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Designing Electrochemical Systems for Energy ConversionObata, Keisuke 06 1900 (has links)
Electrochemical water splitting to hydrogen and oxygen is an attractive approach
to store and convert intermittent renewable energy sources. Energy efficient, cost
effective and durable electrochemical systems are highly required. Firstly, CeOx
coated oxygen evolution electrocatalysts were developed to improve the stability.
Unique permselectivity of the CeOx layer was disclosed, which helps to prevent
dissolution of active metal site. Because oxygen evolution reaction requires a
higher overpotential than hydrogen evolution reaction, kinetically facile oxidation
of soluble redox ions was proposed as an alternative anodic reaction, in which the
oxidized redox ions can be used for succeeding homogeneous reactions, such as
treatment of H2S. How to tune the thermodynamics and the diffusion of candidate
redox ions is discussed for a desired application. In addition to the anodic
reaction, cathodic hydrogen evolution reaction has to be optimized. To maximize
hydrogen evolution performance in near-neutral pH buffered conditions,
concentration overpotentials from local pH and hydrogen on a Pt cathode are
distinguished by mass transport modelling. Finally, stand-alone module was
developed to perform solar-driven redox-mediated H2S splitting to H2 and S under
natural solar irradiation.
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Vanadium-redox flow and lithium-ion battery modelling and performance in wind energy applicationsChahwan, John A. January 2007 (has links)
No description available.
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Engineering of Thermoelectric Materials for Power Generation ApplicationsJovovic, Vladimir January 2009 (has links)
No description available.
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Biological Ion Transporters as Gating Devices for Chemomechanical and Chemoelectrical Energy ConversionSundaresan, Vishnu Baba 01 June 2007 (has links)
This dissertation presents a new class of engineered devices, fabricated from synthetic materials and protein transporters extracted from cell membranes of plants, that use chemomechanical and chemoelectrical energy conversion processes to perform mechanical and electrical work.
The chemomechanical energy conversion concept is implemented in a protein based actuator. The chemical energy is applied as an electrochemical gradient of protons across a membrane assembly formed from phospholipids and SUT4 -a proton-sucrose cotransporter. The membrane assembly forms a physical barrier between two chambers in the actuator. The SUT4 proteins in the membrane assembly balances the applied electrochemical gradient by a concentration gradient of sucrose across the membrane. The sucrose gradient simultaneously generates an osmotic flow which deforms a flexible wall in a constrained chamber of the actuator, thus exhibiting mechanical strain. The sucrose concentration balanced by the protein transporter is used as the control variable for fluid flow through the membrane. The transport properties of the membrane assembly has been characterized for the control variable in the system. The reaction kinetics based model for solute transport through the cotransporter is modified to compute the equilibrium constant for solute binding and fluid translocation rate through the membrane. The maximum initial flux rate through the membrane is computed to be 2.51+/-0.6 ul/ug.cm^2.min for an applied pH4.0/pH7.0 concentration gradient across the membrane. The flux rate can be modulated by varying the sucrose concentration in the actuator. The prototype actuator has been fabricated using the characterized membrane assembly. A maximum deformation of 60microns at steady state is developed by the actuator for 20 mM sucrose concentration in the system.
The chemoelectrical energy conversion concept is based on the electrogenic proton pumps in plasma and vacuolar membranes of a plant cell. A prototype device referred to as a BioCell demonstrates the chemoelectric energy conversion using V-type ATPase extracted from plant cell membranes. The enzyme in the bilayer lipid membrane hydrolyzes ATP and converts the chemical energy from the reaction into a charge gradient across the membrane. Silver-silver chloride electrodes on both the sides of the membrane convert the charge established by the proton pumps into cell voltage. The redox reactions at the surface of the electrodes result in a current through the external load connected to the terminals of the BioCell. The single cell behaves like a constant current power source and has an internal resistance of 10-22kOhms. The specific power from the cell of the membrane assembly is estimated to be around 2microwatts/sq/cm. The demonstration of chemoelectrical energy conversion shows the possibility to use ATP as an alternative source of electrical power to design novel chemo-electro-mechanical devices. / Ph. D.
