This dissertation describes the development of a high-power, plastic-based, thick-film lithium-ion microbattery for use in a hybrid micropower system for autonomous microsensors. A composite porous electrode structure and a liquid state electrolyte were implemented in the microbatteries to achieve the high power capability and energy density. The use of single-walled carbon nanotubes (SWNTs) was found to significantly reduce the measured resistance of the cathodes that use LiAl0.14Mn1.86O4 as active materials, increase active material accessibility, and improve the cycling and power performance without the need of compression. Optimized uncompressed macro cathodes were capable of delivering power densities greater than 50 mW/cm2, adequate to meet the peak power needs of the targeted microsystems. The anodes used mesocarbon microbeads (MCMB) with multi-walled carbon nanotubes (MWNTs) and had significantly better power performance than the cathodes. The thick-film microbattery was successfully fabricated using techniques compatible with microelectronic fabrication processes. A Cyclic Olefin Copolymer (COC)-film was used as both the substrate and primary sealing materials, and patterned metal foils were used as the current collectors. A liquid-state electrolyte and Celgard separator films were used in the microbatteries. These microbatteries had electrode areas of c.a. 2 mm x 2 mm, and nominal capacities of 0.025-0.04 mAh/cell (0.63-1.0 mAh/cm2, corresponding to an energy density of ~6.3-10.1 J/cm2). These COC-based batteries were able to deliver constant currents up to 20 mA/cm2 (100% depth of discharge, corresponding to a power density of 56 mW/cm2 at 2.8 V) and pulse currents up to 40 mA/cm2 (corresponding to a power density of 110 mW/cm2). The high power capability, small size, and high energy density of these batteries should make them suitable for the hybrid micropower systems; and the flexible plastic substrate is also likely to afford some unique integration possibilities for autonomous microsystems. The mechanism by which the SWNTs improved the rate performance of composite cathodes was studied both experimentally and theoretically. It was concluded that the use of SWNT improved cathode performance by improving the electronic contacts to active material particles, which consequently improved the accessibility of these particles and improved the rate capability of the composite cathodes.

