Matching Items (231)
Description
Carbon capture and sequestration (CCS) is one of the important mitigation options for climate change. Numerous technologies to capture carbon dioxide (CO2) are in development but currently, capture using amines is the predominant technology. When the flue gas reacts with amines (Monoethanaloamine) the CO2 is absorbed into the solution and forms an intermediate product which then releases CO2 at higher temperature. The high temperature necessary to strip CO2 is provided by steam extracted from the powerplant thus reducing the net output of the powerplant by 25% to 35%. The reduction in electricity output for the same input of coal increases the emissions factor of Nitrogen Oxides, Mercury, Particulate matter, Ammonia, Volatile organic compounds for the same unit of electricity produced. The thesis questions if this tradeoff between CO2 and other emissions is beneficial or not. Three different methodologies, Life Cycle Assessment, Valuation models and cost benefit analysis are used to identify if there is a net benefit to the society on implementation of CCS to a Pulverized coal powerplant. These methodologies include the benefits due to reduction of CO2 and the disbenefits due to the increase of other emissions. The life cycle assessment using ecoindicator'99 methodology shows the CCS is not beneficial under Hierarchical and Egalitarian perspective. The valuation model shows that the inclusion of the other emissions reduces the benefit associated with CCS. For a lower CO2 price the valuation model shows that CCS is detrimental to the environment. The cost benefit analysis shows that a CO2 price of at least $80/tCO2 is required for the cost benefit ratio to be 1. The methodology integrates Montecarlo simulation to characterize the uncertainties associated with the valuation models.
ContributorsSekar, Ashok (Author) / Williams, Eric (Thesis advisor) / Chester, Mikhail (Thesis advisor) / Allenby, Braden (Committee member) / Arizona State University (Publisher)
Created2012
Description
Utilizing an urban canopy model (UCM) developed by Zhihua Wang, Ph.D. for a research study conducted for the National Asphalt Pavement Association (NAPA), several scenarios were run in order to determine the impact on the mitigation of the urban heat island (UHI) effect. These scenarios included various roof albedo, wall albedo, ground albedo, a combination of all three albedos, roof emissivity, wall emissivity, ground emissivity, a combination of all three emissivities, and normalized building height as independent variables. Dependent variables included canyon air temperature, effective ground temperature, effective roof temperature, effective wall temperature, and sensible heat flux. It was found that emissivity does play a part in reducing the different dependent variables; however, typically emissivity values are already within a preferred range that not much can be done with them. Normalized building height has a minor impact but the impact that it does have upon the different variables is lessened with lower values of the normalized building height. Increasing the wall albedo decreased the canyon air temperature and the effective wall temperature the most compared to the other variables when considering expenses. An increase in roof albedo reduced effective roof temperature and sensible heat flux the most when taking into consideration the cost of changing the albedo of the surface. Larger values of ground albedo helped to reduce the effective ground temperature more than the other variables considered when a budget is necessary.
ContributorsHousenga, Hannah Eileen (Author) / Kaloush, Kamil (Thesis director) / Wang, Zhihua (Committee member) / Civil, Environmental and Sustainable Engineering Programs (Contributor) / Barrett, The Honors College (Contributor)
Created2015-05
Description
In this investigation, copper slag was used as a coarse aggregate in four different mixes of concrete, consisting of 0%, 25%, 50%, and 100% copper slag by volume. Locally available Salt river aggregate was used as a control, and mixes were tested for density, strength, thermal conductivity, specific heat capacity, and thermal diffusivity. Density was shown to increase with increasing copper slag content, increasing an average of 2298 kg/m^3, 2522 kg/m^3, and 2652 kg/m^3 in the 25%, 50%, and 100% mixes. This represents a 15% increase in density from 0% to 100%. Compressive strength testing indicated that the presence of copper slag in concrete provides no definitive strength benefit over Salt River aggregate. This result was expected, as concrete's strength is primarily derived from the cement matrix and not the aggregate. Thermal conductivity showed a decreasing trend with increasing copper slag content. Th control mix had an average conductivity of 0.660 W/m*K, and the 25%, 50%, and 100% mixes had conductivities of 0.649 W/m*K, 0.647 W/m*K, and 0.519 W/m*K, respectively. This represents 21% drop in thermal conductivity over the control. This result was also expected, as materials formed at higher temperatures, like copper slag, tend to have lower thermal conductivities. Specific heat capacity testing yielded results that were statistically indeterminate, though unlike strength testing this arose from inaccurate assumptions made during testing. This also prevented accurate thermal diffusivity results, as diffusivity is a function of density, thermal conductivity, and specific heat capacity. However, given the trends of the first two parameters, it is plausible to say that diffusivity in copper slag concrete would be lower than that of the control ix. All of these results were plugged into ASU's Pavement Temperature Model to see what effect they had in mitigating the UHI effect.
ContributorsLaughlin, Colin (Author) / Kaloush, Kamil (Thesis director) / Phelan, Patrick (Committee member) / Witczak, Kenneth (Committee member) / Barrett, The Honors College (Contributor)
Created2012-05
Description
While public transit systems are perceived to produce lower GHG emission intensities per passenger miles traveled (PMT) and per vehicle miles traveled (VMT), there is a limited understanding of emissions per PMT/VMT across cities, or of how emissions may change across modes (light, metro, commuter, and bus) and time (e.g., with changing electricity mixes in the future). In order to better understand the GHG emissions intensity of public transit systems, a comparative emissions assessment was developed utilizing the National Transit Database (NTD) which reports energy use from 1997 to 2012 of rail and bus systems across the US. By determining the GHG emission intensities (per VMT or per PMT) for each mode of transit across multiple years, the modes of transit can be better compared between one another. This comparison can help inform future goals to reduce GHG emissions as well as target reductions from the mode of transit that has the highest emissions. The proposed analysis of the NTD and comparison of modal emission intensities will be used to develop future forecasting that can guide public transit systems towards a sustainable future.
ContributorsCano, Alex (Author) / Chester, Mikhail (Thesis director) / Seager, Thomas (Committee member) / Civil, Environmental and Sustainable Engineering Programs (Contributor) / Barrett, The Honors College (Contributor) / School of Sustainability (Contributor) / School of Human Evolution and Social Change (Contributor)
Created2014-12
Description
ABSTRACT Water and energy resources are intrinsically linked, yet they are managed separately even in the water scarce America southwest. This study develops a spatially explicit model of water energy inter-dependencies in Arizona and assesses the potential for co beneficial conservation programs. The interdependent benefits of investments in 8 conservation strategies are assessed within the context of legislated renewable energy portfolio and energy efficiency standards. The co- benefits of conservation are found to be significant. Water conservation policies have the potential to reduce statewide electricity demand by 1.0 - 3.0 %, satisfying 3.3 -10 % of the state's mandated energy-efficiency-standard. Adoption of energy -efficiency measures and renewable generation portfolios can reduce non - agricultural water demand by 2.3 - 12 %. The conservation co- benefits are typically not included in conservation plans or benefit cost analyses. Many co-benefits offer negative costs of saved water and energy, indicating that these measures provide water and energy savings at no net cost. Because ranges of costs and savings for water energy conservation measures are somewhat uncertain, future studies should investigate the co-benefits of individual conservation strategies in detail. Although this study focuses on Arizona, the analysis can be extended elsewhere as renewable portfolio and energy efficiency standards become more common nationally and internationally.
ContributorsBartos, Matthew D. (Author) / Chester, Mikhail (Thesis director) / Mays, Larry (Committee member) / Barrett, The Honors College (Contributor)
Created2013-12
Description
Transit-oriented developments (TODs) are a promising strategy to increase public transit use and, as a result, reduce personal car travel. By using TOD infill to increase urban population density and encourage transportation mode-shifting, the potential exists to reduce life-cycle per capita energy use and environmental impacts of the interdependent infrastructure systems. This project specifically examined the Gold Line of light rail and Orange Line of bus rapid transit in Los Angeles, CA.
ContributorsNahlik, Matthew John (Author) / Chester, Mikhail (Thesis director) / Pendyala, Ram (Committee member) / Pincetl, Stephanie (Committee member) / Civil, Environmental and Sustainable Engineering Programs (Contributor) / Barrett, The Honors College (Contributor) / School of Sustainability (Contributor)
Created2013-05
Description
Rapid urbanization of the planet is occurring at an unprecedented pace, primarily in arid and semi-arid hot climates [Golden, J.S., 2004. The built environment induced urban heat island effect in rapidly urbanizing arid regions – a sustainable urban engineering complexity. Environ. Sci. J. Integr. Environ. Res. 1 (4), 321–349]. This growth has manifested itself as a cause of various impacts including elevated urban temperatures in comparison to rural sites known as the Urban Heat Island (UHI) effect [Oke, T.R., 1982. The energetic basis of the urban heat island. Q. J. R. Meteor. Soc. 108, 1–24]. Related are the increased demands for electric power as a result of population growth and increased need for mechanical cooling due to the UHI. In the United States, the Environmental Protection Agency has developed a three-prong approach of (1) cool pavements, (2) urban forestry and (3) cool roofs to mitigate the UHI. Researchers undertook an examination of micro scale benefits of the utilization of photovoltaic panels to reduce the thermal impacts to surface temperatures of pavements in comparison to urban forestry. The results of the research indicate that photovoltaic panels provide a greater thermal reduction benefit during the diurnal cycle in comparison to urban forestry while also providing the additional benefits of supporting peak energy demand, conserving water resources and utilizing a renewable energy source.
