Change search
Refine search result
3456789 251 - 300 of 944
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 251.
    Fruth, Florian
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Vogt, Damian M.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Bladh, R.
    Fransson, Torsten H.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Unsteady forcing vs. efficiency - The effect of clocking on a transonic industrial compressor2013In: ASME 2013 Fluids Engineering Division Summer Meeting: Volume 1A, Symposia: Advances in Fluids Engineering Education; Advances in Numerical Modeling for Turbomachinery Flow Optimization; Applications in CFD; Bio-Inspired Fluid Mechanics; CFD Verification a., ASME Press, 2013, p. V01AT02A010-Conference paper (Refereed)
    Abstract [en]

    A numerical investigation on the impact of clocking on the efficiency and the aerodynamic forcing of the first 1.5 stages of an industrial transonic compressor was conducted. Using unsteady 3D Navier-Stokes equations, seven clocking positions were calculated and analyzed. Efficiency changes due to clocking were up to 0.125%, whereas modal excitation changes up to 31.7%. However, no direct correlation between the parameters of efficiency, stimulus and modal excitation was found as reported by others. It was found that potential forced response risks can be reduced by clocking, resulting only in minor efficiency penalties. Assuming almost sinusoidal behavior of efficiency and stimulus changes, as found in this investigation, both parameters can be set into correlation by using an ellipse interpolation. Direct impact of design changes on efficiency and stimulus through clocking can be deducted from that graph and quick estimations about extrema be made using only 5-6 transient simulations. Results however also stress the importance of considering modal excitation when optimizing for aerodynamic forcing, for which the ellipse interpolation is not necessarily possible. Highest efficiency is achieved with the IGV wake impinging on the stator blade leading edge at mid-span. It was found however that this alone is not a sufficient criteria in case of inclined wakes, as wake impingement at different span positions leads to different efficiencies.

  • 252.
    Fruth, Florian
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Vogt, Damian M.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Fransson, Torsten H.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Influence of the blade count ratio on aerodynamic forcing part II: High pressure transonic turbine2012In: Proceedings of the ASME Turbo Expo, New York: American Society of Mechanical Engineers , 2012, p. 1343-1354Conference paper (Refereed)
    Abstract [en]

    The influence of the Blade Count Ratio (BCR) on the aerodynamic forcing of a transonic high pressure turbine has been investigated numerically. Main focus here was put on the change in unsteady aerodynamics, modal properties and the mode excitation. Using a scaling technique, six different transonic turbine stages with different numbers of scaled blades but maintained steady aerodynamics were generated and further analyzed. In the analysis a non-linear, time marching CFD solver was used and the unsteady, harmonic forces projected onto the mode shapes. For this transonic turbine the unsteady pressure at the rotor blade decreases in amplitude and spanwise distribution from low to high blade count ratios. In chordwise direction a local minimum for intermediate blade count ratios was found for the rotor and stator blades. Mode frequencies decreased monotonically with an increasing BCR. Significant mode changes for modes 5 and 6 of the different BCRs were captured  using the Modal Assurance Criteria. It was found that for these transonic turbines the blade count ratio and reduced frequency are amongst others key parameters for a reduction in aerodynamic forcing. Even though an almost monotonic trend was found for the stator blade excitation, the rotor blade excitation behaves highly non-monotonic. A maximum value in excitation potential was found close to reported blade count ratio values. Optimization of certain modes is possible but case dependent, due to the non-monotonic nature. Moreover it was found that for a minor increase in upstream blade count the mean unsteady forces on the rotor blades is reduced, but the mode excitation not necessarily has to decrease.

  • 253.
    Fruth, Florian
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Vogt, Damian M.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Mårtensson, Hans
    Volvo Aero. Researchers.
    Mayorca, Maria A.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Fransson, Torsten H.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    INFLUENCE OF THE BLADE COUNT RATIO ON AERODYNAMIC FORCING PART I: HIGHLY LOADED TRANSONIC COMPRESSOR2010Conference paper (Refereed)
    Abstract [en]

    The influence of the Blade Count Ratio (BCR) on the aerodynamic forcing of a highly transonic compressor has been investigated. The focus has been put on the unsteady aerodynamics as well as mode excitability and thus High Cycle Fatigue (HCF) risk. A number of compressor stages were investigated that differed in blade count of the stator blade row. Time-resolved aerodynamic forcing results were acquired using a non-linear CFD approach. The results were decomposed into frequency content and combined with modal properties of the various components. It is found that the BCR is a key parameter to reduce generalized force and consequently vibratory HCF stresses. Furthermore a potential in avoiding and/or alleviating potential resonant crossings in the Campbell diagram is reported. The dependency of these aspects from BCR is largely non-linear and for the first time discussed in detail on the basis of a transonic compressor stage.