Kuba har i dagsläget ett högt beroende av importerad olja, för att tillgodose sin växande efterfrågan på elektricitet. Importen sker främst från Venezuela. Detta beroende gör Kuba känsligt för ändringar i oljepriser samt det politiska klimatet. Den nuvarande krisen i Venezuela har haft en betydande inverkan på Kubas elproduktion. Genom att utöka landets förnybara energikällor kan Kuba minska sitt beroende av andra länder och diversifiera sin energiförsörjning. Detta kommer även att leda till en positiv miljöpåverkan då landets CO 2-utsläpp minskar. Kubas geografiska läge har ideala förhållanden för förnyelsebar energigenerering, så som solkraft. Solkraft utvecklas konstant och innehåller en hög potential. Concentrating Solar Power (CSP) är en teknologi där speglar och/eller linser används för att koncentrera solljus till en liten yta som konverterar solljuset till värme. Denna värme kan sedan användas i termodynamiska cykler. Det finns två huvudsakliga problem med implementering av CSP på Kuba. För det första är CSP beroende av momentana väderförhållanden, vilket leder till en oregelbunden elproduktion. För det andra har CSP höga investeringskostnader. För att adressera dessa problem, är det möjligt att implementera CSP i ett redan existerande kraftverk med regelbunden energikälla, d.v.s. skapa ett hybridkraftverk. På så vis uppnås regelbunden elproduktion med signifikant lägre investeringskostnad. Ett sådant existerande kraftverk kan hittas hos många av Kubas sockerbruk. Den här studien undersöker möjligheten att implementera solkraft i sockerbruket Carlos Baliño, beläget i Villa Clara, Kuba. Fabriken är självförsörjande av elektricitet på årlig basis. De använder en Rankine-cykel för att generera el och processvärme som används i sockerframställningen. Bränslet som används är bagasse, en restprodukt efter att sockerjuicen pressats ut ur sockerrören. Fyra CSP-teknologier och tre implementeringslayouts undersöktes, vilket resulterade i att parabolic trough-teknologin och förvärmning av vatten ansågs vara de bästa alternativen för Kuba och Carlos Baliño. Vidare undersöktes två olika scenarier för CSP. Scenario 1 innefattar implementering av CSP i sockerbruket under rådande skick och Scenario 2 består av implementering av CSP efter en investering gjorts i en Condensing Extraction turbin (CEST). Resultatet visar att Carlos Baliño bör investera i CEST innan de implementerar CSP, det vill säga Scenario 2. Detta beror på att i scenario 1 är det inte möjligt att generera elektricitet utanför sockersäsongen, vilket leder till att en stor del av solpotentialen inte kan utnyttjas. Den maximala investeringskostnaden för scenario 1 är 3,7 MUSD, vilket inte är en realistisk kostnad. Den maximala investeringskostnaden för scenario 2 beror av tillgänglig bagasseimport och är 5,9 – 7,2 MUSD. Att investera i CSP rekommenderas ej om bagasseimporten är obegränsad. Givet att bagasseimporten är begränsad skulle CSP-implementeringen leda till en utökad elproduktion av 5,4 – 7,2 GWh/år, en årlig minskning av oljeanvändandet med 16 100 – 21 800 tunnor och minskade CO2-utsläpp med 12 00-16 00 ton årligen. Carlos Baliños ekonomiska resultat skulle öka med 0,5 MUSD/år och den kubanska statens med 0,7 – 0,9 MUSD/år. Framtida studier rekommenderas undersöka möjligheten till generering av el året runt vid Carlos Baliño utan en CEST, solkraftsefterfrågan på nationell nivå och potentiella utvecklingar av solkraft hos Carlos Baliño. / Cuba is currently highly dependent on imported oil, mainly from Venezuela, to meet their growing electricity demand. This dependence makes Cuba sensitive to changes in oil price as well as the political climate. The current crisis in Venezuela has a large impact on Cuba’s electricity generation. By expanding its renewable energy sources Cuba could decrease their dependence on other countries and diversify their energy supply. Moreover, it would have a positive climate impact by reducing the country’s CO2-emissions. Geographically, Cuba has ideal conditions for renewable energy utilization, such as solar power. Solar energy is constantly progressing and is considered a great source of energy. Concentrating Solar Power (CSP) is a technology which applies mirrors and/or lenses to concentrate the sunlight onto a small area which converts the sunlight into heat, possible to use in a thermodynamic cycle. There are mainly two problems with the implementation of CSP in Cuba. Firstly, CSP is a non-dispatchable power generating system since it is dependent on the instantaneous weather conditions. Secondly, it has high investment costs. One way of solving these problems is by implementation CSP in an already existing power plants with a dispatchable source of energy, making it a hybrid power plant. Accordingly, the hybrid power plant would be dispatchable and the investment costs would be significantly lower. Existing power plants can be found in Cuban sugar mills. This study investigates the possibility to implement solar power in the sugar mill Carlos Baliño, located in Villa Clara, Cuba. The factory is currently self-sufficient electricity wise on a yearly basis, using a co-generation Rankine cycle to generate electricity and process heat used in the sugar production. The fuel used is bagasse, a rest product obtained after the sugar juice has been pressed out of the sugar canes. Four CSP-technologies and three implementation layouts were examined, resulting in the parabolic trough-technology and feedwater heating being considered the optimal solution. Furthermore, two different scenarios for CSP was investigated; implementation of CSP in the mill at the current state (scenario 1) or after investing in a Condensing-Extraction Turbine (CEST) (scenario 2). The results show that Carlos Baliño should invest in a CEST before considering implementation of CSP. Off-season operation is not available for scenario 1, leading to a vast amount of solar potential being unexploited. The maximal investment allowed for scenario 1 is 3.7 MUSD, which is not a realistic number. The maximal investment allowed for in scenario 2 is 5.9 – 7.2 MUSD, depending on bagasse import availability. If bagasse import is unlimited, it is not recommended to invest in solar power. Implementation of CSP in scenario 2 regarding bagasse import limits would yearly lead to an additional electricity generation at Carlos Baliño of 5.4 – 7.3 GWh, decrease the oil usage with 16,100 – 21,800 barrels and the CO2-emissons with 1,200 – 1,600 tonnes. Carlos Baliño’s annual yield would increase with 0.5 – 0.6 MUSD/year and the Cuban states annual yield would increase with 0.7 – 0.9 MUSD/year. Future work is recommended to explore alternatives to all year-around electricity generation in Carlos Baliño without investing in a CEST, investigate solar power demand on a national level, and examine possible developments of the suggested solar field, for instance solar-only operation.

This thesis describes the creation of a small-scale Hybrid Power System (HPS) that maximizes energy from a wind turbine and photovoltaic array. Small-scale HPS are becoming an increasingly viable energy solution as fossil fuel prices rise and more electricity is needed in remote areas. Modern HPS typically employ wind speed sensors and three power stages to extract maximum power. Modern systems also use passive rectifiers to convert AC from the wind turbine to DC that is usable by power electronics. This passive system inefficiently wastes power and introduces damaging harmonic noise to the wind turbine. The HPS described in this thesis does not require external wind speed sensors, and has independent wind and solar Maximum Power Point Tracking (MPPT). It converts AC from the wind turbine to DC with a Vienna rectifier that can be controlled to improve efficiency, allow MPPT, and allow Power Factor Correction (PFC). PFC all but eliminates the harmonic noise that can damage the wind turbine. A prototype HPS was built and evaluated that combines the two renewable sources in such a way that only two power stages are necessary, the Vienna rectifier and a step-down converter. This thesis describes the prototype and reports the results obtained.

