We all take for granted that if we press the switch, the lights turn on; that to charge our phone we just need to plug-in the charger and that food is always safely stored in our fridge. but what would happen in the event of a blackout? are we really conscious of how much we rely on electricity? could we survive without it, even for a few days?The current electricity network is strongly centralised, with electricity generated in large power plants and distributed through transmission networks to the final consumers. With increasing energy demand and renewable energies entering the scene, centralised systems have proven to be very stiff: lacking the flexibility to adapt to sudden demand fluctuations and being unable to deal with strong peaks, with the consequent risk of blackouts.Small, decentralised energy systems can be placed closed to the consumers, avoiding distribution losses and adding flexibility to the network. In particular, small cogeneration units can simultaneously generate heat and electricity; thus, also fulfilling our heating requirements and increasing energy efficiency. However, when there is no or little heat demand (e.g. during the summer), the heat produced by the cogeneration engines cannot be utilised and they need to be shut down. This is the reason why small-scale cogeneration cycles are rarely seen and have not been widely adopted yet.This PhD focuses on the injection of water in a specific small-scale cogeneration technology, the micro gas turbine (mGT) cycle. Thanks to water injection, the production of heat and electricity is decoupled; therefore, the operation of the units is not anymore dependant on the heating demand and they can be used any time during the year. The objective of this thesis is to analyse the numerical, experimental and economic aspects of the so-known micro Humid Air Turbine cycle. The aim is to bring mGTs closer to the market so as to contribute to a more secure, future energy network, where blackouts are avoided at all times. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished

Submitted by BENJAMIN KUNTE null (benjamin.kunte@gmail.com) on 2015-12-21T20:22:35Z No. of bitstreams: 1 Benjamin_Dissertation_Final_Version.pdf: 2440898 bytes, checksum: 129503961064a9371fbb24f9408bfbc6 (MD5) / Approved for entry into archive by Cássia Adriana de Sant ana Gatti (cgatti@marilia.unesp.br) on 2015-12-22T13:12:11Z (GMT) No. of bitstreams: 1 Benjamin_Dissertation_Final_Version.pdf: 2440898 bytes, checksum: 129503961064a9371fbb24f9408bfbc6 (MD5) / Made available in DSpace on 2015-12-22T13:12:11Z (GMT). No. of bitstreams: 1 Benjamin_Dissertation_Final_Version.pdf: 2440898 bytes, checksum: 129503961064a9371fbb24f9408bfbc6 (MD5) Previous issue date: 2015-12-18 / Os métodos mais promissores para reduzir gases de efeito estufa, bem como combater o iminente esgotamento das reservas de energia fóssil, são: a) o uso de combustíveis alternativos obtidos a partir da biomassa, como o biogás ou gás de síntese (syngas); b) o aumento da eficiência do sistema através da redução da percentagem de energia útil perdido para o ambiente. Enquanto a otimização da eficiência de uma determinada máquina da central elétrica, por exemplo, turbina a gás ou compressor, é um desenvolvimento muito demorado, a cogeração pode rápida e significativamente aumentar a eficiência global da central. Neste trabalho, análise termodinâmica, econômica e de emissões de um sistema de cogeração baseado em uma microturbina a gás de 200 kW combinado com uma caldeira de recuperação são conduzidas. Além disso, a operação de biogás e syngas é comparada com a operação de gás natural para investigar a pertinência destes dois combustíveis alternativos para o uso em micro turbinas a gás. A central de cogeração proposta mostrou-se tecnicamente viável para todos os combustíveis, porque a microturbina selecionada é disponível em várias versões, específicas para cada combustível, com sistemas de injeção de combustível otimizados. A central apresentou eficiências energéticas globais de 50,9%, 48,6% e 47,9% para operação com gás natural, biogás e syngas, respectivamente. Devido aos preços muito elevados do gás natural e do syngas, a central de cogeração apresentou viabilidade econômica apenas no caso de operação com biogás, com curtos períodos de retorno de aproximadamente 2,8 anos e alta economia anual esperada. Além disso, o biogás tem a maior eficiência ecológica e, portanto, apresentou-se como a melhor alternativa aos combustíveis fósseis. / The most promising methods to reduce greenhouse gases as well as counteract against the imminent depletion of fossil fuels are: a) the use of alternative fuels obtained from biomass, such as biogas or bio-syngas; b) enhancing the power plant efficiency by decreasing the percentage of useful energy lost to the environment. Whereas efficiency optimisation of a particular machine in a power plant, e.g. gas turbine or compressor, is a very longsome development, cogeneration can quickly and significantly increase the overall efficiency of a power plant. In this work, energetic, exergetic, emissions and economic analyses of a cogeneration system consisting of a 200 kW micro gas turbine combined with a heat recovery steam generator are introduced and conducted. Furthermore, biogas and syngas operation are compared to natural gas operation, to investigate the adequacy of these two alternative fuels for use in micro gas turbines. The proposed cogeneration plant proved to be technically feasible for all fuels, because the selected micro gas turbine Capstone C200 is available in various, fuel-specific versions with optimised fuel injection systems. The plant presented overall energetic efficiencies of 50.9%, 48.6% and 47.9% for natural gas, biogas and syngas operation, respectively. Due to very high natural gas and syngas prices, the cogeneration plant presented economic feasibility only in case of biogas operation, with short payback periods of approximately 2.8 years and high expected annual saving. Moreover, biogas has the highest ecologic efficiency and was therefore found to be the best alternative to fossil fuels.

