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Now showing items 1 - 14 of 14

  • Outdoor Air Temperature Measurement:A Semi-Empirical Model to Characterize Shelter Performance

    Bernard, Jeremy   Keravec, Pascal   Morille, Benjamin   Bocher, Erwan   Musy, Marjorie   Calmet, Isabelle  

    Shelters used to protect air temperature sensors from solar radiation induce a measurement error. This work presents a semi-empirical model based on meteorological variables to evaluate this error. The model equation is based on the analytical solution of a simplified energy balance performed on a naturally ventilated shelter. Two main physical error causes are identified from this equation: one is due to the shelter response time and the other is due to its solar radiation sensitivity. A shelter intercomparison measurement campaign performed by the World Meteorological Organization (WMO) is used to perform a non-linear regression of the model coefficients. The regression coefficient values obtained for each shelter are found to be consistent with their expected physical behavior. They are then used to simply classify shelters according to their response time and radiation sensitivity characteristics. Finally, the ability of the model to estimate the temperature error within a given shelter is assessed and compared to the one of two existing models (proposed by Cheng and by Nakamura). For low-response-time shelters, our results reduce the root mean square error by about 15% (0.07 K) on average when compared with other compensation schemes.
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  • Implementation of street trees in solar radiative exchange parameterization of TEB in SURFEX v8.0

    Redon, Emilie   Lemonsu, Aude   Masson, Valéry   Morille, Benjamin   Musy, Marjorie  

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  • Implementation of street trees within the solar radiative exchange parameterization of TEB in SURFEX v8.0

    Redon, Emilie C.   Lemonsu, Aude   Masson, Valery   Morille, Benjamin   Musy, Marjorie  

    The Town Energy Balance (TEB) model has been refined and improved in order to explicitly represent street trees and their impacts on radiative transfer: a new vegetated stratum on the vertical plane, which can shade the road, the walls, and the low vegetation has been added. This modification led to more complex radiative calculations, but has been done with a concern to preserve a certain level of simplicity and to limit the number of new input parameters for TEB to the cover fraction of trees, the mean height of trunks and trees, their specific leaf area index, and albedo. Indeed, the model is designed to be run over whole cities, for which it can simulate the local climatic variability related to urban landscape heterogeneity at the neighborhood scale. This means that computing times must be acceptable, and that input urban data must be available or easy to define. This simplified characterization of high vegetation necessarily induces some uncertainties in terms of the solar radiative exchanges, as quantified by comparison of TEB with a highspatial- resolution solar enlightenment model (SOLENE). On the basis of an idealized geometry of an urban canyon with various vegetation layouts, TEB is evaluated regarding the total shortwave radiation flux absorbed by the elements that compose the canyon. TEB simulations in summer gathered best scores for all configurations and surfaces considered, which is precisely the most relevant season to assess the cooling effect of deciduous trees under temperate climate. Mean absolute differences and biases of 6.03 and +3.50 W m(2) for road, respectively, and of 3.38 and +2.80 W m(2) for walls have been recorded in vegetationless canyons. In view of the important incident radiation flux, exceeding 1000 W m(-2) at solar noon, the mean absolute percentage differences of 3% for both surfaces remain moderate. Concerning the vegetated canyons, we noted a high variability of statistical scores depending on the vegetation layout. The greater uncertainties are found for the solar radiation fluxes received and absorbed by the high vegetation. The mean absolute differences averaged over the vegetation configurations during summertime are 21 : 12 +/- 13 : 39 W m(-2) or 20 : 92 +/- 10 : 87% of mean absolute percentage differences for the total shortwave absorption, but these scores are associated with acceptable biases: 15 : 96 +/- 15 : 93 W m(-2).
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  • Automatically generated zonal models for building air flow simulation: principles and applications

    Musy, Marjorie   Winkelmann, Frederick   Wurtz, Etienne   Sergent, Anne  

    In our formulation of zonal models for calculating room air temperature and flow distributions, the behavior of a room is represented by the connection of SPARK calculation modules. Modules to describe the building walls and various systems have been created. They form the models library. By assembling the appropriate modules, a zonal model of an entire building can be constructed. A model-generating tool called GenSPARK automates this process. SPARK solves the set of equations resulting from this construction to obtain the air flow and temperature distribution in the building. We describe our formulation of zonal models, show how GenSPARK works and give examples of configurations we are able to analyze.
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  • What is the required level of details to represent the impact of the built environment on energy demand?

