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Xu, Jiangang Chemical Sciences & Engineering Faculty of Engineering UNSW. "Coal related bed material agglomeration in pressurized fluidized bed combustion." Awarded by:University of New South Wales. School of Chemical Sciences and Engineering, 2006. http://handle.unsw.edu.au/1959.4/25131.
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The thermodynamic behaviours in a PFBC combustor were simulated for the ash from all of the six coals with sand and limestone as bed material. Ash components determined the ash thermodynamic behaviour at high temperature, and each component had different effects. For assessment of the potential for bed material agglomeration, the temperature at which 15% of the ash would become liquid (T15) was calculated with the coal ash, the cyclone ash and the cyclone ash mixed with varying amounts of limestone. Both the bed ash and fly ash, collected from an industrial PFBC plant, consisted of limestone/lime particles with different extent of sulphation, and coal ash particles. The calcium aluminosilicate material formed on the coal ash particles but not on the limestone particles. The aluminosilicate materials appeared to be formed from fine ash and lime particles at some local hot zones in the boiler. The melted materials may glue ash and bed material particle into large particles leading to bed agglomeration and defluidization. Four mechanisms were proposed for the formation of bed material agglomeration in PFBC, which may occur under different conditions. One mechanism explains the bed material agglomeration with the high localized high temperature zone due to the improper design or operation, while the bed agglomeration through the other three mechanisms results from the unsuitable coals burnt in the PFBC combustor. The maximum char temperature and the minimum T15 were used simultaneously to predict the tendency towards bed material agglomeration in PFBC burning different coals. Both char properties and ash properties should be considered during coal selection process for PFBC, to ameliorate the potential problem of bed agglomeration.
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Kerttu, Mikael. "Low power synthesis of BDD mapped circuits." Licentiate thesis, Luleå tekniska universitet, EISLAB, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-17780.
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Power consumption is an important design constraint for circuits used in portable devices. In this thesis an analytic approach to minimize the power dissipation of Binary Decision Diagram (BDD) mapped digital circuits is presented. Our synthesis approach combines logic minimization, low power optimization and mapping to a Pass Transistor Logic (PTL) multiplexor circuit. The low power optimization procedure utilizes statistical properties for the input signals to reduce the estimated power dissipation. For BDD mapped circuits, the variable order of the underlying BDD heavily affects both the number of nodes (size) and the switching activity for each node. In turn, static power dissipation increases with circuit size, while dynamic power dissipation increases with switching activity and capacitive load. The capacitive load for a mapped node is modeled as the number of incoming edges. The cost model based on a PTL mapping is applied in a heuristic optimization procedure iteratively improving the overall cost by local variable exchanges. Three novel BDD based approximative methods for switching activity estimation are introduced. The first method assumes no temporal signal correlation. The second method assumes temporal correlation on the input signals only. Both of these simplifications allows the low power optimization to be carried out exclusively by local BDD operations. The third method accounts also for temporal correlation of internal signals in the circuit. The latter approach is refined at the cost of computation complexity, whereas the optimization is no longer local. The mapped circuits have in simulation (using a commercially available process model) shown reduced power dissipation characteristic. Furthermore a technique for extracting signal properties from synchronous Finite State Machine (FSM) implementations is described. All computations are performed using decision diagram techniques. As an application of this method, the extracted information is utilized in the presented low power synthesis procedure. Experimental results on MCNC (combinational) and ISCAS89 (sequential) benchmarks show significant reductions of the estimated power dissipation. The ISCAS89 results how an average reduction of 40 percent and up-to 90 percent on individual benchmarks.Godkänd; 2001; 20070313 (ysko)
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Babvey, Sharareh. "Delay and Power Reduction in Deep Submicron Buses." Digital Archive @ GSU, 2005. http://digitalarchive.gsu.edu/cs_theses/5.
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As technology scales down, coupling between nodes of the circuits increases and becomes an important factor in interconnection analysis. In many cases like the deep submicron technology (DSM), the coupling between lines (inter-wire capacitance) is strong and the energy consumption caused by parasitic capacitance is non-negligible. In this work, we employ the differential low-weight encoding [1] to reduce energy and delay (transmission cost) on DSM buses. We propose an enumeration method that reduces the encoder table-size from O(2n) words to O(n) words, for an n-bit DSM bus, and so reduces the memory complexity significantly and facilitates energy and delay reduction due to addressing and fetching data from large lookup tables. We modify the energy and delay equations for DSM buses and develop new representations in terms of number of the same and opposite direction transitions on the bus and use them in our interconnect analysis. We also use these equations to develop formulas for computing the mean transmission cost per bit on DSM buses for both differential low-weight encoding and uncoded schemes. Using the interconnect analysis, we compute a help codeword (from the set of unselected codewords) on the fly and assign to each selected codeword. This low complexity step consists of simple operations and enables us to gain more cost reduction without increasing the table size or number of the bus lines. The simulation results for 16-bit, 32-bit and 64-bit buses at maximum rate (only one extra line added) show that the proposed encoding scheme achieves more than 10% cost reduction, and performs more than 2.5% better than to the original differential low-weight scheme, in the worst case.
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Baree, M. S. "Added power required by ships in bad weather." Thesis, University of Newcastle Upon Tyne, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.353793.
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Allen, Kenneth Guy. "Rock bed thermal storage for concentrating solar power plants." Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/86521.
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Thesis (PhD)--Stellenbosch University, 2014.ENGLISH ABSTRACT: Concentrating solar power plants are a promising means of generating electricity. However, they are dependent on the sun as a source of energy, and require thermal storage to supply power on demand. At present thermal storage – usually molten salt – although functional, is expensive, and a cheaper solution is desired. It is proposed that sensible heat storage in a packed bed of rock, with air as heat transfer medium, is suitable at temperatures of 500 – 600 °C. To determine if this concept is technically feasible and economically competitive with existing storage, rock properties, packed bed pressure drop and thermal characteristics must be understood. This work addresses these topics. No previously published data is available on thermal cycling resistance of South African rock, and there is limited data from other countries in the proposed temperature range for long-term thermal cycling, so samples were thermally cycled. There is rock which is suitable for thermal storage applications at temperatures of 500 – 600 °C. New maps of South Africa showing where potentially suitable rock is available were produced. Dolerite, found extensively in the Karoo, is particularly suitable. Friction factors were measured for beds of different particles to determine the importance of roughness, shape, and packing arrangement. Five sets of rock were also tested, giving a combined dataset broader than published in any previous study. Limitations of existing correlations are shown. The friction factor is highly dependent on particle shape and, in the case of asymmetric particles, packing method. The friction factor varied by up to 70 % for crushed rock depending on the direction in which it was poured into the test section, probably caused by the orientation of the asymmetric rock relative to the air flow direction. This has not been reported before for rock beds. New isothermal correlations using the volume equivalent particle diameter are given: they are within 15 % of the measurements. This work will allow a techno-economic evaluation of crushed rock beds using more accurate predictions of pumping power than could previously be made. Thermal tests below 80 °C show that bed heat transfer is insensitive to particle shape or type. A heat transfer correlation for air in terms of the volume equivalent diameter was formulated and combined with the E-NTU method. The predicted bed outlet temperatures are within 5 °C of the measurements for tests at 530 °C, showing that the influence of thermal conduction and radiation can be reasonably negligible for a single charge/discharge cycle at mass fluxes around 0.2 kg/m2s. A novel method for finding the optimum particle size and bed length is given: The Biot number is fixed, and the net income (income less bed cost) from a steam cycle supplied by heat from the bed is calculated. A simplified calculation using the method shows that the optimum particle size is approximately 20 mm for bed lengths of 6 – 7 m. Depending on the containment design and cost, the capital cost could be an order of magnitude lower than a nitrate salt system.
