Simple Model for the Theoretical Survey of the Green Roof Thermal Behavior

A green roof is an option for the improvement of a building thermal comfort. The objective of this work is to compare respective behaviors of a green roof and a concrete watertight roof vis-à-vis external requests in wet tropical zones. The canopy being considered as uniform, the electric analogy method was used to establish the mathematical models associated to both studied systems of roof. Based on these models, a Matlab computing code was worked out. It ensues from simulation results that in diurnal period, the green roof concrete support top face temperature is lower than that of the concrete watertight roof top face, whereas in night-period the opposite occurs. These results which highlight the energy benefit of the green roof are in agreement with the experimental measurement results obtained at the Laboratory PIMENT of the University of La Reunion. Besides, results of sensitivity analysis done with Fourier Amplitude Sensitivity Test enabled to identify a certain number of the most influential parameters of the proposed model. The above mentioned computing code also forms a help tool for the choice of plants to be experimented on the green roof

Modélisation des dispositifs de revalorisation énergétique des déchets solides et liquides : séchage, méthanisation, incinération : mise en oeuvre d'un outil d'aide à la conception multi-systèmes et multi-modèles

Les stations d'épuration des eaux usées, connues habituellement sous le nom de STEP, produisent des boues biologiques en tant que sous-produits issus du traitement biologique. Ces boues constituent des déchets qu'il faut soit valoriser soit mettre en décharge. Aussi il y a eu Heu de développer de nouvelles filières de valorisation de ce type de déchets (boues) et cela à travers deux solutions : le séchage thermique et la méthanisation qui s'inscrivent de manière unitaire ou complémentaire dans une filière d'oxydation thermique ou de valorisation agricole. Les deux processus permettent d'atteindre deux objectifs : la réduction du volume et du pouvoir fermente s cible et offrent également un potentiel énergétique intéressant. C'est l'étude de ces deux alternatives qui constituent l'objectif de ce travail de recherche, à travers la mise en oeuvre d'un outil d'aide à la conception et aux diagnostics Multi -systèmes Multi - modèles. Le développement de l'outil s'appuie sur deux volets. Le premier volet est à caractère expérimental à travers la mise en oeuvre de dispositifs pilotes associés au séchage et à la méthanisation et le second est à caractère théorique reposant sur la modélisation des processusno abstrac

Modélisation des dispositifs de revalorisation énergétique des déchets solides et liquides (séchage, méthanisation, incinération)

Les stations d'épuration des eaux usées, connues habituellement sous le nom de STEP, produisent des boues biologiques en tant que sous-produits issus du traitement biologique. Ces boues constituent des déchets qu'il faut soit valoriser soit mettre en décharge. Aussi il y a eu Heu de développer de nouvelles filières de valorisation de ce type de déchets (boues) et cela à travers deux solutions : le séchage thermique et la méthanisation qui s'inscrivent de manière unitaire ou complémentaire dans une filière d'oxydation thermique ou de valorisation agricole. Les deux processus permettent d'atteindre deux objectifs : la réduction du volume et du pouvoir fermente s cible et offrent également un potentiel énergétique intéressant. C'est l'étude de ces deux alternatives qui constituent l'objectif de ce travail de recherche, à travers la mise en œuvre d'un outil d'aide à la conception et aux diagnostics Multi -systèmes Multi - modèles. Le développement de l'outil s'appuie sur deux volets. Le premier volet est à caractère expérimental à travers la mise en œuvre de dispositifs pilotes associés au séchage et à la méthanisation et le second est à caractère théorique reposant sur la modélisation des processus.The stations of purification of waste water, usually known under the name of STEP, produce biological sludge as by-products resulting from the biological treatment. This sludge constitute waste which it is necessary either to develop or to put in discharge. Also there was reason to develop new dies of valorization of this type of waste (sludge) and that through two solutions: the thermal drying and the anaerobic fermentation which are registered in a unit or complementary way in a die of thermal oxidation or agricultural valorization. The two processes make it possible to achieve two aims: the réduction of volume and the fermentation capacity and also offer an interesting natural energy. It is the study of thèse two alternatives which constitute the objective of this research task, thiough the development of a tool of assistance to the design and the diagnoses - Multi Systems - Multi models. The development of the tool is pressed on two shutters. The first shutter is an expérimental study through the implementation of devices control associated with drying and with méthanisation and the second is a theoretical study on the modelling of the processes.SAINT DENIS/REUNION-Droit Lettre (974112101) / SudocSudocFranceReunionFRR

Performance Evaluation of Green Roof for Thermal Protection of Buildings In Reunion Island

International audienceGreen roofs provide environmental benefits by protecting buildings against solar radiation and temperature fluctuations and by reducing building's energy consumption by direct shading. Our objective was to evaluate for the first time the performance of an extensive green roof in Reunion Island (Indian Ocean) influenced by a tropical humid climate. The green roof performance was explored by evaluating its effect on temperature fluctuations and heat fluxes during the summer season. The results showed that the presence of plants led to a decrease in temperature under the green roof. Plants also contributed to a lower heat flux exchange through the green roof. The determination of major parameters including U-value, R-value and k-value, demonstrated the thermal and energetic behavior of the green roof and helped to highlight Sedum plant benefits. To conclude, this study has demonstrated the thermal and energetic performance of a green roof based in an area under a tropical humid climate

Analysis and Estimation of Short Term Residual Household Waste Production: Case Study Reunion Island

