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International audience; The current challenge is to reduce the building energy consumption, in hot and humid climates, for which air conditioning is widespread. Up to now, the lack of criteria that identify the available cooling resources and the level of performance of technical solution has represented the major obstacle. To address these issues, the authors propose a new set of indicators to fully inform the decision-making process of the bioclimatic design of fully space-conditioned buildings in a hot and humid climate. This set of indicators provides an overview of the exploitable environmental resource (external air through external convection, natural ventilation and sky radiation cooling) referred as the Environmental Resource Indicators and of the capacity of the building to exploit those resources referred as the Building Performance Indicators. The indicators are implemented for a very basic two-story residential building in the hot, humid climate of Djibouti. The case study shows not only the ability of the indicators to reflect the bioclimatic performances of the buildings but also their ability to give an overview of the building heat exchanges, from which the implication of improper bioclimatic solutions on building cooling consumptions can easily be identified. These indicators are a means to help choose which technical solutions are most suited to the local climate, which is very useful for designers and architects in the early stages of building design.

International audience; In the Sub-Saharan African countries like Djibouti, the energy situation, the high rate of urban areas growth and the inadequate techniques of construction offer an exciting potential for the bioclimatic approach and sustainable construction. However, this poorly explored potential requires an investigation of different construction types in Djibouti and a good knowledge of the behavior of buildings components. Further a low energy building can be obtained because of the good realization of all its components. In fact, roofs call for attention as they represent a large part of a building's total surface area and amount of absorbed solar radiation. The goal of this paper is to investigate the benefit of using double skin-ventilated roofs for reducing cooling load under the Djiboutian climate. It is a first step towards ideas that will transform local construction practices to make them effective in energy, economic and functional dimensions. During investigation, we compared a ventilated roof assembly with traditional configuration after that the consistency of our model was validated with experiment of the literature findings. The computational fluid dynamics (CFD) model has been used for the characterization of the airflow and heat transfer phenomena in the ventilation cavity and provide fundamental information about the thermal performance of the roof. The results show the amount of the energy saving obtainable by the double-skin ventilated roof.

International audience; The aim of this study is to make available new data concerning the validation of CFD (Computational Fluid Dynamics) results through experimental measurements campaigns on full scale mechanically ventilated test rooms. The experimental set-up is based on a new configuration of the test cell “Minibat” (CETHIL – INSA Lyon, France), equipped with a realistic mixing ventilation system. In this paper, experimental – numerical comparisons are presented in terms of mean air velocity for an isothermal situation. The investigations have been focused in the region near the supply air diffuser as the overall air flow in ventilated enclosures is mainly due to the inlet air jet. The results show a decent agreement between measurements and numerical values in terms of velocity profile at the inlet. In addition, the overall flow development in the air jet is well represented numerically. However, there are some discrepancies concerning the point of maximum velocity in the air jet which must be addressed by further investigations, both experimentally and numerically.

On one hand, physical adsorption, also named physisorption, is a process that can be used to storage thermal energy with an energy density higher than sensible or latent storages. On the other hand, in Europe, 26% of the final energy consumption is related to the energy systems of households [1] and 80% of this energy is needed for heating purposes [2] . The consequence is the development of thermal energy storage systems, based on physisoprtion, for building application. The objective of this paper is first to present the basics concerning physisorption heat storage. Then, experimental developments from the literature are reviewed, based on three scales: the material scale, the reactor scale and the system scale. From the review, development of commercial systems faces with scientific and technological issues that must be addressed to reach a higher technology readiness level with an acceptable system cost.

International audience; This paper presents a heat exchanger prototype containing PCM material designed to provide a 1kW heating power during 2 hours (i.e. energy storage of 2kWh). The exchanger is tested in a closed-loop wind tunnel, used to provide constant airflow rates with temperature changes selected so that the PCM is allowed to melt, then to solidify. Temperature and air velocity measurements are achieved for eight airflow rates and the heating power is estimated. The second objective of this work is to provide detailed results suitable with the validation of numerical models. Therefore, the geometry of the exchanger is detailed and the uncertainty associated with the heating power measurement is given. Results show that enough energy is stored in the exchanger, yet the heating power is lower than 1kW before 2 hours because of the use of a of constant airflow rate during the tests. On the other hand, the global behaviour of the heat exchanger is rather simple, which gives confidence in using a simplified approach in further work and help with optimising the current prototype.

