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Pages
- Title
- On Randic Energy of Graphs.
- Creator
-
Burns, Brittany, Mohapatra, Ram, Song, Zixia, Brennan, Joseph, University of Central Florida
- Abstract / Description
-
In this research, we explore the subject of graph energy. We first discuss the connections between linear algebra and graph theory and review some important definitions and facts of these two fields. We introduce graph energy and provide some historical perspectives on the subject. Known results of graph energy are also mentioned and some relevant results are proven. We discuss some applications of graph energy in the physical sciences. Then, Randic energy is defined and results are given and...
Show moreIn this research, we explore the subject of graph energy. We first discuss the connections between linear algebra and graph theory and review some important definitions and facts of these two fields. We introduce graph energy and provide some historical perspectives on the subject. Known results of graph energy are also mentioned and some relevant results are proven. We discuss some applications of graph energy in the physical sciences. Then, Randic energy is defined and results are given and proved for specific families of graphs. We focus on simple, connected graphs that are commonly studied in graph theory. Also, the Laplacian energy of a graph is defined. We then examine the connections between the different types of energies for graphs, beginning with graph energy and Randic energy, followed by Laplacian energy and Randic energy. In our results chapter, we introduce the Petersen graph and calculate the Randic energy of this graph. We also define Stacked-Book graphs and perform some calculations on these graphs. From these calculations, we form a conjecture and discuss some details on how to proceed with the proof of this conjecture. Finally, we summarize our work and details are provided on how this research can be continued.
Show less - Date Issued
- 2016
- Identifier
- CFE0006273, ucf:51043
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006273
- Title
- SMALL-SCALE HYBRID ALTERNATIVE ENERGY MAXIMIZER FOR WIND TURBINES AND PHOTOVOLTAIC PANELS.
- Creator
-
Kerley, Ross, Batarseh, Issa, University of Central Florida
- Abstract / Description
-
This thesis describes the creation of a small-scale Hybrid Power System (HPS) that maximizes energy from a wind turbine and photovoltaic array. Small-scale HPS are becoming an increasingly viable energy solution as fossil fuel prices rise and more electricity is needed in remote areas. Modern HPS typically employ wind speed sensors and three power stages to extract maximum power. Modern systems also use passive rectifiers to convert AC from the wind turbine to DC that is usable by power...
Show moreThis thesis describes the creation of a small-scale Hybrid Power System (HPS) that maximizes energy from a wind turbine and photovoltaic array. Small-scale HPS are becoming an increasingly viable energy solution as fossil fuel prices rise and more electricity is needed in remote areas. Modern HPS typically employ wind speed sensors and three power stages to extract maximum power. Modern systems also use passive rectifiers to convert AC from the wind turbine to DC that is usable by power electronics. This passive system inefficiently wastes power and introduces damaging harmonic noise to the wind turbine. The HPS described in this thesis does not require external wind speed sensors, and has independent wind and solar Maximum Power Point Tracking (MPPT). It converts AC from the wind turbine to DC with a Vienna rectifier that can be controlled to improve efficiency, allow MPPT, and allow Power Factor Correction (PFC). PFC all but eliminates the harmonic noise that can damage the wind turbine. A prototype HPS was built and evaluated that combines the two renewable sources in such a way that only two power stages are necessary, the Vienna rectifier and a step-down converter. This thesis describes the prototype and reports the results obtained.
Show less - Date Issued
- 2011
- Identifier
- CFH0004087, ucf:44799
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH0004087
- Title
- A Report on the international control of atomic energy.
- Creator
-
Barnard, Chester Irving, United States Dept. of State Committee on Atomic Energy
- Date Issued
- 1946
- Identifier
- 2100240, CFDT2100240, ucf:4901
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/FCLA/DT/2100240
- Title
- One world or none.
- Creator
-
Masters, Dexter, Way, Katharine 1903-, Bohr, Niels, Compton, Arthur H., Arnold, H. H., Bethe, Hans, Condon, E. U.
- Date Issued
- 1946
- Identifier
- 2683364, CFDT2683364, ucf:5059
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/FCLA/DT/2683364
- Title
- The atomic bomb.
- Creator
-
Atomic Scientists of Chicago
- Date Issued
- 1946
- Identifier
- 369652, CFDT369652, ucf:5465
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/FCLA/DT/369652
- Title
- THE SIMULATION AND CONTROL OF A GRID-CONNECTED WIND ENERGY CONVERSION SYSTEM.
- Creator
-
McCartney, Shauna, Yuan, Jiann S., University of Central Florida
- Abstract / Description
-
With the rising cost of petroleum, concerns about exhausting the fossil fuels we depend on for energy, and the subsequent impacts that the burning of these types of fuels have on our environment, countries around the world are paying close attention to the development of renewable types of energy. Consequently, researchers have been trying to develop ways to take advantage of different types of clean and renewable energy sources. Wind energy production, in particular, has been growing at an...
Show moreWith the rising cost of petroleum, concerns about exhausting the fossil fuels we depend on for energy, and the subsequent impacts that the burning of these types of fuels have on our environment, countries around the world are paying close attention to the development of renewable types of energy. Consequently, researchers have been trying to develop ways to take advantage of different types of clean and renewable energy sources. Wind energy production, in particular, has been growing at an increasingly rapid rate, and will continue to do so in the future. In fact, it has become an integral part in supplying our future energy needs, making further advancements in the field exceedingly critical. A 2 MW wind energy conversion system (WECS) is presented and has been simulated via the dynamic simulation software Simulink. This WECS consists of a 2 MW permanent magnet synchronous generator connected to the transmission grid through a power conversion scheme. The topology of this converter system consists of a passive AC/DC rectifier as well as a PWM DC/AC IGBT inverter, used to interface the DC link with the grid. The inverter has an integrated current control system for power factor correction to improve output power stability. The described WECS enhances grid-side tolerance by buffering wind power disturbances demonstrated by its capability to isolate the grid from wind speed fluctuations. It also optimizes wind energy capture through harmonic filtering, enhancing output power quality. These findings have the potential to lead to further advancements including the capability for island operation and integration to a smart grid.