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Marine Current Energy ConversionLundin, Staffan January 2016 (has links)
Marine currents, i.e. water currents in oceans and rivers, constitute a large renewable energy resource. This thesis presents research done on the subject of marine current energy conversion in a broad sense. A review of the tidal energy resource in Norway is presented, with the conclusion that tidal currents ought to be an interesting option for Norway in terms of renewable energy. The design of marine current energy conversion devices is studied. It is argued that turbine and generator cannot be seen as separate entities but must be designed and optimised as a unit for a given conversion site. The influence of support structure for the turbine blades on the efficiency of the turbine is studied, leading to the conclusion that it may be better to optimise a turbine for a lower flow speed than the maximum speed at the site. The construction and development of a marine current energy experimental station in the River Dalälven at Söderfors is reported. Measurements of the turbine's power coefficient indicate that it is possible to build efficient turbines for low flow speeds. Experiments at the site are used for investigations into different load control methods and for validation of a numerical model of the energy conversion system and the model's ability to predict system behaviour in response to step changes in operational tip speed ratio. A method for wake measurements is evaluated and found to be useful within certain limits. Simple models for turbine runaway behaviour are derived, of which one is shown by comparison with experimental results to predict the behaviour well.
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The politics of system innovation for emerging technologies : understanding the uptake of off-grid renewable electricity in rural ChileOpazo, Jose January 2014 (has links)
Access to sustainable energy in the developing world has become a fundamental challenge in development and environmental policy in the 21st Century, and rural electrification in developing countries constitutes a central element of access to energy goals. However, traditional ways of providing electricity to dispersed rural populations (i.e. through centralised electricity infrastructure or fuel-based on-site generation) is proving to be ineffective, inefficient and less sustainable than the use of renewable energy technologies (RETs) in off-grid settings. Such ‘system innovations' for sustainable electricity services in rural areas are the focus of this study, which seeks to understand the reasons underlying success or failure in the diffusion of radical innovations. Embracing evolutionary and constructivist theories of socio-technical change and sustainability transitions, the thesis attempts to explain the use and diffusion of PV (photovoltaic) and wind technology in off-grid rural electrification over the last 20 years in Chile, a country where access to rural electricity has increased from 53% to 95%. RETs have contributed to nearly 10% of that increment. By using a framework that combines Strategic Niche Management (SNM), systemic intermediation and power, agency and conflicts in decision making, the thesis analyses the dynamics between the development and adaptation of new technologies and their influence in regime shift through replication, scaling up and translation of new socio-technical practices. The thesis attempts to shed light on processes affecting niche construction and it concludes that internal niche processes are relevant to understanding how radical innovations are structured and stabilised from the aggregation of projects. However, those processes are not only a managerial activity that can be steered but a politically underpinned (and iterative) process between specific (socio-political) settings. The study also highlights the role of systemic intermediaries, government and incumbent actors in the dynamic interaction between emergent niche dynamics and traditional ways of improving electricity access.
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LASER SYNTHESIS OF NANOMATERIALS INCORPORATED WITHIN HIGH SURFACE AREA MATERIALS: APPLICATIONS FOR HETEROGENEOUS CATALYSIS, WATER TREATMENT, AND PHOTOTHERMAL ENERGY CONVERSIONBobb, Julian A 01 January 2018 (has links)
Chemical methods are generally used for the synthesis of active nanoparticles (metals, semi-metals, metal oxides, and etc) supported on high surface area materials. Chemical methods involve using strong solvents, harmful gases (H2 & CO), and high temperature techniques such as high boiling solvents, calcination and pyrolysis. The main drawbacks of using this approach, is the prevalence of chemical agents on nanomaterials which tends to negate its applications. Alternatively, photochemical and photothermal methods are widely being considered for the synthesis and design of nanomaterials.
For these studies, the active nanomaterials incorporated within high surface area materials were prepared by the laser vaporization-controlled condensation (LVCC) technique or by the laser irradiation in solution (LIS) technique. The LVCC technique involves the irradiation of a solid target at the focal point of a laser beam (532 nm, 30 Hz) by the Nd: YAG laser inside a chamber that is sandwiched between two steel plates in the presence of high purity He. Whereas, the LIS technique involves the laser irradiation of chemical precursors in aqueous solvents using an unfocused beam. The LVCC technique was used for the preparation of carbonaceous and N-doped carbonaceous TiO2 support materials from MIL-125(Ti) and NH2-MIL-125(Ti) metal organic frameworks, Ge and GeO2 nanostructures, GeOx/PRGO nanocomposite, and the Fe3O4/PRGO nanocomposite. On the other hand, Pd supported on MIL-125(Ti) and NH2-MIL-125(Ti) nanocatalysts, GeO2/RGO, and the poly(ethylene glycol methacrylate-co-bisacrylamide) hydrogels were all prepared by the LIS technique.