  • 254.
    Fuglesang, Malin
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Assessment of Power Production Possibilities in Two Sawmills in La Palma, Cuba2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The Cuban power sector with its heavy dependency on foreign oil is in much need of investment and development. In the past decade, the Cuban government launched an ‘energy revolution,’ the Revolución energética, which aims at generating electricity from renewable sources. As part of this effort, the country looks toward tapping into its biofuels which mainly consist of bagasse from the sugar industry and wood residues from the forest industry. Against this background, the thesis is a case study of how to use the wood residues from two Cuban sawmills in order to generate electricity. The focus is on electricity generation as the mills have no current need for heat.

    The mills belonging to the state owned company EFI La Palma located in western Cuba are small, with a yearly production of 8400 m3 and 12 500 m3 sawn timber. The wood residues; sawdust, slabs, wood chips and bark, are currently simply dumped in two large deposits near the mills and represent a wasted resource which pollutes the local environment. Three electricity generating alternatives are initially investigated in the literature review: a steam cycle, gasification connected to an internal combustion engine and a Stirling engine using heat from biomass combustion.

    The gasification alternative is deemed most suitable and the thesis evaluates how two downdraft wood gasifiers would perform if connected to the two currently unused diesel generators of 276 kW and 504 kW which are in place in each of the mills. The specific gasifier models examined are the Indian company Ankur’s WBG 250 and WBG 400 and the fuel preparation necessary to use these gasifiers is investigated. The electricity consumption of the mills is compared with the potential electricity generation. It is found that the smaller mill could produce a yearly amount of 1,5 MWh of electricity  for the grid and the larger mill could export 3,2 MWh.  As the engines must be run in dual mode, the net present value of the gasification system is dependent on the level of replacement diesel which according to Ankur will be between 50 and 75 %. In the smaller mill the investment in the gasifier system is profitable at replacement levels greater than 65,4 % and in the larger mill, the investment becomes profitable at replacement levels above  63,8 %. Moreover, the profitability of the investment is highly dependent on the Cuban electricity price which currently is strongly subsidized. The reduction in CO2 emissions are also dependent on the replacement level and  at 75 % replacement level they are found to be 665 tons in the smaller mill and 1272 tons in the larger mill.

  • 255. Fuhrer, C.
    et al.
    Grübel, M.
    Vogt, D. M.
    Petrie-Repar, Paul
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    The influence of non-equilibrium wet steam effects on the aeroelastic properties of a turbine blade row2016In: Proceedings of the ASME Turbo Expo, ASME Press, 2016Conference paper (Refereed)
    Abstract [en]

    Turbine blade flutter is a concern for the manufacturers o steam turbines. Typically, the length of last stage blades of larg steam turbines is over one meter. These long blades are susceptibl to flutter because of their low structural frequency an supersonic tip speeds with oblique shocks and their reflections Although steam condensation has usually occurred by the las stage, ideal gas is mostly assumed when performing flutter analysi for steam turbines The results of a flutter analysis of a 2D steam turbine tes case which examine the influence of non-equilibrium wet stea are presented. The geometry and flow conditions of the test cas are supposed to be similar to the flow near the tip in a stea turbine as this is where most of the unsteady aerodynamic wor contributing to flutter is done. The unsteady flow simulation required for the flutter analysis are performed by ANSYS CFX Three fluid models are examined: ideal gas, equilibrium we steam (EQS) and non-equilibrium wet steam (NES), of whic NES reflects the reality most Previous studies have shown that a good agreement betwee ideal gas and EQS simulations can be achieved if the prescribe ratio of specific heats is equal to the equilibrium polytropic inde of the wet steam flow through the turbine.

