• Energy Research

Global energy demand increas and particulary in the building area is one of several factors having an impact on our life and environment. One of numerous alternative solution to solve this problem, is the development then the using of new construction materials based on vegetal or agriculture wastes as thermal insulator. These biomaterials mainly used in the construction of building envelopes, emission need a low energy consumption for their production thus reducing CO2 emissions. In this presentation, the work carried out over the last ten years at CERTES of the University of Paris Est Créteil related to the development of new eco-friendly materials suitable for thermal insulation and for the sustainable buildings of tomorrow will be presented. A Particular attention will be paid to understanding the multiphysics (thermal, water, mechanical) and multiscale (material and wall) behavior of these new biobased construction materials by taking into account both metrology and numerical modeling aspect.Specific tools and devices developed for the characterization of the hygrothermal properties of these “biocomposites” based on mortar, plaster or polymers reinforced with natural fibers (palm, flax or sisal) will be presented. Some examples of main results carried out from the comparison of numerical simulations of coupled heat and moister transfers to the measurements ones for several kinds of biobased walls will be presented and discussed.

This study aims to assess the thermal behavior of a cement mortar (denoted M15D) incorporating microencapsulated biobased phase change materials at both wall and building scales. A bi-climatic chamber setup was employed to subject the wall to distinct thermal conditions simulating outdoor and indoor environments, using heating and cooling solicitations. Temperature sensors, strategically positioned at various depths, allowed the monitoring of temperature within the walls during the experiments. On a building scale, the thermal performance of M15D was predicted using two mathematical models describing heat transmission in porous systems incorporating phase-change materials. Numerical simulations were carried out using COMSOL Multiphysics and EnergyPlus software. The results obtained were validated against experimental data, at the wall scale and subsequently developed to the building scale. The outcomes highlighted that the incorporation of microencapsulated biobased phase change materials significantly influences both building energy consumption and interior temperature. The heat storage capacity offered by M15D demonstrated a significant impact on thermal performance, leading to energy savings of up to 33% for heating and 31% for cooling, contingent on climate conditions. In conclusion, the integration of biobased phase change materials in the cement mortar (M15D) displays benefits in enhancing thermal performance at building scales.

This study investigates the mechanical and thermophysical performance of cement mortars incorporating microencapsulated phase change materials (mPCMs), which consist of an aqueous dispersion of 100% bio-based fine core–shell particles. A specific protocol was used to manufacture the mortar samples, which ensures a homogeneous particle distribution and prevents microcapsule leakage. The addition of mPCMs to the mortar causesboth a decrease in density, an increase in porosity, and a substantial loss of mechanical strength. Conversely, hotdisk characterization revealed a large improvement in the thermal performance. The system containing 8 wt% mPCMs exhibits a good balance between its mechanical and thermal properties.

A simple device for the measurement of emissivity, thermal conductivity, and diffusivity of opaque materials is described. The measurement method is based on the use of a harmonic excitation of a material sample plate. The front surface of the sample is heated periodically and its temperature is measured using a thermocouple. The sample back surface temperature is obtained by infrared thermography. Half of the sample back surface is covered by a black paint of known emissivity used as a reference to compute the sample surface directional emissivity. Thermal conductivity and diffusivity are simultaneously identified from both real and imaginary parts of experimental and theoretical heat transfer functions. Results are presented for a thermally thick sample of PVC, where the sample thickness is greater than the thermal diffusion length. The identified thermophysical properties are in agreement with literature values and reproducible results are obtained. Moreover, some limitations of the method are considered. First, the black paint layer influence on the heat transfer cannot be neglected in all the frequency ranges of measurement. Secondly, an accurate estimation of the thermal conductivity cannot be obtained without an exact knowledge of the heat transfer coefficient.

Abstract This work aimed to develop a new biocomposite material that could be used as thermal insulation in buildings. The goal was to investigate experimentally the effect of date palm fibers DPF (Phoenix dactylifera L. from Biskra oasis in Algeria) on thermal conductivity, water absorption and mechanical properties of gypsum based materials. Biocomposites containing various DPF filler contents and two different sizes of DPF were prepared. The results showed that the thermal conductivity of the gypsum based materials decreases with increasing the DPF concentration. We have shown that DPF loading may induce a high effect on the mechanical and thermal properties of the composites than the size fiber effect. The compressive and flexural strength of the biocomposites can be improved by adding the adequate fibers contents. This new kind of biocomposites exhibit good thermal and mechanical performances which allow it to be applied as thermal insulation materials.

Due to the high interest of appropriate characterization of PCM and hybrid PCM composites, different research centres and universities are using several material characterization techniques not commonly used with PCM, to study the structure and morphology of these materials. Likewise, physico-chemical stability is a crucial parameter for the performance of latent storage materials during time and its evaluation has been done by using molecular spectroscopy, chemiluminiscence or calorimetric tests. Atomic force microscopy and nanoindentation are also reported to characterize hybrid PCM composites.

Abstract In the present work, the hygrothermal behavior of a wall structure made of a novel biobased material, i.e. date palm fiber reinforced concrete was investigated. In this context, a specific setup was developed which allows simulating a bi-climatic environment with separate outdoor and indoor environments. This device made it possible to apply various scenarios of static / dynamic hygrothermal loading to the outer side of wall, involving variation/cycling of temperature (T) and /or relative humidity (RH). During these experiments, resulting variations of T and RH across the wall thickness were monitored with in-situ sensors. Outstanding thermo-hygric phenomena were highlighted, such as high coupling effect between heat and moisture transfers, resulting from evaporation-condensation and sorption-desorption processes. Besides, significant thermal and hygric inertia was observed through the Date Palme Concrete (DPC) wall. The response time of this DPC wall to temperature variations remains shorter than in the case of humidity variations. Even so, large damping effect is obtained compared to outdoor boundary conditions, which make this DPC wall a good candidate for mitigating overheating during summertime and reducing interstitial condensation as well.