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Total heat released by the heating system (Q t ) versus temperature difference between mean inside and outside air (T i-T o ). The slope gives the global heat loss coefficient (K, W m-2 K-1 ): open circles = unscreened greenhouse, solid circles = screened greenhouse. The straight lines were obtained by linear regression.
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Greenhouse microclimate, energy savings, and crop transpiration were investigated during winter in a glass-covered greenhouse cultivated with a rose crop and equipped with an aluminized thermal screen. Air temperature and humidity profiles were recorded at 0.3, 0.8, and 1.8 m heights inside the greenhouse. Net radiation over and under the rose crop...
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Strawberry cultivation depends on environmental factors, making its cultivation in the greenhouse a challenge in the winter. This study investigated the most appropriate greenhouse cladding material and thermal screen configuration for strawberry production in the winter by considering greenhouse air temperature, relative humidity (RH, vapor pressu...
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... Un método utilizado actualmente para reducir los requisitos de calefacción en invernaderos es la instalación de pantallas térmicas móviles (aluminizadas). El ahorro de energía va desde el 30% al 60% dependiendo del material de la pantalla, las condiciones climáticas exteriores y la estanqueidad del invernadero (Kittas et al., 2003a). ...
... El ahorro de energía debido a la pantalla se estimó en alrededor del 15%. Los resultados subrayan que el efecto básico de la pantalla aluminizada en el comportamiento de los cultivos fue la duplicación de la radiación neta absorbida por el dosel, con consecuencias positivas tanto en el aire como en su temperatura y, por lo tanto, en el crecimiento, desarrollo y condiciones sanitarias condiciones de las plantas de rosas (Kittas et al., 2003a). ...
Adéntrate en el intrigante universo de la producción vegetal intensiva con "Construcción y Climatización de Sistemas de Semi-Forzado y Forzado". Adalberto Hugo Di Benedetto y Danilo Carnelos, expertos en la materia, presentan un análisis profundo de los invernaderos, revelando estrategias para optimizar la tecnología y potenciar la eficiencia en la producción agrícola. Este libro no solo compila datos valiosos, sino que también sirve como guía práctica para comprender y aprovechar al máximo los invernaderos. Los autores exploran las complejidades de la producción vegetal intensiva, ofreciendo conocimientos tecnológicos y conceptuales esenciales, sin perderse en los matices teóricos. A medida que la demanda mundial de alimentos se dispara, los invernaderos emergen como una solución clave. El libro destaca cómo esta tecnología puede transformar la producción agrícola en Argentina, superando los desafíos económicos y ambientales. En un mundo que busca métodos sostenibles y eficientes, "Construcción y Climatización de Sistemas de Semi-Forzado y Forzado" ofrece perspectivas prácticas para diseñadores, proveedores y profesionales agrícolas. Descubre cómo los invernaderos pueden ser la respuesta al aumento de la demanda de alimentos y cómo Argentina, con el conocimiento adecuado, puede liderar la revolución de la producción vegetal intensiva. Este libro no solo informa; inspira a aquellos que buscan un futuro más productivo y sostenible en la agricultura.
... Teitel et al. [25] reported that around 40% of energy savings can be achieved by using aluminised curtains due to the lower heating demand at night. On the other hand, [26] examined the effect of an aluminised thermal curtain on the energy balance and microclimate in greenhouses and reported that the energy savings with an aluminised curtain is 15%. Thermal curtains provide additional thermal resistance by reducing heat transfer in the environment [27,28]. ...
... However, in a large commercial greenhouse where the ratio between the curtain area and the cover area is close to one, the contribution of the thermal curtain to energy savings will be more significant. Kittas et al. [26] reported energy savings of about 15% with a 65%-aluminised thermal screen and indicated that that was a rather low value that could be attributed to screen wear and the small size of their greenhouse. Accordingly, in this study, the ratio of curtain surface area to cover surface area is 0.35. ...