Show less - Date Issued
- 2010
- Identifier
- CFE0003484, ucf:48972
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003484
- Title
- Nuclear power plant simulator.
- Creator
-
Adams, John Jacob, Dennis, John D., Engineering
- Abstract / Description
-
Florida Technological University College of Engineering Thesis; The United States' energy crisis, which has received so much publicity lately , has focused national attention on how we are to meet our energy demands. Proposed energy sources include conventional nuclear power plants, breeder reactor and fusion reactor plants, coal gasification, liquid hydrogen, solar energy, and geothermal energy. All of these except conventional fission plants are still on the drawing board or in the...
Show moreFlorida Technological University College of Engineering Thesis; The United States' energy crisis, which has received so much publicity lately , has focused national attention on how we are to meet our energy demands. Proposed energy sources include conventional nuclear power plants, breeder reactor and fusion reactor plants, coal gasification, liquid hydrogen, solar energy, and geothermal energy. All of these except conventional fission plants are still on the drawing board or in the experimental laboratory, and are described briefly. Government and industry are betting heavily on conventional nuclear power plants. ($40 billion already spent by private utilities for 30 operating plants, 60 under construction, and 75 on order.) A. few unpublicized accidents and more and more complex instrumentation in nuclear power plant control rooms has pointed to a desperate need for more effective ways of training individuals to safely operate these plants. Recognizing this need, General Electric Company designed and built a very realistic computer-driven simulator of a plant control room. The physical enclosures and instrumentation duplicates the Dresden II control room in every way, and response to operator manipulation of controls duplicates that of a real plant. The bulk of this paper describes the simulator and its development. The last section raises questions concerning hazards of continued growth of nuclear power and presents some alternatives.
Show less - Date Issued
- 1973
- Identifier
- CFR0003510, ucf:53015
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFR0003510
- Title
- Optimization of Ocean Thermal Energy Conversion Power Plants.
- Creator
-
Rizea, Steven, Ilie, Marcel, Bai, Yuanli, Vasu Sumathi, Subith, University of Central Florida
- Abstract / Description
-
A proprietary Ocean Thermal Energy Conversion (OTEC) modeling tool, the Makai OTEC Thermodynamic and Economic Model (MOTEM), is leveraged to evaluate the accuracy of finite-time thermodynamic OTEC optimization methods. MOTEM is a full OTEC system simulator capable of evaluating the effects of variation in heat exchanger operating temperatures and seawater flow rates. The evaluation is based on a comparison of the net power output of an OTEC plant with a fixed configuration. Select...
Show moreA proprietary Ocean Thermal Energy Conversion (OTEC) modeling tool, the Makai OTEC Thermodynamic and Economic Model (MOTEM), is leveraged to evaluate the accuracy of finite-time thermodynamic OTEC optimization methods. MOTEM is a full OTEC system simulator capable of evaluating the effects of variation in heat exchanger operating temperatures and seawater flow rates. The evaluation is based on a comparison of the net power output of an OTEC plant with a fixed configuration. Select optimization methods from the literature are shown to produce between 93% and 99% of the maximum possible amount of power, depending on the selection of heat exchanger performance curves. OTEC optimization is found to be dependent on the performance characteristics of the evaporator and condenser used in the plant. Optimization algorithms in the literature do not take heat exchanger performance variation into account, which causes a discrepancy between their predictions and those calculated with MOTEM. A new characteristic metric of OTEC optimization, the ratio of evaporator and condenser overall heat transfer coefficients, is found. The heat transfer ratio is constant for all plant configurations in which the seawater flow rate is optimized for any particular evaporator and condenser operating temperatures. The existence of this ratio implies that a solution for the ideal heat exchanger operating temperatures could be computed based on the ratio of heat exchanger performance curves, and additional research is recommended.
Show less - Date Issued
- 2012
- Identifier
- CFE0004430, ucf:49343
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004430
- Title
- A Systems Approach to Sustainable Energy Portfolio Development.
- Creator
-
Hadian Niasar, Saeed, Reinhart, Debra, Madani Larijani, Kaveh, Wang, Dingbao, Lee, Woo Hyoung, Pazour, Jennifer, University of Central Florida
- Abstract / Description
-
Adequate energy supply has become one of the vital components of human development and economic growth of nations. In fact, major components of the global economy such as transportation services, communications, industrial processes, and construction activities are dependent on adequate energy resources. Even mining and extraction of energy resources, including harnessing the forces of nature to produce energy, are dependent on accessibility of sufficient energy in the appropriate form at the...
