High temperature waste heat recovery has been gaining attention in recent years as it forms one of the largest sources of available energy. A rapid development of thermoelectric (TE) materials that can directly convert heat into electricity through the Seebeck effect, opens promising pathway for harvesting the thermal energy from the surroundings. In order to harvest the high-quality waste heat at elevated temperature, excellent thermal and mechanical stability of the TE materials is critical for a sustainable energy harvesting. In this respect, half-Heusler (hH) alloys are one of the promising high-temperature TE materials due to their high dimensionless thermoelectric figure of merit (zT) along with excellent mechanical and thermal stability. This dissertation demonstrates novel hH compositions and microstructures for the waste heat recovery systems. Focus in the thesis is on development of high performance hH TE materials with excellent in-air thermal stability at high temperatures (>700K). This will allow manufacturing of high efficiency and durable high temperature thermoelectric generators (TEGs). In chapter 3 and 4, a comprehensive optimization of n-type MNiSn and p-type MCoSb (M = Hf, Zr, and Ti) compounds is investigated through systematic control of processing parameters during melting and sintering. The synthesis conditions were controlled to achieve the phase purity, desired microstructure and the enhanced charge-carrier transport. Optimized n-type and p-type compositions are found to exhibit zTmax ~ 1 at 773 K. Chapter 5 describes breakthrough in decoupling of TE parameters in n-type half-Heusler (hH) alloys through multi-scale nanocomposite architecture with tungsten nanoinclusions. The tungsten nanoparticles not only assist electron injection, thereby improving electrical conductivity, but also enhance the Seebeck coefficient through energy filtering effect. The microstructure comprises of disordered phases with feature sizes at multiple length scales, which assists in effective scattering of heat-carrying phonons over diverse mean-free-path ranges. Cumulatively, these effects are shown to result in outstanding thermoelectric performance of zTmax ~ 1.4 at 773 K and zTavg ~ 0.93 between 300 and 973 K. In order to deploy TE materials into a thermal energy conversion device, it is essential to understand the transformation behavior under thermal cycling at high temperatures. In-air thermal stability of the hH compositions is demonstrated in chapter 6. All the optimized compositions are found to be stable below 673 K in-air condition. The n-type MNiSn and p-type NbFeSb compounds were found to show good thermal stability even at higher temperatures (>773K), whereas MCoSb compounds did not exhibit similar level of stability. Building upon the improved material performance and thermal stability, uni-coupled TE generators are demonstrated that exhibit high power density of 13.81 W⸱cm-2 and conversion efficiency of 10.9 % under a temperature difference of 674 K. The uni-couple TEG device shows stable performance for more than 150 hours at 873 K in air. These results are very promising for deployment of TE materials in waste heat recovery systems. / Doctor of Philosophy / Based on the 2012 international energy agency (IEA) report, global waste heat energy is estimated to be in the range of 246 Exajoule (1 EJ = 10¹⁸ J). Tapping even small fraction of this wasted energy through thermal energy harvesting techniques will allow us to generate significant magnitude of green energy. Thermoelectrics (TEs) are one of the most promising thermal energy conversion materials as they offer cost-effective and environmentally friendly option with solid-state silent operation and scalability. Among many different options for high temperature TE materials, half-Heusler system is one of the leading candidates as it has the potential to provide high performance and thermal stability at temperatures as high as 873 K. The progress in developing practical half-Heusler materials has been limited for last two decades. Despite many publications, the maximum figure of merit (zT) of n-type half-Heusler materials has been stagnant (zT ~ 1.0). Further, there has been a lack of focus towards module development that can operate under realistic conditions. This dissertation provides comprehensive studies on novel thermoelectric compositions and nanocomposites that are suitable for manufacturing of high temperature modules. Microstructural architectures proposed here provide the ability to tailor electronic transport and phonon scattering beyond the commonly demonstrated regimes. Optimized materials were successfully implemented in efficient and stable thermoelectric generator exhibiting power density on the order of 13.81 W⸱cm⁻² , which is 1400 % higher than that of the fuel cell (~1 W⸱cm⁻² ).

