Enhancing building energy performance, driven by growing concerns about energy conservation and sustainable development, is renewing interest in passive solar systems. Among the various passive technologies, the strategic development of ventilated solar façade has received increasing attention from engineers and architects in recent years. Depending on their configurations and associated design principles, ventilated solar façade have proven to reduce heating and cooling loads by harnessing solar energy. This article provides a comprehensive review of the state-of-the-art research on passive ventilated solar façade and their integration into building envelopes, focusing on their respective enhancements in terms of energy efficiency and limiting the use of conventional space heating and cooling methods. The different works are divided into four categories based on air circulation techniques. This study is intended to be a valuable resource for academic researchers and a source of inspiration for architects and engineering designers in the development of façade and thermal systems.

This paper presents work intended to characterize air flow and convective heat transfers within a ventilated window. This window is a device that allows for the entry of fresh air into a building while simultaneously preheating it in order to satisfy requirements in terms of air quality and thermal comfort in inhabited spaces. Therefore, this essential component of the building envelope functions herein as a heat exchanger with its own geometric characteristics and exchange conditions. In this research, a dual numerical and experimental approach has been implemented in order to highlight the temperatures, velocities and heat flux fields both at the glazing surfaces and in the ventilated air gaps. Several turbulence models were tested using CFD software (ANSYS-FLUENT®); their results were compared with each other as well as with the experimental results. This study shows that the air gap geometry in the window induces flow disturbances, recirculation phenomena and non-uniform heat exchanges, all of which prove to be important in terms of overall component performance. With regard to modeling and, in particular, at the level of turbulence models, the results obtained indicate that the model GEKO is best suited to the configuration under study when the phenomena of turbulent forced convection dominate the dynamics of the transfers. The k-ε models reveal a tremendous weakness in precisely estimating the problem’s characteristic quantities. From an experimental point of view, local measurements of thermal fluxes and temperatures demonstrate high efficiency with regard to experimental technique, which in turn could be extended to many different configurations for the local evaluation of convection heat transfer.

Façades built with integrated passive solar systems hold great promise for improving the energy performance of buildings and achieving indoor comfort conditions. Among these techniques, solar air preheating systems with different configurations have proven their ability to reduce the energy consumption of buildings during the heating season. In this study, we propose a ventilated solar wall (VSW) with a thermal storage unit intended for preheating ventilation air. The final aim of this study is to determine the thermal performance of the studied VSW over a significant time period (during the heating season) under various climatic conditions when it is integrated into the building envelope. Therefore, for this purpose, a simplified model was developed to be coupled to a building energy simulation (BES) code. The results from the detailed steady-state 2D computational fluid dynamics (CFD) model show that the thermal efficiency of the VSW ranged from 55% to 70% as the air mass flow rate increased from 0.008 kg/s to 0.02 kg/s for a surface of 2.15 m2. These results were used to evaluate the convective heat transfer coefficients in the two air cavities and to validate the simplified model. The results indicate good agreement between the two models.

Thermal energy storage (TES), which features an innovative technology, can enhance energy efficiency in the building sector and reduce CO2 emissions. Due to their high heat storage capacity, phase change materials (PCMs) have impressed many researchers. This paper investigates the energy performance of an individual house integrating a solar Trombe wall containing PCM with respect to heating demand and thermal comfort applications. The thermal energy performance of the design house was simulated using Dymola/Modelica, the thermal building simulation tool, whereby the optimization of objective functions as regards heating demand and thermal comfort was executed using GenOpt, the generic optimization software. Optimization of the solar Trombe wall focuses on the feasibility to find the optimal PCM parameters when running GenOpt, which consist of latent heat, melting temperature, PCM thickness and thermal conductivity, in order to minimize both the annual energy consumption for heating and the number of hours of thermal discomfort. The parametric study was first conducted for each PCM parameter so as to not only observe its effect on the identified energy performance, but also ensure the absence of errors in simulation runs before performing the optimization. The ‘Coordinate Search’ Generalized Pattern Search (GPS) algorithm was applied to minimize the objective function, whereas the ‘Weighted Sum Approach’ was used to solve the multi-objective function problem. Results showed that the higher the latent heat, the lower the heating demand and the greater the thermal comfort. The results of these parametric studies show that for the effect of the parameter on heating, demand is quite limited (1–2 kWh·m−2·year−1) whereas the effect on thermal comfort is more significant. The optimal PCM melting temperature is higher for warmer climates; it is also higher for the studied case applying the optimization method to minimize the objective function by assigning the number of hours of thermal discomfort (from 32.8 ∘C to 35.9 ∘C, depending on weather) than it is when applying the optimization method to reduce the objective function by assigning heating demand (from 31.5 ∘C to 32.9 ∘C, again depending on weather).