AFRIKAANSE OPSOMMING: Gekonsentreerde son-energie kragstasies is n belowende manier om elektrisiteit op te wek, maar hulle is afhanklik van die son as n bron van energie. Om drywing op aanvraag te voorsien moet hulle energie stoor. Tans is termiese stoor – gewoonlik gesmelte sout – hoewel funksioneel, duur, en n goedkoper oplossing word gesoek. Daar word voorgestel dat stoor van voelbare warmte-energie in n gepakte rotsbed met lug as warmteoordrag medium geskik is by temperature van 500 – 600 °C. Om te bepaal of dié konsep tegnies gangbaar en ekonomies mededingend met bestaande stoorstelsels is, moet rotseienskappe, gepakte bed drukval en hitteoordrag verstaan word. Hierdie werk spreek hierdie aspekte aan. Geen voorheen gepubliseerde data is beskikbaar oor die termiese siklus weerstand van Suid-Afrikaanse rots nie, en daar is beperkte data van ander lande in die voorgestelde temperatuurbereik, dus is monsters onderwerp aan termiese siklusse. Daar bestaan rots wat geskik is vir termiese stoor toepassings by temperature van 500 – 600 °C. Nuwe kaarte van Suid-Afrika is opgestel om te wys waar potensieel geskikte rots beskikbaar is. Doleriet, wat wyd in die Karoo voor kom, blyk om veral geskik te wees. Wrywingsfaktore is gemeet vir beddens van verskillende partikels om die belangrikheid van grofheid, vorm en pak-rangskikking te bepaal. Vyf rotsstelle is ook getoets, wat n saamgestelde datastel gee wyer as in enige gepubliseerde studie. Beperkings van bestaande korrelasies word aangetoon. Die wrywingsfaktor is hoogs sensitief vir partikelvorm en, in die geval van asimmetriese partikels, pakkings metode. Die wrywingsfaktor het met tot 70 % gevarieer vir gebreekte rots, afhanklik van die rigting waarin dit in die toetsseksie neergelê is. Dit is waarskynlik veroorsaak deur die oriëntasie van die asimmetriese rots relatief tot die lugvloei rigting, en is nie voorheen vir rotsbeddens gerapporteer nie. Nuwe isotermiese korrelasies wat gebruik maak van die volume-ekwivalente partikel deursnee word gegee: hulle voorspel binne 15 % van die gemete waardes. Hierdie werk sal n tegno-ekonomiese studie van rotsbeddens toelaat wat meer akkurate voorspellings van pompdrywing gebruik as voorheen moontlik was. Termiese toetse onder 80 °C wys dat die warmteoordrag nie baie sensitief is vir partikelvorm en -tipe nie. n Warmte-oordragskorrelasie vir lug in terme van die volume-ekwivalente deursnee is ontwikkel en met die E-NTU-metode gekombineer. Die voorspelde lug uitlaat temperatuur is binne 5 °C van die meting vir toetse by 530 °C. Dit wys dat termiese geleiding en straling redelikerwys buite rekening gelaat kan word vir n enkele laai/ontlaai siklus by massa vloeitempos van omtrent 0.2 kg/m2s. n Oorspronklike metode vir die bepaling van die optimum partikelgrootte en bedlengte word gegee: Die Biot-getal is vas, en die netto inkomste (die inkomste minus die bed omkoste) van n stoomsiklus voorsien met warmte van die bed word bereken. n Vereenvoudigde berekening wat die metode gebruik wys dat die optimum grootte en lengte ongeveer 20 mm en 6-7 m is. Afhangende van die behoueringsontwerp en koste, kan die kapitale koste n orde kleiner wees as dié van n gesmelte nitraatsout stelsel
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Davies, Neil Harvey. "Limestone as a desulphurising sorbent in power generating systems." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337999.
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Clewer, Bernard C. "State estimation and bad data detection in electrical power systems." Thesis, Durham University, 1986. http://etheses.dur.ac.uk/7105/.
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The thesis studies the subjects of bad data detection and state estimation in electrical power systems which are the processes whereby voltage, power flow and switch status measurements gathered continuously in real-time are used in conjunction with a model of the system to calculate the voltage levels at every node in the system. Traditionally the state estimation process requires two stages. The first stage is the pre-processing of the measurements by a bad data detector in an attempt to remove all the measurements which are grossly in error. The second is the calculation of the voltage levels by a state estimator from the remaining measurements which are likely to contain small random errors. Conventional state estimation algorithms are very sensitive to measurement errors, especially switch status errors, and unfortunately it is not possible to ensure that all the measurement errors are removed by the bad data detector. The thesis presents a new algorithm for state estimation utilising linear programming which is able to function in the presence of not only bad analogue measurements but also switch status measurement errors, thus removing the need for a bad data detector. The proposed method of state estimation is also able to include in its model of the system the individual busbars and bus-couplers within a substation. This feature enables the state estimation algorithm to process and provide additional network information thus leading to a more useful and reliable data base.
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Cristaldo, Nelson. "Secure power grid infrastructure simulation and test-bed system creation." FIU Digital Commons, 2007. http://digitalcommons.fiu.edu/etd/2668.
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This thesis describes the design and construction of the test-bed system as well as its implementation to simulate the distributed control scheme. Some important elements of the system incorporate flexible power system network hardware and a data acquisition (DAQ) system to evaluate the issues that could trigger cascaded failures.
The objective of this research was to create an integrated simulation environment that represents the power system devices, the control, the protection, and the communication subsystems in the same simulation environment. We have utilized this simulator to conduct system studies and evaluate the interaction between power system components under steady-state and transient operation. The results of these studies have been used to enhance the system's ability to identify, and respond to the system's dynamic transients; improving the survivability and robustness of the power system during and after a disturbance by utilizing distributed control strategies. Experiments demonstrated in this thesis show the applicability of the developed simulator to conduct system studies and to evaluate the proposed distributed control infrastructure. The results show the advantages of utilizing distributed control and the impact in the system security and reliability.
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Valmari, Tuomas. "Potassium behaviour during combustion of wood in circulating fluidised bed power plants /." Espoo [Finland] : Technical Research Centre of Finland, 2000. http://www.vtt.fi/inf/pdf/publications/2000/P414.pdf.
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Akan, Adem. "Language and Power - How Power Influences Language : A conversation analysis on the TV – show "Breaking Bad"." Thesis, Södertörns högskola, Institutionen för kultur och lärande, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:sh:diva-27899.
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Power displays itself through talk-in-interaction in social situations; it can also present itself through appearances. Appearance is a personal feature that is immediately obvious and available to others to see. A person’s appearance makes a strong statement about ones values, attitude, abilities etc. People display power through different modalities of talk-in-interactions. This study investigates the linguistic tools that people with power tend to use and how a normal everyday person can change their social status by changing and giving out different linguistic signals. Tracing the patterns of what the verbal cues of power is and describes how an everyday character mastered the relationship between language and power.
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Dudley, Trevor Herbert. "Modelling a 100 MWe Pebble Bed Modular Reactor (PBMR) Nuclear Power Plant." Thesis, University of Manchester, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.508894.
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Najar, salwan. "Simulering av 1-Wire sensorer." Thesis, KTH, Skolan för teknik och hälsa (STH), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-104086.
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The 1-wire bus is a communication bus system which is designed to provide data, signals and power over a single signal with low data rates, a high resolution and a long range. It is typically used to communicate with small inexpensive devices, as temperature sensors, which is worked as a slave with the master computer (PC). The 1-wire bus system provides the sufficient control and operation signal, a unique ID serial number of each sensor and it supports multiple temperature sensors by a driving power (Parasite Power) on single line. On the 1-Wire bus system, temperature sensors are supplied by two types of power supplies, external Power supply and Parasitic Power. The aim of this project is to program the microprocessor (Arduino) by using Arduino programming language to work as a temperature sensor type DS18B20 and also as a slave on the 1-Wire bus system. This report explains the 1-Wire bus system techniques and how the communication is achieved between the master and the slave (sensors) to measure the temperature values. The measured temperature values are collected from the output of each active sensor on the 1-Wire bus. These data are displayed by the personal computer (PC) which is worked as a master on the 1-Wire bus, and the data are represent the measured temperature values from twelve active sensors on the bus system. In this thesis, the temperature values from the 12 active sensors can be read and displayed on the master (PC) by using the following programs: Open Logger One Wire (OLOW) program, One Wire Viewer, DigiTemp and OWFS and I validated all the temperature values from these active sensors which are read and monitored by the drive bus programs. The comparison is done among the measured temperature values to see if the active sensors are given accurate temperature values with different drive bus programs. The project shows that the sensors can be connected in a network with the master, by using 1-Wire bus techniques. This thesis will be used by Karolinska University Hospital, and it can also be developed for different requirements in the future.
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Luan, Wenpeng. "Voltage ranking using artificial neural network method." Thesis, University of Strathclyde, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366960.
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Shaik, Khajaahmad. "High-speed low-power 0.5-V 28-nm FD-SOI 5T-cell SRAMs." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066046.
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L'objectif de cette thèse est d'atteindre 0,5 V haute vitesse faible puissance SRAM. Pour ce faire, les cellules SRAM de pointe, des tableaux et des architectures de bus sont examinées. Les questions difficiles sont alors précisées. Pour répondre aux exigences, une cellule de 5T d'alimentation statique de puissance boostée, combiné avec WL boosté et milieu point de détection et d'un tableau de multi divisé BL ouvert sont proposées et évaluées. Pour encore accélérer l'opération d'écriture, un tableau de 4Kb sélectivement stimulé puissance alimentation 5T cell est proposé et évalué par simulation. Nous découvrons que le point milieu de détection avec moitié VDD BL precharge est plus stable lors de lire que la VDD complet conventionnelle precharge. En outre, pour atteindre un bus robuste à grande vitesse de faible puissance 0,5-V,une architecture de bus dynamique avec un bus factice, qui se compose d'un pilote de dynamique et d'un récepteur dynamique, est proposée. Le pilote dynamique permeten particulier de grande vitesse même à 0,5 V avec overdrive porte accrue enchangeant les lignes électriques de VDD/2 en mode veille avec VDD en mode actif. Ilaccélère encore avec l'aide du bus factice cette impulsion gena pour suivre le point dedétection tension du bus pour réduire l'oscillation de l'autobus. Ensuite, unearchitecture de bus 0,5-V 28 nm FD-SOI 32 bits à l'aide de la proposition estevaluaevaluated par simulation. Il s'avère que l'architecture a un potentiel à exploiterun bus 1-pF à 50-mV swing, 1,2 GHz et un courant de veille de 1,1 µA, avec x3-5 plus rapidement et plus de deux ordre plus faible courant de veille que l'architecture statique conventionnelleThe goal of the thesis is to achieve 0.5-V high-speed low-power SRAMs. To do so, state-of-the-art SRAM cells, arrays, and bus-architectures are reviewed. The challenging issues are then clarified as 1) reduction of the minimum operating voltage VDD (Vmin) of the cell, 2) reducing bitline (BL)-active power, and 3) achieving low-power bus architecture. To meet the requirements, a static boosted-power-supply 5T cell, combined with boosted-WL and mid-point-sensing, and an open-BL multi-divided-array are proposed and evaluated. Layout and post-layout simulation with a 28-nm fully-depleted planar-logic SOI MOSFET reveal that a 0.5-V 5T-cell 4-kb array in a 128-kb SRAM core is able to achieve x2-3 faster cycle time and x11 lower power than the counterpart 6T-cell array, suggesting a possibility of a 730-ps cycle time at 0.5 V.To further speed up the write operation, a selectively-boosted-power-supply 5T-cell 4-kb array is proposed and evaluated by simulation, showing that the 4-kb array operates at 350-ps cycle with x6 faster cycle time and x13 lower power than the 6T-cell array, while maintaining a small leakage current. We find out that the mid-point-sensing with half-VDD BL-precharging is more stable during read than the conventional full-VDD precharging. Furthermore, to achieve a 0.5-V low-power high-speed robust bus, a dynamic bus architecture with a dummy bus, which consists of a dynamic driver and a dynamic receiver, is proposed. In particular, the dynamic driver enables high speed even at 0.5 V with increased gate-over-drive by changing the power lines from VDD/2 in the standby mode to VDD in the active mode. It further speeds up with the help of the dummy bus that generates a pulse to track the bus-voltage detecting point for reducing the bus swing. Then, a 0.5-V 28-nm-FD-SOI 32-bit bus architecture using the proposal is evaluated by simulation. It turns out that the architecture has a potential to operate a 1-pF bus at about 50-mV swing, 1.2 GHz, and a standby current of 1.1 µA, with x3-5 faster and more than two-order lower standby current than the conventional static architecture. Based on the results, further challenges to 0.5-V and sub-0.5-V SRAMs are described
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Hanlon-Hyssong, Jaime E. "Modularity of the MIT Pebble Bed Reactor for use by the commercial power industry." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/10945/3701.
