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Julian Rautenberg - One of the best experts on this subject based on the ideXlab platform.
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Refractive displacement of the radio-Emission Footprint of inclined air showers simulated with CoREAS
The European Physical Journal C, 2020Co-Authors: Felix Schlüter, Marvin Gottowik, Tim Huege, Julian RautenbergAbstract:The Footprint of radio Emission from extensive air showers is known to exhibit asymmetries due to the superposition of geomagnetic and charge-excess radiation. For inclined air showers a geometric early-late effect disturbs the signal distribution further. Correcting CoREAS simulations for these asymmetries reveals an additional disturbance in the signal distribution of highly inclined showers in atmospheres with a realistic refractive index profile. This additional apparent asymmetry in fact arises from a systematic displacement of the radio-Emission Footprint with respect to the Monte-Carlo shower impact point on the ground. We find a displacement of $$\sim 1500$$ ∼ 1500 m in the ground plane for showers with a zenith angle of $$85^{\circ }$$ 85 ∘ , illustrating that the effect is relevant in practical applications. A model describing this displacement by refraction in the atmosphere based on Snell’s law yields good agreement with our observations from CoREAS simulations. We thus conclude that the displacement is caused by refraction in the atmosphere.
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refractive displacement of the radio Emission Footprint of inclined air showers simulated with coreas
arXiv: Instrumentation and Methods for Astrophysics, 2020Co-Authors: Felix Schlüter, Marvin Gottowik, Tim Huege, Julian RautenbergAbstract:The Footprint of radio Emission from extensive air showers is known to exhibit asymmetries due to the superposition of geomagnetic and charge-excess radiation. For inclined air showers a geometric early-late effect disturbs the signal distribution further. Correcting CoREAS simulations for these asymmetries reveals an additional disturbance in the signal distribution of highly inclined showers in atmospheres with a realistic refractive index profile. This additional apparent asymmetry in fact arises from a systematic displacement of the radio-Emission Footprint with respect to the Monte-Carlo shower impact point on the ground. We find a displacement of $\sim 1500\,\text{m}$ in the ground plane for showers with a zenith angle of $85^\circ$, illustrating that the effect is relevant in practical applications. A model describing this displacement by refraction in the atmosphere based on Snell's law yields good agreement with our observations from CoREAS simulations. We thus conclude that the displacement is caused by refraction in the atmosphere.
Nesrin Ozalp - One of the best experts on this subject based on the ideXlab platform.
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Solar Carbothermic Reduction of Dolime as a Promising Option To Produce Magnesium and Calcium
Industrial & Engineering Chemistry Research, 2019Co-Authors: Hamed Abedini Najafabadi, Nesrin Ozalp, Michael Epstein, Richard A. DavisAbstract:The use of solar energy to produce metals from their oxides via the carbothermic reduction process is a cleaner alternative to traditional combustion-based processes with an added value of a significantly reduced CO2 Emission Footprint. In this study, the potential contribution of solar energy to the pyrometallurgical production of magnesium was analyzed and compared to the common industrial process. The most energy-consuming step is the carbothermic reduction of the oxide. The reduction was thermodynamically examined and experimentally investigated. While previous studies in the field were based mostly on using MgO, this work focused on dolomite (CaCO3·MgCO3) as the feedstock for the carbothermic reduction process. A thermogravimeter (TGA) was used to investigate the kinetics of the reaction under different conditions. The thermogravimetric results show that a full reduction of MgO in dolime (calcined dolomite, MgO·CaO) is achievable around 1600 °C under atmospheric pressure. According to the results, at...
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Catalytic Solar Thermochemical Processing for Enhance Heat Transfer and Emission-free Production of Hydrogen
Chemical engineering transactions, 2012Co-Authors: Karim Ibrik, Mariam Al-meer, Nesrin OzalpAbstract:Solar thermochemical processing offers production of many commodities via reduced or completely eliminated Emission Footprint. Although solar reactor design and flow configuration play key role in process efficiency, use of right catalyst further enhances the overall efficiency. Our research efforts to explain the physical phenomenon behind the increase of the overall efficiency via catalyst addition showed that there is a direct effect on the heat transfer which in turn effects methane decomposition rate. In this paper, a compilation of our research results on the testing of carbon based catalyst and its impact on the heat transfer is summarized along with kinetics analysis of methane decomposition.
