Matching Items (100)
Description
Objective of the study is to get a clear idea on the cyclic performance of duty operation of Batteries. Batteries are an integral part of solar plants and wind energy farms due to the fact that energy storage is vital in these places. Various types of losses related to the performance are clearly analyzed and studied. Assessment of State Of Health and State Of Charge is critical in order to maximize the performance and lifetime of a battery. Batteries were subjected to temperature and charge/discharge rate variations and found that the state of health degradation was severe at high temperature along with faster rate of charging compared to other evaluation conditions. The entire research was conducted at the Alternative Energy Technology Laboratory located at Arizona State University, Mesa. It involved the use of various instruments namely the Programmable Voltage Regulator for charging, Computerized Battery Analyzer and Programmable Electric Load for discharging and also the PARSTAT potentiostat for measuring the impedance of various battery technologies under study. At first, the Batteries were discharged and based on the time taken, it was charged for the next cycle. Impedance measurement was done at regular cycle intervals in order to study the degradation of health. For every cycle, the battery capacity was also calculated and noted down. . The results obtained show that low and stable impedance over the given cycle life is an important consideration in the selection of batteries according to the applications.
ContributorsGaneshram, Prashanth (Author) / Madakannan, Arunachalanadar (Thesis advisor) / Peng, Xihong (Committee member) / Nam, Changho (Committee member) / Arizona State University (Publisher)
Created2014
Description
A clean and sustainable alternative to fossil fuels is solar energy. For efficient use of solar energy to be realized, artificial systems that can effectively capture and convert sunlight into a usable form of energy have to be developed. In natural photosynthesis, antenna chlorophylls and carotenoids capture sunlight and transfer the resulting excitation energy to the photosynthetic reaction center (PRC). Small reorganization energy, λ and well-balanced electronic coupling between donors and acceptors in the PRC favor formation of a highly efficient charge-separated (CS) state. By covalently linking electron/energy donors to acceptors, organic molecular dyads and triads that mimic natural photosynthesis were synthesized and studied. Peripherally linked free base phthalocyanine (Pc)-fullerene (C60) and a zinc (Zn) phthalocyanine-C60 dyads were synthesized. Photoexcitation of the Pc moiety resulted in singlet-singlet energy transfer to the attached C60, followed by electron transfer. The lifetime of the CS state was 94 ps. Linking C60 axially to silicon (Si) Pc, a lifetime of the CS state of 4.5 ns was realized. The exceptionally long-lived CS state of the SiPc-C60 dyad qualifies it for applications in solar energy conversion devices. A secondary electron donor was linked to the dyad to obtain a carotenoid (Car)-SiPc-C60 triad and ferrocene (Fc)-SiPc-C60 triad. Excitation of the SiPc moiety resulted in fast electron transfer from the Car or Fc secondary electron donors to the C60. The lifetime of the CS state was 17 ps and 1.2 ps in Car-SiPc-C60 and Fc-SiPc-C60, respectively. In Chapter 3, an efficient synthetic route that yielded regioselective oxidative porphyrin dimerization is presented. Using Cu2+ as the oxidant, meso-β doubly-connected fused porphyrin dimers were obtained in very high yields. Removal of the copper from the macrocycle affords a free base porphyrin dimer. This allows for exchange of metals and provides a route to a wider range of metallporphyrin dimers. In Chapter 4, the development of an efficient and an expedient route to bacteriopurpurin synthesis is discussed. Meso-10,20- diformylation of porphyrin was achieved and one-pot porphyrin diacrylate synthesis and cyclization to afford bacteriopurpurin was realized. The bacteriopurpurin had a reduction potential of - 0.85 V vs SCE and λmax, 845 nm.
