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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Spatially explicit electrification modelling insights : Applications, benefits, limitations and an open tool for geospatial electrification modelling

Mentis, Dimitris January 2017 (has links)
Developing countries confront the challenge of generating more electricity to meet demands in a sustainable manner. According to the World Bank’s 2015 Global Tracking Framework, roughly 15% of world population (or 1.1 billion people) lack access to electricity, and many more rely on poor quality electricity supplies. In September 2015, the United Nations General Assembly adopted Agenda 2030 comprised of a set of 17 Sustainable Development Goals (SDGs) and defined by 169 targets. “Ensuring access to affordable, reliable, sustainable and modern energy for all by 2030” is the seventh goal (SDG7). While energy access refers to more than electricity, it is the central focus of this work. Models addressing electrification and access typically need large volumes of reliable energy-related data and information, which in most developing countries have been limited or not available. This paucity of information has decelerated energy planning in the developing World. That situation has fundamentally changed with increasing availability and application of Geographic Information Systems (GIS). GIS layers can provide location specific energy-related information that has not been previously accessible. The focus of this thesis lies on integrating a simple electricity supply model into GIS. In so doing a novel open source spatial electrification tool is developed. It estimates power capacity needs and associated investment (and other) costs for achieving universal access to electricity in developing countries. The dissertation includes a cover essay and six appended papers presenting quantitative methods on coupling selected aspects of GIS and energy systems. It strives to answer three key research questions.  The first research question is: What is the spatially explicit renewable energy potential that can be technically and economically exploited? This information is currently either missing or scattered in developing countries. The provision of low cost, locally available energy can provide a significant opportunity to empower a better standard of living. The first paper presents a GIS based approach to assess the onshore technical wind energy potential on the African continent by applying socioeconomic and geographic restrictions regarding the localization of wind farms and state of the art wind data analysis. The second paper builds on this knowledge and moves one step further by assessing the economic potential and providing cost indicators to assess the viability of wind power (this time in India). The third paper maps the economic wind power potential in Africa based on the methodologies developed in the two preceding papers. Not only wind power but most energy resources have a spatial nature and their availability is linked to geography. Evaluating these other energy sources (solar, hydro etc.) are included and analysed in Papers IV-VI. The second research question is: what is the least-cost set of technologies needed to meet different levels of electricity use accounting for different geographies? Increasing access to electricity effectively requires, inter alia, strategies and programmes that address and account for the geographical, infrastructural and socioeconomic characteristics of a country or region. Paper IV introduces a GIS based methodology to inform electrification planning. It builds on the previous work by taking into account the techno-economic wind, and other resource mapping. This methodology is applied in Nigeria in order to determine the least cost technology mix considering the country’s infrastructure and resource availability on a spatial basis. Paper V utilizes this method and in so doing demonstrates the importance of geospatial calculations in energy access planning. It highlights differences in investment estimates between alternate scenarios with regards to energy demand and technology deployment. Paper VI enhances this methodology and applies it to every square kilometre of Sub-Saharan Africa. The method is subsequently implemented in an Open Source Spatial Electrification Tool (OnSSET) to facilitate education, repeatability and further research. Finally, the third question is: Are there gains to be had by linking geographically explicit analysis with typical (non-spatially explicit) long term energy systems models? The work shows that not only do long-term systems models influence geospatially optimal technology deployment. But vice versa, their output influences long term systems models’ investment profile.  That is because the geospatial disaggregation allows for a better determination of grid versus off-grid connections, and in turn power demand on the national grid. This thesis demonstrates that energy system models should take into consideration the geographic dimension of energy-related parameters, as these play a fundamental role in determining the optimal energy system of a region. / <p>QC 20170524</p>
22

Improvement of the performance of a Demonstration Thermal Power Plant

ORBADIA BUKENYA, RICHARD January 2017 (has links)
Power generation with steam as the working fluid has been proven technology in many developed countries around the world. The advantages in using this technology include its ability to use a wide range of fuel and using the cheapest material (water) as a working fluid. This means that if this technology is invested in it can boost the levels of power generation especially in developing countries where only the minority of the population has access to electricity. Currently there is no power plant in Uganda which uses steam technology despite Uganda being endowed with vast sources of fuel ranging from solar, biomass, geothermal and the recently discovered oil in the Albertan region. Blessed by nature, Uganda has a lot of potential to generate power using steam technologies which power when generated can boost the economic development of the country. Due to a low technology level in the country in areas of power generation, there are few commercial steam power plants which are mainly owned by sugar manufacturers and some of them generate power which is supplied to the National grid. There are however accessible demonstration steam power plants in the engineering faculties at both Makerere and Kyambogo Universities. However, the one at Makerere University is malfunctioned and one can only make a study of the performance of these power plants using the plant at Kyambogo University. This study can help the researcher understand the exact challenges of steam power plants, the performance and how to improve efficiency of performance. / <p>Utbildningsprogram i samarbete med KTH</p>
23

