104 research outputs found
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Diagnosing and Remote Sealing of Leakage in Low-Pressure Sections of Natural Gas Distribution Networks
No full textResidential natural gas is estimated as responsible for almost 15% of California’s total methane (CH4) emissions from natural gas. It is not known what fraction of these emissions is due to fugitive leaks in the low-pressure portions of the natural gas distribution network. This research aimed to diagnose and potentially seal leakage in the low-pressure portions of natural gas distribution networks by using aerosols. This included developing and testing protocols for measuring leakage downstream of the meter in houses and commercial buildings, applying those protocols in 10 different locations, designing a system to seal leaks in those systems remotely, and applying the sealing process in a make-shift pipe network. Only 2 out of the 10 locations tested were above the leakage detection limit in unsealed networks; the variation in gas temperature posed a challenge to diagnosing the leakage rates. The aerosol process employed for remote sealing appeared to be capable of sealing leaks in natural gas distribution pipes but will require more refinement to address the extremely low leakage levels observed in this study
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Energy and Indoor Air Quality Impacts of Compartmentalization and Different Ventilation Strategies in California Multifamily Buildings
No full textCompartmentalization has been proposed as a strategy to improve indoor air quality (IAQ) and energy efficiency in multifamily buildings. California’s 2022 Building Energy Efficiency Standards requires multifamily buildings to either meet a unit airtightness requirement of 0.3 cfm50/ft2 or provide balanced ventilation. While there is consensus that compartmentalization enhances building performance, not enough studies exist to accurately quantify the impacts of different compartmentalization levels on pollutant exposure and energy usage. Furthermore, builders have raised concerns over the difficulty of meeting the airtightness requirement. Such discussion has called into question whether the IAQ benefits and energy savings achieved from compartmentalization justify the current requirement or support a stricter or more lenient requirement. Regulators need this primary data to develop well-informed building codes that promote safety, affordability, and energy efficiency. The study found that new-construction multifamily buildings are meeting the compartmentalization requirement with an average unit leakage of 0.16 cfm50/ft2. Ventilation flow testing suggested that adjusting flow rates down to the minimum ventilation requirement for each unit and installing air filters on dedicated outdoor air intakes could improve IAQ and save energy. Inter-unit transfer of secondhand was modeled to reduce significantly for tighter units, resulting in concentrations below hazardous exposure limits in non-smoking units. Annual energy savings from compartmentalization were estimated to be as much as 6% and GHG savings as much as 10%, however results were highly sensitive to climate zone and ventilation strategy
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Efficient thermal energy distribution in commercial buildings - Final Report
No full textL’avenir du temps de travail et des organisations syndicales sous l’angle de la loi du 5 mars 2017 et de la doctrine marxienne
No full textA travers l'analyse juridique de la réforme du 5 mars 2017 sur le travail "faisable et maniable", nous nous interrogeons sur l'évolution du temps de travail et les impacts pour les travailleurs. Nous nous intéressons particulièrement à l'annualisation du temps de travail et aux heures supplémentaires volontaires. a travers la lecture de certains textes de Karl Marx, nous nous demandons si cette réforme va nous permettre de nous libérer du travail alimentaire, instrumental pour retrouver un travail qui sera essence de l'homme. Nous conclurons qu'au contraire de ce Marx prône, nous nous aliénons encore plus à l'économie grâce à cette réforme.Master [60] en sciences du travail (horaire décalé), Université catholique de Louvain, 201
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Energy impacts of attic duct retrofits in Sacramento houses
No full textInefficiencies in air distribution systems have been identified as a major source of energy loss in US sunbelt homes. Research indicates that approximately 30--40% of the thermal energy delivered to the ducts passing through unconditioned spaces is lost through air leakage and conduction through the duct walls. Field experiments over the past several years have well documented the expected levels of air leakage and the extent to which that leakage can be reduced by retrofit. Energy savings have been documented to a more limited extent, based upon a few field studies and simulation model results. Simulations have also indicated energy loss through ducts during the off cycle caused by thermosiphon-induced flows, however this effect had not been confirmed experimentally. A field study has been initiated to separately measure the impacts of combined duct leak sealing and insulation retrofits, and to optimize a retrofit protocol for utility DSM programs. This paper describes preliminary results from 6 winter and 5 summer season houses. These retrofits cut overall duct leakage area approximately 64%, which translated to a reduction in envelope ELA of approximately 14%. Wrapping ducts and plenums with R-6 insulation translated to a reduction in average flow-weighted conduction losses of 33%. These experiments also confirmed the appropriateness of using duct ELA and operating pressures to estimate leakage flows for the population, but indicated significant variations between these estimates and measured flows on a house by house basis. In addition, these experiments provided a confirmation of the predicted thermosiphon flows, both under winter and summer conditions. Finally, average material costs were approximately 20% of the total retrofit costs, and estimates of labor required for retrofits based upon these experiments were: 0.04 person-hrs/cm{sup 2} of duct sealed and 0.21 person-hrs/m{sup 2} of duct insulated
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Zone conditioning in a California foothill house
No full textThe principal focus of the reported research is the performance of the installed zoned air distribution system in a house located in the foothills northeast of Sacramento California. The 297 m{sup 2} two story house contained a central air conditioner and an air distribution system with four dampered supply duct legs. The air conditioning system included a two speed fan and two speed compressor, with the air handler placed inside a closet and almost all the ducts located inside the building envelope. The uninsulated sheet metal ducts ran inside a space between stories and in interior walls. The performance parameters examined included: (1) duct leakage, (2) duct conduction, (3) zoning performance and (4) equipment efficiency impacts. In conclusion, two major points were made concerning the test house. The first was that substantial energy benefits were obtained by placing the ducts inside the conditioned space. The second was that the energy benefits from zoning the house were not realized, primarily due to thermal stratification and the open floor plan in the house. Secondary impacts lowering zoning performance were the k& of return duct dampers and leakage and conduction losses in the air distribution system. Utility programs or building standards promoting zoning as a means of conserving energy or reducing peak power demand should be aware of the many potential pitfalls that can arise with zone conditioning, particularly with dampered air distribution systems
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Thermal performance of residential duct systems in basements
No full textThere are many unanswered questions about the typical effects of duct system operation on the infiltration rates and energy usage of single- family residences with HVAC systems in their basements. In this paper, results from preliminary field studies and computer simulations are used to examine the potential for improvements in efficiency of air distribution systems in such houses. The field studies comprise thermal and flow measurements on four houses in Maryland. The houses were found to have significant envelope leakage, duct leakage, and duct conduction losses. Simulations of a basement house, the characteristics of which were chosen from the measured houses, were performed to assess the energy savings potential for basement house. The simulations estimate that a nine percent reduction in space conditioning energy use is obtained by sealing eighty percent of the duct leaks and insulating ducts to an R-value of 0.88 {degree}C{center_dot}m{sup 2}/W (5{degree}F{center_dot}ft{sup 2}{center_dot}h/BTU) where they are exposed in the basement. To determine the maximum possible reduction m energy use, simulations were run with all ducts insulated to 17.6 {degree}C{center_dot}m{sup 2}/W (100 {degree}F{center_dot}ft{sup 2}{center_dot}h/BTU) and with no duct leakage. A reduction of energy use by 14% is obtained by using perfect ducts instead of nominal ducts
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