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AN OVERVIEW OF SOLAR THERMAL CRACKING OF NATURAL GAS: CHALLENGES AND SOLUTIONS TOWARDS COMMERCIALIZATION
2011Co-Authors: Nesrin OzalpAbstract:Solar thermal cracking of natural gas has great potential to become an attractive alternative process for hydrogen and carbon black production due to its zero Emission Footprint. However, there are two major problems preventing this process from commercialization: (1) carbon deposition causing reactor clogging, (2) intrinsic losses in energy conversion efficiency as a result of re-radiation losses and inherently transient nature of the solar energy. The second problem in particular applies to all types of solar reactors despite the reactants and products because temperature has the most important impact on reactant to product conversion efficiency. This paper provides a detailed description of these two problems, and summarizes few solutions addressing these challenges.
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A Computational Fluid Dynamics Study on the Effect of Carbon Particle Seeding for the Improvement of Solar Reactor Performance
Journal of Heat Transfer, 2010Co-Authors: Nesrin Ozalp, Anoop KanjirakatAbstract:This study focuses on a technique, referred to as "solar cracking" of natural gas for the coproduction of hydrogen and carbon as byproduct with zero Emission Footprint. Seeding a solar reactor with micron-sized carbon particles increases the conversion efficiency drastically due to the radiation absorbed by the carbon particles and additional nucleation sites formed by carbon particles for heterogeneous decomposition reaction. The present study numerically tries to investigate the above fact by tracking carbon particles in a Lagrangian framework. The results on the effect of particle loading, particle emissivity, injection point location, and effect of using different window screening gases on a flow and temperature distribution inside a confined tornado flow reactor are presented.
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Cleaner pathways of hydrogen, carbon nano-materials and metals production via solar thermal processing
Journal of Cleaner Production, 2010Co-Authors: Nesrin Ozalp, Michael Epstein, Abraham KoganAbstract:This paper describes various solar thermochemical processes for the production of hydrogen, carbon nano particles, industrial grade carbon black, and metals with substantially reduced CO2 Emission Footprint. The paper introduces an innovative approach of a three-dimensional volumetric production of carbon nano particles via thermal cracking of methane gained by carbon seeding as an alternative to the existing two dimensional modes. The paper also describes an alternative pathway for hydrogen production via three consecutive solar thermochemical processes, namely, solar cracking of methane, solar carbo-reduction of ZnO and CO reduction of CdO, providing long term storage of solar energy. Finally, the paper provides an example solar windowed reactor for clean production of hydrogen, and it presents numerical analysis of the solar reactor based on computational fluid dynamics results, simulating one of the major problems with natural gas cracking in solar reactors, namely, carbon contamination of the transparent window and clogging of the reactor.
Anu Ramaswami - One of the best experts on this subject based on the ideXlab platform.
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Articulating a trans-boundary infrastructure supply chain greenhouse gas Emission Footprint for cities: Mathematical relationships and policy relevance
Energy Policy, 2013Co-Authors: Abel Chavez, Anu RamaswamiAbstract:This paper compares the policy relevance and derives mathematical relationships between three approaches for GHG Emissions accounting for cities. The three approaches are: (a) Purely-Geographic Inventory, (b) Trans-boundary Community-Wide Infrastructure Footprint (CIF), and (c) Consumption-Based Footprint (CBF). Mathematical derivations coupled with case study of three US communities (Denver Colorado, Routt Colorado, and Sarasota Florida), shows that no one method provides a larger or more holistic estimate of GHG Emissions associated with communities. A net-producing community (Routt) demonstrates higher CIF GHG Emissions relative to the CBF, while a net-consuming community (Sarasota) yields the opposite. Trade-balanced communities (Denver) demonstrate similar numerical estimates of CIF and CBF, as predicted by the mathematical equations. Knowledge of community typology is important in understanding trans-boundary GHG Emission contributions.