  • 256. Fujii, S.
    et al.
    Kanematsu, Y.
    Kikuchi, Y.
    Nakagaki, T.
    Chiu, Justin NingWei
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Martin, Viktoria
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Techno economic analysis of thermochemical energy storage and transport system utilizing "zeolite Boiler": Case study in Sweden2018In: Energy Procedia, Elsevier, 2018, p. 102-111Conference paper (Refereed)
    Abstract [en]

    Thermochemical energy storage and transport system utilizing zeolite steam adsorption and desorption cycle is one of the methods to resolve the mismatch between industrial surplus heat and heat demands. To generate 60°C hot water utilizing zeolite 13X, zeolite boiler employing moving bed and indirect heat exchanger was developed. Pressurized water is heated up and flash steam is injected into the zeolite bed for adsorption. A quasi - 2D model solving heat and mass conservation equations was developed, leading to a performance characterization of this zeolite boiler. The developed simulation model was used to predict performance of a heat charging device employing moving bed as well. Based on this calculation, a case study, heat transporting between a local steel works and a hotel was examined and all corresponding cost were fixed. The Levelized Cost of Energy (LCOE) results in around 60 €/MWh which is comparable cost against conventional pellet boiler. Sensitivity analysis showed both of cheaper transportation cost and larger zeolite capacity on the one trailer give a comparable impact on the LCOE.

  • 257.
    Gagne, Anton
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Effects of Asymmetry and Other Non-Standard Excitations on Structural Dynamic Forced Response Analysis of Turbomachinery Flow-Path Components2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    A recent paper explored a potential deficiency in the single frequency harmonic response structural dynamic analysis approach typically used to assess a resonant condition in turbomachinery flow path components. This deficiency is prevalent in supersonic flow conditions when non-adjacent stages are present. The previous investigation demonstrated other excitation sources present in complex or supersonic flows could be missed using the typical analysis approach, in some cases leading to large under-prediction of structural response when compared with a baseline transient analysis. This paper presents the results of a follow on study, in which the inclusion of these effects in dynamic analyses is investigated. A representative rotor was created and analyzed for forced response characteristics when individual and combined unsteady content was present. A simple shell and beam 2D model was used to study the forced response behavior using transient and harmonic analyses. The results showed a significant contribution from non-integer forcing as well as from certain integer order forcing. A 3D model was also created for future analysis but did not display the sideband characteristics similar to flow seen in the previous investigation.

  • 258.
    Gaillard, Hugo
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Optimization of export electrical infrastructure in offshore windfarms: Developing an electrical export module in a front-end holistic model for offshore wind plant optimization2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The work focuses on the methods used to develop one particular sub-part of a computer tool for optimizing the final cost of energy in offshore wind parks : the linking infrastructure for bringing electrical power ashore. The thesis is the outcome of a 6-month cooperation with AREVA Wind, within the Wind Plant Solutions department, and is based on previous work done by AREVA, their proprietary database, as well as on publically available technical data.

    Exporting power from an offshore electrical substation down to the grid connection point is nowadays a critical bottleneck in the development of offshore wind energy, where project optimization and cost reduction are for many viewed as powerful levers capable of increasing dramatically its competitiveness on the electricity market.

    The approach and methodology used to develop the model, along with challenges and difficulties encountered are exposed. The necessary outputs are defined, the related equations are carefully examined and give way to choices, simplifications and assumptions so that governing inputs are identified. Eventually, a project optimization algorithm is described and evaluated against available data from existing offshore developments, focusing primarily on decreasing the overall cost of electrical transmission and on the proper choice of technology for the particular project.

    The impact of the proposed algorithm and its sensitivity to varying parameters, as well as its precision and reliability have been estimated and validated with encouraging results allowing for immediate implementation in the industry.  In the thesis, for confidentiality purposes, fictive though realistic scenarios are computed, results presented and commented on, conclusions drawn.

    Finally, implementation and analysis of results on large-scale projects also provides with better understanding of upcoming challenges inherent to new technologies on the verge to be introduced as the industry keeps growing.

  • 259. Gao, Yang
    et al.
    Petrie-Repar, Paul
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Validation of meanline performance prediction method for radial and mixed flow turbine2018In: Institution of Mechanical Engineers - 13th International Conference on Turbochargers and Turbocharging 2018, Institution of Mechanical Engineers , 2018, p. 357-372Conference paper (Refereed)
    Abstract [en]

    This paper describes a meanline performance prediction method which is developed based on a preliminary design tool, namely TOPGEN. The newly proposed method extends the application of former tool to off-design conditions and mixed flow turbine. To achieve this goal, special treatments to incidence loss calculation of mixed flow turbine and throat flow prediction are developed. The method is validated against test data from open literature. The predicted results of radial turbine showed good agreement with test data on whole performance curve. For mixed flow turbine, different loss model combinations were investigated to give insights to mixed flow turbine prediction.

