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.
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.
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 (17.11kWh/m2) is one order of magnitude higher than the cooling one (2.82kWh/m2). 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.
•A numerical model of a combined solar collector and radiative cooler is presented.•A sensitivity analysis determines the most influencing parameters.•The potential of the device to perform the double functionality is demonstrated.
Heatwave weather files are needed to assess building performance under future heatwaves. This paper presents a methodology for producing a minimum set of heatwave weather files, which should be ...representative of the diversity of heatwaves expected in a location of interest. It is a four-step methodology. Weather projections are first collected from the CORDEX project database. Then, heatwaves are identified in the weather data. A list of independent and significant indicators is constructed to characterise the heatwaves. Samples of heatwaves are finally selected based on the list of indicators. The methodology was tested for the location of the Lyon-Saint Exupery Airport. A total of 2229 heatwaves were identified within 1260 years of weather projections. The heatwaves showed a high degree of diversity in terms of weather characteristics. The sampling process selected only 8 representative heatwaves. This number is sufficiently reduced to consider using the reduced set of heatwave weather files for assessing building performance.
•A 4-step methodology is built to select a representative set of future heatwaves.•Heatwaves are identified from climate projection of the CORDEX project.•Building EnergyPlus Weather (EPW) file from simulation data of the CORDEX project.•2229 heatwaves were identified for the location of Lyon Saint-Exupéry Airport.•The sampling process selected only 8 representative heatwaves.
Physisorption heat storage in buildings can be a key technology for a more effective use of heating energy. However, a better understanding of key factors influencing the design and control of such ...systems is necessary. This paper presents the sensitivity analysis of the modeling parameters in the case of an open zeolite 13X/moist air heat storage system for building applications. The quantities of interest are the heat storage density and the discharge power density of the system. At the beginning, the whole analysis space is composed of 21 physical properties and 7 operating conditions and geometrical properties. After a first threshold selection, analysis of variance is carried on the remaining parameters, with a full factorial design of experiments to perform a complete sensitivity analysis of the model. The results show that only 3 thermophysical properties, i.e. the heat of adsorption, the water vapor molar mass and the adsorption equilibrium, and 3 operating conditions and system geometry parameters, i.e. the inlet relative humidity, the bed length and the inlet fluid flow rate, drive the outlet power density and heat storage density. The way those 6 parameters influence the outputs is also discussed and quantitatively assessed.
Display omitted
•An ANOVA sensitivity analysis is carried on an open zeolite 13X heat storage model.•21 physical properties and 7 operating conditions and geometrical properties are analyzed.•Only 6 parameters drive the outlet power density and heat storage density.•Differential heat of sorption is the most influencing parameter for power and energy densities.•Inlet relative humidity is the most influencing operating condition for power and energy densities.
Thermal energy storage is a key technology for heat management and efficient use of renewable energy production. High-power and high-density heat storage in buildings can be achieved with ...physisorption. The present work presents a study of a full-scale zeolite 13X open reactor to be integrated in the ventilation system of a dwelling. An original numerical model of the system is developed and validated using various data obtained from eight sets of experiments. The analysis of the energy chain shows that approximately 70% of absorbed energy is converted into useful heat released on discharge. However, approximately half of the total heat is also directly lost at the outlet of the adsorbent bed. The overall system efficiency is 36%.
•A full-scale zeolite heat storage system is numerically investigated.•A numerical model is extensively validated including sorption isotherm and kinetics.•The model allows analyzing the energy chain represented using the Sankey diagram tool.•On the whole, the system efficiency is only 36%; most of energy is lost during charging phase.
This paper presents a simulation tool chain for the prediction of thermal comfort in passive urban buildings during summer and under heat wave conditions. The tool chain encompasses EnergyPlus ...building energy model and the Urban Weather Generator and UrbaWind tools to consider the impacts of the urban environment on building loads. This chain of tools is computationally efficient and does not require notable expertise for the simulations. To assess its accuracy, this simulation results are compared to in situ measurements. This paper describes the measurement setup, analyzes the measurement results and reveals a satisfactory model accuracy through a comparison to the measurement data. The average nighttime urban heat island between July and September 2020 reached 2.31 °C in the city of Lyon. Not considering the urban heat island effect (employing rural weather files) in urban thermal simulations could induce a 1 °C bias in indoor air temperature predictions. This could also result in overpredicting the cooling potential of natural ventilation during summer. Key parameters of the simulation accuracy are identified. These are the action schedule of occupants in regard to opening devices (shutters, windows and doors) and the urban boundary layer height at night.
•An Urban Thermal Tool Chain simulates the thermal behaviour of urban buildings.•The developed UTTC is devoted to passive buildings under summer conditions.•The UTTC includes EnergyPlus, Urban Weather Generator, and UrbaWind.•In-situ measurements were carried out on four types of buildings in Lyon.•Remarkable correspondence between simulations and measurements.
Display omitted
•We simulate convection movement in DSC capsules with PCM.•We describe qualitatively the convection perturbation on the thermogram.•We quantify the amplitude and the location of the ...perturbation with three correlations.•The correlations are valid for a wide range of measurement conditions.•It is now possible to fix a limiting temperature growth rate to avoid convection perturbation.
The paper investigates the effect of natural convection during differential scanning calorimetry measurements of phase change materials. We performed series of numerical simulations to characterize and quantify the perturbation on the measured thermogram. This perturbation becomes significant at the end of the fusion process. It manifests itself as an increase of the heat flux amplitude which accelerates the fusion process. Three correlations are built from the simulation results. The two first correlations quantify the amplitude of the heat flux deviation. The third correlation locates the time at which the perturbation occurs. The correlations are valid for large DSC capsules (around 1ml), and high Prandtl materials (paraffins, salt hydrates, fatty acids). They enable to define the experimental conditions for which natural convection becomes negligible.
AbstractThis paper delivers a detailed statistical assessment of pavement rehabilitation treatments by delivery methods via studying their performance in terms of pavement indicators (international ...roughness index, rutting depth, and pavement condition rating) and in terms of their pavement service lives. The data include 812 pavement segments that were rehabilitated under six commonly implemented treatments and through six commonly used delivery methods with a focus on public–private partnerships (PPP), which were let or completed in the United States between 1996 and 2011. The treatments include a two-course hot-mix asphalt (HMA) overlay with or without surface milling, concrete pavement restoration; three-course HMA overlay with or without surface milling; three-course HMA overlay with crack and seat of portland cement concrete pavement; 3R (resurfacing, restoration, and rehabilitation) and 4R (resurfacing, restoration, rehabilitation and reconstruction) overlay treatments; and 3R/4R pavement replacement treatments. The delivery methods/PPP types include performance-based contracting, cost-plus-time, incentives/disincentives, design-build and their derivatives, warranties, and lane rentals. To model and forecast pavement performance, a three-stage least-squares approach is employed. For the pavement service life analysis, the elapsed time until the pavement crosses a threshold is investigated, using random parameter hazard-based duration models. Separate models are estimated for each combination of delivery method/PPP type and rehabilitation type. The model estimation results show that several influential factors, such as traffic, weather, and pavement characteristics along with drainage condition affect pavement performance and pavement service life; these factors differ among pavement rehabilitation treatments and delivery methods/PPP types.
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.
PDF