In order to reduce the impact of outdoor extreme weather events on crop production in winter, energy saving in greenhouses that are regularly heated is of great importance in reducing production costs and carbon footprints. For this purpose, the variations in indoor temperature, relative humidity and dew point temperature in the vertical direction (2 m, 4 m, 5.7 m) of thermal curtains in greenhouses were determined. In addition, depending on the fuel used, the curtains’ effects on heat energy consumption, heat transfer coefficient, carbon dioxide equivalents released to the atmosphere and fuel cost were investigated. To reach this goal, two greenhouses with the same structural features were designed with and without thermal curtains. As a result of the study, the indoor temperature and relative humidity values in the greenhouse with a thermal curtain increased by 1.3 °C and 10% compared to the greenhouse without a thermal curtain. Thermal curtains in the greenhouse significantly reduced fuel use (59.14–74.11 m3·night−1). Considering the heat energy consumption, the average heat energy consumption was 453.7 kWh·night−1 in the greenhouse with a curtain, while it was 568.6 kWh·night−1 in the greenhouse without a curtain. The average heat transfer coefficient (U) values were calculated at 2.87 W·m−2 °C with a thermal curtain and 3.63 W·m−2 °C without a thermal curtain greenhouse. In the greenhouse, closing the thermal curtain at night resulted in heat energy savings of about 21%, related to the decrease in U values. The use of a thermal curtain in the greenhouse reduced the amount of CO2 released to the atmosphere (116.6–146.1 kg·night−1) and fuel cost (USD 21.3–26.7·night−1). To conclude, extreme weather events in the outdoor environment adversely affect the plants grown in greenhouses where cultivation is performed out of season. A thermal curtain, used to reduce these adverse effects and the amount of energy consumed, is essential in improving indoor climate conditions, providing more economical greenhouse management and reducing the CO2 released into the atmosphere due to fuel use.
... Reflective thermal screens are widely used in GA for this purpose. Using reflective thermal screens, about 15% energy savings can be achieved [77] which could significantly enhance energy efficiency in GA. ...
Greenhouse aquaponics (GA) can serve as a sustainable food production method, potentially improving food and nutrition security in resource-constrained and hostile climatic zones such as Nepal's Himalayan region. Energy concerns, however, are one of the major barriers to GA adoption in this region. There is a lack of comprehensive energy demand analysis for GA operations. Therefore, in this study, an energy model for GA based on a quasi-static energy balancing technique was developed to estimate energy demand for the Himalayan region. The 2 study was conducted in 19 districts with varied GA dimensions, and a linear-model was fitted to predict yearly energy consumption. Thereafter, relations to estimate the capacity of PV systems for supplying the required energy were devised. Eventually, this study proposes potential energy management strategies to reduce dependency on a single energy source, reduce energy loss, and enhance resilience to energy concerns. Findings suggest, heating the GA is a major energy concern, accounting up to 85% of the overall energy requirement. Thermal evaluation reveals that conduction and convection losses are the most significant, contributing up to 29.5% of total energy consumption. Moreover, this study testifies the effectiveness of thermal energy storage devices in achieving significant energy savings. The proposed energy management strategies can serve as a decision-making tool for optimizing the design and operation of GA. Furthermore, this research serves as a blueprint for addressing aquaponics related energy challenges worldwide, especially in areas with similar climatic conditions, such as the Hindu Kush Himalaya (HKH) region.
... Crops in greenhouses mainly absorb thermal energy in the daytime and release thermal energy at night. Many researchers who study energy balances in greenhouses emphasize that a large portion of radiation that penetrates the cladding is used for transpiration by crops [10,[21][22][23][24]. The energy loads of a greenhouse can be defined as the required energy for maintaining the internal air temperature against heat transfer via conduction, radiation, and convection. ...