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CIVINSThe Modular Pebble Bed Reactor is a small high temperature helium cooled reactor that is being considered for both electric power and hydrogen production. Pebble bed reactors are being developed in South Africa, China and the US. To make smaller 120 Mwe reactors economically competitive with larger 1500 Mwe traditional light water reactors changes in the way these plants are built are needed. Economies of production need to be sufficiently large to compete with economies of scale. MIT (Berte) has been working on developing a modular design and construction strategy for several years. This thesis builds on that work by demonstrating the technical feasibility of implementing the modularity approaches previously developed.
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Allen, Kenneth Guy. "Performance characteristics of packed bed thermal energy storage for solar thermal power plants." Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/4329.
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Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2010.ENGLISH ABSTRACT: Solar energy is by far the greatest energy resource available to generate power. One of the difficulties of using solar energy is that it is not available 24 hours per day - some form of storage is required if electricity generation at night or during cloudy periods is necessary. If a combined cycle power plant is used to obtain higher efficiencies, and reduce the cost of electricity, storage will allow the secondary cycle to operate independently of the primary cycle. This study focuses on the use of packed beds of rock or slag, with air as a heat transfer medium, to store thermal energy in a solar thermal power plant at temperatures sufficiently high for a Rankine steam cycle. Experimental tests were done in a packed bed test section to determine the validity of existing equations and models for predicting the pressure drop and fluid temperatures during charging and discharging. Three different sets of rocks were tested, and the average size, specific heat capacity and density of each set were measured. Rock and slag samples were also thermally cycled between average temperatures of 30 ºC and 510 ºC in an oven. The classical pressure drop equation significantly under-predicts the pressure drop at particle Reynolds numbers lower than 3500. It appears that the pressure drop through a packed bed is proportional to the 1.8th power of the air flow speed at particle Reynolds numbers above about 500. The Effectiveness-NTU model combined with a variety of heat transfer correlations is able to predict the air temperature trend over the bed within 15 % of the measured temperature drop over the packed bed. Dolerite and granite rocks were also thermally cycled 125 times in an oven without breaking apart, and may be suitable for use as thermal storage media at temperatures of approximately 500 ºC. The required volume of a packed bed of 0.1 m particles to store the thermal energy from the exhaust of a 100 MWe gas turbine operating for 8 hours is predicted to be 24 × 103 m3, which should be sufficient to run a 25-30 MWe steam cycle for over 10 hours. This storage volume is of a similar magnitude to existing molten salt thermal storage.
AFRIKAANSE OPSOMMING: Sonenergie is die grootste energiebron wat gebruik kan word vir krag opwekking. ‘n Probleem met die gebruik van sonenergie is dat die son nie 24 uur per dag skyn nie. Dit is dus nodig om die energie te stoor indien dit nodig sal wees om elektrisiteit te genereer wanneer die son nie skyn nie. ‘n Gekombineerde kringloop kan gebruik word om ‘n hoër benuttingsgraad te bereik en elektrisiteit goedkoper te maak. Dit sal dan moontlik wees om die termiese energie uit die primêre kringloop te stoor, wat die sekondêre kringloop onafhanklik van die primêre kringloop sal maak. Dié gevalle studie ondersoek die gebruik van ‘n slakof- klipbed met lug as hitteoordragmedium, om te bepaal of dit moontlik is om hitte te stoor teen ‘n temperatuur wat hoog genoeg is om ‘n Rankine stoom kringloop te bedryf. Eksperimentele toetse is in ‘n toets-bed gedoen en die drukverandering oor die bed en die lug temperatuur is gemeet en vergelyk met voorspelde waardes van vergelykings en modelle in die literatuur. Drie soorte klippe was getoets. Die gemiddelde grootte, spesifieke hitte-kapasiteit en digtheid van elke soort klip is gemeet. Klip en slak monsters is ook siklies tussen temperature van 30 ºC en 510 ºC verkoel en verhit. Die klassieke drukverlies vergelyking gee laer waardes as wat gemeet is vir Reynolds nommers minder as 3500. Dit blyk dat die drukverlies deur ‘n klipbed afhanklik is van die lug vloeispoed tot die mag 1.8 as die Reynolds nommer groter as omtrent 500 is. Die ‘Effectiveness-NTU’ model gekombineerd met ‘n verskeidenheid van hitteoordragskoeffisiënte voorspel temperature binne 15 % van die gemete temperatuur verskil oor die bed. Doloriet en graniet klippe het 125 sikliese toetse ondergaan sonder om te breek, en is miskien gepas vir gebruik in ‘n klipbed by temperature van sowat 500 ºC Die voorspelde volume van ‘n klipbed wat uit 0.1 m klippe bestaan wat die termiese energie vir 8 ure uit die uitlaat van ‘n 100 MWe gasturbiene kan stoor, is 24 × 103 m3. Dit behoort genoeg te wees om ‘n 25 – 30 MWe stoom kringloop vir ten minste 10 ure te bedryf. Die volume is min of meer gelyk aan dié van gesmelte sout store wat alreeds gebou is.
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Wong, Siu-Kei. "Low power techniques on nanometer scale instruction bus and network-on-chip /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202004%20WONGS.
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Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2004.Includes bibliographical references (leaves 73-76). Also available in electronic version. Access restricted to campus users.
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Saari, Juhani. "Power and Resistance in Herman Melville’s Three B’s." Thesis, Stockholms universitet, Engelska institutionen, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-91131.
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This essay examines three of Herman Melville’s shorter fictions: Bartleby, Benito Cereno and Billy Budd. An analysis and comparison is made of the forces of power relations and resistance between the main characters in the three stories. Foucault’s theories of power are used as a basis for the analysis. Apparent power structures such as law and military hierarchy are analysed, but the focus is on more subtle relations based on language, knowledge, conformity with norms, silence, capitalism and position. It is argued that, apart from the apparent power structures, one needs to consider the more subtle power relations and acts of resistance for an understanding in the shifts of power positions. The study examines how the resisting oppressed party in each of the three works of fiction ends up dead, and that on a first reading resistance may seem futile. A further examination of the seemingly re-established conventional order, however, reveals shifts in power positions, shifts that indicate instability in the norms of society. It is argued that positions of power are to some extent reversed in the studied works of fiction, where the dominant party ends up suffering.
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Restrepo, Patiño Carlos Alberto. "Pem fuel cell modeling and converters design for a 48 v dc power bus." Doctoral thesis, Universitat Rovira i Virgili, 2012. http://hdl.handle.net/10803/84031.