Show moreAdequate energy supply has become one of the vital components of human development and economic growth of nations. In fact, major components of the global economy such as transportation services, communications, industrial processes, and construction activities are dependent on adequate energy resources. Even mining and extraction of energy resources, including harnessing the forces of nature to produce energy, are dependent on accessibility of sufficient energy in the appropriate form at the desired location. Therefore, energy resource planning and management to provide appropriate energy in terms of both quantity and quality has become a priority at the global level. The increasing demand for energy due to growing population, higher living standards, and economic development magnifies the importance of reliable energy plans. In addition, the uneven distribution of traditional fossil fuel energy sources on the Earth and the resulting political and economic interactions are other sources of complexity within energy planning. The competition over fossil fuels that exists due to gradual depletion of such sources and the tremendous thirst of current global economic operations for these sources, as well as the sensitivity of fossil fuel supplies and prices to global conditions, all add to the complexity of effective energy planning. In addition to diversification of fossil fuel supply sources as a means of increasing national energy security, many governments are investing in non-fossil fuels, especially renewable energy sources, to combat the risks associated with adequate energy supply. Moreover, increasing the number of energy sources also adds further complication to energy planning. Global warming, resulting from concentration of greenhouse gas emissions in the atmosphere, influences energy infrastructure investments and operations management as a result of international treaty obligations and other regulations requiring that emissions be cut to sustainable levels. Burning fossil fuel, as one of the substantial driving factors of global warming and energy insecurity, is mostly impacted by such policies, pushing forward the implementation of renewable energy polices. Thus, modern energy portfolios comprise a mix of renewable energy sources and fossil fuels, with an increasing share of renewables over time. Many governments have been setting renewable energy targets that mandate increasing energy production from such sources over time. Reliance on renewable energy sources certainly helps with reduction of greenhouse gas emissions while improving national energy security. However, the growing implementation of renewable energy has some limitations. Such energy technologies are not always as cheap as fossil fuel sources, mostly due to immaturity of these energy sources in most locations as well as high prices of the materials and equipment to harness the forces of nature and transform them to usable energy. In addition, despite the fact that renewable energy sources are traditionally considered to be environmentally friendly, compared to fossil fuels, they sometimes require more natural resources such as water and land to operate and produce energy. Hence, the massive production of energy from these sources may lead to water shortage, land use change, increasing food prices, and insecurity of water supplies. In other words, the energy production from renewables might be a solution to reduce greenhouse gas emissions, but it might become a source of other problems such as scarcity of natural resources.The fact that future energy mix will rely more on renewable sources is undeniable, mostly due to depletion of fossil fuel sources over time. However, the aforementioned limitations pose a challenge to general policies that encourage immediate substitution of fossil fuels with renewables to battle climate change. In fact, such limitations should be taken into account in developing reliable energy policies that seek adequate energy supply with minimal secondary effects. Traditional energy policies have been suggesting the expansion of least cost energy options, which were mostly fossil fuels. Such sources used to be considered riskless energy options with low volatility in the absence of competitive energy markets in which various energy technologies are competing over larger market shares. Evolution of renewable energy technologies, however, complicated energy planning due to emerging risks that emanated mostly from high price volatility. Hence, energy planning began to be seen as investment problems in which the costs of energy portfolio were minimized while attempting to manage associated price risks. So, energy policies continued to rely on risky fossil fuel options and small shares of renewables with the primary goal to reduce generation costs. With emerging symptoms of climate change and the resulting consequences, the new policies accounted for the costs of carbon emissions control in addition to other costs. Such policies also encouraged the increased use of renewable energy sources. Emissions control cost is not an appropriate measure of damages because these costs are substantially less than the economic damages resulting from emissions. In addition, the effects of such policies on natural resources such as water and land is not directly taken into account. However, sustainable energy policies should be able to capture such complexities, risks, and tradeoffs within energy planning. Therefore, there is a need for adequate supply of energy while addressing issues such as global warming, energy security, economy, and environmental impacts of energy production processes. The effort in this study is to develop an energy portfolio assessment model to address the aforementioned concerns.This research utilized energy performance data, gathered from extensive review of articles and governmental institution reports. The energy performance values, namely carbon footprint, water footprint, land footprint, and cost of energy production were carefully selected in order to have the same basis for comparison purposes. If needed, adjustment factors were applied. In addition, the Energy Information Administration (EIA) energy projection scenarios were selected as the basis for estimating the share of the energy sources over the years until 2035. Furthermore, the resource availability in different states within the U.S. was obtained from publicly available governmental institutions that provide such statistics. Specifically, the carbon emissions magnitudes (metric tons per capita) for different states were extracted from EIA databases, states' freshwater withdrawals (cubic meters per capita) were found from USGS databases, states' land availability values (square kilometers) were obtained from the U.S. Census Bureau, and economic resource availability (GDP per capita) for different states were acquired from the Bureau of Economic Analysis.In this study, first, the impacts of energy production processes on global freshwater resources are investigated based on different energy projection scenarios. Considering the need for investing on energy sources with minimum environmental impacts while securing maximum efficiency, a systems approach is adopted to quantify the resource use efficiency of energy sources under sustainability indicators. The sensitivity and robustness of the resource use efficiency scores are then investigated versus existing energy performance uncertainties and varying resource availability conditions. The resource use efficiency of the energy sources is then regionalized for different resource limitation conditions in states within the U.S. Finally, a sustainable energy planning framework is developed based on Modern Portfolio Theory (MPT) and Post-Modern Portfolio Theory (PMPT) with consideration of the resource use efficiency measures and associated efficiency risks.In the energy-water nexus investigation, the energy sources are categorized into 10 major groups with distinct water footprint magnitudes and associated uncertainties. The global water footprint of energy production processes are then estimated for different EIA energy mix scenarios over the 2012-2035 period. The outcomes indicate that the water footprint of energy production increases by almost 50% depending on the scenario. In fact, growing energy production is not the only reason for increasing the energy related water footprint. Increasing the share of water intensive energy sources in the future energy mix is another driver of increasing global water footprint of energy in the future. The results of the energies' water footprint analysis demonstrate the need for a policy to reduce the water use of energy generation. Furthermore, the outcomes highlight the importance of considering the secondary impacts of energy production processes besides their carbon footprint and costs. The results also have policy implications for future energy investments in order to increase the water use efficiency of energy sources per unit of energy production, especially those with significant water footprint such as hydropower and biofuels.In the next step, substantial efforts have been dedicated to evaluating the efficiency of different