Theses (IESVic)

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Active magnetic regenerator experimental optimization
(2009-11-30T16:59:27Z) Tura, Armando; Rowe, Andrew Michael
A technology that has the potential to create more efficient and compact refrigeration devices is an Active Magnetic Regenerative Refrigerator (AMRR). An AMRR can operate over a broad range of temperatures, as long as the appropriate refrigerant is implemented. Thus this flexible technology can be used for small, efficient, and simple room temperature refrigerators, as well as efficient gas liquefaction plants (AMRLs). Active Magnetic Regenerator Refrigeration exploits the magnetocaloric effect displayed by magnetic materials whereby a reversible temperature change is induced when the material is exposed to a magnetic field. By using the magnetic materials in a regenerator as the heat storage medium and as the means of work input, one creates an Active Magnetic Regenerator (AMR). In this work, an experimental study of Active Magnetic Regenerators composed of single and multi-materials is carried out. AMRs made up of Gd, Gd.74Tb.26, and Gd.85Er.15 are studied in cycles rejecting heat between 270 K and 311 K. A variety of operating conditions were tested and regenerator performance with respect to heat load, utilization, and frequency was examined. AMR behavior was qualitatively interpreted and a path for performance improvement and future investigations laid.
Aero-elastic Energy Harvesting Device: Design and Analysis
(2015-10-02) Pirquet, Oliver Johann; Nadler, Ben; Crawford, Curran
An energy harvesting device driven by aeroelastic vibration with self-sustained pitching and heaving using an induction based power take off mechanism has been designed and tested for performance under various operating conditions. From the data collected the results show that the device achieved a maximum power output of 48.3 mW and a maximum efficiency of 2.26% at a dimensionless frequency of 0.143. For all airfoils tested the device was shown to be self-starting above 3 m/s. A qualitative description relating to the performance of the device considering dynamic stall and the flow conditions at optimal dimensionless frequency has been proposed and related to previous work. Performance for angles off the wind up to 22 degrees and was observed to have no reduction in power output due to the change in angle to the wind. The device has shown evidence of having a self-governing capability, tending to decrease its power output for heavy windpspeeds, a thorough examination of this capability is recommended for future work.
Affinity purification of NAD+-dependent formate dehydrogenase (EC 1.2.1.2) and activity of FDH in miniature enzyme bioreactors
(2010-04-07T19:56:14Z) Sanderson, Dan; Levin, David Bernard
Formate dehydrogenase from Mycobacterium vaccae (MycFDH) was cloned and expressed from various plasmid constructs that incorporate hexahistidine tags onto the N-and C-termini of the protein. The most successful FDH variant, dual-tagged FDH L-S expressed from pET28a+, was batch-purified using ammonium sulphate precipitation and IMAC to achieve 96% homogeneity. A significant proportion of the expressed protein was insoluble, and the expression protocol did not respond to solubility optimization efforts. Expression of an FDH-NusA fusion variant appeared to be vulnerable to proteolytic degradation in the cell. None of the strains expressing tagged-FDH variants produced clarified lysate activity levels that were consistently as high as those from the original pUC 119 vector. However, it is likely that the protein aggregation problems encountered are due to overloading of the protein production machinery or related causes, rather than to the presence of the tags themselves. A bioengineered FDH protein closely related to MycFDH was also investigated. FDH GAV was immobilized in polyacrylamide gel to create gel discs or hollow cylinder mini-reactors. The apparent Km(formate) for this enzyme was 15.6 ± 3.6 mM in the immobilized state, and 17.2 ± 1.9 mM in aqueous solution. The activity of FDH GAV was reversibly inhibited by the presence of acrylamide monomer but was not affected by ammonium persulfate or TEMED (alone or in combination) after incubation for one minute. The activity of the immobilized enzyme system was determined to be at least partially limited by diffusion. FDH GAV was also included in an in vitro analysis of the Methanol Linear Dissimilation Pathway (MLDP), a three enzyme system of NAD+ - dependent dehydrogenases that oxidize methanol sequentially to CO2. Horse liver alcohol dehydrogenase (EC 1.1.1.1) appeared to be the rate-limiting enzyme under the conditions used in these experiments, most likely due to its limited activity on methanol. The applicability of FDH and the MLDP to industry and bioelectronics is also considered.
