1,720,972 research outputs found
Thermal mass activation by means of night cooling: comparison on different techniques and strategies
No full textEnergy performance of thermally activated hollow core ceilings in an high rise office building
No full textInnovative technologies for transparent building envelopes: experimental assessment of energy and thermal comfort data to facilitate the decision-making process
No full textIn the last years, energy use for building heating, cooling, lighting and ventilation still accounts for more than one third of the total, primary energy demand in the industrialized countries. In this context, the Directive 2010/31/EU EPBD recast was developed, with the purpose of reducing the EU energy consumption, improving the exploitation of renewables and reducing the greenhouse gas emission. In this perspective, the building envelope system needs to be improved. A number of
innovative technologies have been developed but they need to penetrate the market moving from
being prototypes and samples in laboratory to be available and usable technologies.
In this work it is presented a research aimed at facilitating the decisions making process during the
design phase related to building transparent envelopesIndeed, within the national project called
"Bâtiville", a configurator library has been conceived to optimize the choice of envelope
components to design new near-zero energy districts.
The research started with a state of the art and a market survey of some recent innovative solutions
for fenestration. Therefore, some of them have been analysed in-field and in test cells: PCM material to improve the poor thermal inertia of the glass and self-switchable technologies such as thermotropic. Experiments were carried out by means of a test cell located on the roof and exposed
to real boundary condition in order to continuously monitor the thermal behaviour of the transparent prototypes during different seasons. Results concerning the thermal and energy performance of the different technologies have been used to implement the library of the design configurator and they are presented in this work. Some criticism is underlined when dealing with highly dynamic transparent technologies, due to the fact that it is not possible to characterize their behaviour with conventional synthetic parameters. This difficulty was met particularly for the glazing with PCM and the thermotropic glazing.
A new methodology for the design phase is proposed to simplify and optimize the designers' choice among innovative envelope technologies, besides encourage their spread. The experimental results of innovative transparent glazing are presented and discussed, showing promising performances of the innovative technologies analysed
A new method for air exchange efficiency assessment including natural and mixed mode ventilation
No full textThe COVID-19 health crisis highlighted the correlation between air exchange efficiency and virus airborne transmission. Air exchange efficiency is a performance index able to characterize ventilation effectiveness in buildings. Some standards, such as ASHRAE 129, clearly define assessment procedures of air exchange efficiency for mechanical ventilation, adopting tracer gas techniques. However, standardized procedures are based on measurements at the exhaust and cannot be adopted for natural and mixed mode ventilation strategies. In the ‘80s, Sandberg suggested that tracer gas decay technique enables to measure simultaneously the nominal time constant (through air change rate measurements) and the mean age of air in several points of the ventilated zone. This paper aims to present practical issues and uncertainty analysis related to the implementation of this approach, in a new commissioning protocol. For this purpose, we compare the new procedure, based on Sandberg's observation, with the ASHRAE 129 protocol for mechanical ventilation. Results coming from field campaigns show that the difference between air exchange efficiency values obtained using ASHRAE 129 protocol (51.8%) and the new procedure (47.4%) are usually negligible in low airflow rate, considering an average uncertainty of ± 7.0%. Results show that the procedure is robust and that it is technically possible to implement it to natural and mixed-mode ventilation
Investigating the effects of climate on thermal adaptation: A comparative field study in naturally ventilated university classrooms