energy sources from resource use perspective. For this purpose, a system of systems approach is adopted to measure the resource use efficiency of energy sources in the presence of trade-offs between independent yet interacting systems (climate, water, land, economy). Hence, a stochastic multi-criteria decision making (MCDM) framework is developed to compute the resource use efficiency scores for four sustainability assessment criteria, namely carbon footprint, water footprint, land footprint, and cost of energy production considering existing performance uncertainties. The energy sources' performances under aforementioned sustainability criteria are represented in ranges due to uncertainties that exist because of technological and regional variations. Such uncertainties are captured by the model based on Monte-Carlo selection of random values and are translated into stochastic resource use efficiency scores. As the notion of optimality is not unique, five MCDM methods are exploited in the model to counterbalance the bias toward definition of optimality. This analysis is performed under (")no resource limitation(") conditions to highlight the quality of different energy sources from a resource use perspective. The resource use efficiency is defined as a dimensionless number in scale of 0-100, with greater numbers representing a higher efficiency. The outcomes of this analysis indicate that despite increasing popularity, not all renewable energy sources are more resource use efficient than non-renewable sources. This is especially true for biofuels and different types of ethanol that demonstrate lower resource use efficiency scores compared to natural gas and nuclear energy. It is found that geothermal energy and biomass energy from miscanthus are the most and least resource use efficient energy alternatives based on the performance data available in the literature. The analysis also shows that none of the energy sources are strictly dominant or strictly dominated by other energy sources. Following the resource use efficiency analysis, sensitivity and robustness analyses are performed to determine the impacts of resource limitations and existing performance uncertainties on resource use efficiency, respectively. Sensitivity analysis indicates that geothermal energy and ethanol from sugarcane have the lowest and highest resource use efficiency sensitivity, respectively. Also, it is found that from a resource use perspective, concentrated solar power (CSP) and hydropower are respectively the most and least robust energy options with respect to the existing performance uncertainties in the literature.In addition to resource use efficiency analysis, sensitivity analysis and robustness analysis, of energy sources, this study also investigates the scheme of the energy production mix within a specific region with certain characteristics, resource limitations, and availabilities. In fact, different energy sources, especially renewables, vary in demand for natural resources (such as water and land), environmental impacts, geographic requirements, and type of infrastructure required for energy production. In fact, the efficiency of energy sources from a resource use perspective is dependent upon regional specifications, so the energy portfolio varies for different regions due to varying resource availability conditions. Hence, the resource use efficiency scores of different energy technologies are calculated based on the aforementioned sustainability criteria and regional resource availability and limitation conditions (emissions, water resources, land, and GDP) within different U.S. states, regardless of the feasibility of energy alternatives in each state. Sustainability measures are given varying weights based on the emissions cap, available economic resources, land, and water resources in each state, upon which the resource use efficiency of energy sources is calculated by utilizing the system of systems framework developed in the previous step. Efficiency scores are graphically illustrated on GIS-based maps for different states and different energy sources. The results indicate that for some states, fossil fuels such as coal and natural gas are as efficient as renewables like wind and solar energy technologies from resource use perspective. In other words, energy sources' resource use efficiency is significantly sensitive to available resources and limitations in a certain location.Moreover, energy portfolio development models have been created in order to determine the share of different energy sources of total energy production, in order to meet energy demand, maintain energy security, and address climate change with the least possible adverse impacts on the environment. In fact, the traditional (")least cost(") energy portfolios are outdated and should be replaced with (")most efficient(") ones that are not only cost-effective, but also environmentally friendly. Hence, the calculated resource use efficiency scores and associated statistical analysis outcomes for a range of renewable and nonrenewable energy sources are fed into a portfolio selection framework to choose the appropriate energy mixes associated with the risk attitudes of decision makers. For this purpose, Modern Portfolio Theory (MPT) and Post-Modern Portfolio Theory (PMPT) are both employed to illustrate how different interpretations of (")risk of return(") yield different energy portfolios. The results indicate that 2012 energy mix and projected world's 2035 energy portfolio are not sustainable in terms of resource use efficiency and could be substituted with more reliable, more effective portfolios that address energy security and global warming with minimal environmental and economic impacts.
Show less - Date Issued
- 2013
- Identifier
- CFE0005001, ucf:50020
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005001
- Title
- An Introductory Study of The Dynamics of Autorotation for Wind Energy Harvesting.
- Creator
-
Salih, Bilal, Das, Tuhin, Kassab, Alain, Kauffman, Jeffrey, University of Central Florida
- Abstract / Description
-
Wind turbines have been used for decades to harvest wind energy. They are suitable only to work on close to ground, and have several drawbacks that are related to the availability of the wind and the amount of extracted power compared with the cost of construction. On the other hand, there is an abundant wind power that is available at high altitudes. The wind jet streams at high elevations 8 ? 12 kms are pervasive and persistent, and can potentially produce immense wind energy. Even at...
Show moreWind turbines have been used for decades to harvest wind energy. They are suitable only to work on close to ground, and have several drawbacks that are related to the availability of the wind and the amount of extracted power compared with the cost of construction. On the other hand, there is an abundant wind power that is available at high altitudes. The wind jet streams at high elevations 8 ? 12 kms are pervasive and persistent, and can potentially produce immense wind energy. Even at moderate elevations of 4 ? 5 kms, wind power densities are much higher than on ground and more consistent. Consequently, in this thesis research, we investigate the topic of harvesting energy from high altitudes. First, we provide a comprehensive review of two existing theoretical methods that are proposed for airborne wind energy harvesting, the tethered airfoil, and the static autogyro. The latter approach has inherent advantages that warrant further investigation. Autorotation is a well-known phenomenon where a rotor sustains its angular velocity and maintains significant lift in the presence of strong aerodynamic forces and torques generated by interaction with a strong wind field. Autorotation has been researched in the context of free descent of helicopters but has not been considered for energy harvesting. Existing models have mainly focused on statics analysis. In this research, we propose a simple dynamic model of the Autogyro, with the goal of ultimately realizing an Autorotation Energy System (AES). The focus of our work is to provide a preliminary dynamic analysis of autorotation, which is largely absent in current literature, to explore the possibility of using autorotation for designing a multipurpose system that can simultaneously fly at high altitudes and generate energy from the wind. The proposed preliminary dynamic model is used to generate a simulation platform, which is used to explore the autogyros rudimentary maneuvers. Extensive simulation results are provided to evaluate the dynamic performance of AES. Energy harvesting analyses and results are also presented. It is expected that the results will guide the choice of actuations and control that will be necessary for generating combined autorotation and powered flights that would be net energy generating or energy efficient. The research will be relevant for both tethered and untethered AES and could also be incorporated into multi-rotor based UAVs such as quadrotors.
Show less - Date Issued
- 2014
- Identifier
- CFE0005245, ucf:50597
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005245
- Title
- The atomic age : suicide, slavery or socialism?.
