D.Ing. / The thesis describes the development, installation, and testing of a neural network-based steam temperature controller for power plant boilers. Attention is focussed on the mechanical and thermodynamic aspects of the control problem, on the modelling and control aspects of the neural network solution, and on the practical and operational aspects of its implementation. A balance between theoretical and practical considerations is strived for. Experimental data is obtained from an operational coal fired power plant. As a starting point, the importance of good steam temperature control is motivated. The sensitivity of heated elements in boilers to changes in heat distribution is emphasized, and it is shown how various factors influence the heat distribution. The difficulties associated with steam temperature control are discussed, and an overview of developments in advanced steam temperature control on power plant boilers is given. The suitability of neural networks for process modelling and control are explored and the error backpropagation technique is shown to be well suited to the steam temperature control problem. A series of live plant tests to obtain modelling data is described and specific attention is given to discrepancies in the results. The prOcess of selecting the ideal network topology is covered and improvements in modelling accuracy by selecting different model output schemes are shown. The requirements for improving steam temperature control are listed and the philosophy of optimal heat distribution (OHD) control is introduced. Error backpropagation through the heat transfer model is utilized in an optimizer to calculate control actions to various fire-side elements. The scheme is implemented on a power boiler. It is shown that the optimizer manipulates control elements as expected. Problems with fuel-topressure oscillations and erroneous fuel flow measurement are discussed. Due to process oscillations caused by OHD control, a reduction in control quality is evident during mill trips and capability load runbacks. Substantial improvements over normal PID control however, are evident during load ramps.

The aim of the work is to design a plain wood combustion boiler of 60 t/h output. Fuelling component analysis has been added to the basic boiler parameters. Stechiometric calculations were performed for given fuel composition. Thermal efficiency was set after making thermal balance. Separate convective areas and boiler proportions were designed together with separate steam output parameters (temperature, pressure, amount). Design documentation was added.

M.S.

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Air-cooled steam condensers are used in arid regions where adequate cooling water is not available or very expensive. In this thesis the effect of steam-side and air-side effects on the condenser performance, steam distribution and critical dephlegmator length is investigated for air-cooled steam condensers as found in power plants. Solutions are found so that no backflow is present in the condenser. Both single and two-row condensers are investigated. The tube inlet loss coefficients have the largest impact on the critical dephlegmator tube length in both the single and two-row condensers. The critical dephlegmator tube lengths were determined for different dividing header inlet geometries and it was found that a step at the inlet to the dividing header resulted in the shortest tubes. Different ambient conditions were found to affect the inlet steam temperature, the steam flow distribution, heat rejection distribution and the critical dephlegmator length for the single and two-row condensers. There were differences in the steam mass flow distributions for the single and two-row condensers with opposite trends being present in parts of the condenser. The single-row condenser’s critical dephlegmator tube lengths were shorter than those of the two-row condenser for the same ambient conditions. Areas of potential backflow change with different ambient conditions and also differ between a single and two-row condenser. The two-row condenser always have an area of potential backflow for the first row at the first condenser fan unit. / AFRIKAANSE OPSOMMING: Droë lug-verkoelde stoom kondensors word gebruik in droë gebiede waar genoegsame verkoelingswater nie beskikbaar is nie of baie duur is. In hierdie tesis word die effek van stoomkant en lugkant effekte op die vermoë van die kondensor, die stoomvloeiverdeling en kritiese deflegmator lengte ondersoek vir lug-verkoelde stoom kondensors soos gevind in kragstasies. Dit word opgelos sodat daar geen terugvloei in enige van die buise is nie. ʼn Enkel- en dubbelry kondensor word ondersoek. Die inlaatverlieskoëffisiënte van die buise het die grootste impak op die lengte van die kritiese deflegmator buise in beide die enkel- en dubbelry kondensors. Die kritiese deflegmator buis lengtes is bereken vir verskillende verdeelingspyp inlaat geometrië en dit is gevind dat ʼn trap by die inlaat van die verdeelingspyp die kortste buise lewer. Dit is gesien dat verskillende omgewingskondisies die inlaat stoom temperatuur, die stoomvloeiverdeling, die warmteoordrag verdeling en die kritiese lengte van die deflegmator buise vir die enkel- en dubbelry kondensor. Daar was verskille tussen die stoomvloeiverdelings vir die enkel- en dubbelry met teenoorgestelde neigings in dele van die kondensor. Die kritiese deflegmator buis lengte vir die enkelry kondensor was korter as die vir die dubbelry kondensor vir dieselfde omgewingskondisies. Die areas in die kondensor waar terugvloei moontlik kan plaasvind in die kondensor verander met ongewingskondisies en verskil vir die enkel- en dubbelry kondensers. Die dubbelry kondensor het altyd ʼn area van moontlike terugvloei vir die eerste buisry by die eerste kondensor waaiereenheid.