The present work addresses the numerical and experimental study of natural convection inside an asymmetrically heated open double vertical facade. Two heating cases were considered independently, the constant heat flux (Neumann condition) and the constant temperature (Dirichlet condition). The double facade has been modeled using a vertical two-dimensional channel with one wall being maintained at the heating condition and the other one insulated. The boundary conditions at the inlet and outlet were controlled through the addition of adiabatic walls upstream and downstream of the studied area. The airflow is assumed to be laminar and permanent. This study is conducted for several modified Rayleigh numbers ranging from 102 ≤ Ram ≤107 and different aspect ratios (A = 25, 12.5, 8.34, 6.25, and 5). Various parameters have been evaluated and highlighted, namely velocity and temperature profiles. In the first part of this study, the radiative heat transfer is not considered, comparison results give excellent agreement with the experimental work of Webb and Hill [18]. Similarly, the streamline results show a return flow through the outlet of the channel starting from a modified Raleigh value of Ram = 104.

An experimental set-up of triple-glazed supply-air window is developed in this research in order to characterize the window’s thermal performance without solar radiation. By simultaneously measuring the local temperatures and heat fluxes with thermocouples and heat fluxmeters, the heat fluxes determination requires no longer using the correlations of heat transfer coefficients around the window, which are often the source of high uncertainties. Results show that the use of fluxmeters brought a more accurate measure of heat transfers around and in the window. Thereafter, the heat transfer coefficients can be correctly estimated by empirical evidence. Uncertainty analysis is then presented to highlight the reliability of the experimental method. Afterwards, the obtained experimental data are compared with those of numerical model developed by using Fluent® software. A thorough comparison analysis is provided to explain which parameters play a role in deviating the results between the two methods, leading to conclude the validity of numerical model assumptions with respect to the real conditions of experimental set-up.

Cette etude s’interesse a l’evaluation de l’influence des murs vegetalises extensifs (MV) sur le bilan energetique des bâtiments avec un code global de simulation thermique dynamique de bâtiment (TRNSYS). A cet effet, le « Type » developpe a ete utilise pour apporter une nouvelle contribution a la prediction du comportement thermique des murs vegetalises. La premiere partie presente la description du logiciel de simulation thermique dynamique utilise et des modalites d’integration du modele developpe. Puis, la modelisation de l’influence des MV a une echelle plus globale est detaillee. Elle mettra en avant l’influence thermique des MV en periode hivernale sur une maison situee a Lille. Il s’agira donc d’une application a un cas d’etude representatif d’un bâtiment d’habitation existant en milieu urbain.

This article studies a composite solar wall with latent storage (TES) designed to heat rooms inside buildings during the cold season. No numerical model of the composite solar wall is currently available in the Dymola/Modelica software library. The first objective of this work is to develop one such model. The article describes the elementary components, along with the equations that allow modeling the heat transfers and storage phenomena governing both the thermal behavior and performance of the solar wall. This model was built by assembling various existing basic elements from the software's "Building" library (e.g., models of heat transfer by convection, radiation and conduction) and then creating new elements, such as the storage element incorporating the phase change material (PCM). To validate this solar wall model, numerical results are compared to experimental data stemming from a small-scale composite solar wall manufactured in our laboratory, and the experimental set-up could be tested under real weather conditions. After verifying the level of confidence in the model, the energy performance of two solar walls, one with a conventional storage wall (sensible heat storage) the other containing a PCM (the same as in the experiment), are compared. The result indicates that the solar wall incorporating a PCM does not in this case release any more energy in the room to be heated.