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Fuel cells (FC) are electrochemical devices that directly convert the chemical energy of a fuel into electricity. Power systems based on proton exchange membrane fuel cell (PEMFC) technology have been the object of increasing attention in recent years as they appear very promising in both stationary and mobile applications due to their high efficiency, low operating temperature allowing fast startup, high power density, solid electrolyte, long cell and stack life, low corrosion, excellent dynamic response with respect to the other FCs, and nonpolluting emissions to the environment if the hydrogen is obtained from renewable sources. The output-voltage characteristic in a PEMFC is limited by the mechanical devices which are used for regulating the air flow in its cathode, the hydrogen flow in its anode, its inner temperature, and the humidity of the air supplied to it. Usually, the FC time constants are dominated by the fuel delivery system, in particular by the slow dynamics of the compressor responsible for supplying the oxygen. As a consequence, a fast load transient demand could cause a high voltage drop in a short time known as oxygen starvation
phenomenon that is harmful for the FC. Thus, FCs are considered as a slow dynamic response equipment with respect to the load transient requirements. Therefore, batteries, ultracapacitors or other auxiliary power sources are needed to support the operation of the FC in order to ensure a fast response to any load power transient. The resulting systems, known as FC hybrid systems, can limit the slope of the current or the power generated by the FC with the use of current-controlled dc-dc converters. In this way, the reactant gas starvation phenomena can be avoided and the system
can operate with higher efficiency. The purpose of this thesis is the design of a DC-DC converter suitable to interconnect all the different elements in a PEMFC-hybrid 48-V DC bus. Since the converter could be placed between elements with very different voltage levels, a buck-boost structure has been selected. Especially to fulfill the low ripple requirements of the PEMFCs, but also those of the auxiliary storage elements and loads, our structure has inductors in series at both its input and its output. Magnetically coupling these inductors and adding a damping
network to its intermediate capacitor we have designed an easily controllable converter with second-order-buck-like dominant dynamics. This new proposed topology has high efficiency and wide bandwidth acting either as a voltage or as a current regulator. The magnetic coupling allows to control with similar performances the input or the output inductor currents. This characteristic is very useful because the designed current-controlled converter is able to withstand
shortcircuits at its output and, when connected to the FC, it facilitates to regulate the current extracted from the FC to avoid the oxygen starvation phenomenon. Testing in a safe way the converter connected to the FC required to build an FC simulator that was subsequently improved by developing an emulator that offered real-time processing and oxygen-starvation indication. To study the developed converters and emulators with different brands of PEMFCs it was necessary to reactivate long-time inactive Palcan FCs. Since the results provided by the manual reactivation procedure were unsatisfactory, an automatic reactivation system has been developed as a complementary study of the thesis.En esta tesis se avanzo en el diseño de un bus DC de 48 V que utiliza como elemento principal de generación de energía eléctrica una pila de combustible. Debido a que la dinámica de las pilas de combustible están limitadas por sus elementos mecánicos auxiliares de control una variación rápida de una carga conectada a ella puede ocasionar daños. Es por esto que es necesario utilizar elementos almacenadores de energía que puedan suministrar estas rápidas variaciones de carga y convertidores para que gestionen de una forma controlada la potencia del bus DC. Durante la realización de pruebas de los convertidores es de gran importancia utilizar emuladores o simuladores de pilas de combustibles, esto nos permite de una forma económica y segura realizar pruebas criticas antes de conectar los convertidores a la pila. Adicionalmente una nueva topologia de convertidor fue presentada y ésta gestionará la potencia en el bus
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Hanlon-, Hyssong Jaime E. "Modularity of the MIT Pebble Bed Reactor for use by the commercial power industry." (5 MB), 2008. http://handle.dtic.mil/100.2/ADA488083.
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Thesis (M.S. in Nuclear Science and Engineering)--Massachusetts Institute of Technology, May 2008."May 2008." Description based on title screen as viewed on August 26, 2009. DTIIC Descriptor(s): Light Water Reactors, Strategy, Production, Theses, Modular Construction, Construction, Feasibility Studies, Electric Power, Power, Helium, Industries, Hydrogen. DTIC Identifier(s): Modular Pebble Bed Reactor. Includes bibliographical references (p. 112-113). Also available in print.
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Baral, Bishwas. "Directional Comparison Bus Protection Using Superimposed Partial Operating Current Characteristics." ScholarWorks@UNO, 2019. https://scholarworks.uno.edu/td/2584.
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Various directional comparison bus protection methods including widely used superimposed directional element method need to have both voltages and currents from all feeders connected to the zone of protection to find the direction of current for detecting a bus fault or a line fault. The purpose of the thesis is to present a new technique for directional comparison bus protection to discriminate a bus fault from line fault and normal condition. The new technique, which is implementing superimposed directional element method to modify partial operating current characteristics (POC) method to superimposed POC (SPOC) method, does not use voltages from feeders, hence capacitor voltage transformers (CVTs) are no longer needed in the zone of protection. The proposed technique was implemented in 4-bus and IEEE 14-bus test system and was tested using different fault cases including CT saturation and high impedance fault. The proposed technique, SPOC method was compared with POC method with both methods implemented in same test systems and tested with same fault cases. The results show that the proposed technique is successful to detect bus faults with high accuracy and high speed.
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Dicharry, Jeff. "Power System Fault Detection Using Conductor Dynamics." ScholarWorks@UNO, 2005. http://scholarworks.uno.edu/td/289.
Full textAbstract:
Power system fault detection is conventionally achieved using current and potential measurements. An alternate and unconventional form of protective relaying is feasible using rigid bus conductor motion as the means of detection. The research presented focuses on the detection of power system faults using visual displacement of conductor spans. Substation rigid bus conductor motion is modeled using dual spring-mass systems for accurate representation of conductor response to electromagnetic forces generated during system faults. Bundled rigid conductors have advantages including detection independent of system load currents and improved ability to detect polyphase and single phase faults. The dynamic motion of the conductors during the fault is optically monitored with a laser detection system. Timeovercurrent characteristics are derived for the application of fault detection. The response time of the conductor detector system is slower than conventional relays due to the natural frequencies of the conductor span limiting the speed of its displacement. This response time makes the fault detection system using conductor displacement an ideal candidate for a backup relay in power system protection schemes.
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Bull, Douglas Rutherford. "Performance Improvements to a Fast Internally Circulating Fluidised Bed (FICFB) Biomass Gasifier for Combined Heat and Power Plants." Thesis, University of Canterbury. Chemical and Process Engineering, 2008. http://hdl.handle.net/10092/1952.
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This thesis describes the development and experimental testing of a 100 kW dual fluidized bed biomass gasifier (also called a Fast Internally Circulating Fluidized Bed (FICFB) biomass gasifier). This steam-blown gasifier is being studied for its suitability within combined heat and power plant systems for the New Zealand forest products industry. This advanced design of gasifier has the ability to generate producer gas with a lower heating value (LHV) of 11.5-13.4 MJ/Nm3, which is two to three times higher than yielded by conventional gasification systems. This is accomplished because the gasification and combustion processes occur in two physically separated reactors.
Several modifications to the gasifier were required after it was first constructed in order to achieve stable and reliable operation. Producer gas yields were measured through the use of helium as a tracer gas. A new simultaneous producer gas and tar sampling system was developed, allowing accurate samples to be obtained in a matter of minutes.
Experimental testing included a cold testing exercise which provided valuable information on the circulation behaviour of the bed material and char within the gasifier. This helped in achieving stable and reliable operation of the plant. Producer gas yields of 14.6 Nm3/h were recorded with a fuel (radiate pine wood pellets) feed rate of 18.9 kgdry/h. The cold gas efficiency ranged from 16-40 % with limited heat recovery in place, but depended noticeably on the plant operating conditions especially gasification temperature.
The amount of polycyclic aromatic hydrocarbon (PAH) tars measured in the producer gas ranged between 0.9-4.7 g/Nm3 with naphthalene and acenapthylene being the most abundant compounds. The moisture content of the producer gas was determined to be 0.9-1.2 g/gdry gas. It was found that a steam to biomass ratio of 0.45-0.7 kg/kgdry was most favourable for generating a 12-13.4 MJ/Nm3 producer gas while limiting the amount of steam generation. Gasification temperatures above 750 °C encouraged higher producer gas yields and higher cold gas efficiencies. The catalytic bed material olivine (forsterite olivine) was found to increase the producer gas yield by approximately 20 % compared to the non-catalytic bed material greywacke. The use of olivine meant higher cold gas efficiencies were achieved for a given wood feed rate.
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Brits, Yvotte. "Techno-economic analysis of the 100 MW Potchefstroom experimental pebble bed reactor plant / by Yvotte Brits." Thesis, North-West University, 2009. http://hdl.handle.net/10394/3832.
Full textAbstract:
Electricity is directly linked to the economy of a country: when electricity is limited and the price for electricity is very high, the high electricity price will have a negative influence on the economy of the country. Owing to the increasing power shortage in the world, and South Africa in particular, today, the need for reliable and economical electricity has risen drastically.
The 100 MWth (40 MWe) PEPER power plant is a possible alternative that will help fight the lack of reliable, clean and affordable electricity in the world today. Owing to the small consumption area of the PEPER power plant, each city, mine and industry, for example, can have its own PEPER power plant in order to ensure reliable, affordable and sustainable electricity.
This dissertation presents a case study and the relevant economic model for the PEPER power plant in order to determine whether the PEPER power plant may be considered as a possible electricity source. The production costs of the PEPER are presented in US$/kWh and compared with the industrial and household electricity costs (in US$/kWh) of various countries. This is done in order to determine whether it will be economically feasible to construct a First-of-a-kind (FOAK) or Nth-of-a-kind (NOAK) PEPER power plant in the industrial and household sectors of a selected country.
In the economic model of the PEPER plant, the fixed capital investment costs for a FOAK PEPER plant were estimated to be US$367,199,411 and the fixed capital investment costs for a NOAK (eighth) PEPER plant were estimated to be US$238,429,665. The working capital for the first two years of the PEPER plant’s lifetime was estimated to be US$17,228,740. The production cost of the PEPER plant was estimated to be 0.038 US$/kWh. The sensitivity analysis conducted demonstrated that FOAK PEPER plants could be established in countries in which the electricity income is 0.145 US$/kWh or more. NOAK PEPER plants (all the PEPER plants constructed after the eighth PEPER Techno-economic analysis of the 100 MWth PEPER plant Confidential 3 plant is erected) could be established in countries with an electricity income of 0.10 US$/kWh or more.
The PEPER plant presented here could be used:
1. as a training tool;
2. to test fuels and materials;
3. to accumulate high temperature nuclear data; and
4. as an electricity source for the industrial and household sectors of selected countries.Thesis (M.Ing. (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2010
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Strydom, Gerhard. "Xenon-induced axial power oscillations in the 400 MW pebble bed modular reactor / Gerhard Strydom." Thesis, North-West University, 2007. http://hdl.handle.net/10394/2116.