    Lauzet, Nicolas   Morille, Benjamin   Leduc, Thomas   Musy, Marjorie  

    A full coupling between a CFD code, a thermo-radiative model and a building energy simulation model enables Solenemicroclimat software to calculate both building thermal behavior and urban microclimate with the retroaction of buildings on microclimate. However, this full coupling is time consuming and it is legitimate to wonder if it is always necessary to perform such detailed simulations. In the framework of the MERUBBI project, simulations were carried out to answer this question. A set of simulations was designed to explore different kinds of configurations: three cities in France (Nantes, Paris and Strasbourg), three levels of density (from an isolated building to an implementation in the dense city center) and three kinds of buildings (an individual house in Paris, a residential building in Nantes and an office building in Strasbourg). To study the sensitivity of energy demand to the coupling detail, for each thermal flux at the external surfaces of the building, several levels of details were taken into account. For the impact of wind on convection, three modalities were considered: a constant convective heat transfer coefficient, calculated from the wind velocity at 10m; a convective heat transfer coefficient calculated from a vertical wind profile; a convective heat transfer coefficient calculated from the local wind velocity simulated with a CFD code. For the impact of air temperature on convection, two modalities are considered the use of the temperature measured at the nearest meteorological station; a local temperature calculated with the CFD simulation. For the impact of long-wave radiative exchanges, three modalities: the building exchanges with the sky without taking into account the masks of the environment and the longwave radiative exchanges with the other surfaces; the building exchanges with the sky, taking into account the mask effects but not the exchanges with the surrounding surfaces; long-wave exchanges are taken into account with all kinds of surfaces in function of view factors. For the impact of short-wave radiations, two modalities: only direct and diffuse solar fluxes are taken into account; inter-reflections are considered. The results indicate that if the calculation of air temperature and convective heat transfer coefficient have few impacts in all the cases, the way of calculating long-wave and short wave radioactive fluxes has to be carefully considered, in winter as in summer. More detailed recommendations are given according to the density of the site in which the building will be implemented. (C) 2017 Published by Elsevier B.V.
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  • Simulation tools to assess microclimate and building energy - A case study on the design of a new district

    Gros, Adrien   Bozonnet, Emmanuel   Inard, Christian   Musy, Marjorie  

    Since some years, dense cities and compact buildings are promoted as sustainable and energy efficient designs. Nevertheless, urban planning strategies should take into account the interactions between buildings and the Microclimate because the Urban Heat Island (UHI) phenomenon can increase the cooling load of buildings and is strongly influenced by urban morphology, urban landscaping and the thermal properties of buildings and soil. The modification of these parameters, such as building density, can mitigate UHI, with direct and indirect improvement of building energy performances. The case study presented in this paper concerns a new district in La Rochelle (France) named Atlantech. Currently at the design stage, the goal is to transform this old military camp into a zero carbon district. This study was performed in parallel with urban planning using EnviBatE and SOLENE-Microclimate simulation. Two building densities are compared through the impacts on solar irradiance, wind airflows, building indoor temperatures and energy demand. Analysis of reference and densified district highlights various impacts such as the wind velocity decrease, up to 80%, and the effect on an existing nearby building solar irradiation, reduced by 7%. These results underline the potential usefulness of these simulation tools for urban planners at the design stage. (C) 2015 Elsevier B.V. All rights reserved.
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  • A Study on the Impact of Changes in the Materials Reflection Coefficient for Achieving Sustainable Urban Design