An r-f ion source has been constructed for the V.P.I. electrostatic generator. The ion source has been in operation for approximately one thousand hours with an average beam current of one micro-ampere. This beam has been sufficient to test and calibrate the accelerator. Experiments which require beam currents in the order of 100 micro-ampere can now be conducted with the ion source operating at its designed capacity. / Master of Science

It is well known that the seats in a parked vehicle become very hot and uncomfortable on warm days. A new self-powered thermoelectric car seat cooler is presented to solve this problem. This study details the design and optimization of such a device. The design relates to the high level layout of the major components and their relation to each other in typical operation. Optimization is achieved through the use of the ideal thermoelectric equations to determine the best compromise between power generation and cooling performance. This design is novel in that the same thermoelectric device is utilized for both power generation and for cooling. The first step is to construct a conceptual layout of the self-powered seat cooler. Using the ideal thermoelectric equations, an analytical model of the system is developed. The model is validated against experimental data and shows good correlation. Through a non-dimensional approach, the geometric sizing of the various components is optimized. With the optimal design found, the performance is evaluated using both the ideal equations and though use of the simulation software ANSYS. The final design consists of a flat absorber plate embedded into the car seat with a thermoelectric attached to the back. A finned heat sink is used to cool the thermoelectric. The device is shown to generate enough power to provide a reasonable temperature drop in the seat. / Master of Science / It is well known that the seats in a parked vehicle become very hot and uncomfortable on warm days. A new self-powered thermoelectric car seat cooler is presented to solve this problem. The term thermoelectric refers to devices which convert thermal energy directly to electrical energy and can also convert electrical energy to thermal energy. This study details the design and optimization of such a device. Design relates to the layout and relationship of the major components. Optimization refers to the best use the given components to maximize power output and seat cooling. The final design consists of a flat absorber plate embedded into the car seat with a thermoelectric attached to the back. A finned heat sink is used to cool the thermoelectric. The device is shown to generate enough power to provide a reasonable temperature drop in the seat.

In this thesis we analyze lumpability of infinite dimensional dynamical systems. Lumping is a method to project a dynamics by a linear reduction operator onto a smaller state space on which a self-contained dynamical description exists. We consider a well-posed dynamical system defined on a Banach space X and generated by an operator F, together with a linear and bounded map M : X → Y, where Y is another Banach space. The operator M is surjective but not an isomorphism and it represents a reduction of the state space. We investigate whether the variable y = M x also satisfies a well-posed and self-contained dynamics on Y . We work in the context of strongly continuous semigroup theory. We first discuss lumpability of linear systems in Banach spaces. We give conditions for a reduced operator to exist on Y and to describe the evolution of the new variable y . We also study lumpability of nonlinear evolution equations, focusing on dissipative operators, for which some interesting results exist, concerning the existence and uniqueness of solutions, both in the classical sense of smooth solutions and in the weaker sense of strong solutions. We also investigate the regularity properties inherited by the reduced operator from the original operator F . Finally, we describe a particular kind of lumping in the context of C*-algebras. This lumping represents a different interpretation of a restriction operator. We apply this lumping to Feller semigroups, which are important because they can be associated in a unique way to Markov processes. We show that the fundamental properties of Feller semigroups are preserved by this lumping. Using these ideas, we give a short proof of the classical Tietze extension theorem based on C*-algebras and Gelfand theory.

Within the existing available mix of numerical and analytical thermal analysis options, lumped parameter thermal modelling is selected as the operational backbone to develop an improved novel synchronous generator thermal modelling package. The objective is for the creation of a user friendly quick feedback tool, which can serve as a means to make quick machine design thermal calculations and answer customer queries quickly and reliably. Furthermore, thermally improved generator designs will allow for inevitable operational losses to be channelled away from the machine more efficiently. As a result, machine component temperatures will be reduced, allowing lower generator thermal ratings. The end result will be smaller, longer lasting, more efficient generators, with the ability to be adapted with greater ease to particular applications. With the contribution of selected numerical analysis techniques, mainly finite element analysis for the distribution of iron losses, the MySolver thermal modelling package is developed and presented in this thesis. It is this combination of numerical and analytical tools that improves synchronous generator thermal modelling accuracy, but ultimately it is the lumped parameter nature of the thermal models developed that makes MySolver succeed as a reliable quick feedback electrical machine thermal design tool, validated using experimental results for a wide range of operating conditions. The initial part of the thesis analyses the electrical machine thermal modelling techniques available today, indicating advantages and disadvantages associated with each one, and providing a rationale for the selection of lumped parameter modelling to be used by MySolver. The development of the synchronous generator lumped parameter thermal models is detailed, with examples on its construction presented. Subsequently, finite element analysis is utilised to predict the distribution of machine iron losses across the rotor and stator laminations, with the findings applied to MySolver. Furthermore, a study is performed into the lumped parameter discretisation level needed to effectively represent machine windings. MySolver is experimentally verified using experimental data from a fully instrumented synchronous generator and this data is also used to obtain further insight into the temperature distribution within the generator. In the final part results are evaluated and the use of MySolver for modelling and optimising electrical machines is discussed. Finally, appropriate conclusions on the work presented are drawn.