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Browne, Randy M. Sweet John Wood. "This bad business Obeah, violence, and power in a nineteenth-century British Caribbean slave community /." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2009. http://dc.lib.unc.edu/u?/etd,2196.
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Thesis (M.A.)--University of North Carolina at Chapel Hill, 2009.Title from electronic title page (viewed Jun. 26, 2009). "... in partial fulfillment of the requirements for the degree of Master of Arts in the Department of History." Discipline: History; Department/School: History.
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Schonberger, John Karl. "Distributed Control of a Nanogrid Using DC Bus Signalling." Thesis, University of Canterbury. Electrical and Computer Engineering, 2006. http://hdl.handle.net/10092/1072.
Full textAbstract:
A nanogrid is a standalone hybrid renewable system that uses distributed renewable and non-renewable sources to supply power to local loads. The system is based on power electronics, with interface converters allowing the sources to supply power to the system and the loads to draw power from the system. The nanogrid is typically designed such that renewable sources supply the average load demand, while storage and non-renewable generation are used to ensure that the loads enjoy a continuous supply of power in the presence of the stochastic renewable sources. To maintain the power balance in the system while maximising use of the renewable sources, all sources in the system are scheduled according to a supply-side control law. The renewable sources are used wherever possible and the storage is operated as a slack power bus. The storage is controlled to absorb any excess power from the renewable sources and release it to the system when necessary. The non-renewable generation is only brought online when the storage and renewable sources are incapable of balancing the load demand. While the primary method for maintaining the power balance in the nanogrid is scheduling the sources according to a supply-side control law, a demand-side control law may also be used to help maintain the power balance in the system or protect the system from a complete collapse under overload conditions. A demand-side control strategy is implemented by shedding loads when the load exceeds the available generation, beginning with those loads having the lowest utilisation priority. Hybrid renewable systems are typically designed and controlled in a similar manner to the traditional ac power system, operating at 50/60~Hz, and maintaining the power balance in the system using frequency droop for power sharing and central coordination for scheduling the sources. However a nanogrid has different components compared to the ac system, employing power electronic converters to interface the sources and loads to the system. The control flexibility afforded by the use of power electronic interface converters opens the door to new transmission and control possibilities. This thesis evaluates a number of transmission options ranging from dc to high frequency ac in order to determine an operating frequency that is suitable for this niche system. A number of control topologies are also investigated to find a low cost strategy for implementing a supply-side control law. DC is selected as the operating frequency of choice largely for its simpler source interface requirements. A novel control strategy, dc bus signalling (DBS), is proposed as a means of implementing a supply-side control law. Its distributed structure maintains the modularity inherent in the distributed structure of the nanogrid. DBS uses the voltage level of the dc bus to convey system information. With a supply-side control law implemented using DBS, the source and storage interface converters operate autonomously based on the voltage level of the dc bus. The converters not only respond to the level of the dc bus, but they also change the level of the dc bus, automatically controlling other converters in the system. This thesis presents the theory of operation behind this control strategy and outlines a method for implementing a supply-side control law. A method for ensuring that the supply-side control law operates in a practical system where transmission line impedance affects the information conveyed by the dc bus is also given. For completeness, a method for implementing a demand-side control law using DBS is also presented. A simulation model of a nanogrid is presented and results are obtained to demonstrate the operation of DBS. The design of a small experimental system is also presented, and results are obtained to verify the operation of this new control strategy in a practical system. The simulation and experimental results demonstrate the feasibility of implementing supply and demand-side control laws in a nanogrid using DBS, even in the presence of transmission line impedance.
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Venkitasubramanian, Iyer Jayakrishnan. "Variable length pattern coding for power reduction in off-chip data buses." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-2667.
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De, Bod Sadie. "The South African water management framework : Lethabo power station as a case study / Sadie de Bod." Thesis, North-West University, 2012. http://hdl.handle.net/10394/8730.
Full textAbstract:
South Africa is considered to be a water scarce country and it is estimated that by 2030 the
water demand would have surpassed the water supply. There are therefore serious
implications if all sectors of South Africa do not utilise natural water resources efficiently.
The power generation sector is one of the more dominant water users, utilising more than
2 % of the available water resources. Since Eskom is guaranteed a 99.5 % water supply
from the Department of Water Affairs, and they are planning to double their power
generating capacity by 2030, accountability from Eskom’s side is required to ensure water is
managed according to South African standards.
Water management strategies in South Africa are subject to location due to the variation of
water availability and water quality in the different regions. This requires some areas to have
more strict regulations than other areas, but the basic framework within which water is
managed are based on the same policies and strategies. For example, dry cooling
technologies were initially only designed for water scarce areas, but Eskom has committed
to implement dry cooling technology at all new build power stations even though it is more
expensive in terms of capital cost and maintenance.
For the purposes of this study water management is investigated by means of a top down
approach starting on national legislative level, then on departmental executive level, then on
power generation corporate level and finally on power generation business unit level. A
case study on business unit level is conducted at Lethabo power station to determine what
the contributory factors to high water consumption are and what actions are required to
rectify these problems. The aim of this research is therefore to discover how and how well
water management is performed at older Eskom Power Stations within the greater water
management framework existing at corporate and national level in South Africa.
The strategic objectives of the power generation sector should include minimisation of the
footprint of power generation on natural water resources by reducing water usage and
implementing conservation strategies in order to make the power generation sector of South
Africa a world leader in water management. With appropriate management, South African
water resources can be utilised in such a way that it supports a healthy power generation
industry as well as a growing population.Thesis (MIng (Development and Management Engineering))--North-West University, Potchefstroom Campus, 2013
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Wang, Chunyun 1968. "Design, analysis and optimization of the power conversion system for the Modular Pebble Bed Reactor System." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/17026.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 2003.Includes bibliographical references.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
The Modular Pebble Bed Reactor system (MPBR) requires a gas turbine cycle (Brayton cycle) as the power conversion system for it to achieve economic competitiveness as a GenIV nuclear system. The availability of controllable helium turbomachinery and compact heat exchangers are thus the critical enabling technology for the gas turbine cycle. The development of an initial reference design for an indirect helium cycle has been accomplished with the overriding constraint that this design could be built with existing technology and complies with all current codes and standards. Using the initial reference design, limiting features were identified. Finally, an optimized reference design was developed by identifying key advances in the technology that could reasonably be expected to be achieved with limited R&D. This final reference design is an indirect, intercooled and recuperated cycle consisting of a three-shaft arrangement for the turbomachinery system. A critical part of the design process involved the interaction between individual component design and overall plant performance. The helium cycle overall efficiency is significantly influenced by performance of individual components. Changes in the design of one component, a turbine for example, often required changes in other components. To allow for the optimization of the overall design with these interdependencies, a detailed steady state and transient control model was developed. The use of the steady state and transient models as a part of an iterative design process represents the key contribution of this work. A dynamic model, MPBRSim, has been developed.
(cont.) The model integrates the reactor core and the power conversion system simultaneously. Physical parameters such as the heat exchangers' weights and practical performance maps such as the turbine characteristics and compressor characteristics are incorporated into the model. The individual component models as well as the fully integrated model of the power conversion system have been verified with an industry-standard general thermal-fluid code Flownet. With respect to the dynamic model, bypass valve control and inventory control have been used as the primary control methods for the power conversion system. By performing simulation using the dynamic model with the designed control scheme, the combination of bypass and inventory control was optimized to assure system stability within design temperature and pressure limits. Bypass control allows for rapid control system response while inventory control allows for ultimate steady state operation at part power very near the optimum operating point for the system. Load transients simulations show that the indirect, three-shaft arrangement gas turbine power conversion system is stable and controllable. For the indirect cycle the intermediate heat exchanger (IHX) is the interface between the reactor and the turbomachinery systems. As a part of the design effort the IHX was identified as the key component in the system. Two technologies, printed circuit and compact plate-fin, were investigated that have the promise of meeting the design requirements for the system ...
by Chunyun Wang.
Ph.D.
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Xing, Kun. "Modeling, Analysis, and Design of Distributed Power Electronics System Based on Building Block Concept." Diss., Virginia Tech, 1999. http://hdl.handle.net/10919/28123.
Full textAbstract:
The basic Power Electronics Building Block (PEBB) configurations are identified and conceptual PEBB modules are constructed and tested. Using the INCA (Inductance Calculator) parasitic extraction and the Saber circuit simulation software, the microscopic relationships between the parasitics of the packaging layout and their circuit electrical effects are cross-examined. The PEBB module with advanced packaging techniques is characterized in comparison with the wire-bond module. The soft-switching techniques are evaluated for PEBB applications. The Zero-Current-Transition (ZCT) is proved better because the parasitics in the power current flow path are absorbed into the resonant soft-switching operation. This makes the PEBBs insensitive to system integration.
Based on the building block concept, the discrete and large signal average models are developed for simulation, design, and analysis of large-scale PEBB-based systems. New average models are developed for half-bridge PEBB module and Space Vector Modulation (SVM). These models keep the exact information of the discontinuous SVM and the common mode component of the three-phase system. They can be used to construct the computer models of a power electronics system the same as the modularized hardware and perform time domain simulations with very fast speed. Further more, even though the system is modeled based on modularized concept on the ABC coordinates, it can be used to perform small signal analysis on the DQ coordinates as well.