Low temperature difference power systems and implications of multi-phase screw expanders in Organic Rankine Cycles

Öhman, Henrik January 2016 (has links)
New and old data on screw expanders operating with 2-phase mixtures in the admission line has been combined to enable the first public correlation of adiabatic expansion efficiency as a function of entry vapour fraction. Although not yet perfected, these findings have enabled an entirely new approach to the design and optimisation of Organic Rankine Cycles, ORCs. By allowing a continuous variation of vapour fraction at expander entry optima for thermal efficiency, second law efficiency and cost efficiency can be found. Consequently one can also find maxima for power output in the same dimension. This research describes a means of adapting cycle characteristics to various heat sources by varying expander inlet conditions from pure liquid expansion, through mixed fluid and saturated gas expansion, to superheated gas. Thermodynamic analysis and comparison of the above optimisations were a challenge. As most terms of merit for power cycles have been developed for high temperature applications they are often simplified by assuming infinite heat sinks. In many cases they also require specific assumptions on e.g. pinch temperatures, saturation conditions, critical temperatures etc, making accurate systematic comparison between cycles difficult. As low temperature power cycles are more sensitive to the ‘finiteness’ of source and sink than those operating with high temperatures, a substantial need arises for an investigation on which term of merit to use. Along with an investigation on terms of merit, the definition of high level reversible reference also needed revision. Second law efficiency, in the form of exergy efficiency, turned out to be impractical and of little use. A numerical approach, based on a combination of first and second law, was developed. A theory and method for the above is described. Eventually low temperature power cycle test data was compiled systematically. Despite differences in fluid, cycle, temperature levels and power levels the data correlated well enough to allow for a generalised, rough correlation on which thermal efficiency to expect as a function of utilization of source and sink availability. The correlation on thermal efficiency was used to create a graphical method to pre-estimate key economic factors for low temperature site potential in a very simple manner. A major consequence from the findings of this thesis is the reduced dependency on unique choices of process fluid to match heat source characteristics. This development significantly simplifies industrial standardisation, and thereby potentially improves cost efficiency of commercial ORC power generators.
24

Bottenutskov i vattenkraftsdammar : Möjligheter, risker och strömningsmekaniska utmaningar / Bottom Outlets in Hydropower Dams : Opportunities, risks, and fluid-mechanical challenges