Algorithm development for electrochemical impedance spectroscopy diagnostics in PEM fuel cells
(2008-04-10T06:05:02Z) Latham, Ruth Anne.; Harrington, David A.
Analysis and development of a three body heaving wave energy converter
(2009-05-01T20:04:40Z) Beatty, Scott, J.; Buckham, Bradley, Jason; Wild, Peter Martin
A relative motion based heaving point absorber wave energy converter is being co-developed by researchers at the University of Victoria and SyncWave Systems Inc. To that end---this thesis represents a multi-faceted contribution to the development effort. A small scale two-body prototype wave energy converter was developed and tested in a wave tank. Although experimental problems were encountered, the results compare reasonably well to the output of a two degree of freedom linear dynamics model in the frequency domain. A two-body wave energy converter design is parameterized as a basis for an optimization and sensitivity study undertaken to illustrate the potential benefits of frequency response tuning. Further, a mechanical system concept for frequency response tuning is presented. The two degree of freedom model is expanded to three degrees of freedom to account for the tuning system. An optimization procedure, utilizing a Sequential Quadratic Programming algorithm, is developed to establish control schedules to maximize power capture as a function of the control variables. A spectral approach is developed to estimate WEC power capture in irregular waves. Finally, as a case study, the modeling, optimization, and spectral methods are applied to predict performance for a large scale wave energy converter deployed offshore of a remote Alaskan island. Using archived sea-state data and community electrical load profiles, a wave/diesel hybrid integration with the remote Alaskan community power system is assessed to be technologically feasible.
Assessing the impacts of wind integration in the Western Provinces
(2012-12-06) Sopinka, Amy; Van Kooten, G. C.
Increasing carbon dioxide levels and the fear of irreversible climate change has prompted policy makers to implement renewable portfolio standards. These renewable portfolio standards are meant to encourage the adoption of renewable energy technologies thereby reducing carbon emissions associated with fossil fuel-fired electricity generation. The ability to efficiently adopt and utilize high levels of renewable energy technology, such as wind power, depends upon the composition of the extant generation withinthe grid. Western Canadian electric grids are poised to integrate high levels of wind and although Alberta has sufficient and, at times, an excess supply of electricity, it does not have the inherent generator flexibility required to mirror the variability of its wind generation. British Columbia, with its large reservoir storage capacities and rapid ramping hydroelectric generation could easily provide the firming services required by Alberta; however, the two grids are connected only by a small, constrained intertie. We use a simulation model to assess the economic impacts of high wind penetrations in the Alberta grid under various balancing protocols. We find that adding wind capacity to the system impacts grid reliability, increasing the frequency of system imbalances and unscheduled intertie flow. In order for British Columbia to be viable firming resource, it must have sufficient generation capability to meet and exceed the province’s electricity self-sufficiency requirements. We use a linear programming model to evaluate the province’s ability to meet domestic load under various water and trade conditions. We then examine the effects of drought and wind penetration on the interconnected Alberta – British Columbia system given differing interconnection sizes.
Case study of wave power integration into the Ucluelet area electrical grid
(2009-12-07T23:36:17Z) St. Germain, Louise Anne; Rowe, Andrew Michael; Wild, Peter Martin
Technologies exist that can capture and convert wave energy but there are few studies examining systemic integration of wave energy devices. This work examines the potential to use wave energy as a renewable energy resource on Vancouver Island, specifically in the Tofino/Ucluelet area. A model of a wave energy conversion (WEC) device was developed as a module within TRNSYS™ where it can be coupled to a load as well as to a storage medium. For this particular study, wave profiles generated from hourly average data for a location on the west coast of Vancouver Island are used as a resource input. An analysis of the potential to use wave energy is carried out with an emphasis on overall system efficiency and resulting device scaling. The results of the wave energy conversion with and without storage, as well as the general economics of these scenarios, are used to make recommendations regarding technical feasibility of wave power projects on Vancouver Island.