    Al-hafiz, Bisam   Musy, Marjorie   Hasan, Turki  

    A lot of geographers, scientists believe that the current climate has changed. Especially, since the rapid increment of world's population. Indeed, rapid urbanization led to an increased demand of basic facilities, such as public transport services, hospitals, housing &, etc. Accordingly; the urban areas of cities have been expanded compared to rural areas, and many modifications and changes have been happened on their surface's materials. These modifications made our cities hotter than the Countryside, UHI effect phenomenon now well-known. One of the main reasons behind these changes is construction materials in both buildings and urban spaces, which play a major role in affecting the urban temperatures, precisely near-surface air temperatures positively or negatively, which depend mainly on the behaviour of the surface with solar radiation and how the energy is reflected, emitted, and absorbed. Thus, the current study aimed to investigate the direct and indirect impacts of materials reflection coefficient on the environmental performance and external urban surface temperature; by using the SOLENE-microclimate model tool (developed by the laboratory CRENAU - ENSA Nantes); which is a direct effect on external air temperature in terms of sustainability in the urban context. This study applied on one of the most important residential complexes in Mosul city - Iraq as a case study. The results were proved that when used a material with high reflectivity; Comparing low albedo Scenario (1) with high albedo Scenario (3); it can improve the thermal behaviour of building and urban surfaces, where the surfaces temperature of rooftop, walls, urban spaces, road have been changed by, respectively, 25 degrees C, 18 degrees C, 20 degrees C, and 18 degrees C. As well as changed the urban air temperature by 11 degrees C. However, the results showed that in some cases the surface temperatures increased slightly even when reflectivity increased in the scene, (comparison scenario 3 and scenario 5) where the change of albedo value of external walls surfaces have affected increasing the average urban spaces & pavement temperature about 2 degrees C. The tool that is used in this study (SOLENE-microclimate) has effectively helped in achieving all the analysis required successfully, which it represent the most specialized tool in this field. (C) 2017 The Authors. Published by Elsevier B.V.
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  • Bayesian inference method for in situ thermal conductivity and heat capacity identification:Comparison to ISO standard

    Rodler, Auline   Guernouti, Sihem   Musy, Marjorie  

    Non-destructive thermal diagnosis is necessary for identification and quantification of structural defects and verification of construction performances. In this paper, we test different inverse heat transfer models to identify the thermal conductivity of a building's wall in its environment. The approaches proposed and used in this paper rely only on non-intrusive measurements: inside and outside wall surface temperatures and heat flow through the wall. First, a Bayesian statistical dynamic inference method, which has the advantage to quantify the unknown parameter and its credible interval, is presented. This method considers the uncertainties of the measured temperature and heat flow data and of the unknown thermal properties. Markov chain Monte Carlo (MCMC) algorithm is used to explore the posterior distribution. Then, the average and the dynamic procedures ISO 9869 (I. 9869-1, 2014) are introduced. Finally, the probabilistic distributions of the unknown parameters are presented and compared to the standard results. The impact of experimental conditions (average indoor-to-outdoor temperature) and the measurements length on the accuracy of the results are discussed. The relationship between the number of iterations of the MCMC, time series length, shape of the prior distribution and accuracy are studied as well as the simulation time to run the inverse models. The Bayesian approach gives the most accurate results and has the advantage of considering several unknowns (conductivity and volumetric heat capacity), which is not the case for the studied standard. The Bayesian method needs much shorter time series than the ISO standard and produces robust results at all times of year, including when the average indoor-to-outdoor temperature difference was low. (C) 2018 Elsevier Ltd. All rights reserved.
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  • Bayesian inference method for in situ thermal conductivity and heat capacity identification: Comparison to ISO standard

    Rodler, Auline   Guernouti, Sihem   Musy, Marjorie  

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  • Comparison of the impact of three climate adaptation strategies on summer thermal comfort - Cases study in Lyon,France