No description available.

付記する学位プログラム名: 京都大学卓越大学院プログラム「先端光・電子デバイス創成学」 / 京都大学 / 新制・課程博士 / 博士(工学) / 甲第24620号 / 工博第5126号 / 新制||工||1980(附属図書館) / 京都大学大学院工学研究科電気工学専攻 / (主査)教授 土居 伸二, 教授 小嶋 浩嗣, 准教授 薄 良彦, 教授 引原 隆士 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Efficiency is a driving constraint for electrical power systems as global energy demands are ever increasing. Followed by the introduction of diesel generators, electricity has become available in more locations than ever. However, operating a diesel generator on its own is not the most energy efficient. This is because the high crest factor loads, of many applications, decrease the fuel efficiency of a hydrocarbon generator. To understand this, we need to understand how an electrical load affects a generator. Starting with a load profile, a system designer must choose a generator to meet peak demand, marking the first instance where a load profile has influence over a generator. This decision will insure that brownouts do not occur, but, this will lead to poor energy efficiency. We say this because a generator is most energy efficient under heavier loads, meaning, during lighter loads, more fuel will be consumed to produce the same amount of energy. While this may be fine if the peak load was close to the average load, however, the actual crest factor for a typical residential load profile is much higher. This gap between peak and average load means that a generator will spend most of its time operating at its most inefficient point. To compensate for this, and reduce fuel consumption, the Mechatronics Lab at Virginia Tech has developed a mobile hybrid power system (MHPS) to address this problem. The solution was to augment a diesel generator with a battery pack. This allowed us to constrain the generator so that it only operates with fixed efficiency. It is the theory behind this system that will be covered in this thesis. / Master of Science

Diesel engine and generator sets (gensets) have been extensively used for standby and remote power generation over the past hundred years. Due to their use for standby power, these diesel gensets are designed to operate in conjunction with the grid, which relates to a fixed speed operation with a 60 Hz AC output. For operation in remote conditions, such as military and disaster relief applications, this fixed speed operation results in limiting the power output available from the engine, as well as the overall efficiency of the system. The removal of this grid connectivity requirement could result in an increase in system efficiency. At a given load, the engine operates more efficiently at lower speeds, which corresponds to an increase in the system efficiency. This low speed operation also results in lower power output. Knowledge of the load is important in order to determine the most efficient operating point for fixed speed operations. Operating at a higher power output for a given speed also results in higher system efficiency. The addition of a battery pack will allow for a higher apparent load, resulting in higher operating efficiency. The addition of a battery pack will also allow for energy storage, which allows for a higher operating efficiency, as well as "engine off time". A controlled series capacitor converter should be used to ensure that the maximum power is transferred from the genset to the battery/load. Knowledge of the load and equipment available should be used in order to determine the ideal dispatch strategy. Overall, operation at the grid frequency limits the efficiency of the overall system for remote operations where grid frequency is not required. The simulated genset had an efficiency of 24% for a 3 kW when operated at 1800 RPM, and increase from the 17% efficiency at it normal operating speed of 3600 RPM. This corresponded to a fuel savings of 3 gallons over 24 hours of continuous operation. When a battery is incorporated into the system, the efficiency of the system will increase for a given output load. For example, the simulated genset has an efficiency of 15% for a 1 kW load, which increases to 24% when a battery is added and charged at 2 kW. / Master of Science

