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A systematic investigation to understand the use of a novel axial impeller as a part of counter-rotating axial compressor to compress water vapor as refrigerant was undertaken. Blade angle was investigated at first to understand this novel impeller’s geometry. A commercial CFD package, which solves the Reynolds-averaged Navier–Stokes equations, was used to compute the complex flow field of the impeller. Two hub/shroud tip ratios with different speed ratios were numerically simulated. The numerical simulation focused on the water vapor flow from compressor impeller inlet to outlet and the overall performance level and range were predicted. The numerical investigation revealed that at hub/shroud tip ratio of 0.54, maximum pressure ratio reached about 1.24 with isentropic efficiency around 75\% at its design point. Detailed investigation into flow structure showed that a serious secondary flow exists between span ranges of 30–50\%. An enlargement of hub/shroud tip ratio to 0.75 showed that pressure ratio had been improved significantly. By comparing different speed ratios and hub/shroud tip ratios, the study shows potential to utilize this novel axial impeller to compress water vapor as refrigerant.

Neutron and electron spectroscopy reveal diffusion behavior of individual ions in lithium garnets, paving the way towards high-performance aqueous lithium batteries.

Abstract Building integrated photovoltaics (BIPV) perform traditional architectural functions of walls and roofs while also generating electricity. The displacement of utility generated electricity and conventional building materials can conserve fossil fuels and have environmental benefits. A life cycle inventory model is presented that characterizes the energy and environmental performance of BIPV systems relative to the conventional grid and displaced building materials. The model is applied to an amorphous silicon PV roofing shingle in different regions across the US. The electricity production efficiency (electricity output/total primary energy input excluding insolation) for a reference BIPV system (2kWp PV shingle system with a 6% conversion efficiency and 20 year life) ranged from 3.6 in Portland OR to 5.9 in Phoenix, AZ indicating a significant return on energy investment. The reference system had the greatest air pollution prevention benefits in cities with conventional electricity generation mixes dominated by coal and natural gas, not necessarily in cities where the insolation and displaced conventional electricity were greatest.

Stack models require consideration of interactions between cells owing to practical variation of cell model parameters and different location/environment in the stack leading to thermal, electrical and mass transfer gradients. A previously developed voltage/current distribution model (electrical interaction) was extended and validated using two types of anomalies (bus plate material change, partially inactive cell located at the stack center), two anomaly locations and one or two anomalies within the stack. A measurement method for the principal cell interaction damping factor is discussed which can be used to easily and approximately predict the number of cells that are impacted by an anomaly.

Abstract A comprehensive case study life cycle assessment (LCA) was conducted of a 7300 m2, six-story building with a projected 75 year life span, located on the University of Michigan campus. The bottom three floors and basement are used as classrooms and open-plan offices; the top three floors are used as hotel rooms. An inventory of all installed materials and material replacements was conducted covering the building structure, envelope, interior structure and finishes, as well as the utility and sanitary systems. Computer modeling was used to determine primary energy consumption for heating, cooling, ventilation, lighting, hot water and sanitary water consumption. Demolition and other end-of-life burdens were also inventoried. The primary energy intensity over the building’s life cycle is estimated to be 2.3×106 GJ, or 316 GJ/m2. Production of building materials, their transportation to the site as well as the construction of the building accounts for 2.2% of life cycle primary energy consumption. HVAC and electricity account for 94.4% of life cycle primary energy consumption. Water services account for 3.3% of life cycle primary energy consumption, with water heating being the major factor, due to the presence of hotel rooms in this building. Building demolition and transportation of waste, accounts for only 0.2% of life cycle primary energy consumption. All impact categories measured (global warming potential, ozone depletion potential, acidification potential, nutrification potential and solid waste generation) correlate closely with primary energy demand. The challenges in developing a life cycle model of a complex dynamic system with a long service life are explored and the implications for future designs are discussed.