- Creator
-
Levenstein, Aaron
- Date Issued
- 1946
- Identifier
- 363245, CFDT363245, ucf:5272
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/FCLA/DT/363245
- Title
- Freestanding Holey Thin Films for Renewable Energy Storage.
- Creator
-
Marcus, Kyle, Yang, Yang, Zhai, Lei, Dong, Yajie, University of Central Florida
- Abstract / Description
-
The rapid advancement of portable and wearable technologies has challenged research to improve upon current renewable battery energy storage systems. By using nanotechnology, it is now possible to access more of the energy storage theoretical values that have been unattainable thus far. We have developed a method to create freestanding holey thin films through combinations of electrochemical and chemical vapor deposition (CVD) techniques to be used in renewable energy storage systems....
Show moreThe rapid advancement of portable and wearable technologies has challenged research to improve upon current renewable battery energy storage systems. By using nanotechnology, it is now possible to access more of the energy storage theoretical values that have been unattainable thus far. We have developed a method to create freestanding holey thin films through combinations of electrochemical and chemical vapor deposition (CVD) techniques to be used in renewable energy storage systems. Freestanding thin films promote excellent contact between the residual conductive framework and any functionalized active component specific to the designed material. Without requiring any other additives, the as-prepared freestanding thin films can be mechanically and chemically tuned to allow for use in a wide range of applications. Incorporation of micro- and nano-sized holey structures dramatically enhances the electrochemically active surface area, which is essential for facilitating appropriate reactions in conversion type energy storage systems. Combining the freestanding and holey components with an active layer effectively enhances conductivity and reduces the electron transfer distance at the electrode-electrolyte interface. Herein, two separately designed freestanding holey thin films were successfully used as cathode materials for lithium-sulfur battery (Li-S) and magnesium-ion battery (MIB) energy storage systems.
Show less - Date Issued
- 2017
- Identifier
- CFE0007127, ucf:52304
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007127
- Title
- Energy-optimal Guidance of an AUV Under Flow Uncertainty and Fluid-Particle Interaction.
- Creator
-
De Zoysa Abeysiriwardena, Demuni Singith, Das, Tuhin, Kumar, Ranganathan, Elgohary, Tarek, Behal, Aman, University of Central Florida
- Abstract / Description
-
The work presented gives an energy-optimal solution to the guidance problem of an AUV. The presented guidance methods are for lower level control of AUV paths, facilitating existing global planning methods to be carried out comparatively more efficiently. The underlying concept is to use the energy of fluid flow fields the AUVs are navigating to extend the duration of missions. This allows gathering of comparatively more data with higher spatio-temporal resolution. The problem is formulated...
Show moreThe work presented gives an energy-optimal solution to the guidance problem of an AUV. The presented guidance methods are for lower level control of AUV paths, facilitating existing global planning methods to be carried out comparatively more efficiently. The underlying concept is to use the energy of fluid flow fields the AUVs are navigating to extend the duration of missions. This allows gathering of comparatively more data with higher spatio-temporal resolution. The problem is formulated for a generalized two dimensional uniform flow field given a fixed final time andfree end states. This allows the AUVs to navigate to certain spatial positions while maintaining the required temporal resolution of each segment of its mission. The simplistic way the problem is posed allows an analytical closed form solution of the Euler-Lagrange equations. Two dimensional thrust vectors are obtained as optimal control inputs. The control inputs are then incorporated into afeedback structure, allowing the particle to navigate in the presence of disturbance in the flow field. Further, the work also explores the influence of fluid-particle interaction on the control cost and behavior of the particle. The concept of changing the cost weights of the optimal cost formulation in situ has been introduced. Potential applications of the present concept are explored through anobstacle avoidance scenario. The optimal guidance methods are then adapted to non-uniform flow fields with quadratic and discontinuous spatial variation being the primary focus.
Show less - Date Issued
- 2018
- Identifier
- CFE0007169, ucf:52282
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007169
- Title
- SPS: an SMS-based Push Service for Energy Saving in Smartphone's Idle State.
- Creator
-
Dondyk, Erich, Zou, Changchun, Chatterjee, Mainak, Hua, Kien, University of Central Florida
- Abstract / Description
-
Despite of all the advances in smartphone technology in recent years, smartphones still remain limited by their battery life. Unlike other power hungry components in the smartphone, the cellular data and Wi-Fi interfaces often continue to be used even while the phone is in the idle state to accommodate unnecessary data traffic produced by some applications. In addition, bad reception has been proven to greatly increase energy consumed by the radio, which happens quite often when smartphone...
Show moreDespite of all the advances in smartphone technology in recent years, smartphones still remain limited by their battery life. Unlike other power hungry components in the smartphone, the cellular data and Wi-Fi interfaces often continue to be used even while the phone is in the idle state to accommodate unnecessary data traffic produced by some applications. In addition, bad reception has been proven to greatly increase energy consumed by the radio, which happens quite often when smartphone users are inside buildings. In this paper, we present a Short message service Push based Service (SPS) to save unnecessary power consumption when smartphones are in idle state, especially in bad reception areas. First, SPS disables a smartphone's data interfaces whenever the phone is in idle state. Second, to preserve the real-time notification functionality required by some apps, such as new email arrivals and social media updates, when a notification is needed, a wakeup text message will be received by the phone, and then SPS enables the phone's data interfaces to connect to the corresponding server to retrieve notification data via the normal data network. Once the notification data has been retrieved, SPS will disable the data interfaces again if the phone is still in idle state. We have developed a complete prototype for Android smartphones. Our experiments show that SPS consumes less energy than the current approach. In areas with bad reception, the SPS prototype can double the battery life of a smartphone.
Show less - Date Issued
- 2014
- Identifier
- CFE0005157, ucf:50718
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005157
- Title
- Planar Organic Photovoltaic Devices.
