Line-pack management for producing electric power on peak periods

The distribution of natural gas is carried out by means of long ducts and intermediate compression stations to compensate the pressure drops due to friction. The natural gas compressors are usually driven by an electric motor or a gas turbine system, offering possibilities for energy management, one of these consisting in generating energy for use in-plant or to commercialize as independent power producer. It can be done by matching the natural gas demand, at the minimum pressure allowed in the reception point, and the storage capacity of the feed duct with the maximum compressor capacity, for storing the natural gas at the maximum permitted pressure. This allows the gas turbine to drive an electric generator during the time in which the decreasing pressure in duct is above the minimum acceptable by the sink unit. In this paper, a line-pack management analysis is done for an existing compression station considering its actual demand curve for determining the economic feasibility of maintaining the gas turbine system driver generating electricity in a peak and off-peak tariff structure. The potential of cost reduction from the point of view of energy resources (natural gas and electric costs) is also analyzed. (C) 2010 Elsevier Ltd. All rights reserved.

Reducing the impact of EV charging on the electric grid

One of the main objectives of European Commission related to climate and energy is the well-known 20-20-20 targets to be achieved in 2020: Europe has to reduce greenhouse gas emissions of at least 20% below 1990 levels, 20% of EU energy consumption has to come from renewable resources and, finally, a 20% reduction in primary energy use compared with projected levels, has to be achieved by improving energy efficiency. In order to reach these objectives, it is necessary to reduce the overall emissions, mainly in transport (reducing CO2, NOx and other pollutants), and to increase the penetration of the intermittent renewable energy. A high deployment of battery electric (BEVs) and plug-in hybrid electric vehicles (PHEVs), with a low-cost source of energy storage, could help to achieve both targets. Hybrid electric vehicles (HEVs) use a combination of a conventional internal combustion engine (ICE) with one (or more) electric motor. There are different grades of hybridation from micro-hybrids with start-stop capability, mild hybrids (with kinetic energy recovery), medium hybrids (mild hybrids plus energy assist) and full hybrids (medium hybrids plus electric launch capability). These last types of vehicles use a typical battery capacity around 1-2 kWh. Plug in hybrid electric vehicles (PHEVs) use larger battery capacities to achieve limited electric-only driving range. These vehicles are charged by on-board electricity generation or either plugging into electric outlets. Typical battery capacity is around 10 kWh. Battery Electric Vehicles (BEVs) are only driven by electric power and their typical battery capacity is around 15-20 kWh. One type of PHEV, the Extended Range Electric Vehicle (EREV), operates as a BEV until its plug-in battery capacity is depleted; at which point its gasoline engine powers an electric generator to extend the vehicle's range. The charging of PHEVs (including EREVs) and BEVs will have different impacts to the electric grid, depending on the number of vehicles and the start time for charging. Initially, the lecture will start analyzing the electrical power requirements for charging PHEVs-BEVs in Flanders region (Belgium) under different charging scenarios. Secondly and based on an activity-based microsimulation mobility model, an efficient method to reduce this impact will be presented.

Modelling of a Stirling engine with parabolic dish for thermal to electric conversion of solar energy

Stirling engines with parabolic dish for thermal to electric conversion of solar energy is one of the most promising solutions of renewable energy technologies in order to reduce the dependency from fossil fuels in electricity generation. This paper addresses the modelling and simulation of a solar powered Stirling engine system with parabolic dish and electric generator aiming to determine its energy production and efficiency. The model includes the solar radiation concentration system, the heat transfer in the ther- mal receiver, the thermal cycle and the mechanical and electric energy conversion. The thermodynamic and energy transfer processes in the engine are modelled in detail, including all the main processes occur- ring in the compression, expansion and regenerator spaces. Starting from a particular configuration, an optimization of the concentration factor is also carried out and the results for both the transient and steady state regimes are presented. It was found that using a directly illuminated thermal receiver with- out cavity the engine efficiency is close to 23.8% corresponding to a global efficiency of 10.4%. The com- ponents to be optimized are identified in order to increase the global efficiency of the system and the trade-off between system complexity and efficiency is discussed.

