Matching Items (190)
Description
Nanoparticles are ubiquitous in various fields due to their unique properties not seen in similar bulk materials. Among them, core-shell composite nanoparticles are an important class of materials which are attractive for their applications in catalysis, sensing, electromagnetic shielding, drug delivery, and environmental remediation. This dissertation focuses on the study of core-shell type of nanoparticles where a polymer serves as the core and inorganic nanoparticles are the shell. This is an interesting class of supramolecular building blocks and can "exhibit unusual, possibly unique, properties which cannot be obtained simply by co-mixing polymer and inorganic particles". The one-step Pickering emulsion polymerization method was successfully developed and applied to synthesize polystyrene-silica core-shell composite particles. Possible mechanisms of the Pickering emulsion polymerization were also explored. The silica nanoparticles were thermodynamically favorable to self-assemble at liquid-liquid interfaces at the initial stage of polymerization and remained at the interface to finally form the shells of the composite particles. More importantly, Pickering emulsion polymerization was employed to synthesize polystyrene/poly(N-isopropylacrylamide) (PNIPAAm)-silica core-shell nanoparticles with N-isopropylacrylamide incorporated into the core as a co-monomer. The composite nanoparticles were temperature sensitive and could be up-taken by human prostate cancer cells and demonstrated effectiveness in drug delivery and cancer therapy. Similarly, by incorporating poly-2-(N,N)-dimethylamino)ethyl methacrylate (PDMA) into the core, pH sensitive core-shell composite nanoparticles were synthesized and applied as effective carriers to release a rheological modifier upon a pH change. Finally, the research focuses on facile approaches to engineer the transition of the temperature-sensitive particles and develop composite core-shell nanoparticles with a metallic shell.
ContributorsSanyal, Sriya (Author) / Dai, Lenore L. (Thesis advisor) / Jiang, Hanqing (Committee member) / Lind, Mary L. (Committee member) / Phelan, Patrick (Committee member) / Rege, Kaushal (Committee member) / Arizona State University (Publisher)
Created2012
Description
The ability to shift the photovoltaic (PV) power curve and make the energy accessible during peak hours can be accomplished through pairing solar PV with energy storage technologies. A prototype hybrid air conditioning system (HACS), built under supervision of project head Patrick Phelan, consists of PV modules running a DC compressor that operates a conventional HVAC system paired with a second evaporator submerged within a thermal storage tank. The thermal storage is a 0.284m3 or 75 gallon freezer filled with Cryogel balls, submerged in a weak glycol solution. It is paired with its own separate air handler, circulating the glycol solution. The refrigerant flow is controlled by solenoid valves that are electrically connected to a high and low temperature thermostat. During daylight hours, the PV modules run the DC compressor. The refrigerant flow is directed to the conventional HVAC air handler when cooling is needed. Once the desired room temperature is met, refrigerant flow is diverted to the thermal storage, storing excess PV power. During peak energy demand hours, the system uses only small amounts of grid power to pump the glycol solution through the air handler (note the compressor is off), allowing for money and energy savings. The conventional HVAC unit can be scaled down, since during times of large cooling demands the glycol air handler can be operated in parallel with the conventional HVAC unit. Four major test scenarios were drawn up in order to fully comprehend the performance characteristics of the HACS. Upon initial running of the system, ice was produced and the thermal storage was charged. A simple test run consisting of discharging the thermal storage, initially ~¼ frozen, was performed. The glycol air handler ran for 6 hours and the initial cooling power was 4.5 kW. This initial test was significant, since greater than 3.5 kW of cooling power was produced for 3 hours, thus demonstrating the concept of energy storage and recovery.