A combined cycle gas/steam power plant combines a gas turbine (topping cycle) with a steam power plant (bottoming cycle) through the use of a heat recovery steam generator. It uses the hot exhaust of the gas turbine to produce steam which is used to generate additional power in the steam power plant. The aim of this study is to establish the different bottoming cycle performances in terms of the main parameters of heat recovery steam generator and steam cycle for a chosen gas turbine cycle. First of all / for a single steam power cycle, effect of main cycle parameters on cycle performance are analyzed based on first law of thermodynamics. Also, case of existence of a reheater section in a steam cycle is evaluated. For a given gas turbine cycle, three different bottoming cycle configurations are chosen and parametric analysis are carried out based on energy analysis to see the effects of main cycle parameters on cycle performance. These are single pressure cycle, single pressure cycle with supplementary firing and dual pressure cycle. Also, effect of adding a single reheat to single pressure HRSG is evaluated. In single pressure cycle, HRSG generates steam at one pressure level. In dual pressure cycle, HRSG generates steam at two different pressure levels. i.e. high pressure and low pressure. In single pressure cycle with supplementary firing excess oxygen in exhaust gas is fired before entering HRSG by additional fuel input. So, temperature of exhaust gas entering the HRSG rises. Second law analysis is performed to able to see exergy distribution throughout the bottoming plant / furthermore second law efficiency values are obtained for single and dual pressure bottoming cycle configurations as well as basic steam power cycle with and without reheat. It is shown that maximum lost work due to irreversibility is in HRSG for a bottoming cycle in a single pressure gas / steam combined power plant and in boiler for a steam cycle alone. Comparing this with the single pressure cycle shows how the dual pressure cycle makes better use of the exhaust gas in the HRSG that dual pressure combined cycle has highest efficiency values and lost work due to irreversibility in -most significant component- HRSG can be lowered. And also it is shown that by extending the idea of reheat the moisture content is reduced and improvement in the performance is possible for high main steam pressures. Another observation is that supplementary firing increases the steam turbine output compared to the cycle without supplementary firing. The efficiency rises slightly for HP steam pressures higher than 14 MPa at HRSG exit, because the increased steam production also results in increased mass flows removing more energy from the exhaust gas.

Orientador: Takaaki Ohishi / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-13T16:15:59Z (GMT). No. of bitstreams: 1 Santos_ElmaPereira_M.pdf: 11960161 bytes, checksum: 3f762b2c22ed74c7ea44114aeba37c71 (MD5) Previous issue date: 2009 / Resumo: O gás natural é um combustível fóssil que pode ser utilizado tanto na indústria como no comércio, residências e veículos. Uma aplicação importante do gás natural é como fonte primária para geração de energia elétrica em usinas termelétricas. Seu uso possibilita uma maior estabilidade ao Sistema Elétrico Brasileiro, pelo fato de depender menos do nível de água nos reservatórios para atendimento da demanda de energia elétrica. Como o gás natural possui uma estocagem complexa e onerosa, a quantidade de demanda de gás afeta diretamente as suas etapas de produção e transporte, já que toda a quantidade produzida e transportada deverá ser consumida. Desse modo, a operação do sistema de suprimento de gás natural é fortemente dependente das decisões de seus consumidores. As usinas termelétricas estão entre os maiores consumidores de gás, de forma que o despacho das usinas termelétricas afeta fortemente a operação do sistema de gás. Por outro lado, restrições no sistema de suprimento de gás também podem afetar a operação das usinas termelétricas. Esta forte dependência operativa entre estes dois sistemas requer uma operação coordenada para se obter uma operação mais eficiente e segura. Esta tese apresenta um modelo de despacho econômico aplicado a usinas termelétricas que usam gás natural como fonte primária, considerando os custos de produção, transporte de gás natural e de geração de energia elétrica. A modelagem matemática resulta em um problema misto não linear. Para resolução foi utilizada uma abordagem híbrida, que combina um modelo baseado em Programação Linear e um modelo não linear. O problema não linear é resolvido através do método de Newton. / Abstract: Natural gas is a fossil fuel that can be used in industry, trade, residence and vehicles, among others. An important application of natural gas is as a primary source for electricity generation in thermoelectric power plants. In the Brazilian Electric System this source increase the system stability, once it is less dependent of the water level in tanks to serve the demand for power. As natural gas storage it is more complex and expensive, the amount of gas directly affects the production and transportation stages, once the entire amount that is produced and transported must be consumed. Thus, the operation of the supply system of natural gas is strongly dependent on decisions of their consumers. The thermoelectric power plants are among the largest gas consumers, so the dispatch of thermoelectric plants affects strongly the gas system operation. On the other hand, restrictions in the gas supply system may also affect the operation of thermoelectric plants. This strong operative dependence between these two kinds of systems, requires a coordinated operation with the aim of obtaining a more efficient and safer operation. This thesis presents a model of economic dispatch applied to thermoelectric power plants that use natural gas as a primary energy source, considering the costs of production, transportation of the natural gas and electricity generation. The mathematical modeling results in a nonlinear mixed problem. For resolution was used a hybrid approach that combines a model based on Linear Programming and a nonlinear. The nonlinear problem is solved by the Newton's method. / Mestrado / Engenharia de Computação / Mestre em Engenharia Elétrica