Based on the developed models, the system-level interactions in integrated systems are investigated. Three interaction scenarios are presented: (1) the zero-sequence circulation current in paralleled three-phase rectifiers caused by the interleaved discontinuous SVM, (2) the load and source interactions caused by unbalanced load and small signal impedance overlap, and (3) the combined common mode noise caused by both front-end PWM rectifiers and load inverters. The interaction phenomena and mitigation methods are demonstrated through hardware testbed system.
The concept of dc bus conditioning is proposed. The bus conditioner is a bi-directional dc/dc converter programmed as a current controlled current source, which shunts the large signal ac current, which otherwise goes to the dc bus, into an isolated energy storage component. In addition to alleviate the source and load interactions, it increases the load impedance/decreases the bus impedance and provides more stability margins to the distribution system. The dc bus conditioner concept and its functions are demonstrated through system simulation and preliminary hardware experiment.Ph. D.
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Chakkaravarthy, Manoj. "BDD Based Synthesis Flow for Design of DPA Resistant Cryptographic Circuits." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1330025314.
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Mettle, Matilda. "Forced Resettlement in Ghana: The Dam and the Affected People : The Bui Hydroelectric Power Project in Ghana." Thesis, Norges teknisk-naturvitenskapelige universitet, Geografisk institutt, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-17028.
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Forced resettlement is an issue of great humanitarian concern. The disruption it brings to the lives of the people it affects cannot be fully expressed. Many of such people lose the ability of restoring their lives, never to regain it till they die. What is more alarming is when forced resettlement is not caused by conflict or natural disaster but rather conscious development projects like dams, where it is expected that great energy will be channelled towards reducing and if possible avoid the adverse impacts of such forceful resettlement as a matter of human and citizenship right. Sadly, in many instances this never happen. The aim of this study is to find out how the lessons learnt from the Akosombo forced resettlement in Ghana has been used in planning and implementing the on-going Bui forced resettlement also in Ghana. This study also tries to investigate the impacts of the planning and implementation process of the resettlement on the affected communities and households. In order to achieve the above goals, qualitative research methods were employed. The study used in-depth interviews, focus group discussions, direct and participatory observation techniques in accessing the experiences and feelings of the people involved. The informants include the institutions and professionals which undertook the forced resettlement and the affected people. The modernisation and alternative development theories were reviewed to determine which of these approaches is in practice. However, since Ghana claims it is using the World Bank Operational Policy (4.12), which is following an alternative development approach, concepts such as participation and rights are used. Additionally, concepts such as compensation and forced resettlement are also reviewed. It is discovered that, although many lessons have been learnt from the Akosombo forced resettlement, these lessons have not been effectively translated into action plans in order to undertake successful forced resettlement in Ghana. The challenges and errors in planning the Bui resettlement have therefore marred its successful implementation. This has resulted in more adverse impacts on the affected people than good ones such as infertile lands, low farm yield, poor housing structures and total ban on fishing in the Black Volta without alternative fishing grounds.
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Marx, Andrew Morne. "Increasing soft power - a case study of South Africa's bid to host the FIFA 2010 World Cup." Thesis, Stellenbosch : University of Stellenbosch, 2004. http://hdl.handle.net/10019.1/16386.
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Thesis (MA)--University of Stellenbosch, 2004.ENGLISH ABSTRACT: This study attempts to determine if South Africa was actively attempting to boost its soft power or symbolic power during the country’s bid to host the Fifa 2010 World Cup. Preceding works dealing with mega-events identified a number of potential benefits to the hosting nation. Some of these benefits include opportunities for development (sport and socio-economic), nation building, urban regeneration, and marketing. Previous works have focused a great deal on economic and nation building aspects of mega-events. The marketing possibility for a host to develop as a tourist destination has also enjoyed some focus. There also exists a large amount of literature dealing with power – its nature, resources and types. There is for instance structural and relational power while, in the traditional sense, wealth and military might may be seen as power resources. However, the importance and maintenance of soft power – or symbolic or co-optive power, as defined in this study – has been greatly overshadowed by the traditional ideas of power and as a result, neglected by International Relations scholars. This study links the marketing potential of mega-events with the deployment of soft power. The case study specifically deals with South Africa’s World Cup bid as a marketing forum for enhancing the country’s soft power. For such an analysis it is necessary to investigate South Africa’s diplomatic status, global position, relationship with the North and South, and power resources. The importance of soft power being essential to South Africa’s specific situation, global position and future, is also investigated. Using the bid for the 2010 World Cup, this study concludes that South Africa was indeed projecting specifically chosen images of the country with the intention of enhancing the country’s soft power. It is furthermore argued that these images are both a reflection and in support of South Africa’s foreign policy and emerging middle power position.
AFRIKAANSE OPSOMMING: Hierdie studie poog om vas te stel of Suid Afrika doelgerig probeer het om die land se sagte mag te versterk tydens die Fifa 2010 Wêreldbekerbod. Vorige studies oor grootskaalse gebeurtenisse meen dat dit sekere potensieële voordele inhou vir die gasheer. Dit sluit in geleenthede vir ontwikkeling (sport en sosio-ekonomies), nasiebou, en stedelike herlewing en bemarking. Vorige werke het ook meerendeels gefokus op die ekonomiese en nasie-bou aspekte van grootskaalse gebeurtenisse. Die bemarkingsvoordele wat dit inhou vir die gasheer se toerismebedryf is ook gereeld vehandel. Daar bestaan ook vele geskrewe werke oor mag. Verskillende bronne van mag is ondermeer ‘n gewilde onderwerp. Daar is byvoorbeeld strukturele mag en verhoudings mag. Tradisioneel word militêre en ekonomiese vermoëns gesien as bronne van mag. Die belangrikheid van sagte mag of simboliese mag, soos dit in hierdie studie gedefinieër word, is egter tot ‘n groot mate oorskadu deur traditionele idees van mag. Daardeur het Internasionale Betrekkinge akademici dit ook tot ‘n mate afgeskeep. Hierdie studie illustreer die bemarkingspotentiaal wat grootskaalse gebeurtenisse inhou vir sagte mag. Die gevallestudie handel spesifiek oor Suid Afrika se 2010 bod as ‘n potentieële bemarkingsforum vir die bevordering van die land se sagte mag. Die analise het vereis dat Suid Afrika se diplomatieke status, globale posisie, verhouding met die Noorde en Suide, en bronne van mag behandel word. Die belangrikheid van sagte mag vir Suid Afrika se toekoms word ook aangespreek. Die gevolgtrekking is dat Suid Afrika wel gepoog het om sekere gekose beelde na die buiteland te projekteer. Die spesifieke doel met die beelde was om die land se sagte mag uit te brei. ‘n Verdere bevinding is dat die beelde gelyktydig Suid Afrika se buitelandse beleid en ontluikende middel magsposisie gereflekteer het.
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Hongyan, Li. "Dynamic performance of restructured wholesale power markets with learning generation companies an agent-based test bed study /." [Ames, Iowa : Iowa State University], 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3389122.
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Maidadi, Mohaman Bello. "Packed-bed rock thermal energy storage for concetrated solar power: enhancement of storage time and system efficiency." Thesis, Nelson Mandela Metropolitan University, 2013. http://hdl.handle.net/10948/d1020914.
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Solar thermal energy harvesting is a promising solution to offset the electricity demands of a growing population. The use of the technology is however still limited and this can most likely be attributed to the capital cost and also the intermittent nature of solar energy which requires incorporation of a storage system. To make the technology more attractive and effective, cheap means of harvesting solar energy and the development of efficient and inexpensive thermal energy storage devices will improve the performance of solar energy systems and the widespread use of solar energy. Heat storage in a packed-bed rock with air as the working fluid presents an attractive and simple solution for storing solar thermal energy and it is recommended for solar air heaters. A packed-bed rock storage system consists of rocks of good heat capacity packed in a storage tank. The working fluid (air) flows through the bed to transfer its energy. The major concern of the design for a packed-bed rock thermal storage system is to maximize the heat transfer and minimise the pressure drop across the storage tank and hence the pumping power. The time duration the stored energy can be preserved and the air flow wall effect through the bed are the common complications encountered in this system. This study presents an experimental and analytical analysis of a vacuum storage tank with the use of expanded perlite for high temperature thermal energy storage in a packed-bed of rocks. Dolerite rocks are used as the storage medium due to their high heat capacity and as they are locally available. To minimise the pressure drop across the tank, moderate rock sizes are used. The tank contains baffles, allowing an even spread of air to rock contact through the entire tank, therefore improving heat transfer. There is a good correlation between the predicted and the actual results (4 percent) which implies that the baffles incorporated inside the vacuum tank forces the air through the entire tank, thereby resulting in an even lateral temperature distribution across the tank. The investigation of heat loss showed that a vacuum with expanded perlite is a viable solution to high temperature heat storage for an extended period. The research also focuses on the investigation of a proposed low cost parabolic trough solar collector for an air heating system as shown in Figure (1.3). The use of a standard solar geyser evacuated tube (@R130 each) has cost benefits over the industry standard solar tubes normally used in concentrating solar power systems. A mathematical was developed to predict the thermal performance of proposed PTC and it was found that the measured results compared well with the predictions. The solar energy conversion efficiency of this collector is up to 70 percent. This research could impact positively on remote rural communities by providing a source of clean energy, especially for off-grid applications for schools, clinics and communication equipment. It could lead to a significant improvement in the cost performance, ease of installation and technical performance of storage systems for solar heating applications.
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Ratul, Saiful A. "Optimal DG Placement: A Multimethod Analysis." ScholarWorks@UNO, 2016. http://scholarworks.uno.edu/td/2269.
