86,773 research outputs found
The impact of an ideal dynamic building envelope on the energy performance of low energy office buildings
No full textThis paper shows the results of a research activity aimed at assessing the advantages of an ideal adaptive building skin over conventional building envelope systems. The basic idea underlying the research consists in imagining an ideal building envelope system characterised by the capability of continuously changing (within a certain range) some of its thermo-physical and optical properties. The reason for the continuous tuning of thermo-physical and optical properties lies in the assumption that an optimised (fixed) configuration, where the properties do not change over time, is not able to minimise the total energy demand of the building at each moment. For the sake of this purpose, an ideal dynamic WWR (Window-to-Wall Ratio) building envelope system for low energy office buildings was modelled and simulated. An integrated thermal-lighting building simulation tool was used. The energy performance of such a system was then analysed and compared against the performance of a conventional façade realised with best-available technologies. The results of the investigation demonstrated the advantages of a dynamic WWR configuration over a static one. However, the improvements achieved in energy demand were lower than expected. This behaviour is strictly related to the configuration of the building used as a reference, which already showed a very high energy performance. Limitations presented by the research method are also briefly pointed out and discussed
Optimizing the configuration of a façade module for office buildings by means of integrated thermal and lighting simulations in a total energy perspective
No full textThe building enclosure plays a relevant role in the management of the energy flows in buildings and in the exploitation of solar energy at a building scale. An optimized configuration of the façade can contribute to reduce the total energy demand of the building. Traditionally, the search for the optimal façade configuration is obtained by analyzing the heating demand and/or the cooling demand only, while the implication of the façade configuration on artificial lighting energy demand is often not addressed. A comprehensive approach (i.e. including heating, cooling and artificial lighting energy demand) is instead necessary to reduce the total energy need of the building and the optimization of the façade configuration becomes no longer straightforward, because non-linear relationships are often disclosed. The paper presents a methodology and the results of the search for the optimal transparent percentage in a façade module for low energy office buildings. The investigation is carried out in a temperate oceanic climate, on the four main orientations, on three versions of the office building and with different HVAC system's efficiency. The results show that, regardless of the orientations and of the façade area of the building, the optimal configuration is achieved when the transparent percentage is between 35% and 45% of the total façade module area. The highest difference between the optimal configuration and the worst one occurs in the north-exposed façade, while the south-exposed façade is the one that shows the smallest difference between the optimal and the worst configuratio
Functional Nonparametric Model for Time Series: a Fractal Approach for Dimension Reduction
No full textSpectral and angular solar properties of a PCM-filled double glazing unit
No full textBackground
Phase change materials (PCMs) have been proposed as a means to increase the thermal inertia of glazing systems. These materials have optical features that need to be investigated and characterised in order to better understand the potential of these systems and to provide reliable data for numerical simulations.
Methods
The spectral and angular behaviour of different PCM glazing samples, characterised by different thicknesses of PCMs, were investigated by means of commercial spectrophotometer and by means of a dedicated optical test bed that includes a large integrating sphere with a diameter of 0.75 m. Such equipment was necessary because of the highly diffusive behaviour of the PCM layer when in the solid state of aggregation.
Results
The paper provides a data set of luminous and solar properties of glazing units with PCMs in gaps; the data set uses results from an advanced optical facility that overcomes the intrinsic limitations of commercial spectrophotometers in measuring the optical properties of the advanced transparent materials. In detail, transmittance, reflectance and absorptance spectra of double glazing units characterised by different PCM layer thicknesses in the gap, measured at different incident beam angles, are reported. Integrated values calculated according to relevant international standards are thus provided. Optical features of PCM glazing systems are also highlighted and issues related to the integration of these systems in buildings are discussed
Régression non-paramétrique pour des variables aléatoires fonctionnelles mélangeantes
No full textCharacterization of the optical properties of a PCM glazing system
No full textThe optical char acteristics of an advan ced glazin g sy stem are p resented in this p ap er. The investigated glazin g sy stem is based on the incorp oration of a p araffin-based Phase Change M aterial (PCM) into a transp arent comp onent, made of two extra-clear glass p anes and a cavity where the PCM lay er is p laced.
Due to the highly scattering p rop erty of the sy stem (when the PCM is in solid state), the use of a lar ge integr ating sp here equip ment (75 cm diameter) is necessary to obtain reliable results.