Skarin, Jakob January 2017 (has links)
Dammen i en vattenkraftsanläggning används för att avleda vatten till kraftverkets turbiner och för att möjliggöra lagring och reglering av energi. Vid stora flöden i älven, eller när vattnet av någon anledning inte kan passera genom de energiproducerande delarna, måste det avbördas från magasinet. Detta görs med utskov. I de flesta fall i Sverige är utskoven placerade nära ytan, men ibland finns även bottenutskov. Det är vanligt att dessa användes vid anläggningens byggnation för att avleda vatten, och varit avställda sedan dess. Detta arbete syftade att undersöka möjligheten att driftsätta bottenutskov i anläggningar där de är monterade men inte bruk, för att höja dammsäkerheten. I rapportens första del finns en sammanställning av de problem som teoretiskt kan uppstå vid brukandet av bottenutskov, baserat på litteratur samt på erfarenheter i branschen. Den andra delen av rapporten beskriver resultatet från en fallstudie av en specifik anläggning, Båtfors kraftstation. Här har beräkningar gjorts, med handräkningsmetoder samt med datorsimuleringar för att undersöka anläggningens bottenutskov utifrån identifierade teoretiska möjligheter och problem. Ett antal teoretiska problem med bottenutskov har identifierats, däribland: erosion, kavitation, luftmedrivning, drivgods samt problem vid stängning av bottenutskovsluckorna. För Båtfors kraftstation skattades den nuvarande avbördningskapaciteten med handräkningsmetoder till cirka 900 m3/s vid magasinets dämningsgräns (DG), vilket överensstämmer med anläggningens dokumentation. För vardera av de två bottenutskoven beräknades avbördningskapaciteten vid full lucköppning (2,4 m) till cirka 225 m3/s. De handräknade och simulerade värdena jämfördes för olika lucköppningar, där en viss skillnad (cirka 30–40 %) noterades. Inget simuleringsresultat kunde erhållas för full lucköppning som följd av konvergensproblem. Luftrörelsen i Båtfors båttenutskov undersöktes genom simulering. För små lucköppningar, 0,4 och 0,8 m, kunde luft tillföras från utskovskulvertens nedströmssida vilket inte är möjligt när luckan öppnas 1,2 m. Om detta riskerar att ställa till med problem beror på om tillräcklig luftning kan ske genom öppningar i utskovets tak. Risken för kavitation i Båtfors undersöktes genom att jämföra utskovets lägsta tryck i simuleringen med mättnadstrycket för vatten vid 20 °C. Det fastställdes från detta att kavitation ej bör förekomma i denna anläggning, vilket överensstämmer med litteratur. Som slutsats dras att bottenutskov inte är problemfria, men även att stora möjligheter finns. Dessa utskov kan användas för att öka anläggningens avbördningskapacitet och regleramplitud, som nödutskov och för att möjliggöra avsänkning av anläggningens magasin. Det sistnämnda kan dessutom inte åstadkommas på annat sätt. / The dam in a hydroelectric power station serves to divert water to the station’s turbines, and to allow for energy storage and power balancing. When the flow in the river is high or when the energy producing parts of the facility are inoperative, water needs to be discharged from the reservoir. This is done with outlets. In Sweden, most outlets are near the surface, but in some cases bottom outlets are used. Commonly, these outlets were used during the construction of the dam to divert water and have been unused since then. The purpose of this project was to investigate the possibility to recommission bottom outlets in hydropower dams where they are existent but not in use, to increase dam safety. The first part of the report contains a summary of theoretical problems with bottom outlets, based on industry experiences and literature. The second part presents the results of a case study of a specific facility, Båtfors hydroelectric power station. Calculations have been made, both by hand and with computational fluid dynamics, to identify possibilities and problems. Several theoretical problems have been identified, including: erosion, cavitation, insufficient aeration, debris, and problems with closing the outlet gates. The current discharge capacity for Båtfors power station was estimated by hand to slightly over 900 m3/s at the normal reservoir water level, which is consistent with the documentation of the facility. For each of the two bottom outlets, the discharge capacity was calculated to around 225 m3/s with the gate fully open (2.4 m). The values calculated by hand were compared to simulated ones for different gate openings and a certain difference (around 30–40 %) was noted. No simulation results could be obtained with the gate fully opened due to convergence issues. The movement of air in the bottom outlets of Båtfors were studied by simulations. When the gate was opened to a small degree, 0.4 and 0.8 m, air could be supplied from the downstream opening of the outlet conduit which was impossible when the gate was opened 1.2 m. This may cause problems if sufficient aeration cannot be achieved through openings in the outlet ceiling. The risk of cavitation in Båtfors was investigated by comparing the simulated minimum pressure in the outlet with the saturation pressure of water at 20 °C. It was determined that cavitation likely won’t be an issue at this facility, which conforms with literature. It was concluded that several issues can occur when using bottom outlets, but also that several opportunities exist. These outlets can be used to increase the discharge capacity and drawdown range of the facility, as emergency outlets, and to enable lowering of the reservoir water level. The lattermost can furthermore not be achieved by other means.
25

Systemlösningar för lågtempererad uppvärmning

Svensgård, Johan, Larsson, Martin January 2017 (has links)
No description available.
26

Solceller och vindkraftverk : - Samverkan vid elproduktion

Ullman, Emma January 2017 (has links)
No description available.
27

Reducering av effekttoppar i Halmstads fjärrvärmesystem : Modellering av ett teoretiskt laststyrningsschema

Arvidsson, Karl-Henrik, Kristensen, Sophie January 2017 (has links)
On behalf of Halmstads Energi och Miljö (HEM) this paper investigates the possibilities to reduce power peaks in their district heating production through demand side management. The purpose with this paper is to reduce the power peaks with 10 MW and investigate which customers or areas HEM should focus on. In addition, two bottlenecks in the district heating network are analyzed by the effects of demand side management. A theoretical model of demand side management was constructed. The model uses hourly data from production and endeavor to daily average values. The model also included parameters such as storage capacity and manipulated outdoor temperature. The results from demand side management relates to the total daily variations of the district heating system. The demand side management has been applied to a selection of 214 substations and three independent demand side management schemes for the year of 2016, one for each bottleneck and one for the total 214 substations. The choice of substations for demand side management is based on which buildings are connected to them. Criteria for the selection are buildings with high thermal mass, which give high thermal inertia and buildings with high heat demand (large apartment buildings). It is of great interest to investigate how demand side management affects the indoor temperature in selected buildings because limit values cannot be exceeded. The result shows that the power peaks can be reduced by 11.7 MW (mean value) for the whole year excluding the months of spring and summer and for the winter months 13.1 MW (mean value). The reasons why the power peaks can be reduced to a greater extent during the winter months was due to a larger heat demand and heat load variations. Two bottleneck areas applied one theoretic demand side management scheme each where power peaks can be reduced by 0.63 MW(mean value) and 0.7 MW(mean value) excluding spring and summer months and 0.71 and 0.72 only including winter months. The profit from reducing the power peaks for HEM is shorter operating time for the peak heating boilers. The power peaks is later compensated and balanced with renewable bio energy. The simulation from 2016 brings a cost saving to 2.7 million SEK. The profit comprises the cost difference between fossil fuels, natural gas and renewable fuels such as wooden chips. The carbon dioxide reduction during the same period of time was 1671 metric tonne CO2- equivalents.
28

