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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.

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.

(1) A new model for the mass transfer in Direct Contact Membrane Distillation (DCMD) process is developed. The model is based on Direct Simulation Monte Carlo (DSMC) method. It avoids the over simplification of the resistance mechanisms and hence, give more accurate prediction. The model is validated by means of experiments. The influences of the main parameters in DCMD are also studied, including temperature difference between the feed side and the permeate side, the membrane's thickness and the pore size. Moreover, it is proposed to use aerogel as the membrane material. It is shown that the aerogel's hydrophobic property, low thermal conductivity and high porosity offer a much improved performance over the commonly used membrane material PTFE. The fresh water productivity can reach 10.0 kg/m2 per day. / (2) A new energy harvesting method for converting thermal energy to kinetic energy is proposed. This method is based on the rarefied gas phenomenon called Knudsen effect. By Knudsen effect, a gas flow can be generated from temperature difference. In order to generate Knudsen effect, a special material, aerogel, is used. It is a porous material full of holes of dozens of nanometers. Using Direct Simulation Monte Carlo (DSMC) simulation, it is shown that Knudsen effect still works under atmosphere pressure with aerogel material. Accordingly, a device is designed. Based on the numerical simulation, the device can generate about 70 W kinetic energy when driven by a solar panel with intensity of 1 kW/m2. / (3) A solar desalination system is designed. This system is based on a combination of Knudsen compressor and simple solar still. The Knudsen effect is generated from the aerogel driven by solar radiation. As a result, the system operates at lower pressure resulting in enhanced water evaporation process. Based on the simulation, the evaporation rate is significantly increased. It is found that in a typical summer day in tropic region like Hong Kong, such a system can generate about 5 kg fresh water per 1 m2 solar still per day. This number is about 30% higher than the simple direct solar still. Moreover, the proposed technology can be readily combined with other technologies such as condensation heat recovery to further improve the fresh water productivity. The optimal working condition is also studied. / Energy and water are two of the most important issues in the world today. The social and economic health of the world depends on sustainable supply of both energy and water. Especially, these two critical resources are always inextricably linked. To solve the emerging crisis of energy and water, renewable energy technologies is the key. On the other hand, recent advances in Micro-Electro-Mechanical Systems (MEMS) technology have opened new ways for us to use micro/nano scale physical and chemical effects. It is no doubted that the combination of the renewable energy technologies and micro/nano technologies will have great potential and there are plenty of room to explore. / The research presented in this thesis focuses on extending the micro scale effect to the macroscopic applications. Based on this idea, a new energy harvesting method and two new water desalination technologies are proposed, with computer simulations and experiment validations. These include: / Zhang, Peng. / Adviser: Ruxu Du. / Source: Dissertation Abstracts International, Volume: 72-04, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 123-135). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

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.

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.

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

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.

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