To utilize the energy in the thermal effluent, many attempts have been made to use the thermal effluent for agricultural facilities such as greenhouses. As the first step, it is important to estimate the energy loads of the greenhouse for deciding a suitable scale for the heating and cooling. Then, it is available to estimate the energy efficiency of the thermal effluent heat pump system installed in the greenhouse. Therefore, the main objectives of this study were to design and validate an energy model of the experimental greenhouse growing Irwin mangoes and to estimate the annual and maximum energy loads using building energy simulation (BES). Field experiments were conducted in a multi-span plastic-covered greenhouse growing Irwin mangoes to measure the internal environments of the greenhouse and crop characteristics. The energy exchange model of the greenhouse considering crop, cladding, heat pump was developed using BES. The BES model was validated using the data measured at field experiments. The designed model was found to be able to provide satisfactory estimates of the changes of the internal air temperature of the greenhouse (R² = 0.94 and d = 0.97). The hourly energy loads computed by using the validated model were used to analyse the periodic and maximum energy loads according to the growth stage of the cultivated crops. Finally, the energy costs were compared according to the type of energy source based on the calculated annual energy loads. The average energy cost when using the thermal effluent—heat pump system was found to be 68.21% lower than that when a kerosene boiler was used.
... López et al. [38], who used a single air heater in a 20 * 24 m 3-span arched roof greenhouse, reported a ∆ value of 11.2 ℃. Kittas et al. [46] recorded a ∆ value of 10℃ in a 1-span 31 * 6.5 m Venlo-type pipeheated greenhouse. Temperature contours ( Figure 13) revealed homogeneity of temperature within the greenhouse domain with slightly higher temperature concentration patches around the FCUs and low temperatures at the regions adjacent to the boundaries. ...
... López et al. [38], who used a single air heater in a 20 × 24 m 2 3-span arched roof greenhouse, reported a ∆T value of 11.2°C. Kittas et al. [46] recorded a ∆T value of 10°C in a 1-span 31 × 6.5 m 2 Venlo-type pipe-heated greenhouse. Temperature contours ( Figure 13) revealed homogeneity of temperature within the greenhouse domain with slightly higher temperature concentration patches around the FCUs and low temperatures at the regions adjacent to the boundaries. ...
... López et al. [38], who used a single air heater in a 20 * 24 m 3-span arched roof greenhouse, reported a ∆ value of 11.2 ℃. Kittas et al. [46] recorded a ∆ value of 10℃ in a 1-span 31 * 6.5 m Venlo-type pipeheated greenhouse. ...
Accurate evaluation of microclimate conditions in a greenhouse can assist producers to manage crop production and designers to optimize climate control systems. An assessment of the variable thermo-environmental behavior of a heated Venlo-type greenhouse under the influence of naturally changing climate conditions in the Yangtze River Delta region was undertaken. A three-dimensional transient computational fluid dynamics (CFD) model was developed to analyze the airflow pattern and dynamic distribution of temperature and humidity inside the greenhouse. Validation of the numerical model showed a satisfactory agreement between measured and simulated values of air velocity, temperature, and absolute humidity, with mean hourly air temperature mean absolute error (MAE) and root mean square error (RMSE) values of 7.7% and 7.9%, respectively, and mean hourly air humidity MAE and RMSE values of 16.18% and 16.42%, respectively. Simulation results demonstrated that the airflow pattern shaped the distribution of temperature and absolute humidity, and homogeneity of both variables was prevalent inside the greenhouse. These results could be adopted by growers and designers in the Yangtze River Delta region and other sub-tropical climatic regions to improve crop production and optimize climate control systems.
... Other studies conducted by Park et al. Kim et al. and Kittas et al. [6][7][8] experimentally measured the greenhouse inside temperature with and without thermal screens and calculated the heat loss of the greenhouse to estimate energy savings. Geoola et al. [9] and Rasheed et al. [10] measured the overall heat transfer coefficients of the greenhouse screens using the laboratory hot box method. ...