As the heating demands of buildings drop considerably, the use of solar walls makes increasing sense. One of the obstacles to the development of such walls is their need for on-site implementation by specialized companies. On the other hand, a storage wall is generally composed of heavy materials with high inertia, which prevents prefabrication of the solar component. To avoid this problem and allow for solar walls to be prefabricated in the factory, a novel approach to replacing this heavy wall with a lighter storage wall incorporating phase change materials (PCM) has been proposed. This paper aims to demonstrate the impact of PCM on the thermal energy performance once they have been integrated into the storage wall of the composite Trombe wall. Addressed herein will be the heat transfer exchange inside a house located in the northern part of France, where a composite Trombe wall has been fitted without PCM. Three configurations will be investigated—(1) the model house without the solar Trombe wall, defined as the reference configuration; (2) the model house integrating the concrete solar Trombe wall; and (3) the model house integrating the PCM solar Trombe wall. Two setpoint temperatures will be introduced—(a) a constant setpoint of 20 °C, and (b) a variable setpoint of 19 °C (14 h from 7:00 a.m. to 9:00 p.m.) and 16 °C (10 h from 9:00 p.m. to 7:00 a.m.). Furthermore, three different climate conditions will be adopted to run simulations—Paris-Orly, Lyon, and Nice. Dymola/Modelica, a dynamic thermal simulation tool, will be utilized to simulate the thermal performance of these defined configurations. The results obtained, regarding a solar Trombe wall installation that applies two distinct storage walls exposed to the weather of Paris, showed similar minimizations of the one-year energy heating demand inside the bedroom, equal to roughly 20% (i.e., 20.45% of concrete storage wall and 19.90% of PCM storage wall) compared to the reference configuration (i.e., the house with no solar Trombe wall). Based on the imposed setpoint temperature by means of night and day reductions, the resulting heating energy demand in the bedroom, through application of the two storage walls (concrete and PCM) and three different climatic regions could be minimized by 20.34% in Paris, 20.20% in Lyon, and 68.10% in Nice (for the concrete storage wall) vs. the reference configuration; and by 18.79% in Paris, 19.56% in Lyon, and 55.15% in Nice (for the PCM storage wall) vs. the reference configuration.

It is well known that indoor heat distribution can affect energy consumption according to the thermal comfort of the occupants. While most work on this topic has focused on specific heaters and how they distribute heat, this paper proposes a new concept termed virtual heaters. Virtual heaters are a set of two optimized heat distributors that respectively maximize and minimize the energy consumption inside a room while maintaining the same level of thermal comfort. The maximum and minimum virtual heaters are then applied in a comparison with a real heater tested in a specific room at constant thermal comfort in order to quantify its ability to provide comfort while using a minimum amount of energy. To calculate the "virtual heaters", a simplified heat transfer model is formulated and implemented. A volumetric thermal comfort model using the predicted mean vote is also discussed and used. The "simplified" heat transfer model with the thermal comfort constraint is then optimized via a sequential quadratic programming algorithm. The proposed method is applied to the heating of a room subject to an outdoor temperature of - 20 degrees C and compared to experimental results. Results show that the maximum virtual heater consumes approximately 35% more energy than the minimum virtual heater for the case considered herein.

An experimental device was designed to perform the thermal and dynamic study of natural convection airflow in an open vertical channel. The two side walls of the vertical channel are made of Plexiglas allowing the visualization of the flow via the particle image velocimetry (PIV) method. For the two other vertical walls, one is heated at a constant temperature, and the other is insulated with a 9-cm thick polystyrene insulation. The dynamic characterization of convection is carried out by nonintrusive measurements (PIV), and thermal phenomena are analyzed using nonintrusive heat flux instrumentation (simultaneous temperature and velocity measurements have been carried out across the channel at different elevations). Moreover, this study deals with the influence of the Rayleigh number on the measured vertical velocity profiles as well as the thermal flux densities recorded along the heated wall. To do this, different values of the modified Rayleigh numbers were considered in the interval with the channel aspect ratio of A = 5 and A = 12.5. The obtained Nusselt number values have been compared successfully with those of the literature. The impacts of the Rayleigh number and the aspect ratio on the velocity profiles and the convective and radiative heat transfer have been examined.