Computational Fluid Dynamics (CFD) is a promising way, nowadays, to predict the air Flow in enclosures. As a result, the objective of this study is to assess the potential of CFD technique to predict the air Flows driven by buoyancy in heated real-scale rooms. The numerical model is validated using experimental data for fullscale test rooms; therefore, the experimental set-up is rst presented. This is followed by the numerical model description, focusing on its principal elements: computational domain geometry, discretization, turbulence model, radiation model, and thermal boundary conditions. In addition, a simpli ed approach is proposed to integrate a heat source in CFD models: Term source homogeneously spread all over the volume of the heat source. Comprehensive experimental-numerical comparisons are presented in terms of heat transfer to the walls of the test room, heat source behavior, and plume development. The results show that the model developed in this study leads to realistic predictions. Finally, the simpli ed CFD description of heat sources developed here can be extrapolated for other con gurations - di erent power, heat emission (convection/radiation), dimensions, and shape. Consequently, this method can be applied in detailed studies dealing with thermal comfort, indoor air quality, and energy consumption for heated rooms.

This chapter deals with the use of phase change materials integrated in building opaque walls. Many considerations are discussed in this chapter including physical considerations about building envelope heuristic arguments, phase change material integration, experiments and numerical modelling. Even if the integrated phase change material has a good potential for reducing energy demand, further investigations are needed to really assess their use.

International audience; The present paper is the first comprehensive review of the integration of phase change materials in building walls. Many considerations are discussed in this paper including physical considerations about building envelope and phase change material, phase change material integration and thermophysical property measurements and various experimental and numerical studies concerning the integration. Even if the integrated phase change material have a good potential for reducing energy demand, further investigations are needed to really assess their use.

This paper provides a new correlation to determine the heat transfer coefficient between an air flow and a plate made of phase change material (PCM). This correlation was built for the simulation of heat storage units containing PCM plates subjected to an inlet temperature step. The presented correlation has the following form: NuPCM x;t ¼ NuPSM$f PCM. The first term NuPSM is for a plate made of traditional material. The term fPCM is a perturbation due to the phase change in the plate. Each term depends on 5 non-dimensional parameters. One of them represents the advance in the total heating or cooling process, in order to take into account the transient evolution of the convective coefficient. The correlations are built using the Least Squares Method, from series of CDF simulation data. The shape of the perturbation fPCM reveals a complex evolution of the temperature repartition in the PCM plate. Finally, a nodal model of the plate has been developed in order to test the provided new correlation and other correlations available in the literature. The results obtained with the present correlation show better agreements with the CFD results, which make this correlation suitable for the simulation of PCM heat storage systems. This work was supported by the “Corporación Tecnológica de Andalucía” by means of the project “MECLIDE-Soluciones estructurales con materiales especiales para la climatización diferida de edificios” with the collaboration of DETEA. The work was partially funded by the Spanish Government (ENE2011-22722 and ULLE10-4E-1305) and the European Union (COST Action COST TU0802). The authors would like to thank the Catalan Government for the quality accreditation given to their research group (2009 SGR 534).

Radiative cooling is a renewable technology that can complement or partially replace current cooling technologies. Coupling radiative cooling with another technology, such as solar collection could foster its development and implementation in the market. Therefore, a numerical model capable to simulate the behavior of a coupled radiative cooling and solar collection system is developed and presented in this paper. The model is validated with experimental data for both solar collection and radiative cooling operation, and a sensitivity analysis is performed in order to determine the most influencing parameters. Results show the potential of the device to perform the double functionality: solar thermal collector and radiative cooler. As expected the heating power ( 17.11 k W h / m 2 ) is one order of magnitude higher than the cooling one ( 2.82 k W h / m 2 ). The sensitivity analysis determined the existence of an important role played by 5 parameters (air gap thermal conductivity, absorptivity/emissivity of the radiator at 7–14 μm wavelength range, transmissivity of the cover material 2 at 7–14 μm wavelength range, water inlet temperature, and water inlet flow) and 4 combinations of these parameters in the radiative cooling mode.