The objective of this approach is to evaluate the formation of waste production at the communal level in a small island state. The question of waste management is an important issue for all local authorities, but it is even more so in an island context. The small island areas are all the more confronted with this problem insofar as they must combine their own specific characteristics, which can be very restrictive: isolation and remoteness, centralized economy, non-competitive domestic market, geographical and climatic conditions, growing demography, social structure and economic and energy dependence. The list is certainly not exhaustive, but it is sufficient to establish a framework for reflection, where these different specificities interact strongly with the development of these territories. Although they reveal above all remarkable and fragile ecosystems, a bad waste management policy can cause irremediable damage environmentally, economically, and socially. It is therefore important to understand the implications of waste management on the island. This approach introduces an analysis, in order to express the communal specificities of the production of residual household waste, in order to bring contextualized elements of answers to the waste management strategy of Reunion Island. Indeed, dysfunctions have been noted in the collection and transfer process and more particularly, in waste disposal

Life Cycle Analysis of Green Roof Implemented in a Global South Low-Income Country

International audienceEnvironmental protection becomes a global challenge currently. Green roof is one of the innovativeconcepts to face this battle. An increase in its use is noticed in urban areas worldwide. But a question arises: what are the environmental consequences of the green roofs’ life cycle? In this paper, the environmental performance of two complete systems of lighter and heavier green roofs implemented in a global south low-income country are analyzed and compared in order to determine the potential impacts of both types of green roof systems. For proposing solutions aiming at reducing environmental loads of green roofs, Life-Cycle Assessment (LCA) approach was used in the present study. For this purpose, the approach consists of the following phases: definition of the objective, life cycle inventory, characterization of impacts, and interpretation of results. LCA calculations were done with the help of OpenLCA software. Results show that, non treated materials and / or imported ones are more environmentally impactful. Hence, it is profitable to reduce the use of cement, gravel, virgin plastics, and soil as well as imported materials whose transport is done by plane. In addition, use of natural fertilizer for amending the growth substrate and water from well for watering the green roof, is also recommended

Life Cycle Analysis of Green Roof Implemented in a Global South Low-income Country

Environmental protection becomes a global challenge currently. Green roof is one of the innovative concepts to face this battle. An increase in its use is noticed in urban areas worldwide. But a question arises: what are the environmental consequences of the green roofs’ life cycle? In this paper, the environmental performance of two complete systems of lighter and heavier green roofs implemented in a global south low-income country are analyzed and compared in order to determine the potential impacts of both types of green roof systems. For proposing solutions aiming at reducing environmental loads of green roofs, Life-Cycle Assessment (LCA) approach was used in the present study. For this purpose, the approach consists of the following phases: definition of the objective, life cycle inventory, characterization of impacts, and interpretation of results. LCA calculations were done with the help of OpenLCA software. Results show that, non treated materials and / or imported ones are more environmentally impactful. Hence, it is profitable to reduce the use of cement, gravel, virgin plastics, and soil as well as imported materials whose transport is done by plane. In addition, use of natural fertilizer for amending the growth substrate and water from well for watering the green roof, is also recommended

ENERGETIC PERFORMANCE OF A GREEN ROOF IN THE TROPICAL ENVIRONMENT OF LA REUNION ISLAND (INDIAN OCEAN)

International audienceThe green roof technology provides environmental benefits by protecting the base roof membrane of buildings against solar radiation and temperature fluctuations and by helping to reduce building's energy consumption by direct shading. Although several investigations have been performed to explore the energy performance of vegetated roofs as natural cooling devices, there is a lack of data concerning the green roof potential in the southern hemisphere. The aim of our work was to evaluate for the first time the performance of a green roof in La Reunion Island (Indian Ocean) influenced by a tropical humid climate. A green roof based on three kinds of vegetation, namely Plectranthus neochilus, Kalanchoe longiflora and Sedum reflexum species was compared to a reference bituminous roof during the summer season. The green roof performance was explored by evaluating its effect on temperature fluctuations and heat fluxes. The results showed that the presence of plants led to a decrease in temperature reaching 6.7±0.1°C under the green roof. Each plant also contributed to a low heat flux exchange through the green roof. Indeed, Sedum presented an average heat flux exchange of 1.4±0.3% as compared to Plectranthus (2.3±0.2%) and Kalanchoe (2.2±0.4%). Moreover, Sedum also led to a higher restitution of heat gain (63%) than Plectranthus (54%) and Kalanchoe (51%). Finally, the determination of major parameters including U-value, R-value and k-value, demonstrated the thermal and energetic behavior of the green roof and helped to show Sedum properties for a green roof based in the tropical environment of La Reunion Island. To conclude, this study has evaluated for the first time the thermal and energetic performance of a green roof in an Indian Ocean area. Our results contribute to highlight Sedum benefits for a vegetated roof in such an area. Further investigations will be needed to assess if the green roof technology provides a very effective solution for building energy savings in cities under a tropical humid climate

Dynamic Simulation of the Green Roofs Impact on Building Energy Performance, Case Study of Antananarivo, Madagascar

Green roofs improve building energy performance and constitute an alternative to sustainable buildings. A green roof model is dynamically coupled with a building thermal model to assess its energy performance that takes into account the indoor air temperature dynamic changes. Under the climate conditions in Antananarivo, we compared green and conventional roofs. The present study shows that green roofs protect the roof structure under extreme temperature and large temperature fluctuations. For the case of Antananarivo, the amplitude of the temperature fluctuations at the top face of the support is reduced by 28 °C when using green roof. The impact of the green roof on indoor air temperature and energy demand is investigated. The vegetation decreases the maximum indoor air temperature and improves the building thermal comfort during summer days. It has no effect on the minimum indoor air temperature, but additional soil thickness can increase it. In addition, a global sensitivity analysis, which is carried out on the proposed model without considering any specific weather data, allows us to identify the most influential parameters on the energy demand. It has been found that green roofs have almost insignificant thermal impact in insulated buildings; however, their potential prevails over the building envelope and weather characteristics in the case of non-insulated building

Modelling of drying activated sludge: effects of the sludge turn over on drying kinetics

International audienc