Co-Combustion of Municipal Solid Waste and Animal Waste : Experiment and Simulation Studies

Moradian, Farzad January 2013 (has links)
Co-combustion of animal carcasses and slaughterhouse waste products (animal waste), which are classed as high-risk infectious waste, has been considered as a “fuel opportunity” for waste-to-energy boilers. In this study, the impact of co-combustion of animal waste with municipal solid waste (MSW) on operational issues such as bed agglomeration, deposit formation and emission was investigated, employing experimental and theoretical methods. In the experimental section, a series of full-scale tests in a bubbling fluidised-bed boiler were carried out, to determine the effects of animal waste co-combustion on the issues addressed. Two combustion scenarios were considered, identified as the reference (Ref) case and the animal waste (AW) case. In the Ref case, a solid-waste fuel mix, consisting of sorted and pretreated industry and household waste was combusted. In the AW case, 20 wt% AW was added to the reference fuel mix. The collected samples, which included super-heater deposits, fuel mixes and bed and fly ashes, were analysed, using chemical fractionation, SEM-EDX and XRD. In addition, the flue gases´ emission rate were continuously analysed, using FTIR spectrometry. The results showed positive effects from co-combustion of AW, indicating decreased deposit formation and lower risk of bed agglomeration, as well as reduced emissions of NOx and SO2. Moreover, it was found that the concentrations of P, Ca, S and Cl were enriched in the bed materials. In the theoretical section, thermodynamic calculations, with respect to experimental data, were performed to provide greater understanding of the ash transformation behaviour and the related melting temperature. The calculations mainly focused on bed agglomeration, where addition of AW to the MSW considerably reduced the risk of agglomeration. The results of equilibrium products and phase diagram information for the bed ashes suggested melt-induced agglomeration as a possible cause of the formation of sticky layers on the bed particle in the Ref case. Moreover, it was concluded that higher amounts of calcium phosphate and sulfates increased the first melting temperature of the bed ashes in the AW case. / <p><strong>Sponsorship</strong>:</p><p>Waste Refinery and Sparbanksstiftelsen Sjuhärad</p>
29

Fast pyrolysis of biomass at high temperatures

Trubetskaya, Anna January 2016 (has links)
No description available.
30

Influence of fuel mix on mass balance of Cl, S, and K in a long rotary kiln

Nilsson, Simon January 2019 (has links)
Lime is a material with a wide range of applications including land improvement, water treatment as well as the paper-, steel-, and cement industry. Annual worldwide production was estimated at 350 Mt/year for 2016 and 2017 and the production is responsible for a large contribution of the greenhouse gas CO2 to the atmosphere, contributing to global warming. Since there is a need for high temperatures in the production process it is common that fossil fuels are used due to their high energy density and favourable combustion characteristics. Therefore a net emission of CO2 comes from the fuel, but a large amount is also released from the calcination of the raw material, limestone, approximately 1 ton of CO2 is released for every ton of quicklime (CaO) produced. Efforts are being made toward reducing emissions from both the fuel and the limestone. Nordkalk AB, for whom this work has been performed, are aiming to partly replace their use of fossil fuel in their lime kiln in Köping with renewable biomass alternatives. The purpose of this study was to establish a mass balance over the lime kiln in Köping for different limestone and fuel mixes and study the effects they had on mass balance for sulphur, potassium, and chlorine. Five different periods were studied where four of them had fuel mixes consisting of fossil fuels (coal and oil) and in the fifth period olive pomace, a renewable fuel, was added to the fuel mix at 11 % of the net calorific input. It was found that no significant change in product quality occurred and no increase in sulphur and chlorine emissions through the flue gas was detected with this fuel addition. However there were indications from throughput calculations that buildup of corrosive deposits, such as KCl, could be occurring with the addition of olive pomace due to comparatively large input of potassium and chlorine. The increased sulphur input form olive pomace appeared to accumulate in the lime kiln dust mass flow while flue gas emissions remained unchanged. This method of establishing a mass balance is considered to be a good way to understand how different inputs affect the elemental balances over a lime kiln. However the quality of the mass balance is highly dependent on how representative the composition of the mass flows are and how they are acquired.

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