Dimensionamento de um reactor de leito fluidizado para gasificação de biomassa

Na actualidade, quando se procura a diversificação energética, em especial de fontes renováveis, a gasificação surge como uma forma promissora de aproveitamento da biomassa, nomeadamente dos resíduos florestais, para a geração de energia eléctrica. Neste contexto, passou-se em revista as diversas formas de gasificação, a sua evolução histórica e os diversos tipos de reactores com as suas vantagens e desvantagens. De igual forma, foram analisadas as disponibilidades e características da biomassa no mundo e em Portugal, destacando-se as suas potencialidades e as dificuldades no seu aproveitamento. Fez-se o dimensionamento de um reactor-gasificador de leito fluidizado borbulhante à escala piloto, bem como dos equipamentos complementares, sistema de alimentação, ventilador, ciclone, filtro para o gás produzido e gerador eléctrico. As dimensões dum reactor para trabalhos laboratoriais foram determinadas por cálculo das condições hidrodinâmicas, que, também, permitiram calcular o caudal de ar a utilizar. Por balanços materiais, considerando-se uma composição experimental do gás de síntese citada na literatura, determinou-se uma possível composição da alimentação e um caudal de alimentação.

Análise do comportamento dos aerogeradores em situação de anomalia

Actualmente, a utilização de recursos energéticos renováveis é encarada como vital para se alcançar um desenvolvimento sustentável. Dentro destas, a energia eólica apresenta-se como uma das mais sustentáveis e, por isso, teve uma evolução exponencial nos últimos anos. No entanto, apesar da sua maturidade, esta tecnologia apresenta problemas e desafios. As turbinas eólicas apresentam uma elevada taxa de avarias em alguns componentes, nomeadamente a caixa de engrenagens, o gerador eléctrico e as pás. Os tempos de paragem associados às avarias e à sua reparação provocam grandes prejuízos. De modo a evitar as falhas e a permitir a redução dos custos durante o ciclo de vida das turbinas eólicas, existe a necessidade de optimizar as estratégias de manutenção, de forma a maximizar o retorno do investimento nos parques eólicos. Os aerogeradores mais recentes possuem sistemas de monitorização que permitem monitorizar todos os equipamentos constituintes da máquina, possibilitando um acompanhamento mais próximo do real estado de funcionamento dos equipamentos. A monitorização online permite que se reduza a possibilidade de acontecimento de uma falha grave. Este trabalho de investigação analisa as avarias associadas a um dos equipamentos mais importante das turbinas eólicas, a caixa de engrenagens, tendo sido identificadas as principais grandezas que podem ser utilizadas para a previsão de avarias. Este equipamento é crítico dado que origina um dos maiores tempos de indisponibilidade por falha. O resultado das análises efectuadas ao comportamento da caixa de engrenagens perante uma avaria demonstrou que é possível prevê-las. Esta informação é de extrema importância, pois permite um escalonamento eficiente da manutenção e a adopção das estratégias de reparação mais convenientes.

Desenvolvimento de um Range Extender para Veículo Elétrico

Dissertação de mestrado integrado em Engenharia Eletrónica Industrial e de Computadores

Microgeneration of electricity with producer gas in dual fuel mode operation

Among the alternatives to meet the increasing of world demand for energy, the use of biomass as energy source is one of the most promising as it contributes to reducing emissions of carbon dioxide in the atmosphere. Gasification is a technological process of biomass energy production of a gaseous biofuel. The fuel gas has a low calorific value that can be used in Diesel engine in dual mode for power generation in isolated communities. This study aimed to evaluate the reduction in the consumption of oil Diesel an engine generator, using gas from gasification of wood. The engine generator brand used was a BRANCO, with direct injection power of 7.36 kW (10 HP) coupled to an electric generator 5.5 kW. Diesel oil mixed with intake air was injected, as the oil was injected via an injector of the engine (dual mode). The fuel gas was produced in a downdraft gasifier. The engine generator was put on load system from 0.5 kW to 3.5 kW through a set of electrical resistances. Diesel oil consumption was measured with a precision scale. It was concluded that the engine converted to dual mode when using the gas for the gasification of wood decreased Diesel consumption by up to 57%.