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With Power System being restructured in the vision of Smart Grid, it is important now more than ever to find suitable locations to place Distributed Generators (DG). Distributed generators, which may be renewable, are not limited to specific locations as in the case of conventional generators. Several papers have been published that make suggestions on where the optimal location of DG should be in a system. Objectives ranging from loss minimization to total cost minimization have been the factor for such studies. In this study, a new method is introduced that hopes to improve a current system in three ways by maximizing load, minimizing the locational marginal price and improving line contingency scenarios. The proposed methodology is simulated using MATPOWER’s Optimal Power Flow on the IEEE 14 bus test system.
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Reusch, David Clayton. "High Frequency, High Power Density Integrated Point of Load and Bus Converters." Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/26920.
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The increased power consumption and power density demands of modern technologies
combined with the focus on global energy savings have increased the demands on DC/DC power
supplies. DC/DC converters are ubiquitous in everyday life, found in products ranging from
small handheld electronics requiring a few watts to warehouse sized server farms demanding
over 50 megawatts. To improve efficiency and power density while reducing complexity and
cost the modular building block approach is gaining popularity. These modular building blocks
replace individually designed specialty power supplies, providing instead an optimized complete
solution. To meet the demands for lower loss and higher power density, higher efficiency and
higher frequency must be targeted in future designs. The objective of this dissertation is to
explore and propose methods to improve the power density and performance of point of load
modules ranging from 10 to 600W.Ph. D.
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Clark, Jared A. "The Effects of Build Orientation on Residual Stresses in AlSi10Mg Laser Powder Bed Fusion Parts." Youngstown State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1578819644598848.
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Meister, Bradley Carl. "Fluidized bed gasification of biomass and waste fuels with product characterization for close-coupled gasifier-boiler power systems /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2003. http://uclibs.org/PID/11984.
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Muneeb, Ur Rehman Muhammad. "Modular, Scalable Battery Systems with Integrated Cell Balancing and DC Bus Power Processing." DigitalCommons@USU, 2018. https://digitalcommons.usu.edu/etd/6999.
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Traditional electric vehicle and stationary battery systems use series-connected battery packs that employ centralized battery management and power processing architecture. Though, these systems meet the basic safety and power requirements with a simple hard- ware structure, the approach results in a battery pack that is energy and power limited by weak cells throughout life and most importantly at end-of-life. The applications of battery systems can benefit significantly from modular, scalable battery systems capable of advanced cell balancing, efficient power processing, and cost gains via reuse beyond first-use application. The design of modular battery systems has unique requirements for the power electronics designer, including architecture, design, modeling and control of power processing converters, and battery balancing methods. This dissertation considers the requirements imposed by electric vehicle and stationary applications and presents design and control of modular battery systems to overcome challenges associated with conventional systems. The modular battery system uses cell or substring-level power converters to combine battery balancing and power processing functionality and opens the door to new opportunities for advanced cell balancing methods. This approach enables balancing control to act on cell-level information, reroute power around weaker cells in a string of cells to optimally deploy the stored energy, and achieve performance gains throughout the life of the battery pack. With this approach, the integrated balancing power converters can achieve system cost and efficiency gains by replacing or eliminating some of the conventional components inside battery systems such as passive balancing circuits and high-voltage, high-power converters. In addition, when coupled with life prognostic based cell balancing control, the modular system can extend the lifetime of a battery pack by up to 40%. The modular architecture design and control concepts developed in this dissertation can be applied to designs of large battery packs and improve battery pack performance, lifetime, size, and cost.
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Piehl, Hampus. "Wind power integration in island-based smart grid projects : A comparative study between Jeju Smart Grid Test-bed and Smart Grid Gotland." Thesis, Uppsala universitet, Elektricitetslära, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-224531.
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Smart grids seem to be the solution to use energy from renewable and intermittent energy sources in an efficient manner. There are many research projects around the world and two of them are Jeju Smart Grid Test-bed and Smart Grid Gotland. They have in common that they are both island-based projects and connected to the Powergrid on the mainland by HVDC-link. The purpose of this thesis is to compare the two projects and find out what challenges and strategies they have related to wind power integration. The objective of the two projects were somewhat different. Jeju Smart Grid Test-bedare the starting point for South Korea’s smart grid road map, where the objective ultimately is to construct a smart grid on a national scale in South Korea. For Smart Grid Gotland there are three main focus areas; electricity market, power quality and wind power integration. In this thesis focus is on wind power integration. Wind power integration in smart grids would benefit from energy storage technology connected to the wind power-park to even out the power output. Properties for a potential energy storage connected to Näsudden wind power park situated on the southern tip of Gotland has been investigated and the result is that such an energy storage would likely need to be big and expensive, but able to stabilize the power output.
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Louw, Andre Du Randt. "Discrete and porous computational fluid dynamics modelling of an air-rock bed thermal energy storage system." Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/86233.
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Thesis (MScEng)--Stellenbosch University, 2014.ENGLISH ABSTRACT: Concentrating solar power promises to be a potential solution for meeting the worlds energy needs in the future. One of the key features of this type of renewable energy technology is its ability to store energy effectively and relatively cheaply. An air-rock bed thermal energy storage system promises to be an effective and reasonably inexpensive storage system for concentrating solar power plants. Currently there is no such storage system commercially in operation in any concentrating solar power plant, and further research is required before such a system can be implemented. The main research areas to address are the thermal-mechanical behaviour of rocks, rock bed pressure drop correlations and effective and practical system designs. Recent studies have shown that the pressure drop over a packed bed of rocks is dependant on various aspects such as particle orientation relative to the flow direction, particle shape and surface roughness. The irregularity and unpredictability of the particle shapes make it difficult to formulate a general pressure drop correlation. Typical air-rock bed thermal design concepts consist of a large vertical square or cylindrical vessel in which the bed is contained. Such system designs are simple but susceptible to the ratcheting effect and large pressure drops. Several authors have proposed concepts to over-come these issues, but there remains a need for tools to prove the feasibility of the designs. The purpose of this paper is to investigate aDEM-CFD coupled approach that can aid the development of an air-rock bed thermal energy storage system. This study specifically focuses on the use of CFD. A complementary study focusses on DEM. The two areas of focus in this study are the pressure drop and system design. A discrete CFD simulation model is used to predict pressure drop over packed beds containing spherical and irregular particles. DEM is used to create randomly packed beds containing either spherical or irregularly shaped particles. This model is also used to determine the heat transfer between the fluid and particle surface. A porous CFD model is used to model system design concepts. Pressure drop and heat transfer data predicted by the discrete model, is used in the porous model to describe the pressure drop and thermal behaviour of a TES system. Results from the discrete CFD model shows that it can accurately predict the pressure drop over a packed bed of spheres with an average deviation of roughly 10%fromresults found in literature. The heat transfer between the fluid and particle surface also is accurately predicted, with an average deviation of between 13.36 % and 21.83 % from results found in literature. The discrete CFD model for packed beds containing irregular particles presented problems when generating a mesh for the CFD computational domain. The clump logic method was used to represent rock particles in this study. This method was proven by other studies to accurately model the rock particle and the rock packed bed structure using DEM. However, this technique presented problems when generating the surface mesh. As a result a simplified clump model was used to represent the rock particles. This simplified clump model showed characteristics of a packed bed of rocks in terms of pressure drop and heat transfer. However, the results suggest that the particles failed to represent formdrag. This was attributed to absence of blunt surfaces and sharp edges of the simplified clumpmodel normally found on rock particles. The irregular particles presented in this study proved to be inadequate for modelling universal characteristics of a packed bed of rocks in terms of pressure drop. The porous CFD model was validated against experimental measurement to predict the thermal behaviour of rock beds. The application of the porous model demonstrated that it is a useful design tool for system design concepts.