Detta examensarbete har utförts vid Saab Dynamics AB(SBD) i Karlskoga med syftet att studera gamla konstruktioner av set-back-generatorer. En set-back-generator (SBG) ska ge momentan energi vid utskjutning av en projektil genom att en magnet rör sig genom en spole. SBG har funnits länge men har bedömts ge för lite energi för att kunna driva elektronik. Men nya typer av magneter har potential att öka energiutbytet väsentligt. SBD har ett antal äldre SBG:er och arbetet har varit att utifrån dessa undersöka om det går att utvinna mer energi genom ett utbyte av magnet. Andra parametrar som är viktiga för en SBG:s funktion har också studerats och testats i olika konfigurationer i hopp om ytterligare förbättringar. Förväntade resultat har sedan analyserats och jämförts med mätresultat. Med detta som grund har rekommendationer vid en ny konstruktion av SBG levererats. / This bachelor thesis has been performed at Saab Dynamics AB (SBD) in Karlskoga, with the purpose to examine old designs of set-back-generators. A set-back-generator (SBG) shall provide instantaneous energy during firing of a projectile by a magnet moving through a coil. Previous designs of SBG:s is not providing enough energy to power electronics. New types of magnets have the potential to increase the energy yield significantly. SBD has a number of older SBG's and the work is based on these to examine the possibility to extract more energy by exchanging magnet. Other important parameters for an SBG's function has also been studied and tested in different configurations in the hope of further improvements. Expected results has then been analyzed and compared with the measurement results. On this basis suggestions and recommendations on a new SBG design has been delivered.

This thesis details the design and development of a solid-state, high power modulator for driving plasma ion implantation systems. A plurality of modulators can be stacked in a Marx geometry to allow complete voltage (implantation energy) scalability. Unlike a classic Marx modulator, the design employs actively controlled charging and discharging paths. This allows maximum modulation flexibility and efficiency. A hybrid Marx bank - pulse transformer configuration was commissioned in a 20keV 12A plasma ion implantation system for the purpose of photonics research. <p>The design portion of this work is accompanied by an investigation, extension and discretization of the Lieberman analytical model of plasma ion implantation dynamics. The model predicts final implantation concentrations as well as system operational limits in specific plasma conditions. A new extension to the model accounts for subtle time-of-flight effects on accelerating ions. Agreement between modeled and measured ion currents is good.<p>Finally, a collection of material processing experiments conducted with the plasma ion implantation system since its inauguration in February 2006 is briefly presented. In it, a new silicon-based light emitting diode is introduced.

The accuracy, ease of use, and execution time of the finite element method based software Maxwell coupled to the system simulation software Simplorer was evaluated for simulation of hydropower generator - power grid interaction. A generator test rig were modelled in Maxwell and coupled to Simplorer with a strong circuit coupling as a single machine infinite bus system. The accuracy of the model was measured by comparing the simulated output power oscillation frequency and damping characteristics to the measured ones after a torque step. The result shows that the difference in output power oscillation frequency between the model and the generator test rig was small, and that the difference in damping characteristics was significant. The usability of the software package was found to be fair, as were the execution times.

This thesis details the design and development of a solid-state, high power modulator for driving plasma ion implantation systems. A plurality of modulators can be stacked in a Marx geometry to allow complete voltage (implantation energy) scalability. Unlike a classic Marx modulator, the design employs actively controlled charging and discharging paths. This allows maximum modulation flexibility and efficiency. A hybrid Marx bank - pulse transformer configuration was commissioned in a 20keV 12A plasma ion implantation system for the purpose of photonics research. <p>The design portion of this work is accompanied by an investigation, extension and discretization of the Lieberman analytical model of plasma ion implantation dynamics. The model predicts final implantation concentrations as well as system operational limits in specific plasma conditions. A new extension to the model accounts for subtle time-of-flight effects on accelerating ions. Agreement between modeled and measured ion currents is good.<p>Finally, a collection of material processing experiments conducted with the plasma ion implantation system since its inauguration in February 2006 is briefly presented. In it, a new silicon-based light emitting diode is introduced.

I dagsläget när intresset för miljövänlig energi ökar, ses den småskaliga vattenkraften som ett sätt att minska Sveriges import av energi. I Sverige finns det tusentals nedlagda kvarnar och små vattenkraftstationer som med små medel skulle kunna börja leverera energi. I Björkefall i Olofströms kommun finns en privatägd och övergiven kvarn. Detta arbete undersöker möjligheterna till en småskalig vattenkraftstation i denna åt Olofströms Kraft AB. Småskalig, vattenkraft, elkraft, generator, turbin / At present when the interest of environmentally friendly energy increases, small scaled water power is seen as an option to decrease Sweden's import of energy. In Sweden there are thousands of abandoned mills and small water power stations, these could with small means be restored and start to deliver energy again. In Björkefall, Olofströms municipality, there is a individually owned and abandoned mill. This rapport explores the possibilities for a small scale water power station there, for Olofströms Kraft AB. Small scaled, water power, power electronics, generator, turbine