This dissertation consists of four self-contained studies concentrating on the productivity development following major technological breakthroughs. All four studies are concerned with measurement issues of productivity. Three of the papers use a comparative historical perspective and primarily focus on some of the differences and similarities in productivity growth following each technological breakthrough. A fourth paper solely focuses on the ICT revolution and the problems associated with measuring productivity in the Swedish Radio, television and communication equipment (RTC) industry. Paper 1, Technological Breakthroughs and Productivity Growth (with Magnus Henrekson), examines productivity growth following three major technological breakthroughs: the steam power revolution, electrification and the ICT revolution. The distinction between sectors producing and sectors using the new technology is emphasized. A major finding for all breakthroughs is that there is a long lag from the time of the original invention until a substantial increase in the rate of productivity growth can be observed. There is also strong evidence of rapid price decreases for steam engines, electricity, electric motors and ICT products. However, there is no persuasive direct evidence that the steam engine producing industry and electric machinery had particularly high productivity growth rates. For the ICT revolution, the highest productivity growth rates are found in ICT-producing industries. It is argued that one explanation might be that hedonic price indexes are not used for the steam engine and the electric motor. Still, it is likely that the rate of technological development has been much more rapid during the ICT revolution as compared to any of the previous breakthroughs. In paper 2, Do Hedonic Price Indexes Change History? The Case of Electrification, I investigate whether hedonic price indexing would also have large effects on measured price and productivity during electrification. The hedonic methodology is used on historical data for electric motors in Sweden in 1900–35. The results show that PPI-deflated prices for electric motors decreased by 4.8 percent per year based on hedonic price indexes. This indicates that prices decreased considerably more for electric motors compared to total manufacturing. Annual labor productivity growth in Swedish electric machinery in 1919–29 becomes 12.1 percent if the hedonic deflators are used. Thus, there is strong evidence that productivity growth in the electric motor producing industry was very high during the 1920s. In contrast to Sweden, US annual labor productivity growth was only, according to current best estimates, 4.1 percent in electric machinery compared to 5.3 percent in manufacturing in 1919–29. However, hedonic price indexes were not used to calculate US productivity. Finally, it is shown that the price decreases for electric motors in the 1920s were not on par with the price decreases for ICT-equipment in the 1990s, even if hedonic indexing is used in both cases. Paper 3, Parallel Development? Productivity Growth Following Electrification and the ICT revolution, compares labor productivity growth and the contribution to labor productivity growth in Swedish manufacturing during electrification and the ICT revolution. The paper distinguishes between technology-producing, intensive and less intensive technology-using industries during these two technological breakthroughs. The results show that labor productivity growth and the overall contribution to labor productivity growth were considerably higher in technology-producing industries during the ICT revolution compared to electrification. For example, the relative contribution to labor productivity growth in manufacturing from the technology-producing industry was 3.4 percent in 1920–30 compared to 34.4 percent in 1993–2003. On the other hand, the relative contribution to aggregate labor productivity growth was considerably higher in intensive technology-using manufacturing industries during electrification. These findings have an important policy implication, namely that it is much more important how productivity is measured for ICT products in the 1990s than for electric motors in the 1920s. Paper 4, The Swedish ICT Miracle: Myth or Reality?, investigates productivity development in Sweden in the 1990s. The results show that much of the recorded Swedish surge in labor productivity was due to the spectacular growth of the Radio, television and communication equipment (RTC) industry. However, the productivity growth of the RTC industry is very sensitive to value added price deflators. Unlike Sweden, the US uses hedonic price indexes for semiconductors and microprocessors which are important intermediate inputs in the RTC industry. Estimates based on the US intermediate input price deflators for semiconductors and microprocessors suggest that the productivity growth of the Swedish RTC industry during the 1990s can be questioned. This implies that the productivity growth of total manufacturing has also been overestimated. The results for Sweden are also interesting for other countries such as Finland, Ireland and South Korea, where ICT-producing industries have contributed substantially to labor productivity growth / Diss. Stockholm : Handelshögskolan, 2006 S. 1-21: introduction and summary, s. 23-194: 4 papers