A Comparison of methods for sizing energy storage devices in renewable energy systems
(2013-01-15) Bailey, Thomas; Rowe, Andrew Michael; Wild, Peter Martin
Penetration of renewable energy generators into energy systems is increasing. The intermittency and variability of these generators makes supplying energy reliably and cost effectively difficult. As a result, storage technologies are proposed as a means to increase the penetration of renewable energy, to minimize the amount of curtailed renewable energy, and to limit the amount of back-up supply. Therefore, methods for determining an energy system’s storage requirements are being developed. This thesis investigates and details four existing methods, proposes and develops a fifth method, and compares the results of all five methods. The results show that methods which incorporate cost, namely the Dynamic Optimization and the Abbey method, consistently yield the most cost effective solutions. Under excellent renewable energy conditions the results show that the cost-independent methods of Korpaas, Barton, and the Modified Barton method produce solutions that are nearly as cost effective but have greater reliability of energy supply than the Dynamic Optimization and Abbey solutions. This thesis recommends a new path of research for the Modified Barton method: the incorporation of cost through the confidence level. This thesis also recommends the development of new sizing methods from various aspects of the methods presented.
Computational modeling and optimization of proton exchange membrane fuel cells
(2007-11-13T22:40:51Z) Secanell Gallart, Marc; Djilali, Ned; Suleman, Afzal
Improvements in performance, reliability and durability as well as reductions in production costs, remain critical prerequisites for the commercialization of proton exchange membrane fuel cells. In this thesis, a computational framework for fuel cell analysis and optimization is presented as an innovative alternative to the time consuming trial-and-error process currently used for fuel cell design. The framework is based on a two-dimensional through-the-channel isothermal, isobaric and single phase membrane electrode assembly (MEA) model. The model input parameters are the manufacturing parameters used to build the MEA: platinum loading, platinum to carbon ratio, electrolyte content and gas diffusion layer porosity. The governing equations of the fuel cell model are solved using Netwon's algorithm and an adaptive finite element method in order to achieve quadratic convergence and a mesh independent solution respectively. The analysis module is used to solve two optimization problems: i) maximize performance; and, ii) maximize performance while minimizing the production cost of the MEA. To solve these problems a gradient-based optimization algorithm is used in conjunction with analytical sensitivities. The presented computational framework is the first attempt in the literature to combine highly efficient analysis and optimization methods to perform optimization in order to tackle large-scale problems. The framework presented is capable of solving a complete MEA optimization problem with state-of-the-art electrode models in approximately 30 minutes. The optimization results show that it is possible to achieve Pt-specific power density for the optimized MEAs of 0.422 $g_{Pt}/kW$. This value is extremely close to the target of 0.4 $g_{Pt}/kW$ for large-scale implementation and demonstrate the potential of using numerical optimization for fuel cell design.
Coupled operation of a wind farm and pumped storage facility: techno-economic modelling and stochastic optimization.
(2011-12-22) Wild, Kristin; Crawford, Curran; Djilali, Nedjib
This thesis applies a stochastic programming approach to the techno-economic analysis of a wind farm coupled with a pumped storage facility. The production of an optimal day-ahead generating schedule is considered. Wind forecasts contain an element of random error, and several methods of addressing this uncertainty in the optimization process are compared. The methods include robust and reliability-based design optimization in addition to a combination of both approaches, and results indicate that reliability-based design optimization is best-suited to this particular problem. Based on a set of wind forecast error scenarios and historical data, a probability-weighted forecast wind generation scenario set is developed. Reliability constraints are imposed to meet a minimum of 80% of the generating schedule time intervals. This methodology is applied to a case study on Vancouver Island. Preliminary results show that when compared to the base case of a standalone wind farm on Vancouver Island, a wind farm coupled with pumped storage can prove to be economically competitive with pumped storage capital costs below $1.53 million/MW installed pumped storage capacity and a firm energy price of $130/MWh.