In this study, we propose a building energy simulation model of a multi-span greenhouse using a transient system simulation program to simulate greenhouse microenvironments. The proposed model allows daily and seasonal control of screens, roof vents, and heating setpoints according to crop needs. The proposed model was used to investigate the effect of different thermal screens, natural ventilation, and heating setpoint controls on annual and maximum heating loads of a greenhouse. The experiments and winter season weather conditions of greenhouses in Taean Gun (latitude 36.88° N, longitude 126.24° E, elevation 45 m) Chungcheongnam-do, South Korea was used for validation of our model. Nash–Sutcliffe efficiency coefficients of 0.87 and 0.71 showed good correlation between the computed and experimental results; thus, the proposed model is appropriate for performing greenhouse thermal simulations. The results showed that the heating loads of the triple-layered screen were 70% and 40% lower than that of the single-screen and double-screen greenhouses, respectively. Moreover, the maximum heating loads without a screen and for single-, double-, and the triple-layered screens were 0.65, 0.46, 0.41, and 0.34 MJ m⁻², respectively. The analysis of different screens showed that Ph-77 (shading screen) combined with Ph-super (thermal screen) had the least heating requirements. The heating setpoint analysis predicted that using the designed day- and nighttime heating control setpoints can result in 3%, 15%, 14%, 15%, and 40% less heating load than when using the fixed value temperature control for November, December, January, February, and March, respectively.
... This study was conducted to check the feasibility of the earth-to-air heat exchanger without analyzing the greenhouse thermal screen qualitative effect. The studies [9][10][11][12] experimentally measured the internal temperature of the greenhouses with and without thermal screen to calculate energy saving potential of the screen used. Taki et al. [13] modeled different greenhouse shapes with thermal screen and calculated the temperature inside the greenhouse and energy consumption. ...
In this work, we proposed a Building Energy Simulation (BES) dynamic climatic model of greenhouses by utilizing Transient System Simulation (TRNSYS 18) software to study the effect of use of different thermal screen materials and control strategies of thermal screens on heat energy requirement of greenhouses. Thermal properties of the most common greenhouse thermal screens were measured and used in the BES model. Nash-Sutcliffe efficiency coefficients of 0.84 and 0.78 showed good agreement between the computed and experimental results, thus the proposed model appears to be appropriate for performing greenhouse thermal simulations. The proposed model was used to evaluate the effects of different thermal screens including; Polyester, Luxous, Tempa, and Multi-layers, as well as to evaluate control strategies of greenhouse thermal screens, subjected to Daegu city, (latitude 35.53 °N, longitude 128.36 °E) South Korea winter season weather conditions. Obtained results show that the heating requirement of greenhouses with multi-layer night thermal screens was 20%, 5.4%, and 13.5%, less than the Polyester, Luxous, and Tempa screens respectively. Thus, our experiments confirm that the use of multi-layered thermal screen can reduce greenhouse heat energy requirement. Furthermore, screen-control with outside solar radiation at an optimum setpoint of 60 W·m −2 significantly influences the greenhouse's energy conservation capacity, as it exhibited 699.5 MJ · m −2 , the least energy demand of all strategies tested. Moreover, the proposed model allows dynamic simulation of greenhouse systems and enables researchers and farmers to evaluate different screens and screen control strategies that suit their investment capabilities and local weather conditions.
... The authors of [7] note that for microclimate control purposes at the canopy level, it may be necessary to consider the different layers of the crop, as there might be high temperature, stomatal conductance, and transpiration rate differences between the different crop layers. Furthermore, the author of [11] noted that under the big leaf assumption, the averaging processes of the climate parameters in the greenhouse canopies may produce a mean air temperature or velocity within the canopy, which may be significantly different from that above the canopy [39][40][41]. In the case that large temperature differences do exist between the microclimate at the level of the crop and above the crop, the big leaf approach may introduce some errors into the estimation of the stomatal and aerodynamic conductances. ...