This work represents the integration of a hybrid system based on Micro Gas Turbine system available at the division of Heat and Power Technology at KTH and Solid Oxide Fuel Cell.  The MGT available is an externally fired recuperated and the SOFC is of planar type. Before the integration, these two different candidates of environmentally friendly power generation systems are discussed separately. The advantages and performances of the two separate systems are presented. The operation conditions as pressure and temperature are fixed at different stations based on the previous experiments. Keeping the parameters constant a reduction of fuel to the combustor could be achieved. Finally, layout of the hybrid system diagram is suggested and orientation of a computer designed layout is also presented. An efficiency of 65% from SOFC has been achieved and reductions of the fuel by more than 50% to the MGT are noteworthy.

Polygeneration systems attract attention recently because of their high efficiency and low emission compare to the conventional power generation technology. Three different polygeneration systems based on low temperature solid oxide fuel cell, atmospheric solid oxide fuel cell/ micro gas turbine, and pressurized solid oxide fuel cell/ micro gas turbine are mathematically modeled in this study using MATLAB (version 7.12.0.635). These systems are designed to provide space heating, cooling and hot domestic water simultaneously. This report provides the design aspects of such systems. Furthermore, the effects of some important operating properties on the polygeneration systems performance are investigated.

Dans les turbomachines conventionnelles, l’estimation des performances (rendement, puissance et rapport de pression) se fait en général en admettant l’adiabaticité de l’écoulement. Mais, de nombreuses études ayant montré l’influence négative des échanges thermiques internes et externes sur les performances des petites turbomachines dans les faibles charges et aux bas régimes, cette hypothèse ne peut plus être recevable. L’objectif principal de cette thèse est de contribuer à lever l’hypothèse d’adiabaticité.Une étude préalable de l’état de l’art a permis de relever les différents types de transferts thermiques dans les turbomachines et de circonscrire notre étude.Puis, une analyse exergétique généralisée, ayant pour but la prise en compte des deux principes de la thermodynamique, a été effectuée et l’évolution de l’indice de performance caractérisant le niveau d’énergie récupérable en fonction des échanges thermiques est étudiée.Les performances des turbomachines à fluide compressible sont généralement représentées sous forme graphique dans des systèmes de coordonnées adimensionnelles établies avec l’hypothèse d’adiabaticité. Ces cartographies couramment utilisées par les exploitants et constructeurs ne conviennent pas aux machines fonctionnant avec transferts thermiques. L’étude de la similitude des turbomachines thermiques à fluide compressible présentée dans ce travail, propose de nouvelles coordonnées adimensionnelles pouvant être utilisées aussi bien en adiabatique que dans les écoulements avec transferts thermiques.Enfin, nous proposons un protocole de mesures et un modèle numérique pour l’évaluation des transferts thermiques dans un turbocompresseur.Certains résultats obtenus montrent que les performances calculées avec l’hypothèse d’adiabaticité de l’écoulement du fluide sont surestimées. Les nouvelles lois de la similitude proposées généralisent le théorème de Rateau au fluide compressible fonctionnant dans n’importe quelle condition et permettent de calculer les échanges thermiques à chaud à partir des résultats d’essai à froid. Une donnée supplémentaire (température de refoulement) est néanmoins nécessaire pour la prédiction complète des performances et des échanges thermiques.Le modèle numérique de calcul des échanges thermiques proposé donne des résultats en accord avec ceux attendus, mais nécessite des données réelles issues de mesure sur banc pour une validation complète. / In the conventional turbomachines, calculations are done assuming adiabatic flow. But, the negative influence of external and internal heat exchange on the performance of small turbomachines at low loads and low speeds have been shown by many studies in the literature. Then, this assumption is no longer