AFRIKAANSE OPSOMMING: Gekonsentreerde sonkrag beloof om ’n potensiële toekomstige oplossing te wees vir die wêreld se groeiende energie behoeftes. Een van die belangrikste eienskappe van hierdie tipe hernubare energie tegnologie is die vermoë om energie doeltreffend en relatief goedkoop te stoor. ’n Lug-klipbed termiese energie stoorstelsel beloof om ’n doeltreffende en redelik goedkoop stoorstelsel vir gekonsentreerde sonkragstasies te wees . Tans is daar geen sodanige stoorstelsel kommersieël in werking in enige gekonsentreerde sonkragstasie nie. Verdere navorsing is nodig voordat so ’n stelsel in werking gestel kan word. Die belangrikste navorsingsgebiede om aan te spreek is die termies-meganiese gedrag van klippe, klipbed drukverlies korrelasies en effektiewe en praktiese stelsel ontwerpe. Onlangse studies het getoon dat die drukverlies oor ’n gepakte bed van klippe afhanklik is van verskeie aspekte soos partikel oriëntasie tot die vloeirigting, partikel vormen oppervlak grofheid. Die onreëlmatigheid en onvoorspelbaarheid van die klip vorms maak dit moeilik om ’n algemene drukverlies korrelasie te formuleer. Tipiese lug-klipbed termiese ontwerp konsepte bestaan uit ’n groot vertikale vierkantige of silindriese houer waarin die gepakte bed is. Sodanige sisteem ontwerpe is eenvoudig, maar vatbaar vir die palrat effek en groot drukverliese. Verskeie studies het voorgestelde konsepte om hierdie kwessies te oorkom, maar daar is steeds ’n behoefte aanmetodes om die haalbaarheid van die ontwerpe te bewys. Die doel van hierdie studie is om ’n Diskreet Element Modelle (DEM) en numeriese vloeidinamika gekoppelde benadering te ontwikkel wat ’n lug-klipbed termiese energie stoorstelsel kan ondersoek. Hierdie studie fokus spesifiek op die gebruik van numeriese vloeidinamika. ’n Aanvullende studie fokus op DEM. Die twee areas van fokus in hierdie studie is die drukverlies en stelsel ontwerp. ’n Diskrete numeriese vloeidinamika simulasie model word gebruik om drukverlies te voorspel oor gepakte beddens met sferiese en onreëlmatige partikels. DEM word gebruik om lukraak gepakte beddens van óf sferiese óf onreëlmatige partikels te skep. Hierdie model is ook gebruik om die hitte-oordrag tussen die vloeistof en partikel oppervlak te bepaal. ’n Poreuse numeriese vloeidinamika model word gebruik omdie stelsel ontwerp konsepte voor te stel. Drukverlies en hitte-oordrag data, voorspel deur die diskrete model, word gebruik in die poreuse model om die drukverlies- en hittegedrag van ’n TES-stelsel te beskryf. Resultate van die diskrete numeriese vloeidinamikamodel toon dat dit akkuraat die drukverlies oor ’n gepakte bed van sfere kan voorspel met ’n gemiddelde afwyking van ongeveer 10%van die resultatewat in die literatuur aangetref word. Die hitte-oordrag tussen die vloeistof en partikel oppervlak is ook akkuraat voorspel, met ’n gemiddelde afwyking van tussen 13.36%en 21.83%van die resultate wat in die literatuur aangetref word. Die diskrete numeriese vloeidinamika model vir gepakte beddens met onreëlmatige partikels bied probleme wanneer ’n maas vir die numeriese vloeidinamika, numeriese domein gegenereer word. Die "clump"logika metode is gebruik om klip partikels te verteenwoordig in hierdie studie. Hierdiemetode is deur ander studies bewys om akkuraat die klip partikel en die klip gepakte bed-struktuur te modelleer deur die gebruik van DEM. Hierdie tegniek het egter probleme gebied toe die oppervlak maas gegenereer is. As gevolg hiervan is ’n vereenvoudigde "clump"model gebruik om die klip partikels te verteenwoordig. Die vereenvoudigde "clump"model vertoon karakteristieke eienskappe van ’n gepakte bed van klippe in terme van drukverlies en hitte oordrag. Die resultate het egter getoon dat die partikels nie vorm weerstand verteenwoordig nie. Hierdie resultate kan toegeskryf word aan die afwesigheid van gladde oppervlaktes en skerp kante, wat normaalweg op klip partikels gevind word, in die vereenvoudigde "clump"model. Die oneweredige partikels wat in hierdie studie voorgestel word, blykomnie geskik tewees vir die modellering van die universele karakteristieke eienskappe van ’n gepakte bed van klippe in terme van drukverlies nie. Die poreuse numeriese vloeidinamika model is met eksperimentele metings bevestig omdie termiese gedrag van klipbeddens te voorspel. Die toepassing van die poreuse model demonstreer dat dit ’n nuttige ontwerp metode is vir stelsel ontwerp konsepte.
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Link, Werner. "Vom Elend des "offensiven Idealismus" : eine Antwort auf Hellmanns "Traditionslinie" und "Sozialisationsperspektive"." Universität Potsdam, 2004. http://opus.kobv.de/ubp/texte_eingeschraenkt_welttrends/2010/4661/.
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Kohler, Iris. "Graph Theoretical Modelling of Electrical Distribution Grids." DigitalCommons@CalPoly, 2021. https://digitalcommons.calpoly.edu/theses/2301.
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This thesis deals with the applications of graph theory towards the electrical distribution networks that transmit electricity from the generators that produce it and the consumers that use it. Specifically, we establish the substation and bus network as graph theoretical models for this major piece of electrical infrastructure. We also generate substation and bus networks for a wide range of existing data from both synthetic and real grids and show several properties of these graphs, such as density, degeneracy, and planarity. We also motivate future research into the definition of a graph family containing bus and substation networks and the classification of that family as having polynomial expansion.
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Barton, Julie Anastasia. "From The bad beginning to an elusive End : knowledge and power in Lemony Snicket's A series of unfortunate events." Thesis, University of East Anglia, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.580565.
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My thesis analyzes A Series of Unfortunate Events by Lemony Snicket (pseudonym of Daniel Handler), a popular children's book series published between 1999 and 2006. I argue that this series challenges and ultimately subverts the traditional hierarchical power relations evident in the dynamic between the adult author and the child reader. As Maria Nikolajeva argues, "nowhere else are power structures as visible as in children's literature, the refined instrument used for centuries to educate, socialize and oppress a particular social group" (2010, 9). The power play between adults and children, between authors and readers, can be seen as an essential defining characteristic of children's literature, and my thesis asserts that this power play is often enacted in terms of knowledge. I argue that this bestselling thirteen-book series provides a distinctive approach to the role of offering knowledge to a child reader, as Daniel Handler ultimately transcends the typical power hierarchy where an adult must' give' or 'grant' knowledge (of any kind) to a child reader. Instead, he uses what I have termed "metateaching" to teach the child reader how to teach herself, thereby dispensing with the need for an adult authority figure. I begin by examining Handler's use of traditional narratological tropes before moving on to the numerous ways in which he subverts them. Handler utilizes a complex form when writing A Series of Unfortunate Events, invoking strategies allied to postmodernism, such as metafictionality and intertextuality, and he complicates the conventional children's literature reader/author relationship by introducing a didactic yet ultimately unreliable narrator in Lemony Snicket.
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Persarvet, Gustav. "Evaluation of Finite Element Method Based Software for Simulation of Hydropower Generator - Power Grid Interaction." Thesis, Uppsala universitet, Elektricitetslära, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-162659.
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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.
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Mazzoli, Andrea. "TCAD analysis of hot-carrier-stress degradation in p-channel LDMOS power devices." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
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Nowadays, there is an increasing need to develop, reliable and low-cost power devices able to withstand high voltage drops and currents during the off-state and on-state operation, respectively. A useful strategy is represented by the integration on-chip of power devices with CMOS logic and analog technologies. This kind of solution is named BCD (BIPOLAR-CMOS-DMOS) technology.
One of the fundamental power device on which the BCD technology is based is the LDMOS (Laterally-Diffused Metal-Oxide Semiconductor) transistor. The study and understanding of the degradation mechanisms affecting their long-term reliability is of great interest because of the stringent requirements in terms of safety, robustness, etc., basing on the field of application of the circuit in which the devices are integrated.
This work, in collaboration with STMicroelectronics, focuses on the optimization of the p-channel LDMOS transistors and aims at studying and understanding how the Hot Carrier Stress (HCS) degradation impacts their performance for long working times. The behavior of the device is simulated through the Sentaurus TCAD where a HCS degradation model is employed to understand which are the dominant effects of the hot particles within the semiconductor, applying stress conditions aimed at accelerating the degradation mechanisms causing the drift of key parameters.
In this work the focus is on the on-resistance, since it results to be the main parameter affected by degradation. The goal is to understand exactly which is the main cause of such variation in order to be able to allow a technology improvement. The simulations have been calibrated against experimental data.
The on-resistance curve are correctly calibrated under certain stress conditions. The goal of the thesis activity has been achieved with accurate results, bringing to a more detailed description of a p-channel LDMOS power device through the development of a first version of the predictive simulation tool.
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Hsu, Edward Hsuan-Wei. "ELECTRIFICATION OF THE SWEDISH VEHICLE FLEET: CHARGING DEMAND AND THE POWER SYSTEM." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-448286.
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With the transport sector switching to electric energy to reduce greenhouse gas emission, the supply and demand in the energy system are impacted by this transition. Meanwhile, there are not a lot of studies focus on the electrification of the vehicle fleet in Sweden. To fill up the knowledge gap, the paper aims to identify the total required electrical energy and power for the electrification of the vehicle fleet in Sweden. This includes switching passenger vehicles, light and heavy trucks, and buses to battery electric vehicles. An Electric Vehicle Power Demand Model is designed to answer the research question. It is a simplified model that can calculate energy consumption and power demand from an electric vehicle fleet. To simulate the charging schedule, four scenarios are created with differences in charge speed and the use of smart or unregulated charging. Based on the model, the electric vehicle fleet consumes 20.4 TWh of electricity per year, accounting for 14.7% of total demand in Sweden. Combing the vehicle fleet with other energy services, an average hourly peak load of 16.2 GW in summer and 24.3 in winter can be seen, while the available capacity in Sweden is around 27.1. The result indicates that the current Swedish energy system is capable of handling demand from charging the electric vehicle fleet in terms of power capacity for most times. However, undersupply may happen in some extreme condition during the winter due to higher consumption from other energy services. Furthermore, with the increasing share of renewable power in the system, the availability of these power plants can have a direct impact on the supply. This requires smart charging to shift the charging events to prevent peak hours, which can potentially decrease the peak loads up to 2 GW in EV charging demand during peak hours. However, the actual effect of it still requires more study. Lastly, the model created for the research can be used as a research or decision-making tool to estimate the impact of a group of electric vehicles in the future, therefore, contribute to the development of the sustainable energy transition.
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Bayham, Samuel C. "Iron-Based Coal Direct Chemical Looping Process for Power Generation: Experimental Aspects, Process Development, and Considerations for Commercial Scale." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1425759077.
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