Search results for "Insulation"
showing 10 items of 61 documents
Partial discharge of gel insulated high voltage power modules subjected to unconventional voltage waveforms
2016
Performances and duration of the new generation of high voltage power electronic components are dependent on dielectric materials aim to insulating their internal terminals. The presence of defects, some due to faults generated during the manufacturing process, but also due to the internal design of layers and connections, can cause local enhancements of electric field and consequently possible activity of partial discharges phenomena or other effects (aging, tracking) that may result in reduction of device reliability. Furthermore, the usage of unconventional voltage waveforms, like square waves or pulse width modulated waves, additionally increases the electrical aging of the insulation s…
Deformation of bubbles in silicon gel insulation under an alternating electric field
2019
The behavior of silicone gel under electrical stress plays a significant role in the reliability and durability of high voltage electronic power devices due to its widespread use for the insulation of IGBT modules and other components. The charges accumulation at the bubble boundaries leads to significant displacements due to the establishment of Coulombic forces and the high deformability of colloidal system. The main purpose of this work is to validate a numerical approach useful to investigate, for a given silicone gel, the non-linear relation between the applied HVDC stress and the electric field over an air bubble within the insulation bulk. The analysis has been carried out by means o…
Sprint mechanics evaluation using inertial sensor-based technology: A laboratory validation study.
2018
Advances in micro-electromechanical systems have turned magnetic inertial measurement units (MIMUs) into a suitable tool for vertical jumping biomechanical evaluation. Thus, this study aimed to determine whether appropriate reliability and agreement reports could also be obtained when analyzing 20-m sprint mechanics. Four bouts of 20-m sprints were evaluated to determine whether the data provided by a MIMU placed at the lumbar spine could reliably assess sprint mechanics and to examine the validity of the MIMU sensor compared to force plate recordings. Maximal power (P0), force (F0), and velocity (V0), as well as other mechanical determinants of sprint performance associated with the force-…
A bottom-up harmonized energy-environmental models for europe (BOHEEME): A case study on the thermal insulation of the EU-28 building stock
2021
Abstract The paper presents a methodological approach, called “BOttom-up Harmonized Energy-Environmental Models for Europe” (BOHEEME), that combines bottom-up modeling, energy dynamic simulation, and life cycle assessment for evaluating and comparing the energy and environmental effects of different renovation strategies of the residential EU building stocks, from micro to the macro level. The study defines 672 building models representative of the residential EU-28 building stocks built before 2010, called archetypes, and the improvement of their envelope, applying different insulation materials from a traditional one to bio-based materials and studying their environmental effects via LCA.…
Multi-objective optimization of building life cycle performance. A housing renovation case study in Northern Europe
2020
While the operational energy use of buildings is often regulated in current energy saving policies, their embodied greenhouse gas emissions still have a considerable mitigation potential. The study aims at developing a multi-objective optimization method for design and renovation of buildings incorporating the operational and embodied energy demands, global warming potential, and costs as objective functions. The optimization method was tested on the renovation of an apartment building in Denmark, mainly focusing envelope improvements as roof and exterior wall insulation and windows. Cellulose insulation has been the predominant result, together with fiber cement or aluminum-based cladding …
Building integrated solar thermal design: assessment of performances of a low cost solar wall in a typical Italian building
2016
Abstract Present work deals with the topic of building integration of solar thermal collector (BIST) as a refurbishment measure. Such equipment, more than its main function as heating generator, plays a specific role as a building component (envelope finishes, thermal insulation layer, roof cover etc). Consequently, from a heat transfer point of view, an integrated component affects twice the global building balance: supporting the thermal plant (i.e. providing heat for final uses) and modifying the wall heat-transfer pattern (i.e. reducing thermal losses). In turn, the collector performance itself is influenced by the wall structure (back losses reduction). Present work proposes a method f…
An integrated energy simulation and life cycle assessment to measure the operational and embodied energy of a Mediterranean net zero energy building
2022
Abstract Net Zero Energy Buildings can play a key role in reducing the energy use, greenhouse gas emissions and the use of natural resources associated to the built environment. It is widely recognized that in low energy building a shift in relevance may occur from the operational to the embodied impacts. However, building performance assessment focus mostly on the operational phase and on primary energy consumption. This study aims to assess the energy and environmental impacts of a residential net zero energy building expanding the analysis to the full life cycle and to a wide range of environmental impact categories. The methodological approach integrates a non-steady state building ener…
Effect of Sheep Wool Fibers on Thermal Insulation and Mechanical Properties of Cement-Based Composites
2019
The use of sheep wool as a filler of cement in order to produce mortar or plaster involves several advantages for environment and energy. Moreover, it is considered as a waste and, therefore, its use is characterized by low cost. The aim of this paper is to evaluate the influence of wool fibers on thermal conductivity and mechanical properties of cement. The samples were prepared using wool fibers, obtained from a breed of Sicilian sheep, with three different lengths (i.e., 1, 6, and 20 mm). Furthermore, in order to evaluate the influence of fiber content, the samples were prepared by varying the fiber weight fraction. The thermal conductivity of the samples was analyzed by using a heat flo…
Experimental study and physical modeling of simultaneous heat and moisture transfer in bio-sourced insulating materials.
2019
The conventional heat transfer models are not sufficiently suitable for thermal characterization of bio-sourced thermal insulating materials due to their strongly hydrophilic nature. The proposed work in this PhD thesis aims to answer this problem with experimental and theoretical approaches of coupled heat-moisture transfers. In the experimental approach, a thermal insulating material based on Flax Fiber Felt (FFF) is developed and then characterized at different hygrometric conditions with an asymmetric hot plate device. The humidity diffusion characterization of the samples is done using the GAB, GDW and Park theoretical moisture adsorption isotherm models. In the theoretical approach, a…
Investigation on a Bio-Composite Material as Acoustic Absorber and Thermal Insulation
2020
In order to limit the anthropic emissions of CO2, research is currently investigating new materials for the building sector. The main purpose is the reduction in the embodied energy consumption, especially in the residential sector, and consequently the limitation of the direct and indirect utilization of fossil fuels, for the indoor heating, cooling, and ventilation services. Indeed, the residential sector is affected by a high energy demand, thus the choice of improved materials is fundamental to improve the sustainability. All phases: construction, building life, and dismantling are impacting in terms of resource and energy consumption, both associated with the emissions of pollutants in…