  • 260. Gao, Zhan
    et al.
    Raza, Rizwan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Fransson, Torsten
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Zhu, Bin
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Development of Direct Methanol Low Temperature Fuel Cells from a Polygeneration, Perspective2011In: International journal of energy research (Print), ISSN 0363-907X, E-ISSN 1099-114X, Vol. 35, p. 690-696Article in journal (Refereed)
  • 261.
    Gao, Zhan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Raza, Rizwan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Zhu, Bin
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Mao, Zongqiang
    Development of methanol-fueled low-temperature solid oxide fuel cells2011In: International journal of energy research (Print), ISSN 0363-907X, E-ISSN 1099-114X, Vol. 35, no 8, p. 690-696Article in journal (Refereed)
    Abstract [en]

    Low-temperature solid oxide fuel cell (SOFC, 300-600 degrees C) technology fueled by methanol possessing significant importance and application in polygenerations has been developed. Thermodynamic analysis of methanol gas-phase compositions and carbon formation indicates that direct operation on methanol between 450 and 600 degrees C may result in significant carbon deposition. A water steam/methanol ratio of 1/1 can completely suppress carbon formation in the same time enrich H(2) production composition. Fuel cells were fabricated using ceria-carbonate composite electrolytes and examined at 450-600 degrees C. The maximum power density of 603 and 431 mW cm(-2) was achieved at 600 and 500 degrees C, respectively, using water steam/methanol with the ratio of 1/1 and ambient air as fuel and oxidant. These results provide great potential for development of the direct methanol low-temperature SOFC for polygenerations.

  • 262. Gao, Zhan
    et al.
    Raza, Rizwan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Zhu, Bin
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Mao, Zongqiang
    Wang, Cheng
    Liu, Zhixiang
    Preparation and characterization of Sm0.2Ce0.8O1.9/Na2CO3 nanocomposite electrolyte for low-temperature solid oxide fuel cells2011In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 36, no 6, p. 3984-3988Article in journal (Refereed)
    Abstract [en]

    Sm0.2Ce0.8O1.9 (SDC)/Na2CO3 nanocomposite synthesized by the co-precipitation process has been investigated for the potential electrolyte application in low-temperature solid oxide fuel cells (SOFCs). The conduction mechanism of the SDC/Na2CO3 nanocomposite has been studied. The performance of 20 mW cm(-2) at 490 degrees C for fuel cell using Na2CO3 as electrolyte has been obtained and the proton conduction mechanism has been proposed. This communication demonstrates the feasibility of direct utilization of methanol in low-temperature SOFCs with the SDC/Na2CO3 nanocomposite electrolyte. A fairly high peak power density of 512 mW cm(-2) at 550 degrees C for fuel cell fueled by methanol has been achieved. Thermodynamical equilibrium composition for the mixture of steam/methanol has been calculated, and no presence of C is predicted over the entire temperature range. The long-term stability test of open circuit voltage (OCV) indicates the SDC/Na2CO3 nanocomposite electrolyte can keep stable and no visual carbon deposition has been observed over the anode surface. Copyright (C) 2011, Hydrogen Energy Publications, LLC.

  • 263.
    Garay Rosas, Ludwin
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    System Simulation of Thermal Energy Storage involved Energy Transfer model in Utilizing Waste heat in District Heating system Application2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Nowadays continuous increase of energy consumption increases the importance of replacing fossil fuels with renewable energy sources so the CO2 emissions can be reduced. To use the energy in a more efficient way is also favorable for this purpose. Thermal Energy Storage (TES) is a technology that can make use of waste heat, which means that it can help energy systems to reduce the CO2 emissions and improve the overall efficiency. In this technology an appropriate material is chosen to store the thermal energy so it can be stored for later use. The energy can be stored as sensible heat and latent heat. To achieve a high energy storage density it is convenient to use latent heat based TES. The materials used in this kind of storage system are called Phase Change Materials (PCM) and it is its ability of absorbing and releasing thermal energy during the phase change process that becomes very useful.

