Academic literature on the topic 'Grenhouse'

AbstractGlobal suface temperature has showed a rise trend in the last 150 years. This has been mainly attributed to the anthropogenic induced grenhouse gases emissions. However, the role of natural processes is not completely understood and should not be underestimated. In this work, we compare the long term variability of solar activity (as quantified by the sunspot number) with several surface temperature series from different geographical regions (global, hemispheric and latitudinal ranges). The interval of analysis is 1880-2005. The data are analyzed with wavelet multiresolution technique. It has been found that the solar activity long term trend has a maximum around 1970, while air surface temperature series showed maximum (still rising) at 2005. There are differences in the long term trend for Northern and Southern hemispheres. These differences and the relation with solar activity are discussed in this work.

Este trabajo analiza el clima nocturno del invernadero. EL objeto del estudio es el invernadero de plástico sin calefacción, cuyo clima se estudia utilizando modelos CFD, modelos basados en los balance de energía (ES) y s datos experimentales. El fin es doble, por un lado se trata de analizar y comprender el clima nocturno del invernadero, y proponer soluciones a los problemas relacionados con las altas tasas de humedad. Por otro lado se investigan nuevos métodos de simulación del clima del invernadero, métodos basados en el uso conjunto o acoplamiento de modelos CFD y ES , y también basados en la técnica de optimización. El Capitulo 1 introduce el contexto general y los objetivos que plantea el trabajo. El Capitulo 2 estudia el clima nocturno en un invernadero de capa sencilla. Para ello desarrolla un modelo CFD que incluye una UDF (User Define Function) para calcular la tasa de condensación. Una vez validado el modelo se analiza el comportamiento del invernadero bajo distintas condiciones de contorno.. El Capitulo 3 analiza una solución para combatir las bajas temperaturas nocturnas, la pantalla térmica. Los efectos de la pantalla se analizan mediante el uso del CFD. Se lleva a cabo una comparación completa entre el invernadero de capa sencilla y el invernadero con pantalla. El capitulo proporciona información detallada sobre el clima del invernadero y presenta un estudio paramétrico del efecto de la temperatura equivalente del cielo y la cesión de calor desde el suelo en el clima del invernadero con pantalla térmica. EL Capitulo 4 presenta un nuevo método para optimizar el diseño del invernadero. El método se basa en el acoplamiento de dos algoritmos de optimización que operan con el modelo ES. A su vez el modelo ES está conectado con el modelo CFD. El objetivo es doble, por un lado introducir una nueva manera de optimizar el diseño del invernadero, y por el otro lado tratar de resolver uno de los problemas evidenciados en el capítulo 2. El resultado muestra que un material de cubierta de alto poder de reflexión del infrarrojo lejano aportaría mejorías relevantes al clima del invernadero. El Capitulo 5 presenta un modelo acoplado para el estudio del clima del invernadero. EL CFD se utiliza para proporcionar las tasas de ventilación y los coeficientes convectivos al modelo ES. Esta técnica se utiliza para estudiar los efectos de diferentes estrategias de ventilación sobre el régimen de humedad con diferentes condiciones externas. Finalmente, el Capitulo 6 resume las conclusiones y propone algunos temas para futuras investigaciones
This work studied night-time greenhouse climate. The focus was on unheated plastic greenhouses and analyses were carried out using CFD models, Energy balance (ES) models and experimental data. The aims were twofold: on the one hand, it was intended to analyse and understand night-time greenhouse climate and propose solutions to the high-humidity issue. On the other hand, the aim was to investigate novel simulation approaches based on the coupling of CFD and ES models as well as the use of optimisation algorithms to study greenhouse climate. Chapter 1 is an introductory chapter which includes the general context and overall research objectives. Chapter 2 studies night-time climate in single-layer greenhouses by means of CFD. The model is validated and condensation User Defined Function (UDF) is introduced which accounted for the condensation rate found on the inner face of the greenhouse cover. Chapter 3 studies a commonly used solution to the issue of low night-time temperature. A thermal screen was analysed by means of CFD simulations. A thorough comparison was made between single-layer and screened greenhouses and detailed information was provided in order to build a framework for taking decisions as to whether to use a screen or not. Chapter 4 introduces a novel approach to optimizing greenhouse design; the approach relies on two optimization algorithms linked to an ES model which was coupled to a CFD model. The aim of the study was twofold: on the one hand to introduce a method offering a general approach for optimizing greenhouse design and on the other, to attempt to solve one of the issues highlighted in Chapter 2. It was shown that using a highly reflective covering material would have a theoretically significant impact on greenhouse performance. Chapter 5 introduces a coupled model for studying greenhouse climate. The CFD was used to provide the ventilation rate and convective coefficients for the ES model. This approach was applied to study the effects of different ventilation strategies on humidity under different outside air conditions. Finally Chapter 6 summarizes the conclusions and proposes themes for future research.