Thesis (D. Tech. (Electrical Engineering)) -- Central University of Technology, Free State, 2014 / For a sustainable and clean electricity production in isolated rural areas, renewable energies appear to be the most suitable and usable supply options. Apart from all being renewable and sustainable, each of the renewable energy sources has its specific characteristics and advantages that make it well suited for specific applications and locations. Solar photovoltaic and wind turbines are well established and are currently the mostly used renewable energy sources for electricity generation in small-scale rural applications. However, for areas in which adequate water resources are available, micro-hydro is the best supply option compared to other renewable resources in terms of cost of energy produced. Apart from being capital-cost-intensive, the other main disadvantages of the renewable energy technologies are their resource-dependent output powers and their strong reliance on weather and climatic conditions. Therefore, they cannot continuously match the fluctuating load energy requirements each and every time. Standalone diesel generators, on the other hand, have low initial capital costs and can generate electricity on demand, but their operation and maintenance costs are very high, especially when they run at partial loads. In order for the renewable sources to respond reliably to the load energy requirements, they can be combined in a hybrid energy system with back-up diesel generator and energy storage systems. The most important feature of such a hybrid system is to generate energy at any time by optimally using all available energy sources. The fact that the renewable resources available at a given site are a function of the season of the year implies that the fraction of the energy provided to the load is not constant. This means that for hybrid systems comprising diesel generator, renewable sources and battery storage in their architecture, the renewable energy fraction and the energy storage capacity are projected to have a significant impact on the diesel generator fuel consumption, depending on the complex interaction between the daily variation of renewable resources and the non-linear load demand. V This was the context on which this research was based, aiming to develop a tool to minimize the daily operation costs of standalone hybrid systems. However, the complexity of this problem is of an extremely high mathematical degree due to the non-linearity of the load demand as well as the non-linearity of the renewable resources profiles. Unlike the algorithms already developed, the objective was to develop a tool that could minimize the diesel generator control variables while maximizing the hydro, wind, solar and battery control variables resulting in saving fuel and operation costs. An innovative and powerful optimization model was then developed capable of efficiently dealing with these types of problems. The hybrid system optimal operation control model has been simulated using fmincon interior-point in MATLAB. Using realistic and actual data for several case studies, the developed model has been successfully used to analyse the complex interaction between the daily non-linear load, the non-linear renewable resources as well as the battery dynamic, and their impact on the hybrid system’s daily operation cost minimization. The model developed, as well as the solver and algorithm used in this work, have low computational requirements for achieving results within a reasonable time, therefore this can be seen as a faster and more accurate optimization tool.

This thesis is a study on integration of photovoltaic generators into an existing diesel-unreliable grid connected system at the Lebanese village of Khiam. The main goal of implementing PV-diesel hybrid system is to reduce diesel consumption and the import of fossil fuel used in electricity power supply. Before designing the system, it is necessary to create a load profile for 120 households and pre-design the size of the PV generator, the capacity of storage system and inverter type/size selection. The load profile data is based on the average of monthly energy consumption gathered from Khiam village households. Detailed simulations and financial analysis are performed with HOMER to compare different systems and their viability. The simulations include four different designs starting from the existing system, diesel generator with unreliable grid, followed by PV generator and unreliable grid, PV and diesel generator and ended with the complete hybrid system. Once the Hybrid system is determined a detailed design is done to optimize the lowest cost PV-diesel hybrid system. The final simulated PV-diesel hybrid system is suggested with a PV capacity of 270 kWp, existing diesel capacity with 200 kVA, an inverter output of 115 kW and battery bank nominal capacity is 1872 kWh. The system renewable fraction is 53% and the project life cycle is 25 years. The PV-diesel hybrid system is projected to produce electricity at a cost of 0.12 USD/kWh. This cost is significantly lower than the 0.26 USD/kWh paid to the diesel operator, as well as lower than 0.13 USD/kWh paid to the utility grid. In addition, and according to the given information from the owner, an estimated diesel consumption of 104000 ltr/year, the simulation result shows diesel consumption at 40000 ltr/year. The reduced carbon dioxide production by 65%, from 776 to 272 tons per year, provides further justification for the PV installation in a commercial PV-diesel hybrid system.

Orientador: José Luz Silveira / Resumo: Nesse trabalho são apresentadas propostas de sistemas híbridos de geração de energia (SHGE) para o fornecimento de energia elétrica. O Caso 1 propõe um SHGE conectado à rede elétrica (on-grid) para atender a demanda elétrica de edifícios urbanos. O Caso 2 propõe um SHGE aplicado a áreas rurais com disponibilidade de rede elétrica local. O Caso 3 considera uma propriedade rural sem rede elétrica local, portanto propõe-se um SHGE com armazenamento de energia (off-grid). Os três casos são analisados em termos técnicos, econômicos e ambientais para três cidades brasileiras: Fortaleza (CE), Guaratinguetá (SP) e Florianópolis (SC). Para o dimensionamento do SHGE, desenvolve-se um algoritmo de otimização cuja função objetivo é a minimização do custo de geração de energia elétrica. Utiliza-se o software LINGO para a determinação da solução ótima do arranjo SHGE para cada caso. A análise econômica leva em consideração os custos de investimento, operação e manutenção para determinação do período de retorno (payback) e da receita anual esperada. A análise ambiental é feita através do cálculo da eficiência ecológica dos sistemas de geração de energia estudados. Os resultados mostram que o Caso 2 – SHGE on-grid: Propriedade Rural possui o menor período de retorno de investimento, entre 1 e 2 anos. Para todos os casos, a cidade de Fortaleza é onde evidencia-se o menor custo de investimento dos SHGE e, consequentemente, menor custo de geração de eletricidade dada seus elevados potenciais en... (Resumo completo, clicar acesso eletrônico abaixo) / Mestre