is not possible to implement active climate control systems. Likewise, in developed countries where this practice has been established for more than 4 decades, there is a permanent interest in reducing the use of fossil fuels associated with climate control practices due to the economic and environmental cost. Therefore, in recent years, technological innovations that allow the implementation of passive climate control systems for greenhouse climate control have gained importance. In this work, a compilation of more than 350 studies developed worldwide since 2005 was carried out, from each of these works the relevant technical information was rescued and analyzed. The results found allowed us to identify that the use of these systems can increase the production of vegetables such as tomatoes by more than 35% and reduce the use of fossil fuels by more than 50%, which generates lower economic and environmental costs, contributing to the sustainability of food production.La producción agrícola en cultivos bajo invernadero cobra cada mas relevancia a nivel mundial, esto no es una excepción en Latinoamérica y el Caribe, donde cada año las áreas bajo este sistema de cultivo, crecen en superficie y en diversidad de cultivos. Así mismo los efectos del cambio climático o de algunos fenómenos de variabilidad climática, propician que en el interior de las principales estructuras de invernadero implementadas en algunas ocasiones se generen condiciones de microclima inadecuadas para el crecimiento y desarrollo de las plantas, afectado los rendimientos de los cultivos y por ende en la sostenibilidad de este tipo de sistemas de producción de alimentos. También es importante mencionar que, en algunos países subdesarrollados debido a la condición económica local, no es posible la implementación de sistemas de climatización activa, así mismo en países desarrollados donde esta practica ya esta establecida hace mas de 4 décadas, existe un interés permanente de reducir el uso de combustibles fósiles asociados a prácticas de climatización debido al costo económico y ambiental. Por lo tanto, en los últimos años han cobrado importancia las innovaciones tecnológicas que permiten la implementación de sistemas de climatización pasiva para la adecuación microclimatica de invernaderos. En este trabajo se realizó una recopilación de mas de 350 estudios desarrollados a nivel mundial desde el año 2005, de cado uno de estos trabajos se rescató y analizo la información técnica relevante. Los resultados encontrados permitieron identificar que el uso de estos sistemas puede aumentar la producción de hortalizas como el tomate en mas de un 35% y permiten reducir el uso de combustibles fósiles en mas del 50%, lo cual genera menores costos económico y ambientales, contribuyendo como tala a la sostenibilidad de la producción de alimentos

Greenhouse Management for Better Vegetable Quality, Higher Nutrient Use Efficiency and Healthier Soil

Greenhouse cultivation provides an artificially controlled environment for the year-round production of vegetables, and has played an increasingly important role in agriculture production systems in recent decades. Recent works have shown that improving greenhouse conditions can promote the growth of vegetables and enhance the uptake of nutrients, leading to better vegetable quality. Meanwhile, greenhouse conditions not only directly influence soil nutrient cycling processes and properties, but also indirectly affect them by regulating vegetable root growth and plant–soil interactions. This Special Issue features twelve original research articles that deal with the effects of novel greenhouse practices and strategies on the yield and quality of horticulture crops, as well as greenhouse soil properties. Among these publications, three studied the effects of fertilizers, including organic and macro- and micro-nutrient fertilizers, on the growth and nutrient uptake of vegetables. Two articles described the effects of water and nutrient supply using irrigation or hydroponic supplying systems on the yield and quality of vegetables. Four articles investigated the effects of environmental conditions (mainly light and temperature) on the growth and quality of vegetables. In terms of degenerated greenhouse soil, three articles showed how reductive soil disinfestation decreased soil salinity, improved soil quality, and inactivated soil-borne pathogens