L’augmentation des températures et des risques de sécheresses du fait des changements climatiques impose une adaptation rapide des pratiques culturales afin de protéger les cultures face à l’augmentation des stress thermiques et hydriques. De plus, limiter l’émission de gaz à effet de serre à l’origine de ces changements climatiques nécessite le développement d’énergies renouvelables, mais ce développement se heurte dans certains pays à des conflits d’usage, alors qu’une part importante du territoire est déjà dédiée à l’agriculture. L’agrivoltaïsme consiste à installer des panneaux photovoltaïques sur des terres cultivées, ce qui permet de produire une électricité renouvelable tout en protégeant les cultures face aux canicules et aux sécheresses, et ainsi de répondre à ces deux problématiques. Cette pratique pourrait être particulièrement utile pour les serres de tomate dans lesquelles l’ombrage est déjà utilisé pour protéger les plantes, et où une structure capable de supporter les panneaux est déjà en place. L’utilisation de panneaux mobiles (agrivoltaïsme dynamique) permet d’ajuster l’ombrage aux besoins de la plante. Cependant, cette pratique provoque un ombrage temporaire dont l’effet sur les cultures n’est pas encore suffisamment bien compris pour optimiser leur pilotage et maximiser les rendements et la qualité de la culture. Cette thèse examine l'impact de l'ombrage sur la croissance végétative, la physiologie, le rendement et la qualité des plants de tomates. Elle étudie les effets de l'ombrage appliqué à différentes échelles spatiales et temporelles, allant de l'organe à la plante et variant en intensité sur une base horaire ou saisonnière. Elle s’appuie sur deux expérimentations réalisées sous serre agrivoltaïque en 2021 et 2022 à Alénya (Pyrénées-Orientales, France). Différentes modalités d’ombrage ont été étudiées, selon le moment de la journée où l’ombrage a été appliqué sur les plantes (en fin de matinée, en début de matinée et en fin d’après-midi, et en début d’après-midi) et comparées à une modalité témoin réalisée dans une serre identique sans panneaux photovoltaïques. Les données expérimentales ont été utilisées pour adapter et calibrer un modèle structure-fonction de la tomate (FSPM) développé dans l’unité PSH, ce qui a permis d'analyser l’effet de l’ombrage à l’échelle de la plante entière
Due to climate change, farming practices must be adapted to protect crops from increased heat and water stress. Additionally, limiting greenhouse gas emissions requires the development of renewable energies. However, in some countries, conflicts of use arise when a large part of the land is already dedicated to agriculture. Agrivoltaics is the practice of installing photovoltaic panels on cultivated land to produce renewable electricity while also protecting crops from heatwaves and drought, and thus it addresses both these issues. This practice could be particularly useful for tomato greenhouses, where shading is already used to protect the plants and where a structure capable of supporting the panels is already in place. The use of mobile panels (dynamic agrivoltaics) makes it possible to adjust shading to the needs of the plant. However, this practice causes temporary shading, the effect of which on crops is not yet fully understood, making it difficult to optimise their stirring policy and maximise crop yields and quality. This thesis examines the impact of shading on the vegetative growth, physiology, yield, andquality of tomato plant. It studies the effects of shading applied at different spatial and temporal scales, ranging from the organ to the plant and varying in intensity on an hourly or seasonal basis. The experiments were conducted in an agrivoltaic greenhouse in Alénya (Pyrénées-Orientales, France) in 2021 and 2022. Various shading treatments were investigated, depending on the daily pattern of plant shading (late morning, early morning, late afternoon, and afternoon) compared to a control grown in a similar greenhouse without photovoltaic panels. The experimental data were used to adapt and calibrate a tomato structure-function model (FSPM) developed in the PSH laboratory, which made it possible to analyse the effect of shading at the whole plant level

MENVM
Department of Geography and Geo-Information Sciences
Fuel wood is regarded as a major source of energy around the world, particularly in developing nations. Most rural communities around the world, consider forests as the repository of stored energy. The high dependence on forests as a source of fuel wood has a major impact on vegetation because trees take a long time to regenerate to maturity, hence high dependence leads to deforestation. Fuel wood is used for household needs, such as cooking and heating and its uses contribute to the emissions of Green House Gases (GHG) such as CO2, CH4, and Black Carbon amongst others. The study assesses household energy use, the amount of carbon dioxide emitted from the combustion of fuel wood, the extent of de-vegetation and strategies to ensure sustainable energy provisions in the case study areas. Primary and secondary methods were used to collect data. The data were analysed using Statistical Package for the Social Sciences (SPSS 21.0), showing the frequency distribution, measures of central tendency and chi-square to determine the extent of fuel wood used in relation to electricity. The primary data were collected through personal observations, field surveys, interviews and questionnaires, while secondary data included the 2011 South Africa Census data and remote sensing images, which with the aid of GIS, were used in mapping the vegetation change.