The sp ectral transmission, reflection and absorp tion coefficients of the PCM glazin g sy stem are measured b etween 400 and 2000 nanometers, and the integr ated valu es are calcu lated accordin g to the relevant standards. The optical p rop erties are determined with a maximu m relative error of 4% (on the sum of the transmission, reflection and absorption coefficients), when the PCM lay er is either in comp lete solid state or liqu id state. The average error for all the op tical p rop erties is 2%.
Different thicknesses of the PCM lay er are used in order to assess the dep endency of the optical p rop erties on the PCM lay er thickness. The angular dep endency is also investigated for beam angle up to 45 deg
Modelling and validation of a single-storey flexible double-skin façade system with a building energy simulation tool
No full textDouble skin facades are adaptive envelopes designed to improve building energy use and comfort performance. Their adaptive principle relies on the dynamic management of the cavity's ventilation flow and, when available, of the shading device. They can also be integrated with the environmental systems for heating, cooling, and ventilation. However, in most cases, the possible exploitation of the ventilation airflow is not fully enabled, as the adoption of only one or two possible airpath limits the possibility that this facade architecture offers, meaning that flexible interaction with the environmental systems cannot be planned. This work aims to develop, using an existing software tool for building energy simulation, a numerical model of a flexible double-skin facade module capable of fully exploiting the adaptive features of such an envelope concept by switching between different cavity ventilation strategies. Leveraging the "Double Glass Facade" component available in IDA ICE, a new model for a flexible double-skin facade module was developed, and its performance in replicating the thermophysical behaviours of such a dynamic system was assessed by comparison with experimental data collected through a dedicated experimental activity using one the outdoor test cells of the TWINS facility in Torino (Italy). The accuracy of the predictions of the new model for a flexible double-skin facade was in line with that obtained by the conventional "Double Glass Facade" component to simulate traditional double-skin facades. The mean bias errors obtained were lower than 1.5 degrees C and 4 W/m2, for air and surface temperature values and for transmitted long-wave or short-wave heat flux values, respectively. By establishing a new archetype model to study the performance and optimal integration of a large class of double-skin facade modules, including fully flexible ones, this work demonstrates the possibility of modifying existing models in building energy simulation tools to study unconventional building envelope model solutions such as adaptive facade systems
Modelling double skin façades (DSFs) in whole-building energy simulation tools: Validation and inter-software comparison of naturally ventilated single-story DSFs
No full textBuilding energy simulation (BES) tools offer the possibility to integrate double skin façade (DSF) technologies into whole building simulation through dedicated modules or possible workarounds. However, the reliability of such tools in predicting the dynamic heat and mass transfer processes within the DSFs is still to be determined. Therefore, this paper aims to assess the performance of four popular BES tools (i.e. EnergyPlus, TRNSYS, IDA-ICE and IES-VE) in predicting the thermal behaviour of one-storey naturally ventilated DSF in three different ventilation modes. To evaluate their capability to predict thermophysical quantities, we compared the simulation results with experimental data. The results show that it is not possible to identify a tool that outperforms the others for all the analysed quantities, especially for the cavity air temperature, which is the least accurate parameter in all software due to underestimation of the daytime peak. IES-VE seems to be most accurate for Supply Air and Thermal Buffer modes when shading is deployed, while EnergyPlus appears most accurate for Outdoor Air Curtain mode. When it comes to surface temperatures and transmitted solar radiation, TRNSYS appears to be the best-performing software. In addition, this study investigated the challenges that designers may face when modelling a naturally ventilated DSF using whole-building simulation tools. Moreover, the investigation elucidates the challenges that have a more significant effect on the performance of the BES tools in order to reinforce their reliability
Relation between daylight availability and electric lighting in a single-family house
No full textDaylight availability is an important aspect that can potentially improve both the quality and the energy performance of buildings. However, it is not always straightforward easy to assure that an increase in the daylight availability leads to a reduction of electric energy use for artificial lighting. In this study, experimental measurements and numerical simulations were conducted to analyse the relation between the uses of artificial light and the daylighting availability for different groups of users who lived for one month each in a Zero Emission Building single-family house located in Trondheim, Norway. The use of electric lighting and the outdoor environment conditions (irradiance and illuminance on the horizontal plan) were recorded through advanced daylighting simulations, carried out with DIVA-for-Rhino, the daylighting availability during the periods of occupancy was then reconstructed, using as input data the outdoor environmental variable recorded during the experimental analysis. The results show that the coefficient of correlation between daylight availability and the artificial light is in general low and the use of artificial lighting seems to be largely independent from the availability of natural light
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