Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Physics, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Vita. / Includes bibliographical references. / by Paolo Rava. / Ph.D.

No description available.

Este trabalho tem como objetivo avaliar a viabilidade da aplicação de técnicas de otimização robusta (OR) no planejamento da operação de reservatórios para geração de energia hidrelétrica. A OR é uma técnica de otimização que visa encontrar resultados que sejam menos sensíveis às incertezas nas variáveis do modelo através da minimização da variância da função objetivo para diferentes cenários. Desta forma foi desenvolvido um modelo de otimização robusta aplicado à operação de reservatórios para a geração de energia hidrelétrica, chamado HIDRO-OR, utilizando o software General Algebraic Modeling System (GAMS). Para estudo de caso foram utilizados os dados da UHE Sinop, a ser instalada no rio Teles Pires MT. Inicialmente foi realizada uma análise de sensibilidade utilizando diferentes combinações dos coeficientes de ponderação da função objetivo e três conjuntos de cenários. Nesta abordagem, o modelo resultou em vertimentos indesejados para realizar a diminuição do desvio padrão dos resultados entre os diferentes cenários. Uma solução encontrada para o problema foi realizar a otimização em duas etapas. Na primeira etapa ocorre a otimização robusta propriamente dita e são fixados os resultados para o primeiro mês de operação. Na segunda etapa, apenas a função objetivo principal é otimizada e, assim, são corrigidos os vertimentos indesejados. No entanto, com a otimização em duas etapas, não ocorreram mudanças na operação do reservatório para os diferentes coeficientes de ponderação. Ao final do trabalho conclui-se que, apesar dos resultados da análise de sensibilidade terem sido praticamente iguais com a otimização em duas etapas, estes podem ser considerados robustos pois são factíveis para todos os cenários. Por fim, são realizadas sugestões para a continuidade das pesquisas utilizando as técnicas de OR para a operação de usinas hidrelétricas. / This work aims to evaluate the feasibility of robust optimization techniques (OR) for reservoir management for hydropower production. The OR is an optimization technique which aims to find results that are less sensitive to the randomness of variables in the model by minimizing the variance of the objective function for different scenarios. One OR model was developed to the operation of reservoirs for hydropower production, called HYDRO-OR, using the software General Algebraic Modeling System (GAMS). As study case, data from the Sinop hydropower plant were used, which will be constructed in the Teles Pires river - MT. First, a sensitivity analysis was performed using different combinations of weigh coefficients of the objective function with three sets of scenarios. Preliminary results in this approach showed that the model resulted in unwanted spills to force the reduction of the standard deviation of the results from different scenarios. To correct this, the model was reconfigured to perform the optimization in two stages, the first one being the OR itself in which the results were obtained for the first month of planning. In the second step, the model was optimized again for subsequent months. In this case the model corrected the unnecessary spills but the results were quite similar for the three combinations of the weight coefficients. However the results can be considered robust because it is feasible for all scenarios. Finally, suggestions are made for further studies using the techniques of OR for the operation of hydropower plants.