ContributorsPeyton-Levine, Tobin (Author) / Phelan, Patrick (Thesis advisor) / Trimble, Steve (Committee member) / Wang, Robert (Committee member) / Arizona State University (Publisher)
Created2012
Description
It is possible in a properly controlled environment, such as industrial metrology, to make significant headway into the non-industrial constraints on image-based position measurement using the techniques of image registration and achieve repeatable feature measurements on the order of 0.3% of a pixel, or about an order of magnitude improvement on conventional real-world performance. These measurements are then used as inputs for a model optimal, model agnostic, smoothing for calibration of a laser scribe and online tracking of velocimeter using video input. Using appropriate smooth interpolation to increase effective sample density can reduce uncertainty and improve estimates. Use of the proper negative offset of the template function has the result of creating a convolution with higher local curvature than either template of target function which allows improved center-finding. Using the Akaike Information Criterion with a smoothing spline function it is possible to perform a model-optimal smooth on scalar measurements without knowing the underlying model and to determine the function describing the uncertainty in that optimal smooth. An example of empiric derivation of the parameters for a rudimentary Kalman Filter from this is then provided, and tested. Using the techniques of Exploratory Data Analysis and the "Formulize" genetic algorithm tool to convert the spline models into more accessible analytic forms resulted in stable, properly generalized, KF with performance and simplicity that exceeds "textbook" implementations thereof. Validation of the measurement includes that, in analytic case, it led to arbitrary precision in measurement of feature; in reasonable test case using the methods proposed, a reasonable and consistent maximum error of around 0.3% the length of a pixel was achieved and in practice using pixels that were 700nm in size feature position was located to within ± 2 nm. Robust applicability is demonstrated by the measurement of indicator position for a King model 2-32-G-042 rotameter.
ContributorsMunroe, Michael R (Author) / Phelan, Patrick (Thesis advisor) / Kostelich, Eric (Committee member) / Mahalov, Alex (Committee member) / Arizona State University (Publisher)
Created2012
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
An investigation is undertaken of a prototype building-integrated solar photovoltaic-powered thermal storage system and air conditioning unit. The study verifies previous thermodynamic and economic conclusions and provides a more thorough analysis. A parameterized model was created for optimization of the system under various conditions. The model was used to evaluate energy and cost savings to determine viability of the system in several circumstances, such as a residence in Phoenix with typical cooling demand. The proposed design involves a modified chest freezer as a thermal storage tank with coils acting as the evaporator for the refrigeration cycle. Surrounding the coils, the tank contains small containers of water for high-density energy storage submerged in a low freezing-point solution of propylene glycol. The cooling power of excess photovoltaic and off-peak grid power that is generated by the air conditioning compressor is stored in the thermal storage tank by freezing the pure water. It is extracted by pumping the glycol across the ice containers and into an air handler to cool the building. Featured results of the modeling include the determination of an optimized system for a super-peak rate plan, grid-connected Phoenix house that has a 4-ton cooling load and requires a corresponding new air conditioner at 4.5 kW of power draw. Optimized for the highest payback over a ten year period, the system should consist of a thermal storage tank containing 454 liters (120 gallons) of water, a 3-ton rated air conditioning unit, requiring 2.7 kW, which is smaller than conventionally needed, and no solar photovoltaic array. The monthly summer savings would be $45.The upfront cost would be $5489, compared to a conventional system upfront cost of $5400, for a payback period of 0.33 years. Over ten years, this system will provide $2600 of savings. To optimize the system for the highest savings over a twenty year period, a thermal storage tank containing 272 liters (72 gallons) of water, a 40-m2 photovoltaic array with 15% efficiency, and a 3.5-ton, 3.1-kW rated air conditioning unit should be installed for an upfront cost of $19,900. This would provide monthly summer savings of $225 and 1062 kWh grid electricity, with a payback period of only 11 years and a total cost savings of $12,300 over twenty years. In comparison, a system with the same size photovoltaic array but without storage would result in a payback period of 16 years. Results are also determined for other cooling requirements and installation sizes, such that the viability of this type of system in different conditions can be discussed. The use of this model for determining the optimized system configuration given different constraints is also described.