Dead Volume Effects in Passive Regeneration: Experimental and Numerical Characterization
(2015-09-17) Liu, Yifeng; Rowe, Andrew Michael
The regenerator is the key component in magnetic cycles for refrigeration and heat pumping. It works as temporal thermal energy storage and separates two thermal reservoirs. Regenerators are typically made up of porous structures which may create complex flow pathways for the heat transfer fluid through the regenerator. The periodically reversing flow allows the thermal energy exchange with the packing material in the regenerators. The performance of such thermal devices depends greatly on the geometry of the porous structure, material properties as well as operating conditions. This thesis is a study about the thermo-hydraulic properties of passive regenerators under oscillating flow conditions. The first part of the thesis presents a passive regenerator testing apparatus used to measure temperature distribution and pressure drop for various types of regenerators. Three kinds of loose spheres packed regenerator beds are characterized, and the regenerator effectiveness is evaluated. In the second part of the thesis, a numerical model is developed for the predictions of pressure drop and temperature field, and the theoretical findings are applied to experimentally obtained data to interpret regenerator performance. The dead volume is investigated quantitatively and considered to affect the regenerator performance adversely.
Design and Analysis of a Nested Halbach Permanent Magnet Magnetic Refrigerator
(2013-08-19) Tura, Armando; Rowe, Andrew Michael
A technology with the potential to create efficient and compact refrigeration devices is an active magnetic regenerative refrigerator (AMRR). AMRRs exploit the magnetocaloric effect displayed by magnetic materials whereby a reversible temperature change is induced when the material is exposed to a change in applied magnetic field. By using the magnetic materials in a regenerator as the heat storage medium and as the means of work input, one creates an active magnetic regenerator (AMR). Although several laboratory devices have been developed, no design has yet demonstrated the performance, reliability, and cost needed to compete with traditional vapor compression refrigerators. There are many reasons for this and questions remain as to the actual potential of the technology. The objective of the work described in this thesis is to quantify the actual and potential performance of a permanent magnet AMR system. A specific device configuration known as a dual-nested-Halbach system is studied in detail. A laboratory scale device is created and characterized over a wide range of operating parameters. A numerical model of the device is created and validated against experimental data. The resulting model is used to create a cost-minimization tool to analyze the conditions needed to achieve specified cost and efficiency targets. Experimental results include cooling power, temperature span, pumping power and work input. Although the magnetocaloric effect of gadolinium is small, temperature spans up to 30 K are obtained. Analysis of power input shows that the inherent magnetic work is a small fraction of the total work input confirming the assumption that potential cycle efficiencies can be large. Optimization of the device generates a number of areas for improvement and specific results depend upon targeted temperature spans and cooling powers. A competitive cost of cooling from a dual-nested-Halbach configuration is challenging and will depend on the ability to create regenerator matrices with near-ideal adiabatic temperature change scaling as a function of temperature.
Design Principles and Performance Metrics for Magnetic Refrigerators Operating Near Room Temperature
(2014-02-19) Arnold, Daniel Sean Robert; Rowe, Andrew Michael
In the past decade, active magnetic regenerative (AMR) refrigeration technology has progressed towards commercial application. The number of prototype systems and test apparatuses has steadily increased thanks to the worldwide research efforts. Due to the extensive variety of possible implementations of AMR, design methods are not well established. This thesis proposes a framework for approaching AMR device design. The University of Victoria now has three functional AMR Refrigerators. The newest system constructed in 2012 operates near-room-temperature and is intended primarily as a modular test apparatus with a broad range of control parameters and operating conditions. The design objectives, considerations and analysis are presented. Extensive data has been collected using the machines at the University of Victoria. Performance metrics are used to compare the devices. A semi-analytical relationship is developed that can be used as an effective modelling tool during the design process.
A Detailed Analysis of Guard-Heated Wall Shear Stress Sensors for Turbulent Flows
(2013-07-30) Ale Etrati Khosroshahi, Seyed Ali; Bhiladvala, Rustom
This thesis presents a detailed, two-dimensional analysis of the performance of multi-element guard-heated hot-film wall shear stress microsensors for turbulent flows. Previous studies of conventional, single-element sensors show that a significant portion of heat generated in the hot-film travels through the substrate before reaching the fluid, causing spectral and phase errors in the wall shear stress signal and drastically reducing the spatial resolution of the sensor. Earlier attempts to reduce these errors have focused on reducing the effective thermal conductivity of the substrate. New guard-heated microsensor designs proposed to overcome the severe deficiencies of the conventional design are investigated in this thesis. Guard-heaters remove the errors associated with substrate heat conduction, by forcing zero temperature gradient at the edges and bottom face of the hot-film, and hence, block the indirect heat transfer to the flow. Air and water flow over the sensors are studied numerically to investigate design, performance and signal strength of the guard-heated sensors. Our results show, particularly for measurements in low-conductivity fluids such as air, that edge guard-heating needs to be supplemented by a sub-surface guard-heater, to make substrate conduction errors negligible. With this two-plane guard-heating, a strong non-linearity in the standard single-element designs can be corrected, and spectral and phase errors arising from substrate conduction can be eliminated.