ContributorsArero, Jaro (Author) / Gust, Devens (Thesis advisor) / Moore, Ana (Committee member) / Gould, Ian (Committee member) / Arizona State University (Publisher)
Created2014
Description
This is a two-part thesis: Part 1 of this thesis tests and validates the methodology and mathematical models of the International Electrotechnical Commission (IEC) 61853-2 standard for the measurement of angle of incidence (AOI) effects on photovoltaic modules. Flat-plate photovoltaic modules in the field operate under a wide range of environmental conditions. The purpose of IEC 61853-2 is to characterize photovoltaic modules' performance under specific environmental conditions. Part 1 of this report focuses specifically on AOI. To accurately test and validate IEC 61853-2 standard for measuring AOI, meticulous experimental setup and test procedures were followed. Modules of five different photovoltaic technology types with glass superstrates were tested. Test results show practically identical relative light transmission plots for all five test modules. The experimental results were compared to theoretical and empirical models for relative light transmission of air-glass interface. IEC 61853-2 states "for the flat glass superstrate modules, the AOI test does not need to be performed; rather, the data of a flat glass air interface can be used." The results obtained in this thesis validate this statement. This work was performed in collaboration with another Master of Science student (Surynarayana Janakeeraman) and the test results are presented in two masters theses. Part 2 of this thesis is to develop non-intrusive techniques to accurately measure the quantum efficiency (QE) of a single-junction crystalline silicon cell within a commercial module. This thesis will describe in detail all the equipment and conditions necessary to measure QE and discuss the factors which may influence this measurement. The ability to utilize a non-intrusive test to measure quantum efficiency of a cell within a module is extremely beneficial for reliability testing of commercial modules. Detailed methodologies for this innovative test procedure are not widely available in industry because equipment and measurement techniques have not been explored extensively. This paper will provide a literature review describing relevant theories and measurement techniques related to measuring the QE of a cell within a module. The testing methodology and necessary equipment will be described in detail. Results and conclusions provide the overall accuracy of the measurements and discuss the parameters affecting these measurements.
ContributorsKnisely, Brett (Author) / Tamizhmani, Govindasamy (Thesis advisor) / Rogers, Bradley (Committee member) / Macia, Narciso (Committee member) / Arizona State University (Publisher)
Created2013
Description
Novel materials for Li-ion batteries is one of the principle thrust areas for current research in energy storage, more so than most, considering its widespread use in portable electronic gadgets and plug-in electric and hybrid cars. One of the major limiting factors in a Li-ion battery's energy density is the low specific capacities of the active materials in the electrodes. In the search for high-performance anode materials for Li-ion batteries, many alternatives to carbonaceous materials have been studied. Both cubic and amorphous silicon can reversibly alloy with lithium and have a theoretical capacity of 3500 mAh/g, making silicon a potential high density anode material. However, a large volume expansion of 300% occurs due to changes in the structure during lithium insertion, often leading to pulverization of the silicon. To this end, a class of silicon based cage compounds called clathrates are studied for electrochemical reactivity with lithium. Silicon-clathrates consist of silicon covalently bonded in cage structures comprised of face sharing Si20, Si24 and/or Si28 clusters with guest ions occupying the interstitial positions in the polyhedra. Prior to this, silicon clathrates have been studied primarily for their superconducting and thermoelectric properties. In this work, the synthesis and electrochemical characterization of two categories of silicon clathrates - Type-I silicon clathrate with aluminum framework substitution and barium guest ions (Ba8AlxSi46-x) and Type-II silicon clathrate with sodium guest ions (Nax Si136), are explored. The Type-I clathrate, Ba8AlxSi46-x consists of an open framework of aluminium and silicon, with barium (guest) atoms occupying the interstitial positions. X-ray diffraction studies have shown that a crystalline phase of clathrate is obtained from synthesis, which is powdered to a fine particle size to be used as the anode material in a Li-ion battery. Electrochemical measurements of these type of clathrates have shown that capacities comparable to graphite can be obtained for up to 10 cycles and lower capacities can be obtained for up to 20 cycles. Unlike bulk silicon, the clathrate structure does not undergo excessive volume change upon lithium intercalation, and therefore, the crystal structure is morphologically stable over many cycles. X-ray diffraction of the clathrate after cycling showed that crystallinity is intact, indicating that the clathrate does not collapse during reversible intercalation with lithium ions. Electrochemical potential spectroscopy obtained from the cycling data showed that there is an absence of formation of lithium-silicide, which is the product of lithium alloying with diamond cubic silicon. Type II silicon clathrate, NaxSi136, consists of silicon making up the framework structure and sodium (guest) atoms occupying the interstitial spaces. These clathrates showed very high capacities during their first intercalation cycle, in the range of 3,500 mAh/g, but then deteriorated during subsequent cycles. X-ray diffraction after one cycle showed the absence of clathrate phase and the presence of lithium-silicide, indicating the disintegration of clathrate structure. This could explain the silicon-like cycling behavior of Type II clathrates.