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Analysis of energy conversion systems, including material and global warming aspectsZhang, Mingyuan 12 October 1995 (has links)
With the rapid increase of the world energy demand and
consumption, the method and techniques to analyze, improve
and optimize energy conversion systems have to deal not only
with direct fuel exergy (energy) consumption, but also with
other resources, which have associated exergy consumptions,
and with environmental impacts, such as global warming.
A general method for energy conversion system analysis
is presented in this thesis. This method uses exergy as a
measure to compare and analyze the natural resource
consumption (both fuels and materials) and the global
warming impact of different energy conversion systems for
their life-time. The method, which adds the fuel production
exergy and material exergy into consideration, allows more
complete exergy analyses to be conducted. The global warming
impact due to the chemical emissions and impact associated
with direct exergy consumption (fuel consumption) as well as
system equipment materials consumption of the energy
conversion system are considered together in this thesis.
Based on the concept of exergy, the Total Equivalent
Resource Exergy (TERE), which includes both direct resource
exergy consumption and resource exergy needed to recover the
total equivalent global warming gases of the energy
conversion system, is proposed in this thesis. TERE uses
exergy as a criterion to compare the energy conversion
systems and providing information of how effective a system
is regarding the use of natural resources. The calculation
of TERE values for the selected energy conversion systems
indicates that the resource exergy and the environmental
impact exergy are both substantial impacts and should be
compared together. This concept of TERE can be used as the
objective function for energy system design and
optimization. / Graduation date: 1996
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Investigation into direct conversion with medium energy He-ion beamsGuild-Bingham, Avery A. 17 February 2005 (has links)
The Department of Energy (DOE) Nuclear Energy Research Initiative (NERI)
Direct Energy Conversion project has identified the fission fragment magnetic collimator
reactor (FFMCR) as a promising direct fission fragment conversion concept. The US
DOE NERI Proof-of-Principle Project at Texas A&M is focused on experimental
verification of FFMCR operation principles. The purpose of this experiment was to test
design parameters of a scaled prototype of a direct energy collector chamber of the
FFMCR. The charge collection efficiency was found using a He+ ion beam to be
approximately 88% for beam energies ranging from 20 to 80 keV. The 2.4 10^12 ± 10%
ohm resistor used in the experiment holds-up under the stress of high voltage to 40 kV.
Electric current leakage tests of the charge collection device also indicate that Teflon® is
quite sufficient as an insulator for potentials as high as 40 kV. It is suggested that the
present work be extended to determine power efficiencies and to achieve results with
higher beam energies.
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Thermodynamic and economic feasibility analysis of a 20 MW ocean thermal energy conversion (OTEC) power plantUpshaw, Charles Roberts 30 July 2012 (has links)
Ocean Thermal Energy Conversion (OTEC) is the process of harnessing the temperature differential that exists in the equatorial oceans between the warm surface water and the cool water thousands of feet below to produce electricity. Due to the massive scale of the ocean thermal resources, OTEC power generation is appealing. The purpose of this thesis was to investigate OTEC and assess its potential viability as an energy source from both engineering and economic perspectives.
This thesis provides an introduction to the research, and outlines the scope of the project in Chapter 1. Chapter 2 proves an overview of OTEC, from the basic operation and viable locations, to information on some of the major components that make up the plant. Chapter 3 describes the thermodynamics, heat transfer, and fluid mechanics that govern the physical operation of the OTEC plant. Chapter 4 provides an analysis of different plant design parameters to examine effects different parameters have on plant operations and equipment sizing. Chapter 5 describes the cost estimation for an OTEC plant, and provides subsequent analysis by comparing the estimated cost with other technologies and electricity prices from four island communities.
The primary research of this thesis was the development of an integrated thermal fluids systems model of a closed-cycle OTEC power plant for the purpose of analyzing the effects of key design parameters on the plant performance. A simple Levelized Cost of Electricity (LCOE) economic model was also developed and integrated with the Thermal Fluid Systems model in order to assess the potential economic viability of a 20 MW OTEC power plant. The analyses from these models suggest that OTEC is definitely viable from an engineering standpoint, but economic viability for a 20 MW plant would likely be limited to small or remote island communities. / text
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