ContributorsMagerman, Beth Francine (Author) / Phelan, Patrick (Thesis director) / Goodnick, Stephen (Committee member) / Chhetri, Nalini (Committee member) / Barrett, The Honors College (Contributor) / School of Sustainability (Contributor) / Mechanical and Aerospace Engineering Program (Contributor)
Created2013-05
Description
Solar cells are an increasingly important energy source for meeting growing energy demands. Organic photovoltaics in particular have potential in this area due to their low cost and the relative abundance of their constituents. One concern with the inverted configuration (a type of OPV with increased long-term stability) is their reliance on activation by ultraviolet (UV) light. Here we examine the incorporation of a new electron transport layer (ETL) material, zinc tin oxide (ZTO), in order to assess its interaction with UV light. Current-voltage characteristics were analyzed using a 420 nm cutoff filter to control UV light exposure. ZTO proved to be an adequate alternative to ZnO when comparing photovoltaic response. However, no improvement was found in terms of UV light activation. In addition, recent works show that oxygen plasma treatment of metal oxides used for hole transport layers modifies the work function and yields higher efficiency devices. Spin cast benzyl phosphonic acid self-assembled monolayers (BPA SAMs) provide similar results without the need for plasma treatment. Here we examine the use of BPA SAMs in standard devices utilizing PV2000, a proprietary active layer blend made by Plextronics. The use of BPA SAMs on a nickel oxide hole transport layer deepened the work function significantly, yielding greater device performance.
ContributorsJackson, Skyler (Author) / Phelan, Patrick (Thesis director) / Gust, Devans (Committee member) / Barrett, The Honors College (Contributor)
Created2014-05
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
Portable devices rely on battery systems that contribute largely to the overall device form factor and delay portability due to recharging. Membraneless microfluidic fuel cells are considered as the next generation of portable power sources for their compatibility with higher energy density reactants. Microfluidic fuel cells are potentially cost effective and robust because they use low Reynolds number flow to maintain fuel and oxidant separation instead of ion exchange membranes. However, membraneless fuel cells suffer from poor efficiency due to poor mass transport and Ohmic losses. Current microfluidic fuel cell designs suffer from reactant cross-diffusion and thick boundary layers at the electrode surfaces, which result in a compromise between the cell's power output and fuel utilization. This dissertation presents novel flow field architectures aimed at alleviating the mass transport limitations. The first architecture provides a reactant interface where the reactant diffusive concentration gradients are aligned with the bulk flow, mitigating reactant mixing through diffusion and thus crossover. This cell also uses porous electro-catalysts to improve electrode mass transport which results in higher extraction of reactant energy. The second architecture uses porous electrodes and an inert conductive electrolyte stream between the reactants to enhance the interfacial electrical conductivity and maintain complete reactant separation. This design is stacked hydrodynamically and electrically, analogous to membrane based systems, providing increased reactant utilization and power. These fuel cell architectures decouple the fuel cell's power output from its fuel utilization. The fuel cells are tested over a wide range of conditions including variation of the loads, reactant concentrations, background electrolytes, flow rates, and fuel cell geometries. These experiments show that increasing the fuel cell power output is accomplished by increasing reactant flow rates, electrolyte conductivity, and ionic exchange areas, and by decreasing the spacing between the electrodes. The experimental and theoretical observations presented in this dissertation will aid in the future design and commercialization of a new portable power source, which has the desired attributes of high power output per weight and volume and instant rechargeability.