admissible. The main objective of this thesis is to help remove the assumption of adiabaticity.A study of the state of art has identified the different kinds of heat transfer and defined the limits of our investigations.Afterwards, a generalized exergy analysis whose main goal is to take into account the two principles of thermodynamics has been made and the variation of exergy performance versus heat transfer has been studied.The maps currently used are made with the assumption of adiabaticity. The laws of similarity in turbomachines working with compressible fluid studied propose new dimensionless coordinates that can be used in any operating condition (adiabatic or not).Finally, we present a measurement protocol and a numerical model for calculating heat transfer in a turbocharger.Some results from our work indicate that the performance of thermal turbomachinery announced regardless of thermal heat exchanges are found to be overestimated.The new laws of similarity proposed generalize the Rateau’s theorem to compressible fluid flow in any operating condition and can be used to calculate heat transfer from adiabatic test results. Supplementary information is still required for the complete prediction of performance and heat transfer.The numerical model for calculating heat transfer gives some results that are in agreement with those expected. But actual data from test bench are required for complete validation.

No description available.

Concentrated Solar Power (CSP) constitutes one suitable solution for exploiting solar resources for power generation. In this context, parabolic dish systems concentrate the solar radiation onto a point focusing receiver for small-scale power production. Given the modularity feature of such system, the scale-up is a feasible option; however, they offer a suitable solution for small scale off-grid electrification of rural areas. These systems are usually used with Stirling engines, nevertheless the coupling with micro-gas turbines presents a number of advantages, related to the reliability of the system and the lower level of maintenance required. The OMSoP project, funded by the European Union, aims at the demonstration of a parabolic dish coupled with an air-driven Brayton cycle. By looking at the integrated system, a key-role is played by the solar receiver, whose function is the absorption of the concentrated solar radiation and its transfer to the heat transfer fluid. Volumetric solar receivers constitute a novel and promising solution for such applications; the use of a porous matrix for the solar radiation absorption allows reaching higher temperature within a compact volume, while reducing the heat transfer losses between the fluid and the absorption medium. The aim of the present work is to deliver a set of optimal design specifications for a volumetric solar receiver for the OMSoP project. The work is based on a Multi-Objective Optimization algorithm, with the objective of the enhancement of the receiver thermal efficiency and of the reduction of the pressure drop. The optimization routine is coupled with a detailed analysis of the component, based on a Computational Fluid Dynamics model and a Mechanical Stress Analysis. The boundary conditions are given by the OMSoP project, in terms of dish specifications and power cycle, whilst the solar radiation boundary is modelled by means of a Ray Tracing routine. The outcome of the analysis is the assessment of the impact on the receiver performance of some key design parameters, namely the porous material properties and the receiver geometrical dimensions. From the results, it is observed a general low pressure drop related to the nominal air mass flow, with several points respecting the materials limitations. One design point is chosen among the optimal points, which respects the OMSoP project requirements for the design objectives, i.e. a minimum value of efficiency of 70%, and pressure losses below 1%. The final receiver configuration performs with an efficiency value of 86%, with relative pressure drop of 0.5%, and it is based on a ceramic foam absorber made of silicon carbide, with porosity value of 0.94.  Moreover, the detailed analysis of one volumetric receiver configuration to be integrated in the OMSoP project shows promising results for experimental testing and for its actual integration in the system.