Sähkögeneraattoriosien hitsauksen tuottavuuden kehittäminen

Hitsauksen tuottavuuteen vaikuttavat hitsausmäärä, käytetyt prosessit ja laatu. Työn teoriaosuudessa tutustutaan hitsauksen tuottavuuteen sekä suunnittelullisesta että valmistuksellisesta näkökulmasta. Hitsauksen laadulliset asiat, kuten laatustandardit ja vaatimukset käydään läpi keskittyen standardin SFS-EN ISO 3834 kattaviin laatuvaatimuksiin. Rikkomaton ja rikkova aineenkoetus ja yleisimmät hitsausvirheet esitetään yleisellä tasolla. Hitsausprosesseista esitetään MIG/MAG- ja MAG-täytelankahitsauksen sekä pulssihitsauksen perusteet. Tässä diplomityössä tutkitaan pulssihitsauksen soveltuvuutta sähkögeneraattorin staattoripaketin eripariliitoksen hitsaukseen ja kykyä parantaa sekä tuottavuutta että laatua. Tutkimus perustuu koehitsauksiin ja niiden perusteella tehtyihin johtopäätöksiin. Lisäksi pohditaan sisätuulettimien hitsauksen kehittämistä ja annetaan kehitysehdotus valmistusprosessista. Koehitsauksien perusteella pulssihitsaus on hyvä prosessiparannus staattoripakettien hitsaukseen. Kohdistettu valokaari ja alhaisempi lämmöntuonti verrattuna perinteiseen MAG-hitsaukseen sekä hitsauksen yksinkertaisuus tuovat etuja eripariliitoksen hitsauksen laatuun. Kustannuslaskelmien myötä hitsausprosessin muutoksen odotetaan tuovan kustannussäästöjä. Hitsauslaadun parantuessa ja jälkityöstön määrän vähentyessä hitsausprosessin muutos on kannattava.

The oscillatory bioelectrical signal from plants explained by a simulated electrical model and tested using Lempel-Ziv complexity

This paper demonstrates the oscillatory characteristics of electrical signals acquired from two ornamental plant types (Epipremnum pinnatum and Philodendron scandens - Family Araceae), using a noninvasive acquisition system. The electrical signal was recorded using Ag/AgCl superficial electrodes inside a Faraday cage. The presence of the oscillatory electric generator was shown using a classical power spectral density. The Lempel and Ziv complexity measurement showed that the plant signal was not noise despite its nonlinear behavior. The oscillatory characteristics of the signal were explained using a simulated electrical model that establishes that for a frequency range from 5 to 15 Hz, the oscillatory characteristic is higher than for other frequency ranges. All results show that non-invasive electrical plant signals can be acquired with improvement of signal-to-noise ratio using a Faraday cage, and a simple electrical model is able to explain the electrical signal being generated. (C) 2010 Elsevier B.V. All rights reserved.

A case study of compact cogeneration using various fuels

A method for studying the technical and economic feasibility of absorption refrigeration systems in compact cogenerators is presented. The system studied consists of an internal combustion engine, an electric generator and a heat exchanger to recover residual heat from the refrigeration water and exhaust gases. As an application, a computer program simulates the cogeneration system in a building which already has 75 kW of installed electric power. The maximum electric and refrigeration demands are 45 kW and 76 kW respectively. This study simulates the system performance, utilizing diesel oil, sugar cane alcohol and natural gas as possible fuels. (C) 1997 Elsevier B.V. Ltd.

Microgeração de energia eletrica (abaixo de 100kw) utilizando turbina tesla modificada

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Desenvolvimento de aplicativo de análise técnica e econômica para adaptação de uma roda d’água acionada por cima para geração de energia elétrica no meio rural

