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T.D.G.S., "Tubular Daylight Guidance Systems", are natural lighting processes based on the transport of light. In 1990, they were judged by Littlefair as the most innovative technology in daylighting [1]. From 1982 to 2020, this paper is a state of the art on the different processes of tubular daylight guide systems. The key words used to carry out the census are: light pipe; light tube; light guide; sun pipes; solar pipes; solar light pipes; daylight pipes; tubular skylight; sun scoop; tubular daylighting device; tubular daylight guide systems; mirrored light pipe. A classification by type of process is proposed (collection, transport or diffusion) for each technology identified in the literature., Les D.G.L.T., "Dispositifs de Guides Lumineux Tubulaires", sont des processus d'éclairement naturel basés sur le transport de la lumière. En 1990, ils ont été jugés par Littlefair comme la technologie la plus innovante en matière d'éclairement naturel [1]. Cet article fait le point sur les différents procédés des systèmes tubulaires de guidage de la lumière du jour de 1982 à 2020. Les mots clés utilisés pour effectuer le recensement sont : conduit de lumière ; tube de lumière ; guide de lumière ; tube solaire ; conduit de lumière du jour ; puits de lumière tubulaire ; conduit de lumière réfléchissant ; systèmes tubulaires de guidage de la lumière du jour. Une classification par type de procédé est proposée (collecte, transport ou diffusion) pour chaque technologie identifiée dans la littérature.

This paper focuses on the part of Tubular Daylight Guide Systems (TDGS): the Mirrored Light-Pipe (MLP). MLP is part of the multiple specular reflection conveyors. They allow daylight to be transported and distributed in dark rooms far from traditional openings while limiting heat transmission. It involves collecting, concentrating, and diffusing sunlight using a dome placed on the roof. It is then conveyed through a highly reflective tube and diffused into a building's room using a diffuser. Previous work (Malet-Damour et al., 2017, 2016) has shown that it was necessary to identify and study the climate in which the light pipe will be installed. A state-of-the-art of experimental and numerical results was conducted over the period from1990 to 2019. It revealed that the behavior of the light pipe depends strongly on the indoor (area to be illuminated) and outdoor (meteorology) environment. This paper presents the experimental observations of studies conducted from 2013 to 2015 on Mirrored Light-Pipe in Reunion Island. The climate in which the experiment was undertaken is presented with a focus on illuminance. In 2019, this study is the only one analyzing the performance of the light pipe in extreme situations of extreme sunlight conditions (maximum global illuminance of around 200 Klux). Experimental results based on various scenarios quantified the impact of the reflection coefficient of the area to be illuminated, the presence of an anticyclonic dome, the type of sky or the ideal position of a sub-dome deflector. The results are very encouraging.

This study is being conducted to evaluate the effects of Phase Change Materials (PCM) on thermal comfort in buildings in Reunion Island. Experimental and numerical approaches are used to determine the criteria for the integration of bio-based PCM. A full-scale platform is divided into two rooms, where a layer of PCM is applied to one surface of the test room. Results show that the application of PCM delays the temperature rises and its maximum is reduced by up to 4 degrees. Finally, the experimental results are compared to those of a Dynamic Thermal Simulation (DTS) program to evaluate the ability of such programs to predict the thermal behavior of the building with and without PCM.

The use of phase change materials (PCMs) as a building integrated thermal storage may contribute to improving building energy performances. This article focuses on the integration of PCMs in the roof with a non-ventilated air layer, in order to assess thermal performances of a dedicated test cell, especially for thermal comfort. An experimental equipment was set up at Reunion Island under tropical and humid climatic conditions. A mathematical model, based on the apparent heat capacity method is used to predict the actual impact of PCMs on energy consumption as well as thermal comfort. Once the comparisons are performed with simulations, the use of the psychrometric chart, Predicted Mean Vote and Predicted Percentage of Dissatisfied indexes, shows that in the tested configurations, thermal comfort can be improved. Indeed, as well as to enhance the thermal energy storage, the given configuration also reduce the solar radiation through the roof, due to the reflective properties of PCMs panel surfaces. A positive effect on inside air temperature of the full-scale experimental test cell is particularly observed.