ContributorsSalloum, Kamil S (Author) / Posner, Jonathan D (Thesis advisor) / Adrian, Ronald (Committee member) / Christen, Jennifer (Committee member) / Phelan, Patrick (Committee member) / Chen, Kangping (Committee member) / Arizona State University (Publisher)
Created2010
Description
Many expect renewable energy technologies to play a leading role in a sustainable energy supply system and to aid the shift away from an over-reliance on traditional hydrocarbon resources in the next few decades. This dissertation develops environmental, policy and social models to help understand various aspects of photovoltaic (PV) technologies. The first part of this dissertation advances the life cycle assessment (LCA) of PV systems by expanding the boundary of included processes using hybrid LCA and accounting for the technology-driven dynamics of environmental impacts. Hybrid LCA extends the traditional method combining bottom-up process-sum and top-down economic input-output (EIO) approaches. The embodied energy and carbon of multi-crystalline silicon photovoltaic systems are assessed using hybrid LCA. From 2001 to 2010, the embodied energy and carbon fell substantially, indicating that technological progress is realizing reductions in environmental impacts in addition to lower module price. A variety of policies support renewable energy adoption, and it is critical to make them function cooperatively. To reveal the interrelationships among these policies, the second part of this dissertation proposes three tiers of policy architecture. This study develops a model to determine the specific subsidies required to support a Renewable Portfolio Standard (RPS) goal. The financial requirements are calculated (in two scenarios) and compared with predictable funds from public sources. A main result is that the expected investments to achieve the RPS goal far exceed the economic allocation for subsidy of distributed PV. Even with subsidies there are often challenges with social acceptance. The third part of this dissertation originally develops a fuzzy logic inference model to relate consumers' attitudes about the technology such as perceived cost, maintenance, and environmental concern to their adoption intention. Fuzzy logic inference model is a type of soft computing models. It has the advantage of dealing with imprecise and insufficient information and mimicking reasoning processes of human brains. This model is implemented in a case study of residential PV adoption using data through a survey of homeowners in Arizona. The output of this model is the purchasing probability of PV.
ContributorsZhai, Pei (Author) / Williams, Eric D. (Thesis advisor) / Allenby, Braden (Committee member) / Phelan, Patrick (Committee member) / Arizona State University (Publisher)
Created2010
Description
Water heaters that are manufactured for swimming pools come in several forms, most of which require an electrical input for a source of power. Passive-circulation systems, however, require no electrical power input because fluid circulation occurs as a result of thermal gradients. In solar-based systems, thermal gradients are developed by energy collected from sunlight. The combination of solar collection and passive circulation yields a system in which fluids, particularly water, are heated and circulated without need of assistance from external mechanical or electrical sources. The design of such a system was adapted from that of forced-circulation solar collector systems, as were the equations describing its thermodynamic properties. The design was developed based on such constraints as material corrosion resistance, overall system cost, and location-controlled size limitations. The thermodynamic description of the designed system was adjusted on the basis of the designed system’s physical aspects, such as the configuration and material of each component within the solar collector. Numerical analysis performed with the altered thermodynamic equations projected a total energy gain of 7.39 W between 9:00 and 10:00 A.M. and a total energy gain of 13.12 W between 4:00 and 5:00 P.M. The temperature of heated water exiting the collector system was projected to be 17.62°C in the morning and 25.56°C in the afternoon. The morning projection utilized an initial fluid temperature of 12°C and an ambient air temperature of 13°C, while the afternoon projection utilized an initial fluid temperature of 17°C and an ambient air temperature of 22°C. Field testing of the designed passive thermosyphon solar collector system was performed over a period of about one month with one temperature measurement taken at the collector outlet in the morning and another taken in the afternoon. For an ambient air temperature of 13°C, the linear regression developed from the morning dataset yielded an outlet water temperature of 20°C and that for the afternoon dataset yielded an outlet water temperature of 39°C for an ambient air temperature of 17°C. The percentage error between the projected and measured results was 13.51% for the morning period and 52.58% for the afternoon period. Numerical simulation and field data demonstrated that while the collector system operated successfully, its effects were limited to the volume of water immediately surrounding the outlet of the system; the rate of circulation within the system was too low for there to be a meaningful increase in the temperature of the water body at large. The stated results demonstrate that while the particular configuration of passive circulation solar collection technology developed in this instance is capable of transferring solar thermal energy to water without additional energy sources, significant modifications are necessary in order to improve the effectiveness of the technology. Such changes may come from improvements in material availability or alterations to the configuration of components of the collector system.
ContributorsZimmerman, Julia Elizabeth (Author) / Garcia, Margaret (Thesis director) / Phelan, Patrick (Committee member) / Civil, Environmental and Sustainable Eng Program (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05