The steel type AISI 4130 (ultra-high strength steel) is an alloy of low carbon and its main alloying elements are chromium and molybdenum, which improves the toughness of the weld metal. It has numerous applications, especially where the need for high mechanical strength. It is widely used in equipment used by the aviation industry, such as cradle-tomotor, and this is the motivation for this study. Cots are of fundamental importance, because the engine supports and maintains balance in the fixed landing gear. This equipment is subjected to intense loading cycles, whose fractures caused by fatigue are constantly observed. Will be determined the effects caused by re-welding the structure of aeronautical equipment, and will also study the microstructure of the metal without welding. The studies will be done on materials used in aircraft, which was given to study. The results provide knowledge of microstructure to evaluate any type of fracture that maybe caused by fatigue. Fatigue is a major cause of aircraft accidents and incidents occurred, which makes the study of the microstructure of the metal, weld and re-solder the knowledge essential to the life of the material. The prevention and control of the process of fatigue in aircraft are critical, since the components are subjected to greater responsibility cyclic loading

Projeto e implantação de pequena central de geração hidrelétrica: análise de caso

The objective of this work is to study the implantation feasibility of a small hydropower system in a rural area in Guaratinguetá. Due to its location and accessibility, and the costs involved in extending the public distribution line to the property it could turn become viable the construction of an individual electric generation system. As alternatives, a solar photovoltaic system and combustion engine-electric generator systems were considered. However, the existence of a small river inside the property, the construction of a micro hydropower plant was taken into account. The choice of the micro power hydropower plant was determined by the owner and was based on the costs. The topographic and hydrological profiles as well as the geometrical characteristics of the system, including the civil infrastructure needed and the more adequate turbine, were determined. Finally, the cost spreadsheet was set and the results were compared with those calculated for the extension of the available public distribution system

Low Voltage Ride-through in DFIG Wind Generators by Controlling the Rotor Current without Crowbars

Among all the different types of electric wind generators, those that are based on doubly fed induction generators, or DFIG technology, are the most vulnerable to grid faults such as voltage sags. This paper proposes a new control strategy for this type of wind generator, that allows these devices to withstand the effects of a voltage sag while following the new requirements imposed by grid operators. This new control strategy makes the use of complementary devices such as crowbars unnecessary, as it greatly reduces the value of currents originated by the fault. This ensures less costly designs for the rotor systems as well as a more economic sizing of the necessary power electronics. The strategy described here uses an electric generator model based on space-phasor theory that provides a direct control over the position of the rotor magnetic flux. Controlling the rotor magnetic flux has a direct influence on the rest of the electrical variables enabling the machine to evolve to a desired work point during the transient imposed by the grid disturbance. Simulation studies have been carried out, as well as test bench trials, in order to prove the viability and functionality of the proposed control strategy.

Diseño de sistema de pitch pasivo para aerogeneradores en entornos urbanos

El presente proyecto desarrolla el diseño de un sistema de pitch pasivo para aerogeneradores en entornos urbanos en el marco del proyecto SWIP (Soluciones, componentes y herramientas novedosos e innovadores para la integración de la energía eólica en áreas urbanas y suburbanas) En primer lugar se describe el marco de trabajo así como una introducción teórica de energía eólica y de sistemas de pitch o de control de paso de pala. Aquí son presentados los fundamentos del accionamiento del pitch pasivo diseñado. A continuación se presenta el mecanismo diseñado y los cálculos sobre él efectuados para el ajuste de sus parámetros de funcionamiento. Posteriormente se plantea el análisis estructural de los distintos casos de carga a los que estará sometido y el estudio de su respuesta dinámica a perturbaciones reales con las que trabajará durante su funcionamiento normal. Por último, se aclaran otra serie de factores como la seguridad y el sobredimensionamiento del generador y se hace un análisis económico del diseño junto con una comparativa con las tecnologías alternativas existentes. ABSTRACT The present project develops the design of a passive pitch system for wind turbines for urban and sub-urban areas for the SWIP European Project (New innovative solutions, components and tools for the integration of wind energy in urban and peri-urban áreas) Firstly, the framework is described, as well as a theoretical introduction to wind energy and pitch systems. Here, the principles of the designed passive pitch mechanism are presented. Subsequently, the designed mechanism is presented together with the calculations on it for the adjustment of its working parameters. After that, the structural analyses for the different load cases that will affect the design are studied. Afterwards, the dynamic response of the system to real perturbations during its operation is studied. Finally, some concepts concerning security issues or oversizing of the electric generator are considered and an economic analysis is performed for the design and also to compare it with the alternative existing technologies.