Commercial Buildings and complexes are no longer just national heat and power network energy loads, but they are becoming part of a smarter grid by including their own dedicated local heat and power generation. They do this by utilising both heat and power networks/micro-grids. A building integrated approach of Combined Heat and Power (CHP) generation with photovoltaic power generation (PV) abbreviated as CHPV is emerging as a complementary energy supply solution to conventional (i.e. national grid based) gas and electricity grid supplies in the design of sustainable commercial buildings and communities. The merits for the building user/owner of this approach are: to reduce life time energy running costs; reduce carbon emissions to contribute to UK’s 2020/2030 climate change targets; and provide a more flexible and controllable local energy system to act as a dynamic supply and/or load to the central grid infrastructure. The energy efficiency and carbon dioxide (CO2) reductions achievable by CHP systems are well documented. The merits claimed by these solutions are predicated on the ability of these systems being able to satisfy: perfect matching of heat and power supply and demand; ability at all times to maintain high quality power supply; and to be able to operate with these constraints in a highly dynamic and unpredictable heat and power demand situation. Any circumstance resulting in failure to guarantee power quality or matching of supply and demand will result in a degradation of the achievable energy efficiency and CO2 reduction. CHP based local energy systems cannot rely on large scale diversity of demand to create a relatively easy approach to supply and demand matching (i.e. as in the case of large centralised power grid infrastructures). The diversity of demand in a local energy system is both much greater than the centralised system and is also specific to the local system. It is therefore essential that these systems have robust and high performance control systems to ensure supply and demand matching and high power quality can be achieved at all times. Ideally this same control system should be able to make best use of local energy system energy storage to enable it to be used as a flexible, highly responsive energy supply and/or demand for the centralised infrastructure. In this thesis, a comprehensive literature survey has identified that there is no scientific and rigorous method to assess the controllability or the design of control systems for these local energy systems. Thus, the main challenge of the work described in this thesis is that of a controller design method and modelling approach for CHP based local energy systems. Specifically, the main research challenge for the controller design and modelling methodology was to provide an accurate and stable system performance to deliver a reliable tracking of power drawn/supplied to the centralised infrastructure whilst tracking the require thermal comfort in the local energy systems buildings. In the thesis, the CHPV system has been used as a case study. A CHPV based solution provides all the benefits of CHP combined with the near zero carbon building/local network integrated PV power generation. CHPV needs to be designed to provide energy for the local buildings’ heating, dynamic ventilating system and air-conditioning (HVAC) facilities as well as all electrical power demands. The thesis also presents in addition to the controller design and modelling methodology a novel CHPV system design topology for robust, reliable and high-performance control of building temperatures and energy supply from the local energy system. The advanced control system solution aims to achieve desired building temperatures using thermostatic control whilst simultaneously tracking a specified national grid power demand profile. The theory is innovative as it provides a stability criterion as well as guarantees to track a specified dynamic grid connection demand profile. This research also presents: design a dynamic MATLAB simulation model for a 5-building zone commercial building to show the efficacy of the novel control strategy in terms of: delivering accurate thermal comfort and power supply; reducing the amount of CO2 emissions by the entire energy system; reducing running costs verses national rid/conventional approaches. The model was developed by inspecting the functional needs of 3 local energy system case studies which are also described in the thesis. The CHPV system is combined with supplementary gas boiler for additional heating to guarantee simultaneous tracking of all the zones thermal comfort requirements whilst simultaneously tracking a specified national grid power demand using a Photovoltaics array to supply the system with renewable energy to reduce amount of CO2 emission. The local energy system in this research can operate in any of three modes (Exporting, Importing, Island). The emphasise of the thesis modelling method has been verified to be applicable to a wide range of case studies described in the thesis chapter 3. This modelling framework is the platform for creating a generic controlled design methodology that can be applied to all these case studies and beyond, including Local Energy System (LES) in hotter climates that require a cooling network using absorption chillers. In the thesis in chapter 4 this controller design methodology using the modelling framework is applied to just one case study of Copperas Hill. Local energy systems face two types of challenges: technical and nontechnical (such as energy economics and legislation). This thesis concentrates solely on the main technical challenges of a local energy system that has been identified as a gap in knowledge in the literature survey. The gap identified is the need for a controller design methodology to allow high performance and safe integration of the local energy system with the national grid infrastructure and locally installed renewables. This integration requires the system to be able to operate at high performance and safely in all different modes of operation and manage effectively the multi-vector energy supply system (e.g. simultaneous supply of heat and power from a single system).

<p>The Renewable Energies play a rather small role so far in the overall mixture for power generation, but they increasingly gain in importance. Nevertheless an independent marketability is not given yet. To reach the development goals which are requested by the European Commission, a monetary sponsorship at the expense of electricity consumers is required. Can this governmental interference be justified? Which problems arise with the subvention?</p>

No description available.

The Renewable Energies play a rather small role so far in the overall mixture for power generation, but they increasingly gain in importance. Nevertheless an independent marketability is not given yet. To reach the development goals which are requested by the European Commission, a monetary sponsorship at the expense of electricity consumers is required. Can this governmental interference be justified? Which problems arise with the subvention?

No Abstract Available

To improve photovoltaic system efficiencies, concentrating spectral dividers are used to separate solar light, and to focus each spectral portion onto photovoltaic cells of matching spectral response. In this investigation, an optical analysis is developed to study the feasibility for use of a Fresnel half-lens as a concentrating spectral divider. To facilitate the analysis, an existing curved-base linear Fresnel lens ray-trace model has been modified and expanded. Solar limb-darkening has been incorporated into the theory by means of a digitized sun model. The lens model allows for variation of lens geometrical characteristics. Transmission losses due to Fresnel reflection and bulk absorption are taken into account. The distribution of the concentrated solar flux in the lens image plane is modeled such that spectral regions may be examined separately. Concentration ratio profiles are used to derive and evaluate a quantity of spectral separation.A computer program has been used to generate data, based on the theoretical model, for example lenses. The spectral separation, transmission and concentration properties for each example lens have been systematically studied with respect to lens geometry. The effects of solar limb-darkening are determined by comparison with the data from a model that assumes a uniform solar source. Results of the study are discussed in detail.Ball State UniversityMuncie, IN 47306

In response to the global climate change and environmental protection needs, more and more nations take renewable energies as one of the major future energy policies for its characteristics of clean, low greenhouse gas emission and self-productivity. Among Taiwan¡¦s many renewable energy development, wind energy is always on the list. Wind energy will not only avoid the problems of carbon dioxide which cause greenhouse effect, but also refrain pollution caused by fossil fuel or nuclear energy. The induction generator is a fundamental component of a wind machine. It¡¦s electric port and control can be classified into single fed control and double fed control. Through various comparisons of control and operation, double fed control seems to be more stable at present. Double fed induction generator may continuously produce power at island state without the supply of reactive power from parallel capacitor or the synchronous generator. which is the biggest advantage than single fed induction. , In other words, double fed induction generator may supply power independently. The induction generator is a time-varying and non-linear component. So the traditional rule of scalar control is not adopted in the thesis. The induction generator can be linearized by using vector control, and the power flow can also be directed with the control of its composition of rotor current vector and the controller is designed under the above methodology. The thesis aims to simulate, analyze and compare the steady and transient states of single fed and double fed wind generators with the purposes a more through understanding of the controller and its operation.