ContributorsRaghavan, Rahul (Author) / Chan, Candace K. (Thesis advisor) / Crozier, Peter (Committee member) / Petuskey, William T (Committee member) / Arizona State University (Publisher)
Created2013
Description
This study evaluates two 16 year old photovoltaic power (PV) plants to ascertain degradation rates and various failure modes which occur in a "hot-dry" climate. The data obtained from this study can be used by module manufacturers in determining the warranty limits of their modules and also by banks, investors, project developers and users in determining appropriate financing or decommissioning models. In addition, the data obtained in this study will be helpful in selecting appropriate accelerated stress tests which would replicate the field failures for the new modules and would predict the lifetime for new PV modules. The two power plants referred to as Site 4A and -4B with (1512 modules each) were initially installed on a single axis tracking system in Gilbert, Arizona for the first seven years and have been operating at their current location in Mesa, Arizona for the last nine years at fixed horizontal tilt Both sites experience hot-dry desert climate. Average degradation rate is 0.85%/year for the best modules and 1.1%/year for all the modules (excluding the safety failed modules). Primary safety failure mode is the backsheet delamination though it is small (less than 1.7%). Primary degradation mode and reliability failure mode may potentially be attributed to encapsulant browning leading to transmittance/current loss and thermo-mechanical solder bond fatigue (cell-ribbon and ribbon-ribbon) leading to series resistance increase. Average soiling loss of horizontal tilt based modules is 11.1%. About 0.5-1.7% of the modules qualify for the safety returns under the typical 20/20 warranty terms, 73-76% of the modules qualify for the warranty claims under the typical 20/20 power warranty terms and 24-26% of the modules are meeting the typical 20/20 power warranty terms.
ContributorsYedidi, Karan Rao (Author) / Govindasamy, Tamizhmani (Thesis advisor) / Devarajan, Srinivasan (Committee member) / Narciso, Macia (Committee member) / Arizona State University (Publisher)
Created2013
Description
Battery performance has been studied at different temperature, C rate. Different types of batteries have been used. Capacity and impedance are two factors, which are focused in the thesis. To evaluate battery performance and battery conditions, the SOC (state of charge) determination methods have been studied in the thesis. There are two types of batteries divided in three groups: group I. Ni-Cd battery (2V, 8Ah); group II. Lead-acid battery (2V, 8Ah); and group III. Lead-acid battery (2V, 25Ah). The impedance testing is using electrochemical impedance spectroscopy methods. AC impedance method has been used to test different state of charge (100%, 80%, 60%, 40%, 20%). For the corrosion part, the corrosion rate of metal material in the heat transfer fluids has been tested at different temperature. Hastelloys C-276 in eutectic molten salts a mixture of NaCl, KCl and ZnCl2 using potentiodynamic method (swap from ± 30 mV in 0.2 mV.s-1). The lowest corrosion rate of Hastelloy C-276 is 5.51 µm per year at 250 °C. Particularly, the corrosion rate of Hastelloy C-276 jumps up to 53.33 µm per year at 400 °C.