Determining the quality and quantity of heat produced by proton exchange membrane fuel cells with application to air-cooled stacks for combined heat and power
(2010-07-19T17:43:38Z) Schmeister, Thomas; Wild, Peter Martin; Djilali, Nedjib
This thesis presents experimental and simulated data gathered specifically to assess air-cooled proton exchange membrane (PEM) fuel cells as a heat and electrical power source for residential combined heat and power (CHP). The experiments and simulations focused on the air-cooled Ballard Nexa fuel cell. The experimental characterization provided data to assess the CHP potential of the Nexa and validate the model used for the simulations. The model was designed to be applicable to any air-cooled PEM fuel cell. Based on hourly load data, four Nexa fuel cells would be required to meet the peak electrical load of a typical coastal British Columbia residence. For a year of operation with the four fuel cells meeting 100% of the electrical load, simultaneous heat generation would meet approximately 96% of the space heating requirements and overall fuel cell efficiency would be 70%. However, the temperature of the coolant expelled from the Nexa varies with load and is typically too low to provide for occupant comfort based on typical ventilation system requirements. For a year of operation, the coolant mean temperature rise is only 8.3 +/- 3.4 K above ambient temperature. To improve performance as a CHP heat engine, the Nexa and other air-cooled PEM fuel cells need to expel coolant at temperatures above 325 K. To determine if PEM fuel cells are capable of achieving this coolant temperature, a model was developed that simulates cooling system heat transfer. The model is specifically designed to determine coolant and stack temperature based on cooling system and stack design (i.e. geometry). Simulations using the model suggest that coolant mass flow through the Nexa can be reduced so that the desired coolant temperatures can be achieved without the Nexa stack exceeding 345 K during normal operation. Several observations are made from the presented research: 1) PEM fuel cell coolant air can be maintained at 325 K for residential space heating while maintaining the stack at a temperature below the 353 K Nafion design limits chosen for the simulations; 2) The pressure drop through PEM cooling systems needs to be considered for all stack and cooling system design geometries because blower power to overcome the pressure drop can become very large for designs specifically chosen to minimize stack temperature or for stacks with long cooling channels; 3) For the air-cooled Nexa fuel cell stack, heat transfer occurring within the fuel cell cooling channels is better approximated using a constant heat flux mean Nusselt correlation than a constant channel temperature Nusselt correlation. This is particularly true at higher output currents where stack temperature differences can exceed 8 K.
Development and application of in-fibre Bragg grating based biomedical pressure sensors
(2008-07-15T23:30:01Z) Dennison, Christopher Raymond Stuart; Wild, Peter
Two in-fibre Bragg grating based optical pressure sensors were developed to address the limitations of conventional solid-state electronic biomedical sensors. The first sensor, developed for intervertebral disc pressure measurements varying over several MPa, had a major diameter of only 400 μm and sensing area of 0.03 mm2. This sensor was validated in spine biomechanics studies and was shown to: give accurate and repeatable measurements, be compatible with the small (e.g. cervical) discs, and alter disc mechanics less than the current alternative sensor. This sensor is also the smallest, most mechanically compliant disc pressure sensor presented to date. The second FBG sensor was developed to measure sub-kPa pressure variations and had a major diameter and sensing area of only 200 μm and 0.02 mm2, respectively. This sensor achieves sub-kPa repeatability through a novel design that is approximately 100 times smaller than other FBG sensors presented with sub-kPa pressure repeatability.