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Civil Engineering, 1981 / Bibliography: leaves 264-269. / by John Jay Shaw. / Ph. D. / Ph. D. Massachusetts Institute of Technology, Department of Civil Engineering

HETA utbildningar i Härnösand har ett ångkraftverk för undervisningssyfte som kyls ner med vatten från en underjordisk bassäng på cirka 329 m³. Syftet med detta examensarbete har varit att undersöka hur bassängen med spillvärmen från kraftverket kan användas som ett säsongslager i kombination med en befintlig 7,8 kW värmepump för att värma upp maskinhallen i deras laboratoriebyggnad. Ett kalkylark skapades i Microsoft Excel för att kunna genomföra beräkningarna. Då mätdata saknades skapades ett simulerat scenario baserat på temperaturstatistik och körschema för kraftverket från år 2017. Transmissionsförluster beräknades för bassängen och maskinhallen. För bassängen användes mestadels observationsdata och kännedom hos personalen, medan maskinhallens isolering i huvudsak fick uppskattas efter byggår. Resultatet blev att värmepumpen med aktuellt körschema kunde täcka cirka 45 % av maskinhallens årliga uppvärmningsbehov. Av de 276 GJ som tillfördes genom kylning av ångkraftverket under ett år beräknades endast 2,7 % kunna utnyttjas till uppvärmning av maskinhallen, på grund av för lite isolering i bassängen. De största begränsningarna för högre täckning och större nyttjande av spillvärmen bedömdes vara placeringen i tid av kraftverkets körningar, och värmepumpens effekt. Om körningarna skulle förläggas i huvudsak till november–april och värmepumpen ersättas med en på 10 kW, skulle 74 % av värmebehovet kunna täckas och över 18 % av spillvärmen utnyttjas. Andra saker som förbättrad isolering i bassängen och större vattenvolym bedömdes också kunna förbättra bassängens kapacitet som energilager. / HETA Education in Härnösand has a steam power plant for educational purposes which is cooled with water from a 329 m³ underground basin. The purpose of this thesis has been to examine how the basin with the waste heat can be used as seasonal thermal energy storage with an existing 7.8 kW heat pump in order to heat the machine room of their lab building. A spreadsheet was created in Microsoft Excel in order to carry out the calculations. As no measurement data was available, a simulated scenario was created based on temperature statistics and the operating schedule for the power plant from the year 2017. Transmission losses were calculated for the basin and the machine room. For the basin, mostly observational data and knowledge among the staff were used, while the insulation for the machine room mainly had to be estimated based on the construction year. The result was that the heat pump, with the current operating schedule, could cover around 45% of the yearly heating demand of the machine room. Of the 276 GJ that were added through cooling of the power plant during a year, according to calculations, only 2,7% could be used for heating the machine hall, due to lacking insulation in the basin. The greatest limitations for achieving a higher heating coverage and a greater usage of the waste heat were assessed to be the placement in time of the power plant runs, and the effect of the heat pump. If the runs would be placed mainly in November–April, and the heat pump replaced with a 10 kW one, around 74% of the heating demand could be covered and 18 % of the waste heat used. Other things, such as increased insulation in the basin and larger water volume were also assessed to be able to increase the capacity of the basin as heat storage.