The neurobiological processes involved in establishing sleep regulation are vulnerable to environmental exposures as early as seven weeks of gestation. Studies have linked in utero pesticide exposure to childhood sleep-disordered breathing. However, the impact of in utero pesticide exposure on the sleep health of adolescents remains unexplored.Data from 137 mother-adolescent pairs from a Mexico City cohort were analyzed. We used maternal urinary 3-phenoxybenzoic acid (3-PBA, pyrethroid metabolite) and 3, 5, 6-trichloro-2-pyridinol (TCPy, chlorpyrifos metabolite) from trimester three to estimate in utero pesticide exposure. Among adolescents, we obtained repeated measures of objectively assessed sleep duration, midpoint, and fragmentation using wrist-actigraphy devices for 7 consecutive days in 2015 and 2017. Unstratified and sex-stratified associations between maternal urinary 3-PBA and TCPy and adolescent sleep measures were examined using generalized linear mixed models (GLMMs). We also examined the interactive effects of maternal pesticide exposure and offspring sex on sleep outcomes.3-PBA and TCPy were detected in 44.4% and 93% of urine samples, respectively. Adjusted findings demonstrated that higher exposure to maternal TCPy was associated with longer sleep duration and later sleep timing. Findings from interaction tests between maternal pesticide exposure and offspring sex were not statistically significant, although adjusted sex-stratified findings showed that the association between TCPy with duration and midpoint was evident only among female offspring. To illustrate, those in the highest tertile of exposure had a 59 minute (95% CI: 12.2, 104.8) (p, trend = 0.004) longer sleep duration and a 0.6 hour (95% CI: 0.01, 1.3) (p, trend = 0.01) later sleep midpoint. We found no significant associations between 3-PBA and sleep outcomes.Within a cohort of mother-adolescent pairs, we found associations between maternal prenatal pesticide exposure and longer sleep duration and later sleep timing among adolescent offspring. Further, this association may be female-specific.

The performance of thermoelectric (TE) materials has improved tremendously over the past decade. The intrinsic thermal and electrical properties of state-of-the-art TE materials demonstrate that the potential for widespread practical TE applications is very large and includes TE generators (TEGs) for automotive waste heat recovery. TE materials for automotive TEG applications must have good intrinsic performance, be thermomechanically compatible, and be chemically stable in the 400 K to 850 K temperature range. Both n-type and p-type varieties must be available at low cost, easily fabricated, and durable. They must also form robust junctions and develop good interfaces with other materials to permit efficient flows of electrical and thermal energy. Among the TE materials of interest for automotive waste heat recovery systems are the skutterudite compounds, which are the antimony-based transition-metal compounds RTE4Sb12, where R can be an alkali metal (e.g., Na, K), alkaline earth (e.g., Ba), or rare earth (e.g., La, Ce, Yb), and TE can be a transition metal (e.g., Co, Fe). We synthesized a considerable quantity of n-type and p-type skutterudites, fabricated TE modules, incorporated these modules into a prototype TEG, and tested the TEG on a production General Motors (GM) vehicle. We discuss our progress on skutterudite TE module fabrication and present module performance data for electrical power output under simulated operating conditions for automotive waste heat recovery systems. We also present preliminary durability results on our skutterudite modules.

Concerns over non-renewable fossil fuel supply and climate change have been driving the Renaissance of bio-based materials. To substantiate environmental claims, the impacts of bio-based materials are typically quantified by applying life cycle assessment(LCA). The internationally agreed LCA standards provide generic recommendations on how to evaluate the environmental impacts of products and services but do not address details that are specifically relevantfor the life cycles of bio-based materials. Here, we provide an overview of key issues and methodologies explicitly pertinent to the LCA of bio-based materials. We argue that the treatment of biogenic carbon storage is critical for quantifying the greenhouse gas emissions of bio-based materials in comparison with petrochemical materials. We acknowledge that biogenic carbon storage remains controversial but recommend accounting for it, depending on product-specific life cycles and the likely time duration of carbon storage. If carbon storage is considered, co-product allocation is nontrivial and should be chosen with care in order to:(i) ensure that carbon storage is assigned to the main product and the co-product(s) in the intended manner and (ii) avoid double counting of stored carbon in the main product and once more in the co-product(s). Land-use change, soil degradation, water use, and impacts on soil carbon stocks and biodiversity are important aspects that have recently received attention. We explain various approaches to account for these and conclude that substantial methodological progress is necessary, which is however hampered by the complex and often case- and site-specific nature of impacts. With the exception of soil degradation, we recommend preliminary approaches for including these impacts in the LCA of bio-based materials. The use of attributional versus consequential LCA approaches is particularly relevant in the context of bio-based materials. We conclude that it is more challenging to prepare accurate consequential LCA studies, especially because these should account for future developments and secondary impacts around bio-based materials which are often difficult to anticipate and quantify. Although hampered by complexity and limited data availability, the application of the proposed approaches to the extent possible would allow obtaining a more comprehensive insight into the environmental impacts of the production, use, and disposal of bio-based materials. © 2013 Elsevier B.V. All rights reserved.