Development and validation of an active magnetic regenerator refrigeration cycle simulation
(2006-08-10T17:35:10Z) Dikeos, John; Rowe, Andrew
An alternative cycle proposed for refrigeration and gas liquefaction is active magnetic regenerator (AMR) refrigeration. This technology relies on solid materials exhibiting the magnetocaloric effect, a nearly reversible temperature change induced by a magnetic field change. AMR refrigeration devices have the potential to be more efficient than those using conventional refrigeration techniques but, for this to be realized, optimum materials, regenerator design, and cycle parameters must be determined. This work focuses on the development and validation of a transient one-dimensional finite element model of an AMR test apparatus. The results of the model are validated by comparison to room temperature experiments for varying hot heat sink temperature, system pressure, and applied heat load. To demonstrate its applicability, the model is then used to predict the performance of AMRs in situations that are either time-consuming to test experimentally or not physically possible with the current test apparatus.
Development of a rig and testing procedures for the experimental investigation of horizontal axis kinetic turbines
(2012-04-30) Lartiga, Catalina; Crawford, Curran
The research detailed in this thesis was focused on developing an experimental testing system to characterize the non-dimensional performance coeﬃcients of horizontal axis kinetic turbines, including both wind turbines and tidal turbines. The testing rig was designed for use in a water tunnel with Particle Image Velocimetry (PIV) wake survey equipment to quantify the wake structures. Precision rotor torque measurement and speed control was included, along with the ability to yaw the rotor. The scale of the rotors were purposefully small, to enable rapid-prototyping techniques to be used to produce many diﬀerent test rotors at low cost to furnish a large experimental dataset. The ﬁrst part of this work introduces the mechanical design of the testing rig developed for measuring the output power of the scaled rotor models with consideration for the requirements imposed by the PIV wake measurements. The task was to design a rig to ﬁt into an existing water tunnel facility with a cross sectional area of 45 by 45 cm, with a rotor support structure to minimize the ﬂow disturbance while allowing for yawed inﬂow conditions. A rig with a nominal rotor diameter of 15 cm was designed and built. The size of the rotor was determined by studying the ﬂuid similarities between wind and tidal turbines, and choosing the tip speed ratio as a scaling parameter. In order to maximize the local blade Reynolds number, and to obtain diﬀerent tip speed ratios, the rig allows a rotational speed in the range of 500 to 1500 RPM with accurate rotor angular position measurements. Rotor torque measurements enable rotor mechanical power to be calculated from simulation results. Additionally, it is included in this section a description of the instrumentation for measurement and the data acquisition system. It was known from the outset that measurements obtained in the experiments would be subject to error due to blockage eﬀects inherent to bounded testing facilities. Thus, the second part of this work was dedicated to developing a novel Computational Fluid Dynamics (CFD) methodology to post-process the experimental data acquired. This approach utilizes the velocity ﬁeld data at the rotor plane obtained from the water tunnel PIV test data, and CFD simulations based on the actuator disk concept to account for blockage without the requirement for thrust data which would have been unreliable at the low forces encountered in the tests. Finally, the third part of this work describes the practical aspects of the laboratory project, including a description of the operational conditions for turbine testing. A set of preliminary measurements and results are presented, followed by conclusions and recommendations for future work. Unfortunately, the water tunnel PIV system was broken and thus unavailable for more than a year, so only mechanical measurements were possible with the rig during the course of this thesis work.
