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- All Subjects: energy
- Creators: Arizona State University
Description
With the increasing penetration of converter interfaced renewable generation into power systems, the structure and behavior of the power system is changing, catalyzing alterations and enhancements in modeling and simulation methods.
This work puts forth a Hybrid Electromagnetic Transient-Transient Stability simulation method implemented using MATLAB and Simulink, to study power electronic based power systems. Hybrid Simulation enables detailed, accurate modeling, along with fast, efficient simulation, on account of the Electromagnetic Transient (EMT) and Transient Stability (TS) simulations respectively. A critical component of hybrid simulation is the interaction between the EMT and TS simulators, established through a well-defined interface technique, which has been explored in detail.
This research focuses on the boundary conditions and interaction between the two simulation models for optimum accuracy and computational efficiency.
A case study has been carried out employing the proposed hybrid simulation method. The test case used is the IEEE 9-bus system, modified to integrate it with a solar PV plant. The validation of the hybrid model with the benchmark full EMT model, along with the analysis of the accuracy and efficiency, has been performed. The steady-state and transient analysis results demonstrate that the performance of the hybrid simulation method is competent. The hybrid simulation technique suitably captures accuracy of EMT simulation and efficiency of TS simulation, therefore adequately representing the behavior of power systems with high penetration of converter interfaced generation.
This work puts forth a Hybrid Electromagnetic Transient-Transient Stability simulation method implemented using MATLAB and Simulink, to study power electronic based power systems. Hybrid Simulation enables detailed, accurate modeling, along with fast, efficient simulation, on account of the Electromagnetic Transient (EMT) and Transient Stability (TS) simulations respectively. A critical component of hybrid simulation is the interaction between the EMT and TS simulators, established through a well-defined interface technique, which has been explored in detail.
This research focuses on the boundary conditions and interaction between the two simulation models for optimum accuracy and computational efficiency.
A case study has been carried out employing the proposed hybrid simulation method. The test case used is the IEEE 9-bus system, modified to integrate it with a solar PV plant. The validation of the hybrid model with the benchmark full EMT model, along with the analysis of the accuracy and efficiency, has been performed. The steady-state and transient analysis results demonstrate that the performance of the hybrid simulation method is competent. The hybrid simulation technique suitably captures accuracy of EMT simulation and efficiency of TS simulation, therefore adequately representing the behavior of power systems with high penetration of converter interfaced generation.
ContributorsAthaide, Denise Maria Christine (Author) / Qin, Jiangchao (Thesis advisor) / Ayyanar, Raja (Committee member) / Wu, Meng (Committee member) / Arizona State University (Publisher)
Created2018
Description
The molecular modification of semiconductors has applications in energy
conversion and storage, including artificial photosynthesis. In nature, the active sites of
enzymes are typically earth-abundant metal centers and the protein provides a unique
three-dimensional environment for effecting catalytic transformations. Inspired by this
biological architecture, a synthetic methodology using surface-grafted polymers with
discrete chemical recognition sites for assembling human-engineered catalysts in three-dimensional
environments is presented. The use of polymeric coatings to interface cobalt-containing
catalysts with semiconductors for solar fuel production is introduced in
Chapter 1. The following three chapters demonstrate the versatility of this modular
approach to interface cobalt-containing catalysts with semiconductors for solar fuel
production. The catalyst-containing coatings are characterized through a suite of
spectroscopic techniques, including ellipsometry, grazing angle attenuated total reflection
Fourier transform infrared spectroscopy (GATR-FTIR) and x-ray photoelectron (XP)
spectroscopy. It is demonstrated that the polymeric interface can be varied to control the
surface chemistry and photoelectrochemical response of gallium phosphide (GaP) (100)
electrodes by using thin-film coatings comprising surface-immobilized pyridyl or
imidazole ligands to coordinate cobaloximes, known catalysts for hydrogen evolution.