This article presents the numerical simulation of the energy effect of a solar mask created by a green wall on the thermal performance of a building envelope in a temperate climate in order to integrate it into thermal calculation codes. The document describes primarily the adaptation of a simplified prediction model. The simplified model was developed and validated on the basis of tests carried out with an experimental controlled occultation device by integrating all external parameters influencing heat exchanges (conduction, convection and radiation). A first validation of the numeric resolution algorithm of the preliminary model was realised. Then the model was supplemented by considerations related to the characteristics of the selected plants: ivy and Virginia creeper, such as the semi-transparent appearance of foliage plants and their geometric distribution. The numerical prediction was very close to the experimental values, and the mean error was about 1 degrees C. This difference makes it possible to validate the developed model.

The present study focuses on the thermal characterization of an insulation material made from recycled textile fibers for building applications, which qualifies as a semi-transparent medium. Experimental and numerical studies have been carried out to determine the radiative flux ratio for such a recycled textile fiber-based insulation for three thicknesses (5.35 mm, 5.67 mm and 6.64 mm). The inverse method, which relies on reflection and transmission measurements using a Fourier-Transform Infrared Spectrometer coupled to an integrating sphere, has been applied along with a least squares procedure. The relevant radiative properties of recycled textile insulation material are obtained by minimizing the deviation between experimental and theoretical data. The effective thermal conductivity of the fibrous insulation is measured at room temperature by means of a fluxmeter device. The radiative thermal conductivity is estimated by implementing the Rosseland model, while phonic conductivity is derived from the effective thermal conductivity. The radiative thermal conductivity displays a very limited effect in comparison with phonic thermal conductivity; the latter varies according to thickness, which in turn is determined by fiber density and size. Phonic thermal conductivity accounts for 26% of the effective thermal conductivity and moreover constitutes a large share (74%) relative to the radiative conductivity. The maximum radiative thermal conductivity value equals 0.0102 W m(-1) K-1 for a thickness of 5.67 mm, with this value dropping slightly to 0.010 W m(-1) K-1 for a thickness of 6.46 mm, and to a minimum value of 0.0096 W m(-1) K-1 at a 5.35-mm thickness.

First, this article introduces a comparison between experimental results and the results issued from a numerical model of a composite Trombe solar wall incorporating a concrete storage wall with the help of the Dymola/Modelica software. The validation of the model is realized from the comparison between simulated and measured heat flux, external and internal surface temperatures and fluid temperatures in a ventilated air layer. Then, the numerical model is used to simulate a composite solar wall where the concrete storage wall is replaced by a mortar mixed with microencapsulated phase change material (PCM). This allows to study and compare the thermal behavior and the energy performances of the two composite solar walls.

This paper presents the results of the validation of an experimental method for studying the thermal benefits of green facades. The main aim is to evaluate the impact of plants occultation on energy performance of a vertical wall in the temperate climate of the city of Lille in northern France. An experimental platform consisting of three identical prototypes (three boxes as thermal labs) has been designed and instrumented. Each prototype has been highly insulated from each face except from the vertical southern wall which was realized with a poor thermal conductivity material. The following measurements were taken: ambient temperature (outside and inside thermal labs), external and internal surface temperatures of southern walls, heat fluxes transferred through south verticals walls (reference and vegetalized walls), solar incident radiation and wind velocity variation under instantaneous real climatic conditions. This enabled the analysis of the variation of energy balance according to the presence or not of a shading effect on the south vertical walls as well as their coverage rate. Several tests were performed on the three experimental thermal labs by imposing a leaf coverage rate which differs during each measurement. The results have shown that masking reduces the outside temperature and enhances the interior thermal comfort especially during summer. (C) 2017 Elsevier B.V. All rights reserved.