- Creator
-
Alzubi, Feras, Khondaker, Saiful, Chow, Lee, Schelling, Patrick, Gesquiere, Andre, University of Central Florida
- Abstract / Description
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Organic Photovoltaic devices (OPV) are considered to be attractive candidates for clean and renewable energy source because of their potential for low cost of fabrication, easy processing, and their mechanical flexibility. The device efficiency of OPV cells are limited by several factors. Among them are: (i) donor-acceptor interface, (ii) morphology of the materials, (iii) electrode-organic semiconductor (OSC) interface and (iv) device architecture such as active material thickness and...
Show moreOrganic Photovoltaic devices (OPV) are considered to be attractive candidates for clean and renewable energy source because of their potential for low cost of fabrication, easy processing, and their mechanical flexibility. The device efficiency of OPV cells are limited by several factors. Among them are: (i) donor-acceptor interface, (ii) morphology of the materials, (iii) electrode-organic semiconductor (OSC) interface and (iv) device architecture such as active material thickness and electrode separation. Although, the donor-acceptor interface has been studied in detail, the commonly prevalent vertical OPV device structure does not allow a good understanding of the other key issues as the vertical structure limits one of the electrode to be a transparent electrode as well as introducing inseparable relation between the electrodes separation and the active material thickness. In addition, it is also well known that the charge transport in OSC is anisotropic and the charge mobility is better in lateral direction rather than vertical direction. In order to address some of these issues, we fabricated OPV devices in a planar device structure where cathode and anode of dissimilar metals are in-plane with each other and their photovoltaic behaviors were studied. We used poly(3-hexylthiophene) and [6,6]-pheny1 C61-butyric acid methy1 ester (P3HT:PCBM) blend as an active material. In particular, we present a detailed study about the effects of the structural parameters such as the channel length, the active layer thickness, and the work function of the electrodes on the open circuit voltage (Voc), short circuit current (Isc), fill factor (FF) and the power conversion efficiency (PCE).In order to determine the suitable anode and cathode for the planar organic photovoltaic (P-OPV) structure, we first fabricated and measured organic field effect transistor (OFET) devices with different contacts and studied the effect of barrier height at the P3HT:PCBM/electrode interface on the device output and transport properties. The study showed a clear effect of varying the contact material on the charge injection mechanism and on the carriers mobilities. The results have also shown that Au with high hole mobility and on current in the p-channel can be used as an anode (holes extractor) in the P-OPV device while In, Cr, and Ti that showed a reasonable value of electron mobility can be good candidates for cathode (electron extractor). We also found that, Ag, Al, and Mg showed large barrier which resulted in large threshold voltage in the I-V curve making them undesired cathode materials in the P-OPV device. We then fabricated P-OPV devices with Au as an anode material and varied the cathode material to study the effect of the interface between the P3HT:PCBM layer and the cathode material. When Al, Mg, or Ag used as a cathode material no PV behavior was observed, while PV behavior was observed for In, Cr, and Ti cathode materials. The PV behavior and the characteristic parameters including Voc, Isc, FF and PCE were affected by varying the cathode material. The results have shown that the P-OPV device performance can be affected by the cathode material depending on the properties and the work function of the metal.We have also studied the effect of varying the P3HT:PCBM layer thickness at a fixed channel length for Cr and Ti cathode materials and Au as anode. While Voc and FF values do not change, Isc and PCE increase with increasing the layer thickness due to the increase of the light absorption and charges generation. Moreover, we studied the effect of varying the channel length at a fixed film thickness; and showed that the values of Isc and PCE increase with decreasing channel length while Voc and FF maintain the same value. In this thesis we will also present the results on experimentally defining and testing the illuminated area in the P-OPV device by using different measurement set-ups and different electrodes patterns. The results prove that the illuminated area in the P-OPV device is the area enclosed between the two electrodes. Lastly, we will present the effect of the P3HT:PCBM ratio on the P-OPV device performance. We show that 1:2 ratio is the optimized ratio for the P-OPV device. The detailed results in this thesis show a potential opportunity to help improving and understanding the design of OPV device by understanding the effects of the device structural parameters.
Show less - Date Issued
- 2013
- Identifier
- CFE0004804, ucf:49754
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004804
- Title
- Design and Optimization of a Wave Energy Harvester Utilizing a Flywheel Energy Storage System.
- Creator
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Helkin, Steven, Lin, Kuo-Chi, Gordon, Ali, Raghavan, Seetha, University of Central Florida
- Abstract / Description
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This thesis details the design and optimization of a buoy used to collect renewable energy from ocean waves. The proposed buoy is a point absorber(-)a device that transforms the kinetic energy of the vertical motion of surface waves into electrical energy. The focus of the research is on the mechanical system used to collect the energy, and methods to improve it for eventual use in an actual wave energy harvester. A flywheel energy storage system was utilized in order to provide an improved...
Show moreThis thesis details the design and optimization of a buoy used to collect renewable energy from ocean waves. The proposed buoy is a point absorber(-)a device that transforms the kinetic energy of the vertical motion of surface waves into electrical energy. The focus of the research is on the mechanical system used to collect the energy, and methods to improve it for eventual use in an actual wave energy harvester. A flywheel energy storage system was utilized in order to provide an improved power output from the system, even with the intermittent input of force exerted by ocean waves. A series of laboratory prototypes were developed to analyze parameters that are important to the success of the point absorb mechanical system. By introducing a velocity-based load control scheme in conjunction with flywheel energy storage, it was seen that the average power output by the prototype was increased. The generator load is controlled via a relay switch that removes electrical resistance from the generator(-)this sacrifices time during which power is drawn from the system, but also allows the buoy to move with less resistance. A simulation model was developed in order to analyze the theoretical wave absorber system and optimize the velocity threshold parameters used in the load control. Results indicate that the power output by the system can be substantially improved through the use of a flywheel energy storage control scheme that engages and disengages the electrical load based on the rotational velocity of the flywheel system. The results of the optimization are given for varying-sized generator systems input into the simulation in order to observe the associated trends.