    In this thesis a simulation model for a system of thermal energy transportation has been developed. The background comes from district heating systems ability of using surplus heat from industrials and large scale power plants. The idea is to implement transportation of heat by trucks closer to the demand instead of distributing heat through very long pipes. The heat is then charged into containers that are integrated with PCM and heat exchangers.

    A mathematical model has been created in Matlab to simulate the system dynamics of the logistics of the thermal energy transport system. The model considers three main parameters: percentage content of PCM in the containers, annual heat demand and transport distance. How the system is affected when these three parameters varies is important to visualize. The simulation model is very useful for investigation of the economic and environmental capability of the proposed thermal energy transportation system. Simulations for different scenarios show some expected results. But there are also some findings that are more interesting, for instance how the variation of content of PCM gives irregular variation of how many truck the system requires, and its impact on the economic aspect. Results also show that cost for transporting the heat per unit of thermal energy can be much high for a small demands compared to larger demands.

  • 264.
    Garrido Galvez, Jorge
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Wang, Wujun
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Nilsson, Martin
    Cleanergy Company.
    Laumert, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    A Detailed Radiation Heat Transfer Study of a Dish-Stirling Receiver: the Impact of Cavity Wall Radiation Properties and Cavity Shapes2015In: SOLARPACES 2015: INTERNATIONAL CONFERENCE ON CONCENTRATING SOLAR POWER AND CHEMICAL ENERGY SYSTEMS / [ed] Rajpaul, V; Richter, C, American Institute of Physics (AIP), 2015Conference paper (Refereed)
    Abstract [en]

    A detailed 3-D radiation analysis of a dish-Stirling cavity receiver is carried out to estimate the cavity steady-state temperatures in order to assess the receiver integrity, lifetime and efficiency performance. For this purpose, a parabolic dish was modeled with 5.2 m focal length, 8.84 m aperture diameter and 2.1 mrad typical surface error. Three generic cavity shapes (cylindrical, diamond-shaped and reverse-conical) with three different emissivities (0.2, 0.4 and 0.7) are studied. Worst-case scenario heat generations (total absorbed radiation), maximum steady-state temperatures and energy balances of the cavities are calculated to evaluate the receiver performance. The results show that reverse-conical cavities can significantly reduce cavity wall peak temperatures (by 40-120 K), improve the temperature evenness and decrease the radiation losses by 4-5%. Regarding radiation properties, low reflectivities present lower steady-state temperatures even for low/moderate direct solar fluxes. Due to the lower temperatures, lower total thermal losses are also expected.

  • 265.
    Garrido, Jorge
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Abou-Taouk, A.
    Laumert, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Characterization of a Stirling cavity receiver performance in the KTH high-flux solar simulator and comparison with real Dish-Stirling data2018In: AIP Conference Proceedings, American Institute of Physics Inc. , 2018Conference paper (Refereed)
    Abstract [en]

    This paper presents the experimental results of the Cleanergy's C11S solar engine-generator tested in the KTH solar simulator. The paper focuses on the analysis of the thermal performance of the cavity receiver used in the C11S module. Multiple temperature measurements were taken on the tubes of the receiver, inside the cavity and on the internal surface of the cavity. These values allowed characterizing the temperature distribution all around the cavity receiver for the validation of thermal models and the estimation of the thermal losses. Moreover, this paper shows a comparison of the operating characteristics of the C11S module under the real operating conditions and the laboratory ones. It was observed that the temperatures of the receiver in the High Flux Solar Simulator (HFSS) resemble well the real temperatures. Thereby, the KTH solar lab provides proper irradiance levels to operate solar receivers at representative working conditions.

  • 266.
    Garrido, Jorge
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Aichmayer, Lukas
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Abou-Taouk, Abdallah
    Cleanergy, Regnbagsgatan 6, S-41755 Gothenburg, Sweden..
    Laumert, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Experimental and numerical performance analyses of a Dish-Stirling cavity receiver: Geometry and operating temperature studies2018In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 170, p. 913-923Article in journal (Refereed)
    Abstract [en]