International audience; The use of bio-based materials in buildings has become more and more significant last years. In most of the cases, their health properties and natural provenance have made them a great solution to face global climate warming and the new policies to reduce building energy consumption. In many thermal problems, bio-based materials can allow to optimize the building thermal behavior according to its energy consumption and inside comfort conditions. So it is when they are used as an insulation material in the building. However, it is not the case in this paper. In fact, the bio-based matter is rather used as a desiccant wheel to control air conditioning inside the building.The aim of this paper is to numerically verify if it is possible to use a bed of wood chips as a hygroscopic material (or a desiccant matter) in order to modify the relative humidity inside the building in Reunion Island and so improve thermal comfort. A simple model of heat and mass transfer between a bed of wood chips and building inside air has been set up and implemented into a validated building simulation code named ISOLAB.Numerical simulations were set up for the four climate zones of the island regulations and a focus has been made on the low altitude one (with high, solar irradiation, temperature and relative humidity).Simulation results give the thermal behavior of the building particularly the temperature and relative humidity of inside air temperature, and temperature and moisture content of wood chips. The obtained results lead to determine if the wood chips bed is suitable for the reference building and to verify its technical feasibility (wood species, size of the bed, integration to the building, etc.). The results show that the use of a WCB help to decrease the building inside air temperature and water content up to 10°C less and 11.6 g.kg-1 less. These are the ways to improve inside comfort conditions.Indeed, comfort analysis have shown the possibility to significantly increase building users’ thermal comfort when coupled with a fan and natural ventilation, like the regulation needs for low altitude climate. In this case, a gain of 68% of year time is achieved for a building equipped with WCB system compared to one without it (6308 hours of comfort over a year with the WCB against 350 hours without WCB). So the WCB seems to be able to help reducing cooling loads in tropical climate conditions.

In a concerning global energy context, the construction industry must be able to respond both in terms of energy management and the comfort of its buildings⿿ occupants. In this context, innovative devices using daylighting can provide an obvious answer. The Tubular Devices Guide Systems (TDGS) are innovative daylighting processes based on light transport. They offer a real response to the diurnal energy consumption (frequently in tertiary). However, today's design will make tomorrow's building. This is why it is necessary to better adjust our prediction tools to optimize the use of these technologies and their coupling to active processes (artificial lighting). The literature reveals a disparity in performance prediction tools for light pipes. Two causes are targeted: the adjustment of semi-empirical models and their accuracy. This article offers some solutions to both problems. We propose a new form of model (improved accuracy) associated with a generalized modelling protocol (response to the adjustment) through a model generator named HEMERA. Our approach is organized around a Galilean sequence, i.e., we rely on observation and results of an experimental study in real weather conditions to better understand the phenomena and validate the developed model. Energy autonomy and user comfort in the building are at the heart of our concern, and we will provide evidence to validate the use of TDGS in buildings. In this context, we propose an energy equivalence between the light pipe and artificial lighting.

In Reunion Island, many buildings have been equipped with PV panels on their roofs in order to produce electricity. These PV systems were built to increase the penetration of renewable energies in the public electricity grid and so reduce greenhouse effect gases emissions. This type of installation was designed just in order to produce electricity but many works have shown that PV systems integrated to walls can also cool or heat the buildings. This paper presents how PV systems integrated to building can be used to help meeting energy needs in two microclimates of the island by cooling or heating the building where it is installed. To show this, a building simulation code able to model BIPV buildings is used.

In this paper, the electrical energy generation of photovoltaic (PV) arrays is discussed for three cities on the island of Réunion (the Republic of France) located in the Indian Ocean. Each PV array has a different orientation as it is placed at different parts of the roof of a residential house that supposedly is a sustainable building. The electrical energy generation is obtained by using EnergyPlus software and measured solar radiation data. The highest generation of electric energy is found for the PV array located at the north roof surface. The generation of electric energy at the east-facing PV array is larger than that at the west-facing PV array. The electrical energy generation for the city of Le Port on the coast is higher than that for the cities of Cilao, and Plaine des Cafres that are located in the mountains of Réunion.