Show less - Date Issued
- 2011
- Identifier
- CFE0004118, ucf:49113
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004118
- Title
- Computational Approach to Electrocatalysis.
- Creator
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Dhakal, Nagendra, Stolbov, Sergey, Rahman, Talat, Ishigami, Masa, Masunov, Artem, University of Central Florida
- Abstract / Description
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The main objective of this work is to understand the theoretical basis of the working principle of the Hydrogen fuel cell. We seek the physical basis of the Rational Design Technique, the smart way of preselecting materials from the material-pool, implemented in our study anticipating highly promising electrocatalysts for promoting the conversion of chemical energy stored in hydrogen molecules into the electrical energy. It needs the understanding of the relationship among the compositions of...
Show moreThe main objective of this work is to understand the theoretical basis of the working principle of the Hydrogen fuel cell. We seek the physical basis of the Rational Design Technique, the smart way of preselecting materials from the material-pool, implemented in our study anticipating highly promising electrocatalysts for promoting the conversion of chemical energy stored in hydrogen molecules into the electrical energy. It needs the understanding of the relationship among the compositions of the materials under consideration, their electronic structure and catalytic activities. We performed the first principle DFT calculations to achieve the goal.Our work is focused first on the issues in hydrogen oxidation reaction taking place in anode compartment of the cell. Next comes up with the issues with Oxygen Reduction Reaction taking place in cathode compartment. Finally, we focus on mechanisms underlying binding of small molecules on substrates.Platinum perfectly catalyzes hydrogen oxidation reaction on the hydrogen fuel cell anodes. However, it has at least two drawbacks: a) it is too expensive; b) it has a low tolerance to CO poisoning. Pt-Ru bi-functional catalysts are more tolerant to CO, but they are still very expensive. In this work, we performed first-principle studies of stability and reactivity of M/W (110) structures, where M = Pd, Ru, Au monolayers. All three systems are found to be stable: formation energy of MLs is significantly higher than cohesive energy of the M-elements. The calculated binding energies of H, H2, OH, CO, and H2O were used to obtain the reaction free energies. Analysis of the free energies suggests that Au-W bonding does not activate sufficiently Au monolayer, whereas Ru/W (110) is still too reactive for the CO removal. Meanwhile, Pd/W (110) is found to catalyze hydrogen oxidation and at the same time to be highly tolerant to the CO poisoning. The latter finding is explained by the fact that CO binds much weaker to Pd on W (110) than to Pt, while the OH binding is strong enough to ensure CO oxidation. The obtained results are traced to the electronic structure of the systems.Oxygen Reduction Reaction (ORR) is the heart core reaction in fuel cells, Proton Exchange Membrane Fuel cell and DEMFC. However, the reaction is not so obvious and need suitable electrocatalyst. Pt or Pt-based catalysts are found to be the best catalyst so far. But, its cost and shortage make it not feasible economically. Moreover, lower onset potential (maximal electrode potential at which the reaction can proceed) of such catalysts is offering another limitation to fuel cell performance. Research has been conducted in many directions for lowering the cost by replacing the Pt with some other elements of lower cost or reducing the Pt-load in the material; and even more finding the material performing better than Pt. In this paper, we've tried to understand the ORR mechanism and look for the material that could be potential option to Pt. Our calculations suggest that for monolayer of Pt on 5 layered slab of Nb or Mo the onset potential is the same as for Pt, while cost of these systems are much lower than that of Pt. Presence of water changes the reaction rate very minimum. Rational design method facilitates the research of selecting the appropriate catalyst and saves time and effort significantly. The result shows that the d-band center model is not accurate to describe the reactivity of the catalyst.For decades, adsorbates' binding energy (????) has been used as an indicator of the adsorbate-substrate bond strength (??????). Thus, although one can compute accurately any ?? models to gauge bond-strength are developed and applied to rationalize and anticipate ????'s because that is a key aspect in the rational search for efficient catalysts. Yet bond-strength alone fails to predict ???? trends. Therefore, quantifying and understanding the difference between ???? and ?????? is essential to catalysts design. Indeed, the adsorbate-substrate bond formation perturbs the substrate's electronic charge density, which reduces ???? by the energy attached to such perturbation: ??????????. Here, with the example of carbon monoxide adsorption on metal-doped graphene, we show that ?????????? may exceed 1 eV and render an unusual situation: although the EB of CO to the Au-doped graphene indicates that binding does not happen, we find evidence of a strong bond between CO and the substrate. Thus, in this case, the large ?????????? totally disrupt the equivalency between ?????? and ???? we also propose a method to compute ?????????? that bypasses dealing with an excited electronic state of the system.
Show less - Date Issued
- 2017
- Identifier
- CFE0006583, ucf:51336
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006583
- Title
- THE EFFECTS OF A SINGLE EXERCISE BOUT ON PLASMA LEPTIN CONCENTRATION IN OBESE MALES.
- Creator
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Kyriazis, George, Angelopoulos, Theodore, University of Central Florida
- Abstract / Description
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Recent findings suggest that leptin may be regulated in response to abrupt changes in energy homeostasis. Therefore, it is conceivable that transient changes in energy balance induced by exercise may also regulate leptin synthesis and secretion. As such, we hypothesized that acute increases energy expenditure (i.e. exercise), may regulate leptin concentrations in obese individuals. Fifteen healthy obese males underwent either a single exercise session of moderate intensity (58.4 % ± 4.0 of...
Show moreRecent findings suggest that leptin may be regulated in response to abrupt changes in energy homeostasis. Therefore, it is conceivable that transient changes in energy balance induced by exercise may also regulate leptin synthesis and secretion. As such, we hypothesized that acute increases energy expenditure (i.e. exercise), may regulate leptin concentrations in obese individuals. Fifteen healthy obese males underwent either a single exercise session of moderate intensity (58.4 % ± 4.0 of VO2max) for 60 min (n=8), or served as controls (n=7). The exercise session elicited an energy expenditure of 567±80 Kcal. No significant changes in plasma leptin (pre 23.5± 30.2; post 24.3± 34.3; 24h-post 34.9± 66.6; 48h-post 33.8±64.0 ng/ml), or insulin levels (pre 16.1± 9.2 vs. post 8.1± 9.1; 24h-post 14.3± 9.9; 48h-post 13.8± 10.2 ?U/ml) were detected immediately after the intervention. Baseline plasma leptin levels were positively correlated with BMI (r=0.65; p<0.01), body weight (r=0.64; p<0.01), % body fat (r=0.90; p<0.01) and were negatively correlated with VO2max (r=-0.82; p<0.01). The results of the present study suggest that acute exercise of moderate intensity and duration may not affect leptin concentration.