The polymer grafting chemistry and subsequent cobaloxime attachment is applicable to
both the (111)A and (111)B crystal face of the gallium phosphide (GaP) semiconductor,
providing insights into the surface connectivity of the hard/soft matter interface and
demonstrating the applicability of the UV-induced immobilization of vinyl monomers to
a range of GaP crystal indices. Finally, thin-film polypyridine surface coatings provide a
molecular interface to assemble cobalt porphyrin catalysts for hydrogen evolution onto
GaP. In all constructs, photoelectrochemical measurements confirm the hybrid
photocathode uses solar energy to power reductive fuel-forming transformations in
aqueous solutions without the use of organic acids, sacrificial chemical reductants, or
electrochemical forward biasing.
conversion and storage, including artificial photosynthesis. In nature, the active sites of
enzymes are typically earth-abundant metal centers and the protein provides a unique
three-dimensional environment for effecting catalytic transformations. Inspired by this
biological architecture, a synthetic methodology using surface-grafted polymers with
discrete chemical recognition sites for assembling human-engineered catalysts in three-dimensional
environments is presented. The use of polymeric coatings to interface cobalt-containing
catalysts with semiconductors for solar fuel production is introduced in
Chapter 1. The following three chapters demonstrate the versatility of this modular
approach to interface cobalt-containing catalysts with semiconductors for solar fuel
production. The catalyst-containing coatings are characterized through a suite of
spectroscopic techniques, including ellipsometry, grazing angle attenuated total reflection
Fourier transform infrared spectroscopy (GATR-FTIR) and x-ray photoelectron (XP)
spectroscopy. It is demonstrated that the polymeric interface can be varied to control the
surface chemistry and photoelectrochemical response of gallium phosphide (GaP) (100)
electrodes by using thin-film coatings comprising surface-immobilized pyridyl or
imidazole ligands to coordinate cobaloximes, known catalysts for hydrogen evolution.
The polymer grafting chemistry and subsequent cobaloxime attachment is applicable to
both the (111)A and (111)B crystal face of the gallium phosphide (GaP) semiconductor,
providing insights into the surface connectivity of the hard/soft matter interface and
demonstrating the applicability of the UV-induced immobilization of vinyl monomers to
a range of GaP crystal indices. Finally, thin-film polypyridine surface coatings provide a
molecular interface to assemble cobalt porphyrin catalysts for hydrogen evolution onto
GaP. In all constructs, photoelectrochemical measurements confirm the hybrid
photocathode uses solar energy to power reductive fuel-forming transformations in
aqueous solutions without the use of organic acids, sacrificial chemical reductants, or
electrochemical forward biasing.
ContributorsBeiler, Anna Mary (Author) / Moore, Gary F. (Thesis advisor) / Moore, Thomas A. (Thesis advisor) / Redding, Kevin E. (Committee member) / Allen, James P. (Committee member) / Arizona State University (Publisher)
Created2018
Description
A Microbial fuel cell (MFC) is a bio-inspired carbon-neutral, renewable electrochemical converter to extract electricity from catabolic reaction of micro-organisms. It is a promising technology capable of directly converting the abundant biomass on the planet into electricity and potentially alleviate the emerging global warming and energy crisis. The current and power density of MFCs are low compared with conventional energy conversion techniques. Since its debut in 2002, many studies have been performed by adopting a variety of new configurations and structures to improve the power density. The reported maximum areal and volumetric power densities range from 19 mW/m2 to 1.57 W/m2 and from 6.3 W/m3 to 392 W/m3, respectively, which are still low compared with conventional energy conversion techniques. In this dissertation, the impact of scaling effect on the performance of MFCs are investigated, and it is found that by scaling down the characteristic length of MFCs, the surface area to volume ratio increases and the current and power density improves. As a result, a miniaturized MFC fabricated by Micro-Electro-Mechanical System(MEMS) technology with gold anode is presented in this dissertation, which demonstrate a high power density of 3300 W/m3. The performance of the MEMS MFC is further improved by adopting anodes with higher surface area to volume ratio, such as carbon nanotube (CNT) and graphene based anodes, and the maximum power density is further improved to a record high power density of 11220 W/m3. A novel supercapacitor by regulating the respiration of the bacteria is also presented, and a high power density of 531.2 A/m2 (1,060,000 A/m3) and 197.5 W/m2 (395,000 W/m3), respectively, are marked, which are one to two orders of magnitude higher than any previously reported microbial electrochemical techniques.
ContributorsRen, Hao (Author) / Chae, Junseok (Thesis advisor) / Bakkaloglu, Bertan (Committee member) / Phillips, Stephen (Committee member) / Goryll, Michael (Committee member) / Arizona State University (Publisher)
Created2016
Description
Cadmium Telluride (CdTe) possesses preferable optical properties for photovoltaic (PV) applications: a near optimum bandgap of 1.5 eV, and a high absorption coefficient of over 15,000 cm-1 at the band edge. The detailed-balance limiting efficiency is 32.1% with an open-circuit voltage (Voc) of 1.23 V under the AM1.5G spectrum. The record polycrystalline CdTe thin-film cell efficiency has reached 22.1%, with excellent short-circuit current densities (Jsc) and fill-factors (FF). However, the Voc (~900 mV) is still far below the theoretical value, due to the large non-radiative recombination in the polycrystalline CdTe absorber, and the low-level p-type doping.
Monocrystalline CdTe/MgCdTe double-heterostructures (DHs) grown on lattice-matched InSb substrates have demonstrated impressively long carrier lifetimes in both unintentionally doped and Indium-doped n-type CdTe samples. The non-radiative recombination inside of, and at the interfaces of the CdTe absorbers in CdTe/MgCdTe DH samples has been significantly reduced due to the use of lattice-matched InSb substrates, and the excellent passivation provided by the MgCdTe barrier layers. The external luminescent quantum efficiency (η_ext) of n-type CdTe/MgCdTe DHs is up to 3.1%, observed from a 1-µm-thick CdTe/MgCdTe DH doped at 1017 cm-3. The 3.1% η_ext corresponds to an internal luminescent quantum efficiency (η_int) of 91%. Such a high η_ext gives an implied Voc, or quasi-Fermi-level splitting, of 1.13 V.
To obtain actual Voc, the quasi-Fermi-level splitting should be extracted to outside the circuit using a hole-selective contact layer. However, CdTe is difficult to be doped p-type, making it challenging to make efficient PN junction CdTe solar cells. With the use of MgCdTe barrier layers, the hole-contact layer can be defective without affecting the voltage. P-type hydrogenated amorphous silicon is an effective hole-selective contact for CdTe solar cells, enabling monocrystalline CdTe/MgCdTe DH solar cells to achieve Voc over 1.1 V, and a maximum active area efficiency of 18.8% (Jsc = 23.3 mA/cm2, Voc = 1.114 V, and FF = 72.3%). The knowledge gained through making the record-efficiency monocrystalline CdTe cell, particularly the n-type doping and the double-heterostructure design, may be transferable to polycrystalline CdTe thin-film cells and improve their competitiveness in the PV industry.
Monocrystalline CdTe/MgCdTe double-heterostructures (DHs) grown on lattice-matched InSb substrates have demonstrated impressively long carrier lifetimes in both unintentionally doped and Indium-doped n-type CdTe samples. The non-radiative recombination inside of, and at the interfaces of the CdTe absorbers in CdTe/MgCdTe DH samples has been significantly reduced due to the use of lattice-matched InSb substrates, and the excellent passivation provided by the MgCdTe barrier layers. The external luminescent quantum efficiency (η_ext) of n-type CdTe/MgCdTe DHs is up to 3.1%, observed from a 1-µm-thick CdTe/MgCdTe DH doped at 1017 cm-3. The 3.1% η_ext corresponds to an internal luminescent quantum efficiency (η_int) of 91%. Such a high η_ext gives an implied Voc, or quasi-Fermi-level splitting, of 1.13 V.
To obtain actual Voc, the quasi-Fermi-level splitting should be extracted to outside the circuit using a hole-selective contact layer. However, CdTe is difficult to be doped p-type, making it challenging to make efficient PN junction CdTe solar cells. With the use of MgCdTe barrier layers, the hole-contact layer can be defective without affecting the voltage. P-type hydrogenated amorphous silicon is an effective hole-selective contact for CdTe solar cells, enabling monocrystalline CdTe/MgCdTe DH solar cells to achieve Voc over 1.1 V, and a maximum active area efficiency of 18.8% (Jsc = 23.3 mA/cm2, Voc = 1.114 V, and FF = 72.3%). The knowledge gained through making the record-efficiency monocrystalline CdTe cell, particularly the n-type doping and the double-heterostructure design, may be transferable to polycrystalline CdTe thin-film cells and improve their competitiveness in the PV industry.
ContributorsZhao, Yuan (Author) / Zhang, Yong-Hang (Thesis advisor) / Bertoni, Mariana (Committee member) / King, Richard (Committee member) / Holman, Zachary (Committee member) / Arizona State University (Publisher)
Created2016
Description
Residential air conditioning systems represent a critical load for many electric
utilities, especially for those who serve customers in hot climates. In hot and dry
climates, in particular, the cooling load is usually relatively low during night hours and
early mornings and hits its maximum in the late afternoon. If electric loads could be
shifted from peak hours (e.g., late afternoon) to off-peak hours (e.g., late morning), not
only would building operation costs decrease, the need to run peaker plants, which
typically use more fossil fuels than non-peaker plants, would also decrease. Thus, shifting
electricity consumption from peak to off-peak hours promotes economic and
environmental savings. Operational and technological strategies can reduce the load
during peak hours by shifting cooling operation from on-peak hours to off-peak hours.
Although operational peak load shifting strategies such as precooling may require
mechanical cooling (e.g., in climates like Phoenix, Arizona), this cooling is less
expensive than on-peak cooling due to demand charges or time-based price plans.
Precooling is an operational shift, rather than a technological one, and is thus widely
accessible to utilities’ customer base. This dissertation compares the effects of different
precooling strategies in a Phoenix-based utility’s residential customer market and
assesses the impact of technological enhancements (e.g., energy efficiency measures and
solar photovoltaic system) on the performance of precooling. This dissertation focuses on
the operational and technological peak load shifting strategies that are feasible for
residential buildings and discusses the advantages of each in terms of peak energy
savings and residential electricity cost savings.
utilities, especially for those who serve customers in hot climates. In hot and dry
climates, in particular, the cooling load is usually relatively low during night hours and
early mornings and hits its maximum in the late afternoon. If electric loads could be
shifted from peak hours (e.g., late afternoon) to off-peak hours (e.g., late morning), not
only would building operation costs decrease, the need to run peaker plants, which
typically use more fossil fuels than non-peaker plants, would also decrease. Thus, shifting
electricity consumption from peak to off-peak hours promotes economic and
environmental savings. Operational and technological strategies can reduce the load
during peak hours by shifting cooling operation from on-peak hours to off-peak hours.
Although operational peak load shifting strategies such as precooling may require
mechanical cooling (e.g., in climates like Phoenix, Arizona), this cooling is less
expensive than on-peak cooling due to demand charges or time-based price plans.
Precooling is an operational shift, rather than a technological one, and is thus widely
accessible to utilities’ customer base. This dissertation compares the effects of different
precooling strategies in a Phoenix-based utility’s residential customer market and
assesses the impact of technological enhancements (e.g., energy efficiency measures and
solar photovoltaic system) on the performance of precooling. This dissertation focuses on
the operational and technological peak load shifting strategies that are feasible for
residential buildings and discusses the advantages of each in terms of peak energy
savings and residential electricity cost savings.
ContributorsArababadi, Reza (Author) / Parrish, Kristen (Thesis advisor) / Reddy, T A (Committee member) / Jackson, Roderick K (Committee member) / Arizona State University (Publisher)
Created2016
Description
Buildings consume nearly 50% of the total energy in the United States, which drives the need to develop high-fidelity models for building energy systems. Extensive methods and techniques have been developed, studied, and applied to building energy simulation and forecasting, while most of work have focused on developing dedicated modeling approach for generic buildings. In this study, an integrated computationally efficient and high-fidelity building energy modeling framework is proposed, with the concentration on developing a generalized modeling approach for various types of buildings. First, a number of data-driven simulation models are reviewed and assessed on various types of computationally expensive simulation problems. Motivated by the conclusion that no model outperforms others if amortized over diverse problems, a meta-learning based recommendation system for data-driven simulation modeling is proposed. To test the feasibility of the proposed framework on the building energy system, an extended application of the recommendation system for short-term building energy forecasting is deployed on various buildings. Finally, Kalman filter-based data fusion technique is incorporated into the building recommendation system for on-line energy forecasting. Data fusion enables model calibration to update the state estimation in real-time, which filters out the noise and renders more accurate energy forecast. The framework is composed of two modules: off-line model recommendation module and on-line model calibration module. Specifically, the off-line model recommendation module includes 6 widely used data-driven simulation models, which are ranked by meta-learning recommendation system for off-line energy modeling on a given building scenario. Only a selective set of building physical and operational characteristic features is needed to complete the recommendation task. The on-line calibration module effectively addresses system uncertainties, where data fusion on off-line model is applied based on system identification and Kalman filtering methods. The developed data-driven modeling framework is validated on various genres of buildings, and the experimental results demonstrate desired performance on building energy forecasting in terms of accuracy and computational efficiency. The framework could be easily implemented into building energy model predictive control (MPC), demand response (DR) analysis and real-time operation decision support systems.
ContributorsCui, Can (Author) / Wu, Teresa (Thesis advisor) / Weir, Jeffery D. (Thesis advisor) / Li, Jing (Committee member) / Fowler, John (Committee member) / Hu, Mengqi (Committee member) / Arizona State University (Publisher)
Created2016
Description
Lithium ion batteries have emerged as the most popular energy storage system, but they pose safety issues under extreme temperatures or in the event of a thermal runaway. Lithium ion batteries with inorganic separators offer the advantage of safer operation. An inorganic separator for lithium ion battery was prepared by an improved method of blade coating α-Al2O3 slurry directly on the electrode followed by drying. The improved separator preparation involves a twice-coating process instead of coating the slurry all at once in order to obtain a thin (~40 µm) and uniform coat. It was also found that α-Al2O3 powder with particle size greater than the pore size in the electrode is preferable for obtaining a separator with 40 µm thickness and consistent cell performance. Unlike state-of-the-art polyolefin separators such as polypropylene (PP) which are selectively wettable with only certain electrolytes, the excellent electrolyte solvent wettability of α-Al2O3 allows the coated alumina separator to function with different electrolytes. The coated α-Al2O3 separator has a much higher resistance to temperature effects than its polyolefin counterparts, retaining its dimensional integrity at temperatures as high as 200ºC. This eliminates the possibility of a short circuit during thermal runaway. Lithium ion batteries assembled as half-cells and full cells with coated α-Al2O3 separator exhibit electrochemical performance comparable with that of polyolefin separators at room temperature. However, the cells with coated alumina separator shows better cycling performance under extreme temperatures in the temperature range of -30°C to 60°C. Therefore, the coated α-Al2O3 separator is very promising for application in safe lithium-ion batteries.
ContributorsSharma, Gaurav (Author) / Lin, Jerry Y.S. (Thesis advisor) / Chan, Candace (Committee member) / Kannan, Arunachala (Committee member) / Arizona State University (Publisher)
Created2016