This paper deals with the experimental evaluation of a roof-mounted multi-reflective radiant barrier (MRRB), installed according to the state of the art, on a dedicated test cell. An existing experimental device was completed with a specific system for the regulation of the airflow rate in the upper air layer included in a typical roof from Reunion Island. Several experimental sequences were conducted to determine the thermal resistance of the roof according to several parameters and following a specific method. The mean method, well known in international standards (ISO 9869 - 1994) for the determination of the thermal resistance using dynamic data, was used. The method was implemented in a building simulation code in order to allow the determination of the thermal indicator automatically. Experimental results are proposed according to different seasonal periods and for different values of the airflow rate in the upper air layer., cited By (since 1996) 1

International audience; This article deals with a new configuration using a phase change material (PCM) in a complex roof on a dedicated test cell. For the first time and in real conditions, an experimental device using phase change material was set up for a tropical and humid climate such as that in Reunion Island. Results showed that in the configurations tested and for a non-ventilated air layer, the measured temperatures were on either side of the PCM’s melting point. It means that the PCM is able to store thermal energy in the daytime and release it at night. Furthermore, this study has made it possible to determine the thermal resistance of the roof via a mean method meeting international standards (ISO 9869) using dynamic data. The test was implemented in a multi-zone building software in order to automatically determine the thermal indicator.

As in Reunion Island, France, around 61% of electricity is produced by using coal and fuel oil with high greenhouse emissions, it is beneficial to the environment to produce electricity from solar energy. Therefore, there is a large push to generate electricity from solar energy by use of photovoltaic (PV) arrays. However, it is important to have high efficiency of electricity generation, that is, to locate PV arrays in an optimal direction. The investigated PV systems may take 1, 2, 4, and 12 tilts per year. For the PV arrays facing the north-south direction, this paper reports investigations of their optimum tilts and the maximum amounts of generated electricity. The investigated PV arrays are located in the towns of Saint-Benoit, Les Avirons, Piton Saint-Leu, and Petite-France in Reunion Island. To obtain optimal tilt of the PV arrays for electricity production from solar energy, EnergyPlus software and GenOpt software are used with Hooke-Jeeves optimization routine. For the investigated PV arrays, the percentage gains in energy, exergy, avoided fossil energy, and the percentage decrease in CO2 emission are around 5% when compared with that of the PV array that takes only one optimum tilt per year. x-audience © 2011 John Wiley & Sons, Ltd.

International audience; This paper presents initial values of global and diffuse luminous efficacy at Saint-Pierre (Reunion Island). Firstly, data used were measured for a period of 6 months, from February to June 2008. During this period, all defined day-types have been studied (clear, cloudy and intermediate). Generally, the meteorological database of Reunion does not contain information for illuminance values. On the other hand, the local meteorological center has a 60-years-old database for solar irradiance (W.m-2). So it is important to determine Luminous Efficacy in order to find illuminance from solar irradiance (or luminance from solar radiance). The measured data were analyzed, and empirical constant models were developed and presented in this paper in order to determine luminous efficacy under different sky conditions. A comparison between these empirical constants (models) and existing models has been made. The method used to define sky conditions (overcast, intermediate and clear) and day-types characterization as well as classification will be presented in this work.

This article deals with both an experimental study and a numerical model of the thermal behaviour of a building whose roof is equipped with photovoltaic panels (PV panels). The aim of this study is to show the impact of the PV panels in terms of level of insulation or solar protection for the building. Contrary to existing models, the one presented here will allow us to determine both the temperature field of the building and the electric production of the PV array. Moreover, an experimental study has been conducted in La Reunion Island, where the climate is tropical and humid, with a strong solar radiation. In such conditions, it is important to minimise the thermal load through the roof of the building. The thermal model is integrated in a building simulation code and is able to predict the thermal impact of PV panels installed on buildings in several configurations and also their production of electricity. Basically, the PV panel is considered as a complex wall within which coupled heat transfer occurs. Conduction, convection and radiation heat transfer equations are solved simultaneously to simulate the global thermal behaviour of the building envelope including the PV panels; this is an approach we call ‘ integrated modelling ’ of PV panels. The experimental study is used to give elements of validation for the numerical model and a sensitivity analysis has been run to put in evidence the governing parameters. It has been shown that the radiative properties of the PV panel have a great impact on the temperature field of the tested building and the determination of these parameters has to be taken with care.