Show less - Date Issued
- 2005
- Identifier
- CFE0000508, ucf:46459
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000508
- Title
- LANDFILL GAS TO ENERGY: INCENTIVES & BENEFITS.
- Creator
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Amini, Hamid, Reinhart, Debra, University of Central Florida
- Abstract / Description
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Municipal solid waste (MSW) management strategies typically include a combination of three approaches, recycling, combustion, and landfill disposal. In the US approximately 54% of the generated MSW was landfilled in 2008, mainly because of its simplicity and cost-effectiveness. However, landfills remain a major concern due to potential landfill gas (LFG) emissions, generated from the chemical and biological processes occurring in the disposed waste. The main components of LFG are methane (50...
Show moreMunicipal solid waste (MSW) management strategies typically include a combination of three approaches, recycling, combustion, and landfill disposal. In the US approximately 54% of the generated MSW was landfilled in 2008, mainly because of its simplicity and cost-effectiveness. However, landfills remain a major concern due to potential landfill gas (LFG) emissions, generated from the chemical and biological processes occurring in the disposed waste. The main components of LFG are methane (50-60%) and carbon dioxide (40-50%). Although LFG poses a threat to the environment, if managed properly it is a valuable energy resource due to the methane content. Currently there are over 550 active LFG to energy (LFGTE) facilities in the US, producing renewable energy from LFG. A major challenge in designing/operating a LFGTE facility is the uncertainty in LFG generation rate predictions. LFG generation rates are currently estimated using models that are dependent upon the waste disposal history, moisture content, cover type, and gas collection system, which are associated with significant uncertainties. The objectives of this research were to: (1) Evaluate various approaches of estimating LFG generation and to quantify the uncertainty of the model outcomes based on case-study analysis, (2) Present a methodology to predict long-term LFGTE potential under various operating practices on a regional scale, and (3) Investigate costs and benefits of emitting vs. collecting LFG emissions with regards to operation strategies and regulations. The first-order empirical model appeared to be insensitive to the approach taken in quantifying the model parameters, suggesting that the model may be inadequate to accurately describe LFG generation and collection. The uncertainty values for the model were, in general, at their lowest within five years after waste placement ended. Because of the exponential nature, the uncertainty increased as LFG generation declined to low values decades after the end of waste placement. A methodology was presented to estimate LFGTE potential on a regional scale over a 25-year timeframe with consideration of modeling uncertainties. The methodology was demonstrated for the US state of Florida, and showed that Florida could increase the annual LFGTE production by more than threefold by 2035 through installation of LFGTE facilities at all landfills. Results showed that diverting food waste could significantly reduce fugitive LFG emissions, while having minimal effect on the LFGTE potential. Estimates showed that with enhanced landfill operation and energy production practices, LFGTE power density could be comparable to technologies such as wind, tidal, and geothermal. More aggressive operations must be considered to avoid fugitive LFG emissions, which could significantly affect the economic viability of landfills. With little economic motivation for US landfill owners to voluntarily reduce fugitive emissions, regulations are necessary to increase the cost of emitting GHGs. In light of the recent economic recession, it is not likely that a carbon tax will be established; while a carbon trading program will enforce emission caps and provide a tool to offset some costs and improve emission-reduction systems. Immediate action establishing a US carbon trading market with carbon credit pricing and trading supervised by the federal government may be the solution. Costs of achieving high lifetime LFG collection efficiencies are unlikely to be covered with revenues from tipping fee, electricity sales, tax credits, or carbon credit trading. Under scenarios of highly regulated LFG emissions, sustainable landfilling will require research, development, and application of technologies to reduce the marginal abatement cost, including: (1) Diverting rapidly decomposable waste to alternative treatment methods, (2) Reducing fugitive emissions through usage daily/intermediate covers with high oxidation potential, (3) Increasing the lifetime LFG collection efficiency, and (4) Increasing LFG energy value - for instance by producing high-methane gas through biologically altering the LFG generation pathway.
Show less - Date Issued
- 2011
- Identifier
- CFE0003960, ucf:48682
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003960
- Title
- DO IMMIGRANT STUDENTS CONSUME LESS ENERGY THAN NATIVE-BORN AMERICAN STUDENTS?.
- Creator
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Lei, Lei, Pals, Heili, University of Central Florida
- Abstract / Description
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This paper uses a sociological model to compare the residential energy consumption between immigrant students and native-born American students and to explain the difference by demographic characteristics, values, and specific attitudes. Further, it tries to explore whether the relationship between immigration status and residential energy consumption is mediated by value orientation towards frugality and specific attitudes towards energy conservation. The data of an online survey among...
Show moreThis paper uses a sociological model to compare the residential energy consumption between immigrant students and native-born American students and to explain the difference by demographic characteristics, values, and specific attitudes. Further, it tries to explore whether the relationship between immigration status and residential energy consumption is mediated by value orientation towards frugality and specific attitudes towards energy conservation. The data of an online survey among native-born and foreign-born students at the University of Central Florida are used. The results suggest that immigrants consume less energy at home than native-born Americans, but the time stayed in the US doesn't have an impact on the energy consumption of immigrants. In addition, the results do not show evidence that value orientation towards frugality and specific attitudes toward energy conservation mediate the relationship between immigration status and energy consumption at home.
Show less - Date Issued
- 2011
- Identifier
- CFE0003629, ucf:48855
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003629