    Higher performance cavity receivers are needed to increase the competitiveness of solar power plants. However, the design process needs to be improved with more relevant experimental and numerical analyses. Thereby, the performance of four different Dish-Stirling cavities is investigated experimentally analyzing the influence of the cavity aperture diameter and shape at various operating temperatures. Temperatures inside the cavity receiver were collected together with the electrical power produced by the engine-generator. Then, a thermal system simulation was modelled and a comprehensive multi-parameter and multi-operation validation was performed. To improve this validation, the temperature distribution across the receiver tubes was analyzed in order to relate temperatures on the irradiated region with the non-irradiated one, where thermocouples can measure. The simulations were later used to obtain cavity receiver efficiencies, temperatures and loss breakdowns. The results show that the cavity receiver must be studied in optimization processes in conjunction with the other system components. Moreover, the reverse-conical cavity was found to be more efficient than a nearly cylindrical shape. Regarding the cavity receiver thermal losses, radiation and natural convection present similar contributions in the system under study. Finally, it was found that thermocouples installed on a non-irradiated region can be used to obtain peak receiver temperatures if the measurements are rectified by a correction value proportional to the DNI.

  • 267.
    Garrido, Jorge
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Aichmayer, Lukas
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Abou-Taouk, Abdallah
    Azelio, Regnbagsgatan 6, S-41755 Gothenburg, Sweden..
    Laumert, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Experimental and numerical performance analyses of Dish-Stirling cavity receivers: Radiative property study and design2019In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 169, p. 478-488Article in journal (Refereed)
    Abstract [en]

    The solar receiver performance has a direct impact on the CSP power plant performance and, thereby, its levelized cost of electricity. Improved receiver designs supported by new advanced numerical tools and experimental validation campaigns directly help to make CSP technology more competitive. This paper presents an experimental and numerical investigation of the influence of the cavity receiver radiative properties and the thermal power input on the Dish-Stirling performance. Three cavity coatings are experimentally investigated: the original cavity material (Fiberfrax 140), Pyromark 2500 and Pyro-paint 634-ZO. Moreover, simulations validated with the experimental measurements are utilized to define a higher performance cavity receiver for the Eurodish system. The results indicate that the absorptivity of the cavity should be as low as possible to increase the receiver efficiency whereas the optimum emissivity depends on the operating temperatures. If the cavity temperature is lower than the absorber temperature, low emissivities are recommended and vice-versa. All material/coatings analyzed for the cavity provide similar receiver efficiencies, being Fiberfrax 140 slightly more efficient. Finally, a total receiver efficiency of 91.5% is reached by the proposed Eurodish cavity receiver when operating under the most favorable external conditions. 

  • 268.
    Garrido, Jorge
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Aichmayer, Lukas
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Wang, Wujun
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Laumert, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Characterization of the KTH high-flux solar simulator combining three measurement methods2017In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 141, p. 2091-2099Article in journal (Refereed)
    Abstract [en]

    This paper presents the characterization of the first Fresnel lens-based High-Flux Solar Simulator (HFSS) showing the evaluation of the total thermal radiative power dependent on the aperture radius at the focal plane. This result can be directly applied to calculate the thermal power input into any solar receiver tested in the KTH HFSS. Three measurement setups were implemented and their results combined to assess and verify the characterization of the solar simulator: a thermopile sensor measuring radiative flux, a CMOS camera coupled with a Lambertian target to obtain flux maps, and a calorimeter to measure the total thermal power within an area of 300×300 mm. Finally, a Monte Carlo analysis was performed to calculate the total uncertainties associated to each setup and to combine them to obtain the simulator characterization. The final result shows a peak flux of 6.8 ± 0.35 MW/m2 with a thermal power of 14.7 ± 0.75 kW within an aperture of 180 mm in diameter at the focal plane, and a thermal-electrical conversion efficiency of 25.8 ± 0.3%. It was found very good repeatability and a stable energy output from the lamps during the experiments.