ContributorsChu, Ximo (Author) / Madakannan, Arunachalanadar (Thesis advisor) / Peng, Xihong (Committee member) / Nam, Changho (Committee member) / Arizona State University (Publisher)
Created2013
Description
Organic optoelectronic devices have remained a research topic of great interest over the past two decades, particularly in the development of efficient organic photovoltaics (OPV) and organic light emitting diodes (OLED). In order to improve the efficiency, stability, and materials variety for organic optoelectronic devices a number of emitting materials, absorbing materials, and charge transport materials were developed and employed in a device setting. Optical, electrical, and photophysical studies of the organic materials and their corresponding devices were thoroughly carried out. Two major approaches were taken to enhance the efficiency of small molecule based OPVs: developing material with higher open circuit voltages or improved device structures which increased short circuit current. To explore the factors affecting the open circuit voltage (VOC) in OPVs, molecular structures were modified to bring VOC closer to the effective bandgap, ∆EDA, which allowed the achievement of 1V VOC for a heterojunction of a select Ir complex with estimated exciton energy of only 1.55eV. Furthermore, the development of anode interfacial layer for exciton blocking and molecular templating provide a general approach for enhancing the short circuit current. Ultimately, a 5.8% PCE was achieved in a single heterojunction of C60 and a ZnPc material prepared in a simple, one step, solvent free, synthesis. OLEDs employing newly developed deep blue emitters based on cyclometalated complexes were demonstrated. Ultimately, a peak EQE of 24.8% and nearly perfect blue emission of (0.148,0.079) was achieved from PtON7dtb, which approaches the maximum attainable performance from a blue OLED. Furthermore, utilizing the excimer formation properties of square-planar Pt complexes, highly efficient and stable white devices employing a single emissive material were demonstrated. A peak EQE of over 20% for pure white color (0.33,0.33) and 80 CRI was achieved with the tridentate Pt complex, Pt-16. Furthermore, the development of a series of tetradentate Pt complexes yielded highly efficient and stable single doped white devices due to their halogen free tetradentate design. In addition to these benchmark achievements, the systematic molecular modification of both emissive and absorbing materials provides valuable structure-property relationship information that should help guide further developments in the field.
ContributorsFleetham, Tyler Blain (Author) / Li, Jian (Thesis advisor) / Alford, Terry (Committee member) / Adams, James (Committee member) / Arizona State University (Publisher)
Created2014
Description
With ever increasing use of natural gas to generate electricity, installed natural gas fired microturbines are found in residential areas to generate electricity locally. This research work discusses a generalized methodology for assessing optimal capacity and locations for installing natural gas fired microturbines in a distribution residential network. The overall objective is to place microturbines to minimize the system power loss occurring in the electrical distribution network; in such a way that the electric feeder does not need any up-gradation. The IEEE 123 Node Test Feeder is selected as the test bed for validating the developed methodology. Three-phase unbalanced electric power flow is run in OpenDSS through COM server, and the gas distribution network is analyzed using GASWorkS. The continual sensitivity analysis methodology is developed to select multiple DG locations and annual simulation is run to minimize annual average losses. The proposed placement of microturbines must be feasible in the gas distribution network and should not result into gas pipeline reinforcement. The corresponding gas distribution network is developed in GASWorkS software, and nodal pressures of the gas system are checked for various cases to investigate if the existing gas distribution network can accommodate the penetration of selected microturbines. The results indicate the optimal locations suitable to place microturbines and capacity that can be accommodated by the system, based on the consideration of overall minimum annual average losses as well as the guarantee of nodal pressure provided by the gas distribution network. The proposed method is generalized and can be used for any IEEE test feeder or an actual residential distribution network.