Effect of chordwise flexibility and depth of submergence on an oscillating plate underwater propulsion system
(2010-11-15T17:54:13Z) Barannyk, Oleksandr; Buckham, Bradley Jason; Oshkai, Peter
The first part of this work was dedicated to the experimental study of basic principles of oscillating plate propulsors undergoing a combination of heave translation and pitch rotation. The oscillation kinematics are inspired by swimming mechanisms employed by fish and some other marine animals. The primary attention was the propulsive characteristics of such oscillating plates, which was studied by means of direct force measurements in the thrust-producing regime. Experiments were performed at constant Reynolds number and heave amplitude. By varying the Strouhal number, experimental depth and chordwise exibility of the plate it was possible to investigate corresponding changes in thrust and hydromechanical efficiency. After numerous measurements it was possible to establish an optimal set of parameters, including the system's driving frequency, the ratio of rigid to flexible segment length of the plate and the range of Strouhal number, that led to a peak efficiency near 80%. The experiments for different values of chordwise flexibility showed that greater flexibility increases the propulsive effciency and thrust compared with similar motion of the purely rigid foil. By submerging the plate at different depths, it was observed that the proximity of the propulsor to the channel floor led to overall increase in the thrust coefficient. However the increase in thrust coefficient was pronounced in the range from middepth to the floor of the water tunnel. The special case when the upper plate's edge is tangential to the undisturbed free surface is discussed separately. The second part of this work introduces a semianalytic approach for calculating the influence of piezoelectric (PZT) actuators on the free vibration characteristics of an Euler-Bernoulli clamped free beam. The beam represents a simplifled version of the fish tail whose stiffness is proposed to be controlled by placing a pair of PZT actuators in strategic regions along the caudal area of the tail. This approach, according to earlier studies, improves efficiency if tail natural frequency matches tailbeat frequency. The approach used an existing form of a transfer matrix technique developed for the analysis of non-proportionally damped slender beams. The PZT dynamics were incorporated into this recursive procedure through a modification that accounted for the tendency of the PZT patches to couple the dynamics of the node points of the segmented Euler-Bernoulli beam. To ensure stability of the system, an angular ve- locity feedback law, originally motivated by vibration suppression applications, was chosen for the PZT actuators. The sensitivities of the tail modes of vibration to the location of the PZT elements and the control gain were determined. Mode shapes for the revised modes were determined and it was shown that the first, second and the third modes maintained similar norms as tail shapes observed in anguilliform, sub- carangiform, and thunniform regimes of swimming. Using a semianalytic approach, it was shown that PZT location heavily in uences the frequency distribution of the modes of vibration. The control gain, when chosen within the limit of saturation voltage, is shown to be an effective control lever for vibration suppression and at rising the tail stiffness during rapid acceleration when the fish accelerates. However, the single PZT patch does not provide significant frequency adjustments such that different swimming modes could be employed efficiently with a single mechanical tail system primary actuator. To pursue such versatility for the sh tail, the tail structure must be very flexible to accommodate the significant frequency increase caused by the addition of the PZT material. Also, the use of additional PZT patches and negative control gains must be considered in order to use the PZT's to drop the higher modes (second and third) down into the frequency range of the primary actuation system, presuming the tail and primary actuator are designed for a thunniform regime of swimming.
The effects of CO2 abatement policies on power system expansion
(2011-08-31) Fox, Conrad; Rowe, Andrew Michael; Wild, Peter Martin
Human development owes a great debt to cheap plentiful energy. Historically, abundant and energy dense materials such as coal, oil and more recently natural gas, have played an important role in powering our economies. To this day, any study analysing the short-term costs and benefits of energy system expansion, will continue to favour fossil fuels. At the same time, there is increasing concern about the levels of human made greenhouse gasses such as CO2 (the major by product of burning fossil fuels) and their forecasted effects on the global climate. This thesis investigates the consequences of using political intervention to internalize the cost of future negative effects of anthropogenic CO2 emissions. More specifically, this thesis investigates the effects of regulatory and market based instruments for curbing CO2 emissions from electric power systems in terms of both cost and efficacy. A model is developed to approximate the yearly changes in generation capacity and electricity supply mixture of a power system subject to the constraints of carbon abatement policies. The model proposes a novel approach for incorporating investment in non-dispatchable, intermittent wind generation capacity as a decision variable in the planning process. The model also investigates the effects of the stochastic nature of input parameters through the use of Monte Carlo simulation. To explore many features of this model, the Ontario power system is chosen for a case study because of its diverse portfolio of both generation technologies and political objectives. Five policies are simulated and compared with a ‘business-as-usual’ base case in which no carbon abatement policy is imposed. No single policy can meet all of the political objectives being investigated; however, some policies are clear winners in terms of specific objectives. Due to the broad scope of this work, the study finds many conclusions, such as: - Aggressive policies do not always promote heavy investment in intermittent wind generation sources. - On a $/tCO2 avoided basis, aggressive policies are expensive. Modest policies (very small penalties for CO2 emissions) are very sensitive to the uncertainties in future fuel prices and load profiles. - Investment in nuclear capacity is very responsive to the severity of CO2 penalty. The study also concludes that the most aggressive policies produce the greatest overall reductions in CO2 emissions.

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