Models for the evapotranspiration of greenhouse crops are needed both for accurate irrigation and for the simulation or management of the greenhouse climate. For this purpose, several evapotranspiration models have been developed and presented, all based on the Penman–Monteith approach, the “big-leaf” model. So, on the one hand, relatively simple models have been developed for irrigation scheduling purposes, and on the other, “knowledge–mechanistic” models have been developed for climate control purposes. These models differ in the amount of detail about variables, such as stomatal and aerodynamic conductance. The aim of this review paper is to present the variables and parameters affecting greenhouse crop transpiration, and to analyze and discuss the existing models for its simulation. The common sub-models used for the simulation of crop transpiration in greenhouses (aerodynamic and stomatal conductances, and intercepted radiation) are evaluated. The worth of the multilayer models for the simulation of the mass and energy exchanges between crops and air are also analyzed and discussed. Following the presentation of the different models and approaches, it is obvious that the different applications for which these models have been developed entail varying requirements to the models, so that they cannot always be compared. Models developed in different locations (high–low latitudes or for closed or highly ventilated greenhouses) are discussed, and their sensitivity to different parameters is presented.
... In order to save energy in cold-weather regions, a greenhouse covering material should be opaque to IR radiation in the range 7000-14000 nm. Further energy-saving measures can also be attained by using different types of thermal screens (Fernandez Rodriguez et al., 2003;Kittas et al., 2003). Heat is lost from inside a greenhouse through the cladding material by radiation, convection and conduction. ...
This article reviews issues and opportunities related to greenhouse and screenhouse cover materials and presents industry perspectives. A literature survey shows that various greenhouse cover materials (glass, rigid and flexible plastic sheets and screens) are used in different regions of the world. These materials differ in their physical, chemical, mechanical and radiometric properties. Selection of the type of cover material by growers depends on many factors and is mainly affected by local tradition, which is related to the geographical climate, solar radiation intensity, crop value, cost of the cover material and its life span. Over the years, cover materials have been improved to enable higher light transmittance, a change in the characteristics of the transmitted light, reduced heat loss and hence higher energy saving and prevention of condensation and droplet formation on the inner surface of the cover. Furthermore, properties of cover materials have been changed to enable reductions in insect invasion into greenhouses/screenhouses on the one hand and to improve orientation of beneficial insects in the house on the other. Nowadays, different glass surface treatments or suitable cover materials, and sometimes a combination of the two, are in the vicinity to be used in order to increase the uniformity of the greenhouse climate and enhance plant growth, for example, diffused glass that scatters the light. Next to that, micro structures are combined with nanostructures, such as anti-reflection treatments (AR-glass), and also hydrophilic film with anti-fog additives, which can be used in order to improve light transmission. Recently, solar cells were incorporated into cover materials to generate electricity and semi-transparent plastic sheets that can generate electricity were developed and tested. In addition to the topics mentioned above, this article considers the deterioration of cover materials as a result of different environmental effects. It also briefly presents methods to measure properties of cover materials.
... Here, a box made of specific test materials is provided the same heat energy, and the temperature inside the box is then measured for comparison. Moreover, some experimental studies (Kittas et al., 2003;Teitel et al., 2009;Park et al., 2015) have analyzed the thermal screen materials by observing the internal temperature of a greenhouse with and without the screens. Many types of thermal screens are available in the market, and researchers have estimated their efficiencies using different methods. ...
In winter, thermal screens are widely used to reduce heat loss from greenhouse to save energy. Unfortunately , not much data are available to the farmer to compare thermal screens while selecting the one that meets their specific requirements. Thus, there is a need to investigate the thermal performance of thermal screens. To address this issue, the Building Energy Simulation (BES) model of a hot box was used to calculate the overall heat transfer coefficient (U-value) of the thermal screens. To validate the model, computed and experimental U-values of single-and double-layered polyethylene (PE) material were compared. This validated model was used to predict the U-values of the selected thermal screens under defined weather conditions. We quantified the U-values of each selected material and significant changes in their U-values were noted in response to different weather conditions. Notably, the thermal properties of the tested screens were taken from the previous literature to calculate U-values using the BES model. The U-values of the thermal screens can help researchers and farmers evaluate their screens and make pre-design decisions that suit their investment capabilities.