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Social Actors and Key Policy Levers for Mitigating the Greenhouse Gas Footprint of U.S. Cities
2013Co-Authors: Anu RamaswamiAbstract:AbstractThis article links policy outputs in city climate action plans with environmental outcomes. This task is challenging because different human activities in cities vary in terms of their contributions to greenhouse gas (GHG) Emissions and because the engineered infrastructures that support these activities extend well beyond the city scale. I present a generalizable quantitative approach that uses the transboundary infrastructure supply chain GHG Emission Footprints of cities to identify key actors and policy levers most effective in reducing the global GHG impact of cities. This infrastructure supply chain GHG Emission Footprint represents the life-cycle energy associated with provisioning key infrastructure services-water, energy, food, shelter, sanitation, mobility, connectivity, and public spaces-to support the activities of households, businesses, and industries in cities.Introduction: Greenhouse Gas Footprints of Cities and Mitigation PlansCities are hubs of human activity; the everyday actions of myriad households, businesses, and industries located within a city's geopolitical boundary. Measuring greenhouse gas (GHG) Emissions associated with cities is confounded by the relatively small spatial scale of cities compared with the large-scale engineered infrastructures in which they are embedded; that is, the electricity grid, transportation networks, water-supply lines, and wastewater treatment networks that serve cities. As a result, human activities in cities are highly dependent on transboundary infrastructure provisions, defined formally as the provision of water, energy, food, shelter (building materials), sanitation/waste management, mobility, connectivity, and public spaces to homes, businesses, and industries located within the city (Chavez and Ramaswami, 2013; Ramaswami, in press). In addition to infrastructures, there is also the movement of other goods and services between cities resulting in the flow of embodied GHG between cities. To address these confounding factors, cities have started measuring not only direct energy use and GHG Emissions within city boundaries (called a source-based GHG Emissions inventory), but also transboundary, life-cycle-based GHG Emission Footprints of cities that are based upon human activities. First developed for the city of Denver in 2006, infrastructure supply chain GHG Emissions Footprints combine the life-cycle energy (inboundary and transboundary) associated with provisioning key infrastructure services with communitywide collective use of these infrastructures by homes, businesses, and industries colocated in cities (Ramaswami et al, 2008). Consider for example, water or electricity supply to a city that supports communitywide use of water and energy, respectively.The resulting transboundary infrastructure supply chain Footprints have since been tested in more than 20 U.S. cities and show that direct inboundary GHG Emissions can contribute less than onehalf of a city's overall infrastructure-related GHG Emissions Footprint, particularly in cities that import a significant percentage of their electricity, such as Denver (shown in exhibit la). Environmental Protection Agency (EPA) statistics (EPA, 2011) indicate that less than 5 percent of U.S. counties have significant electric power generation infrastructure within their geopolitical boundaries; thus, about 95 percent of U.S. cities import electricity similar to the case of Denver in exhibit la. Even after transboundary GHG Emissions associated with imported electric power are allocated to cities, transboundary contributions from the provision of other infrastructures - such as energy supply (fuel) for transportation, fuel supply for the built environment, food supply, construction materials (for example, cement), water supply, and sanitation (wastewater treatment) - can be significant. See exhibit la, in which all the infrastructure sectors are mapped to human activities; for example, the use of cars in a city results in direct inboundary tailpipe Emission (shown solid), whereas the transboundary energy to produce fuel used by the vehicles is shown hatched. …
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Greenhouse Gas Emission Footprints and Energy Use Benchmarks for Eight U.S. Cities
Environmental science & technology, 2010Co-Authors: Tim Hillman, Anu RamaswamiAbstract:A hybrid life cycle-based trans-boundary greenhouse gas (GHG) Emissions Footprint is elucidated at the city-scale and evaluated for 8 US cities. The method incorporates end-uses of energy within city boundaries, plus cross-boundary demand for airline/freight transport and embodied energy of four key urban materials [food, water, energy (fuels), and shelter (cement)], essential for life in all cities. These cross-boundary activities contributed 47% on average more than the in-boundary GHG contributions traditionally reported for cities, indicating significant truncation at city boundaries of GHG Emissions associated with urban activities. Incorporating cross-boundary contributions created convergence in per capita GHG Emissions from the city-scale (average 23.7 mt-CO2e/capita) to the national-scale (24.5 mt-CO2e/capita), suggesting that six key cross-boundary activities may suffice to yield a holistic GHG Emission Footprint for cities, with important policy ramifications. Average GHG contributions from var...
Felix Schlüter - One of the best experts on this subject based on the ideXlab platform.