    Morille, Benjamin   Musy, Marjorie  

    Nowadays, the study of the outside thermal comfort is more and more taking into consideration in the urban design process. In a climate change context, town planners have to find solutions to mitigate the effects of the global warming and to ensure that outside spaces designed in new districts will remain liveable. In the framework of the EVA project, simulations were carried out to compare the effect of three urban cooling strategies on the thermal comfort in summer. Various urban greenery types, water aspersion systems and cooling materials are applied to three districts in Lyon, France. A set of simulations was designed to explore different configurations: - cooling strategies were first applied one by one in each district, - a composition of the three strategies is considered in a second step to optimize their effect, - cumulative effect is finally investigated by deducing one of the components from the optimized configuration. Simulations were performed using Solene-microclimat which realizes the full coupling between a CFD code and a thermo-radiative model. In this way, Solene-microclimat enables to calculate and evaluate the evolution on the urban microclimate at a district scale considering physical parameters in a completely discretized way. Modules have been introduced in this model to represent different kinds of adaptation strategies such as vegetation (green roofs and walls, trees, lawns) and water aspersion. For each case, the daily variations of surface and air temperatures fields are obtained and compared. The resulting mean radiant temperature is evaluated and investigated for the studied space of each district. Finally, the thermal comfort is assessed using the UTCI index. Findings indicate that vegetation, in particular when including trees is the more efficient, due to its shading effect. Even if water aspersion can strongly lower the surface temperatures, its effect on thermal comfort is local and limited compared to the effect of vegetation. Due to reflection effects, high albedo materials are less efficient concerning external thermal comfort. (C) 2017 The Authors. Published by Elsevier
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  • Direct and Indirect Impacts of Vegetation on Building Comfort:A Comparative Study of Lawns,Green Walls and Green Roofs

    Malys, Laurent   Musy, Marjorie   Inard, Christian  

    Following development and validation of the SOLENE-microclimat tool, the underlying model was used to compare the impacts of various greening strategies on buildings' summer energy consumption and indoor comfort. This study distinguishes between direct and indirect impacts by successively implementing the test strategies on both the studied building and surrounding ones; it also considers insulated vs. non-insulated buildings. Findings indicate that green walls have a direct effect on indoor comfort throughout the entire building, whereas the effect of green roofs is apparently primarily confined to the upper floor. Moreover, the indirect effect of a green wall is greater, mainly due to the drop in infrared emissions resulting from a lower surface temperature. It has also been proven that the indirect effects of green walls and surrounding lawns can help reduce the loads acting on a non-insulated building.
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  • Generation of a zonal model to simulate natural convection in a room with a radiative/convective heater

    Musy, Marjorie   Wurtz, Etienne   Winkelmann, Frederick   Allard, Francis  

    A zonal model of room air convection is formulated. It consists of a set of coupled equations determined by heat and mass balance on each of the 24 cells into which the room is divided, convection from the room surfaces and radiant exchange among the room surfaces. The equations are solved iteratively with the SPARK object-oriented simulation environment to determine the room air flow and temperature distribution. The plume caused by warm air rising from a heater is modeled. Calculated air temperatures agree with measurements in an experimental room to within 1.0°C except near the ceiling, where the agreement is to within 1.3°C.
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  • Assessment of direct and indirect impacts of vegetation on building comfort:A comparative study of lawns,green walls and green roofs

    Musy, Marjorie   Malys, Laurent   Inard, Christian  

    Following development and validation of the Solene-microclimat tool, the model was used to compare the impacts of various "greening strategies" on buildings' summer energy consumption and indoor comfort. The studied strategies were greening walls, roofs, and ground (lawns). Solene-microclimat enables to simulate simultaneously a building's thermal behavior and the microclimate at the district scale, with the retroaction of buildings on climate. Distinguishing between direct (due to the modification of building' characteristics) and indirect impacts (due to the modification of boundary conditions) of these surfaces is also possible. Thus, the strategies were successively implemented on the studied building, the surroundings, and both of them. The simulations were carried out using Solene-microclimat considering insulated vs. non-insulated buildings. Findings confirm that the direct and indirect effects of theses surfaces are almost negligible on insulted buildings. For non-insulated ones, green walls have a direct effect on indoor comfort throughout the entire building, whereas the effect of green roofs is primarily confined to the upper floor. Moreover, the indirect effect of a green wall is greater, mainly due to the drop in infrared emissions resulting from a lower surface temperature. It has also been proven that the indirect effects of green walls and surrounding lawns can help reduce the loads acting on a non-insulated building. Direct and indirect effect can't be directly added. This is particularly interesting for heritage buildings or highly glazed ones the refurbishment of which is often difficult. (C) 2017 The Authors. Published
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  • Assessment of Direct and Indirect Impacts of Vegetation on Building Comfort: A Comparative Study of Lawns, Green Walls and Green Roofs

    Musy, Marjorie   Malys, Laurent   Inard, Christian  

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