Power generation from biomass based renewable energy technologies is a promising option in retrofitting our dependence in conventional power generation processes. The development of any society is not possible without sustainable energy and access to energy creates that environment that allows the world to thrive. Electricity access especially in developing regions of the world is of particular interest. This work provides results on electricity efficiency, the economic feasibility and environmental impact of biomass based power technologies in small scale setting using Aspen Plus software. The power generation processes analysed on standalone basis include - micro gas turbine, gas turbine, steam turbine, Stirling engine and internal combustion engine. Some of the processes are optimized in the design to suit the specific climate and available wood waste stream in Nigeria is considered in this work. Simulation results indicate that gas engines power technologies gave a better electric performance of more than 30% with its integration with biomass gasification technology in production of fuel gas. The stirling engine power technology shows a good prospect despite its yet to be commercial status. The modification of the engine (removal regenerator) gives a better electric efficiency. Also result shows that internal combustion engine process emits more of nitric oxides compared to other technologies which create doubts over its environmental compatibility. Economic studies show that for small scale power generation, internal combustion engines and stirling engines are economic feasible. Also, steam turbine and gas turbine illustrate why they are mostly applied in medium/large scale biomass power generation specially recommended to regions where more biomass resource are produced. The micro gas turbine power technology can also be applied in small scale despite its high total investment capital. Furthermore, the study shows that about from 1.8 million tonnes per year of saw dust (wood waste) produced from lumber industries in Nigeria, about 1.3 TWh of electricity can be generated from 1000 MW power plant. Power generation via the utilization of biomass prove to be a possible path to Nigeria’s economic, social and environmental sustainability but the extent to which this can achieved is strongly dependent institutional framework, investment, incentives and information policies. / Program: Masterutbildning i energi- och materialåtervinning

Dans les turbomachines conventionnelles, l’estimation des performances (rendement, puissance et rapport de pression) se fait en général en admettant l’adiabaticité de l’écoulement. Mais, de nombreuses études ayant montré l’influence négative des échanges thermiques internes et externes sur les performances des petites turbomachines dans les faibles charges et aux bas régimes, cette hypothèse ne peut plus être recevable. L’objectif principal de cette thèse est de contribuer à lever l’hypothèse d’adiabaticité.Une étude préalable de l’état de l’art a permis de relever les différents types de transferts thermiques dans les turbomachines et de circonscrire notre étude.Puis, une analyse exergétique généralisée, ayant pour but la prise en compte des deux principes de la thermodynamique, a été effectuée et l’évolution de l’indice de performance caractérisant le niveau d’énergie récupérable en fonction des échanges thermiques est étudiée.Les performances des turbomachines à fluide compressible sont généralement représentées sous forme graphique dans des systèmes de coordonnées adimensionnelles établies avec l’hypothèse d’adiabaticité. Ces cartographies couramment utilisées par les exploitants et constructeurs ne conviennent pas aux machines fonctionnant avec transferts thermiques. L’étude de la similitude des turbomachines thermiques à fluide compressible présentée dans ce travail, propose de nouvelles coordonnées adimensionnelles pouvant être utilisées aussi bien en adiabatique que dans les écoulements avec transferts thermiques.Enfin, nous proposons un protocole de mesures et un modèle numérique pour l’évaluation des transferts thermiques dans un turbocompresseur.Certains résultats obtenus montrent que les performances calculées avec l’hypothèse d’adiabaticité de l’écoulement du fluide sont surestimées. Les nouvelles lois de la similitude proposées généralisent le théorème de Rateau au fluide compressible fonctionnant dans n’importe quelle condition et permettent de calculer les échanges thermiques à chaud à partir des résultats d’essai à froid. Une donnée supplémentaire (température de refoulement) est néanmoins nécessaire pour la prédiction complète des performances et des échanges thermiques.Le modèle numérique de calcul des échanges thermiques proposé donne des résultats en accord avec ceux attendus, mais nécessite des données réelles issues de mesure sur banc pour une validation complète. / In the conventional turbomachines, calculations are done assuming adiabatic flow. But, the negative influence of external and internal heat exchange on the performance of small turbomachines at low loads and low speeds have been shown by many studies in the literature. Then, this assumption is no longer admissible. The main objective of this thesis is to help remove the assumption of adiabaticity.A study of the state of art has identified the different kinds of heat transfer and defined the limits of our investigations.Afterwards, a generalized exergy analysis whose main goal is to take into account the two principles of thermodynamics has been made and the variation of exergy performance versus heat transfer has been studied.The maps currently used are made with the assumption of adiabaticity. The laws of similarity in turbomachines working with compressible fluid studied propose new dimensionless coordinates that can be used in any operating condition (adiabatic or not).Finally, we present a measurement protocol and a numerical model for calculating heat transfer in a turbocharger.Some results from our work indicate that the performance of thermal turbomachinery announced regardless of thermal heat exchanges are found to be overestimated.The new laws of similarity proposed generalize the Rateau’s theorem to compressible fluid flow in any operating condition and can be used to calculate heat transfer from adiabatic test results. Supplementary information is still required for the complete prediction of performance and heat transfer.The numerical model for calculating heat transfer gives some results that are in agreement with those expected. But actual data from test bench are required for complete validation.