Full text linkIn educational buildings, adaptive strategies can be adopted for the achievement of thermal comfort and reduction of energy consumption. Since climate can largely affect thermal comfort, there is a need for understanding its role in the definition of different adaptive capacities, thermal neutrality, comfort, and preference. To this end, 17 naturally ventilated university classrooms from 10 different buildings located in two sub-climates of Italy (Mediterranean climate) and France (Continental climate) were analysed. In total, 1377 questionnaires associated with environmental parameters were collected. The same educational stage (i.e. university classrooms) and operation mode (i.e. naturally ventilated during the heating period) were investigated to remove possible biases related to their influence on thermal comfort perception. Field studies show that despite French students performing less adaptive actions, their neutral temperature (TN) was 3.1 °C lower than the Italian ones (TN,ITALY = 23.6 °C and TN,FRANCE = 20.5 °C) and this difference was statistically significant. Adaptation as a function of the sub-climate was evident from the comparison with the PMV-PPD model. Neutral temperatures calculated with PMV were higher than those obtained from TSV, and the difference increased for the French colder climate. Practically, students’ adaptation to colder environments can be deployed to ensure comfort while reducing the heating demand
Empirical and comparative validation of an original model to simulate the thermal behaviour of outdoor test cells
No full textCalorimetric methods for the performance assessment (e.g. for the determination of the solar factor) of transparent building components have been largely applied in indoor laboratories under steady-state conditions and in outdoor test cells under dynamic boundary conditions provided by real weather. In the latter case the accuracy of the measurements depends significantly on the temporary storage of energy in the test cell envelope. An analysis by Pagliano et al. (2017) developed a dedicated lumped thermal model in Matlab environment in order to improve the design of calorimeters for the measurement of the solar factor by minimizing the energy storage effects in the envelope of the calorimeter and estimating precisely their entity. The developed model was based on literature studies on buildings’ dynamic energy simulations and adopted some common hypotheses used by existing building energy simulation software tools. However, when modelling light-mass and highly insulated buildings, such as test cell facilities, small variations in the power inputs can generate significant variations of the internal temperatures, challenging for the model to follow accurately. In order to verify the accuracy of the developed model in predicting the thermal behaviour of an outdoor test cell, an extensive validation work has been carried out. In particular, this paper summarises (i) an experimental validation carried out using a data set from the BESTLab facility, located at the research centre Électricité de France R&D Les Renardières (FR) and (ii) an intermodel comparison between the code developed in the Matlab environment and TRNSYS, a well-established building energy simulation tool. Concerning the validation at the BESTLab, the results show that the model is able to predict the temperature evolution of the internal air and of the internal surfaces of the envelope with good accuracy, with residuals lying within a range of ± 1 °C; reasons for discrepancies between measurements and predictions are discussed in the paper. As regards the intermodel comparison, the correspondence between the two software tools is generally good, with residuals lying most of the time within a range of ± 0.5 °C. The residuals are lower for the intermodel comparison, partly because input values are in this case not affected by uncertainty. Although TRNSYS and the developed Matlab code adopt some similar assumptions and simplifications, they also present some modelling differences that are highlighted in the paper. © 2017 Elsevier B.V
Developing a new adaptive heat balance model to enhance thermal comfort predictions and reduce energy consumption
No full textAccurate thermal comfort prediction is essential for enhancing both thermal comfort and energy efficiency in buildings. The heat balance and adaptive models, while widely used, have been often questioned in relation to their strengths and limitations. To overcome these challenges, a comprehensive understanding of both the physical parameters influencing heat exchange and occupants’ adaptive capacities is essential. This study introduces an analytical method to formulate a new adaptive heat balance model, the adPMV, which integrates the strengths of both models considering various parameters influencing thermal perception. The model integrates the PMV with an adaptive factor associated with the running mean outdoor temperature, in line with adaptive theory. Tested on 1377 samples from European university classrooms, the adPMV demonstrates enhanced accuracy (MAE=0.74, RMSE=1.01, MBE=-0.11) compared to PMV and other adaptive heat balance models. Validation on naturally ventilated university classrooms from ASHRAE's databases further confirms promising results, showcasing reduced error indices (MAE=0.68, RMSE=0.81, MBE=-0.03). Notably, using adPMV setpoints not only improves thermal sensation prediction accuracy but also leads to a substantial reduction in heating demand, reaching up to 40 %. The adaptability of this model to different contexts, such as building types, climates, and HVAC system operations, presents it as a versatile tool for exploring adaptive principles
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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