ContributorsKamdar, Krutak (Author) / Karady, George G. (Thesis advisor) / Ayyanar, Raja (Committee member) / Holbert, Keith E. (Committee member) / Arizona State University (Publisher)
Created2014
Description
The utilization of solar energy requires an efficient means of its storage as fuel. In bio-inspired artificial photosynthesis, light energy can be used to drive water oxidation, but catalysts that produce molecular oxygen from water are required. This dissertation demonstrates a novel complex utilizing earth-abundant Ni in combination with glycine as an efficient catalyst with a modest overpotential of 0.475 ± 0.005 V for a current density of 1 mA/cm2 at pH 11. The production of molecular oxygen at a high potential was verified by measurement of the change in oxygen concentration, yielding a Faradaic efficiency of 60 ± 5%. This Ni species can achieve a current density of 4 mA/cm2 that persists for at least 10 hours. Based upon the observed pH dependence of the current amplitude and oxidation/reduction peaks, the catalysis is an electron-proton coupled process. In addition, to investigate the binding of divalent metals to proteins, four peptides were designed and synthesized with carboxylate and histidine ligands. The binding of the metals was characterized by monitoring the metal-induced changes in circular dichroism spectra. Cyclic voltammetry demonstrated that bound copper underwent a Cu(I)/Cu(II) oxidation/reduction change at a potential of approximately 0.32 V in a quasi-reversible process. The relative binding affinity of Mn(II), Fe(II), Co(II), Ni(II) and Cu(II) to the peptides is correlated with the stability constants of the Irving-Williams series for divalent metal ions. A potential application of these complexes of transition metals with amino acids or peptides is in the development of artificial photosynthetic cells.
ContributorsWang, Dong (Author) / Allen, James P. (Thesis advisor) / Ghirlanda, Giovanna (Committee member) / Redding, Kevin (Committee member) / Arizona State University (Publisher)
Created2014
Description
This dissertation examines the nexus of three trends in electricity systems transformations underway worldwide—the scale-up of renewable energy, regionalization, and liberalization. Interdependent electricity systems are being envisioned that require partnership and integration across power disparities. This research explores how actors in the Mediterranean region envisioned a massive scale-up of renewable energy within a single electricity system and market across Europe, North Africa, and the Middle East. It asks: How are regional sociotechnical systems envisioned? What are the anticipated consequences of a system for a region with broad disparities and deep sociopolitical differences? What can be learned about energy justice by examining this vision at multiple scales? A sociotechnical systems framework is used to analyze energy transformations, interweaving the technical aspects with politics, societal effects, and political development issues. This research utilized mixed qualitative methods to analyze Mediterranean electricity transformations at multiple scales, including fieldwork in Morocco and Germany, document analysis, and event ethnography. Each scale—from a global history of concentrating solar power technologies to a small village in Morocco—provides a different lens on the sociotechnical system and its implications for justice. This study updates Thomas Hughes’ Networks of Power, the canonical history of the sociotechnical development of electricity systems, by adding new aspects to sociotechnical electricity systems theory. First, a visioning process now plays a crucial role in guiding innovation and has a lasting influence on the justice outcomes. Second, rather than simply providing people with heat and light, electrical power systems in the 21st century are called upon to address complex integrated solutions. Furthermore, building a sustainable energy system is now a retrofitting agenda, as system builders must graft new infrastructure on top of old systems. Third, the spatial and temporal aspects of sociotechnical energy systems should be amended to account for constructed geography and temporal complexity. Fourth, transnational electricity systems pose new challenges for politics and political development. Finally, this dissertation presents a normative framework for conceptualizing and evaluating energy justice. Multi-scalar, systems-level justice requires collating diverse ideas about energy justice, expanding upon them based on the empirical material, and evaluating them with this framework.
ContributorsMoore, Sharlissa (Author) / Hackett, Ed J. (Thesis advisor) / Minteer, Ben (Committee member) / Parmentier, Mary Jane (Committee member) / Wetmore, Jameson (Committee member) / Arizona State University (Publisher)
Created2015