The growing need of mobile power sources with high energy density and the robustness to operate also in the harshest environmental surroundings lead to the idea of downscaling gas turbines to ì-scale. Classified as PowerMEMS devices, a couple of design attempts have emerged in the last decade. One of these attempts was the Belgian “PowerMEMS” design started back in 2003 and aiming towards a ì-scale gas turbine rated at 1 kW of electrical power output.<p>This PhD thesis presents the scientific evaluation and development history of different combustion chamber designs based upon the “PowerMEMS” design parameters. With hydrogen as chosen fuel, the non-premixed diffusive “micromix” concept was selected as combustion principle. Originally designed for full scale gas turbine applications in two different variants, consequently the microcombustor development had to start with the downscaling of these two principles towards ì-scale. Both principles have the advantage to be inherently safe against flashback, due to the non-premixed concept, which is an important issue even in this small scale application when burning hydrogen. By means of water analogy and CFD simulations the hydrogen injection system and the chamber geometry could be validated and optimized. Besides the specific design topics that emerged during the downscaling process of the chosen combustion concepts, the general difficulties of microcombustor design like e.g. high power density, low Reynolds numbers, short residence time, and manufacturing restrictions had to be tackled as well.<p>As full scale experimental test campaigns are still mandatory in the field of combustion research, extensive experimental testing of the different prototypes was performed. All test campaigns were conducted with a newly designed test rig in a combustion lab modified for microcombustion investigations, allowing testing of miniaturized combustors according to full engine requirements with regard to mass flow, inlet temperature, and chamber pressure. The main results regarding efficiency, equivalence ratio, and combustion temperature were obtained by evaluating the measured exhaust gas composition. Together with the performed ignition and extinction trials, the evaluation and analysis of the obtained test results leads to a full characterization of each tested prototype and delivered vital information about the possible operating regime in a later UMGT application. In addition to the stability and efficiency characteristics, another critical parameter in combustor research, the NOx emissions, was investigated and analyzed for the different combustor prototypes.<p>As an advancement of the initial downscaled micromix prototypes, the following microcombustor prototype was not only a combustion demonstrator any more, but already aimed for easy module integration into the real UMGT. With a further optimized combustion efficiency, it also featured an innovative recuperative cooling of the chamber walls and thus allowing an cost effective all stainless steel design.<p>Finally, a statement about the pros and cons of the different micromix combustion concepts and their correspondent combustor designs towards a possible ì-scale application could be given. / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished