Theses and Dissertations from UMD

Permanent URI for this communityhttp://hdl.handle.net/1903/2

New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM

More information is available at Theses and Dissertations at University of Maryland Libraries.

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Subject: search.filters.subject.Alternative Energy

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Now showing 1 - 3 of 3
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    Performance Prediction of Scalable Fuel Cell Systems for Micro-Vehicle Applications.
    (2010) St. Clair, Jeffrey Glen; Cadou, Christopher P; Aerospace Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Miniature (< 500g) bio-inspired robotic vehicles are being developed for a variety of applications ranging from inspection of hazardous and remote areas to environmental monitoring. Their utility could be greatly improved by replacing batteries with fuel cells consuming high energy density fuels. This thesis surveys miniature fuel cell technologies and identifies direct methanol and sodium borohydride technologies as especially promising at small scales. A methodology for estimating overall system-level performance that accounts for the balance of plant (i.e. the extra components like pumps, blowers, etc. necessary to run the fuel cell system) is developed and used to quantify the performance of two direct methanol and one NaBH4 fuel cell systems. Direct methanol systems with water recirculation offer superior specific power (400 mW/g) and specific energy at powers of 20W and system masses of 150g. The NaBH4 fuel cell system is superior at low power (<5W) because of its more energetic fuel.
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    On the interaction of wind energy with climate and weather
    (2010) Barrie, Daniel; Kirk-Davidoff, Daniel B; Atmospheric and Oceanic Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    This study focuses on the interaction of large-scale wind energy with the atmosphere; namely, the impact that a substantial development of the wind resource may have on climate and weather as well as the impact that anthropogenic global warming (AGW) may have on the amount of available energy in the wind. A large downstream climate response to wind turbines distributed throughout the central United States is shown in model results from the Community Atmosphere Model (CAM). The mean response takes the form of a stationary Rossby wave. Furthermore, a case study is shown where the wind turbines altered a storm system over the North Atlantic. The resulting magnitude of the anomalous 500 hPa geopotential height field is comparable to the range of forecast uncertainty, which indicates that impacts induced in weather systems may be forecastable Building on this work, a thorough examination of wind farm and atmospheric parameters, including wind farm size, position, and parameterization as well as atmospheric static stability and jet strength is carried out using an idealized version of the Weather Research and Forecasting (WRF) model. Downstream impacts were found to grow in magnitude as wind farm size and the value of damping used to parameterize the wind turbines was increased. Altering the position of the wind farm with respect to the westerlies and synoptic disturbances revealed that the interaction between baroclinic instabilities and the wind farm enables downstream propagation and growth of the wind farm impacts. However, far downstream impacts were observed to be somewhat independent of the wind farm position, i.e., similar downstream effects were noted for model runs initialized with wind farms 20° of longitude from each other. By increasing atmospheric static stability, a fast saturation of wind farm-induced anomalies was observed throughout the atmosphere. This observation is surprising in light of the increased phasing between surface and upper atmospheric anomalies when static stability is low. Anomalies were able to propagate farther downstream over a shorter period of time when jet strength was increased. To study projected climate change impacts on the wind resource, data from the third phase of the Coupled Model Intercomparison Project (CMIP3) and the North American Regional Climate Change Assessment Project (NARCCAP) were studied. The results are dominated by substantial intermodel variability; however, many of the models project an increase in wind speeds and energy over the central United States. This increase in wind energy is related to an increase in low-frequency, high-speed transient wind speeds, which have a high power density due to the cubic relationship between wind speed and power.
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    SPATIAL AND SEASONAL DISTRIBUTION OF CARBON DIOXIDE EMISSIONS FROM FOSSIL-FUEL COMBUSTION; GLOBAL, REGIONAL, AND NATIONAL POTENTIAL FOR SUSTAINABLE BIOENERGY FROM RESIDUE BIOMASS AND MUNICIPAL SOLID WASTE
    (2009) Gregg, Jay Sterling; Dubayah, Ralph; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Combustion of fossil fuels releases carbon dioxide (CO2) into the atmosphere, and has led to an increase in the atmospheric concentration of CO2. CO2 is a greenhouse gas, and the increase in concentration leads to an increase in global temperatures and global climatic change. Fossil-fuel consumption, along with cement production, is responsible for 80% of anthropogenic carbon emissions and consumption of fossil fuels continues to increase. Despite its importance to the global climate and the global carbon cycle, data for fossil fuel CO2 emissions are traditionally maintained only on national levels and annual time steps. A method is developed to improve the spatiotemporal resolution to the leading energy consuming countries of the world. The method uses energy consumption datasets as well as other ancillary datasets to apportion national annual emissions totals into sub-national and monthly emissions datasets by fuel type. Emissions patterns are highly variable both temporally and spatially by fuel type, and detailed information on the distribution of emissions improves our understanding of the global carbon cycle and leads to better understanding of the spatial and seasonal distribution of the drivers of global change.
    In the endeavor to develop alternatives to fossil fuels, advanced biomass energy has garnered much attention because of its renewable nature and its potential to approach carbon-neutrality. As co-products, agricultural and forestry residues as well as municipal solid waste (MSW) are potential low-cost and sustainable biomass feedstocks for energy production. The role of residue biomass within the future global energy portfolio is projected and quantified under the context of environmental and economic sustainability. The potential for residue biomass is projected for the next century under a reference (business-as-usual) scenario and a scenario that includes a hypothetical climate policy that limits carbon emissions. While residue biomass alone cannot replace fossil fuels, a substantial amount of energy potentially could come from this resource, particularly in a global economic market under a climate policy that caps CO2 emissions from fossil fuels.