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Refractive displacement of the radio-Emission Footprint of inclined air showers simulated with CoREAS
The European Physical Journal C, 2020Co-Authors: Felix Schlüter, Marvin Gottowik, Tim Huege, Julian RautenbergAbstract:The Footprint of radio Emission from extensive air showers is known to exhibit asymmetries due to the superposition of geomagnetic and charge-excess radiation. For inclined air showers a geometric early-late effect disturbs the signal distribution further. Correcting CoREAS simulations for these asymmetries reveals an additional disturbance in the signal distribution of highly inclined showers in atmospheres with a realistic refractive index profile. This additional apparent asymmetry in fact arises from a systematic displacement of the radio-Emission Footprint with respect to the Monte-Carlo shower impact point on the ground. We find a displacement of $$\sim 1500$$ ∼ 1500 m in the ground plane for showers with a zenith angle of $$85^{\circ }$$ 85 ∘ , illustrating that the effect is relevant in practical applications. A model describing this displacement by refraction in the atmosphere based on Snell’s law yields good agreement with our observations from CoREAS simulations. We thus conclude that the displacement is caused by refraction in the atmosphere.
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refractive displacement of the radio Emission Footprint of inclined air showers simulated with coreas
arXiv: Instrumentation and Methods for Astrophysics, 2020Co-Authors: Felix Schlüter, Marvin Gottowik, Tim Huege, Julian RautenbergAbstract:The Footprint of radio Emission from extensive air showers is known to exhibit asymmetries due to the superposition of geomagnetic and charge-excess radiation. For inclined air showers a geometric early-late effect disturbs the signal distribution further. Correcting CoREAS simulations for these asymmetries reveals an additional disturbance in the signal distribution of highly inclined showers in atmospheres with a realistic refractive index profile. This additional apparent asymmetry in fact arises from a systematic displacement of the radio-Emission Footprint with respect to the Monte-Carlo shower impact point on the ground. We find a displacement of $\sim 1500\,\text{m}$ in the ground plane for showers with a zenith angle of $85^\circ$, illustrating that the effect is relevant in practical applications. A model describing this displacement by refraction in the atmosphere based on Snell's law yields good agreement with our observations from CoREAS simulations. We thus conclude that the displacement is caused by refraction in the atmosphere.
Tim Huege - One of the best experts on this subject based on the ideXlab platform.
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Refractive displacement of the radio-Emission Footprint of inclined air showers simulated with CoREAS
The European Physical Journal C, 2020Co-Authors: Felix Schlüter, Marvin Gottowik, Tim Huege, Julian RautenbergAbstract:The Footprint of radio Emission from extensive air showers is known to exhibit asymmetries due to the superposition of geomagnetic and charge-excess radiation. For inclined air showers a geometric early-late effect disturbs the signal distribution further. Correcting CoREAS simulations for these asymmetries reveals an additional disturbance in the signal distribution of highly inclined showers in atmospheres with a realistic refractive index profile. This additional apparent asymmetry in fact arises from a systematic displacement of the radio-Emission Footprint with respect to the Monte-Carlo shower impact point on the ground. We find a displacement of $$\sim 1500$$ ∼ 1500 m in the ground plane for showers with a zenith angle of $$85^{\circ }$$ 85 ∘ , illustrating that the effect is relevant in practical applications. A model describing this displacement by refraction in the atmosphere based on Snell’s law yields good agreement with our observations from CoREAS simulations. We thus conclude that the displacement is caused by refraction in the atmosphere.
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refractive displacement of the radio Emission Footprint of inclined air showers simulated with coreas
arXiv: Instrumentation and Methods for Astrophysics, 2020Co-Authors: Felix Schlüter, Marvin Gottowik, Tim Huege, Julian RautenbergAbstract:The Footprint of radio Emission from extensive air showers is known to exhibit asymmetries due to the superposition of geomagnetic and charge-excess radiation. For inclined air showers a geometric early-late effect disturbs the signal distribution further. Correcting CoREAS simulations for these asymmetries reveals an additional disturbance in the signal distribution of highly inclined showers in atmospheres with a realistic refractive index profile. This additional apparent asymmetry in fact arises from a systematic displacement of the radio-Emission Footprint with respect to the Monte-Carlo shower impact point on the ground. We find a displacement of $\sim 1500\,\text{m}$ in the ground plane for showers with a zenith angle of $85^\circ$, illustrating that the effect is relevant in practical applications. A model describing this displacement by refraction in the atmosphere based on Snell's law yields good agreement with our observations from CoREAS simulations. We thus conclude that the displacement is caused by refraction in the atmosphere.