ContributorsGolden, Jay S. (Author) / Carlson, Joby (Author) / Kaloush, Kamil (Author) / Phelan, Patrick (Author)
Created2006-12-26
Description
Engineered pavements cover a large fraction of cities and offer significant potential for urban heat island mitigation. Though rapidly increasing research efforts have been devoted to the study of pavement materials, thermal interactions between buildings and the ambient environment are mostly neglected. In this study, numerical models featuring a realistic representation of building-environment thermal interactions, were applied to quantify the effect of pavements on the urban thermal environment at multiple scales. It was found that performance of pavements inside the canyon was largely determined by the canyon geometry. In a high-density residential area, modifying pavements had insignificant effect on the wall temperature and building energy consumption. At a regional scale, various pavement types were also found to have a limited cooling effect on land surface temperature and 2-m air temperature for metropolitan Phoenix. In the context of global climate change, the effect of pavement was evaluated in terms of the equivalent CO2 emission. Equivalent CO2 emission offset by reflective pavements in urban canyons was only about 13.9e46.6% of that without building canopies, depending on the canyon geometry. This study revealed the importance of building-environment thermal interactions in determining thermal conditions inside the urban canopy.
ContributorsYang, Jiachuan (Author) / Wang, Zhi-Hua (Author) / Kaloush, Kamil (Author) / Dylla, Heather (Author)
Created2016-08-22
Description
Oxidative aging is an important factor in the long term performance of asphalt pavements. Oxidation and the associated stiffening can lead to cracking, which in turn can lead to the functional and structural failure of the pavement system. Therefore, a greater understanding of the nature of oxidative aging in asphalt pavements can potentially be of great importance in estimating the performance of a pavement before it is constructed. Of particular interest are the effects of aging on asphalt rubber pavements, due to the fact that, as a newer technology, few asphalt rubber pavement sections have been evaluated for their full service life. This study endeavors to shed some light on this topic. This study includes three experimental programs on the aging of asphalt rubber binders and mixtures. The first phase addresses aging in asphalt rubber binders and their virgin bases. The binders were subjected to various aging conditions and then tested for viscosity. The change in viscosity was analyzed and it was found that asphalt rubber binders exhibited less long term aging. The second phase looks at aging in a laboratory environment, including both a comparison of accelerated oxidative aging techniques and aging effects that occur during long term storage. Dynamic modulus was used as a tool to assess the aging of the tested materials. It was found that aging materials in a compacted state is ideal, while aging in a loose state is unrealistic. Results not only showed a clear distinction in aged versus unaged material but also showed that the effects of aging on AR mixes is highly dependant on temperature; lower temperatures induce relatively minor stiffening while higher temperatures promote much more significant aging effects. The third experimental program is a field study that builds upon a previous study of pavement test sections. Field pavement samples were taken and tested after being in service for 7 years and tested for dynamic modulus and beam fatigue. As with the laboratory aging, the dynamic modulus samples show less stiffening at low temperatures and more at higher temperatures. Beam fatigue testing showed not only stiffening but also a brittle behavior.
ContributorsReed, Jordan (Author) / Kaloush, Kamil (Thesis advisor) / Mamlouk, Michael (Committee member) / Zapata, Claudia (Committee member) / Arizona State University (Publisher)
Created2010
Description
In the middle of the 20th century in the United States, transportation and infrastructure development became a priority on the national agenda, instigating the development of mathematical models that would predict transportation network performance. Approximately 40 years later, transportation planning models again became a national priority, this time instigating the development of highly disaggregate activity-based traffic models called microsimulations. These models predict the travel on a network at the level of the individual decision-maker, but do so with a large computational complexity and processing time requirement. The vast resources and steep learning curve required to integrate microsimulation models into the general transportation plan have deterred planning agencies from incorporating these tools. By researching the stochastic variability in the results of a microsimulation model with varying random number seeds, this paper evaluates the number of simulation trials necessary, and therefore the computational effort, for a planning agency to reach stable model outcomes. The microsimulation tool used to complete this research is the Transportation Analysis and Simulation System (TRANSIMS). The requirements for initiating a TRANSIMS simulation are described in the paper. Two analysis corridors are chosen in the Metropolitan Phoenix Area, and the roadway performance characteristics volume, vehicle-miles of travel, and vehicle-hours of travel are examined in each corridor under both congested and uncongested conditions. Both congested and uncongested simulations are completed in twenty trials, each with a unique random number seed. Performance measures are averaged for each trial, providing a distribution of average performance measures with which to test the stability of the system. The results of this research show that the variability in outcomes increases with increasing congestion. Although twenty trials are sufficient to achieve stable solutions for the uncongested state, convergence in the congested state is not achieved. These results indicate that a highly congested urban environment requires more than twenty simulation runs for each tested scenario before reaching a solution that can be assumed to be stable. The computational effort needed for this type of analysis is something that transportation planning agencies should take into consideration before beginning a traffic microsimulation program.
ContributorsZiems, Sarah Elia (Author) / Pendyala, Ram M. (Thesis advisor) / Ahn, Soyoung (Committee member) / Kaloush, Kamil (Committee member) / Arizona State University (Publisher)
Created2010