International audience; This article deals with a numerical model of the thermal behaviour of a building roof equipped with phase change materials (PCM). The study puts in evidence the first results of the proposed model based on the apparent heat capacity method. A backward Euler scheme and a finite difference discretization method have been used. The model was integrated in a multizone building simulation code and is able to predict both the whole temperature of each building component and the thermal impact of PCMs installed in buildings for several configurations. A first experimental study has been conducted for a tropical and humid climate, using a full-scale outdoor test cell equipped with PCMs installed as a component of the ceiling. It allowed to give elements of validation for the numerical model, through a validation process including comparisons with measurements A sensitivity analysis has also been run to highlight the influencing parameters of the thermal model. The first results from comparisons between model predictions and measurements are encouraging and show a convenient agreement for the given configuration under field conditions.

International audience; This article deals with the optimization and validation of a thermal model of photovoltaic panels integrated to buildings. The PV thermal model is implemented in the building simulation code ISOLAB and have already been the subject of previous works. The optimization is made by using the generic optimization program GenOpt. First, these two programs are presented. Secondly, the case study is presented both experimental and modeling way, and main results of previous work are given. Thirdly, the validation methodology is described. Fourthly, the coupling between ISOLAB and GenOpt is presented, and optimization and validation criteria are given. Finally, results of the experimental optimization are presented and the model is validated.

The aim of this paper is to briefly recall heat transfer modes and explain their integration within a software dedicated to building simulation (CODYRUN). Detailed elements of the validation of this software are presented and two applications are finally discussed. One concerns the modeling of a flat plate air collector and the second focuses on the modeling of Trombe solar walls. In each case, detailed modeling of heat transfer allows precise understanding of thermal and energetic behavior of the studied structures. Recent decades have seen a proliferation of tools for building thermal simulation. These applications cover a wide spectrum from very simplified steady state models to dynamic simulation ones, including computational fluid dynamics modules (Clarke, 2001). These tools are widely available in design offices and engineering firms. They are often used for the design of HVAC systems and still subject to detailed research, particularly with respect to the integration of new fields (specific insulation materials, lighting, pollutants transport, etc.).

This paper deals with a simplified model of radiative heat transfer in building enclosures with low emissivity walls. The approach is based on an existing simplified model, well known and used in building multizone simulation codes, for the long wave exchanges in building enclosures. This method is simply extended to the case of a cavity including a very low emissivity wall, and it is shown that the obtained formalism is similar to the one used in the case of the based model, convenient for enclosures with only black walls (blackbody assumption). The proposed model has been integrated into a building simulation code and is based on simple examples; it is shown that intermediate results between the imprecise initial simple model and the more precise detailed model, the net-radiosity method, can be obtained. Finally, an application of the model is made for an existing experimental test cell including a radiant barrier insulation product, well used in Reunion Island for thermal insulation of roofs. With an efficacy based on the very low emissivity of their surfaces and the consequent decrease in radiative heat transfer through the wall in which they are included, the proposed simplified model leads to results very close to those of the reference method, the net-radiosity method.

This paper deals with a sensitivity analysis of a thermal model. An integrated thermal modelling of photovoltaic panels (PV panels) has been built. In the case studied in this paper, the PV panel is considered like a solar protection of the building. The modelling has been run for Reunion Island climate, which has a strong solar radiation as encountered in tropical and humid conditions. The thermal model studied here has already been presented in a precedent work. In this work, the model has been validated, for comparing the results predicted and that measures showed significant differences. A sensitivity analysis seemed necessary to highlight the parameters that have the most influence on the thermal model. This will see which parameters to focus on during a future optimization of the model.