  • 269.
    Garrido, Jorge
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Sjöqvist, R.
    Laumert, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Mechanical coupling behavior of a dish-Stirling receiver: Influence on the absorber tube stresses2019In: AIP Conference Proceedings, American Institute of Physics (AIP), 2019, Vol. 2126, article id 050003Conference paper (Refereed)
    Abstract [en]

    The solar receiver tubes work under the highest temperatures and heat flux conditions, being their thermo-mechanical design critical to assure a safe and durable operation. Finite Element Analyses are traditionally utilized to assess the stresses for lifetime calculations. However, the real boundary conditions for these analyses are not well known yet. Thereby, this paper presents an experimental and numerical study to determine more realistic boundary conditions. Firstly, four deflection measurements are measured simultaneously by high-accuracy laser meters. Secondly, three types of boundary conditions are simulated trying to fit the experimental deflections: fixed, elastic and remote displacement. Finally, the stresses at critical regions are compared for each simulation. The results show that, unlike fixed support, remote displacement boundary conditions can obtain realistic deflection results but must be re-adjusted for each specific support, and elastic support fails to capture the manifold rotations. Using remote displacement stress results as reference for the case under study, fixed support leads to deviations in the stresses of at least 50% whilst elastic support can provide some similar stress results.

  • 270.
    Gaudray, Gordon
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    A behavioral model of solar/diesel/Li-ion hybrid power systems for off-grid applications: Simulation over a lifetime of 10 years in constant use2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Remote hybrid power systems (RHPS) serve local off-grid loads or various island grids when no grid extension is possible. They combine renewable resources, conventional generators and energy storage systems in order to balance the load at any moment, while ensuring power quality and energy security similar to large centralized grids. Modelling such a complex system is crucial for carrying out proper simulations for predicting the system’s behavior and for optimal sizing of components. The model should include an estimation of the renewable resource availability over the period of the simulation, a prediction of the load consumption and time variation, the choice of technologies, a prior dimensioning approach, an energy dispatching strategy between the components and, finally, the behavioral model of all components.

    This study limits its scope to the simulation of a RHPS composed of solar PV panels, a diesel generator set, and a Li-ion battery bank supplying a dynamic isolated load with a daily demand variation between 10 kW and 80 kW. Methods for building load scenarii are explained first and then, rules of thumbs for selecting the technologies and pre-sizing the components are reviewed. Commonly used dispatching strategies are described before detailing the algorithm of a Matlab behavioral model for the system’s components with an emphasis on the proper prediction of performance and aging for the Li-ion battery model. Finally, a 10-year simulation is carried out over a case study and the results are analyzed.

  • 271.
    Gebrelibanos, Kalekirstos Gebremariam
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Feasibility Study of Small Scale Standalone Wind Turbine for Urban Area: Case study: KTH Main Campus2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The recent worldwide economic crisis, climate change and global warming have emphasized that the need for low carbon emissions while also ensuring the economic feasibility. In this paper, wind power potential of ETD in KTH was investigated. The technical and economical feasibility of tower mounted small scale standalone wind turbine installation is conducted. The potential of wind power production was statistically analysed. The average wind speed data of four-season interval of one year period (2011) which its measurement was taken on the roof top of the ETDB, and this was adopted and analysed in order to find out the potential of wind power generation. The Rayleigh distribution probability was applied to calculate the wind speed distribution at KTH, by doing so the annual wind power potential at the area and annual energy production of the chosen wind turbine was estimated, after the selection of a proper wind turbine have been made upon the site conditions. Therefore, the study result shows that installation of the wind turbine at 24 meters hub height for this particular area will have a better performance of annual energy production, capacity factor, carbon savings and better economical value than the current turbine installed at 17 meters height at the ETD. The economic evaluation shows that the turbine can save an electricity bill of US$3661.05 per year and cover 1.84% of the electricity consumption of the ETD by reducing its respective CO2 emission from the electricity use at the department. Moreover, the payback period of the turbine installation with the inclusion of the green certificate is approximately 14 years which is more feasible if it is considered for small wind turbines too, which is already in practice for renewables including wind power in Sweden.

  • 272.
    Geerolf, Laurent
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    The Biogas Sector Development: Current and future trends in Western and Northern Europe2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The following study attempts to provide a comparative analysis of the biogas production activities in 15 countries in Western and Northern Europe. The goal is, for each country, to gather all the available information about the present status of the biogas sector and then to evaluate the possible trends for future development in terms of main biogas production pathways, valorization, volumes, market dynamics, etc.First, a review of the current biogas production, including feedstock types and valuation pathways, is carried on. Then, national supporting schemes are reviewed and assessed in order to estimate their future impact on the production capacity. An estimate of the production volumes in year 2022 is attempted, based on the extrapolation of current support schemes and national objectives. The prognosis towards year 2022 is further subjected to sensitivity analysis with the breakdown per valorization method and feedstock input types, as well as with the probable variability of financial support schemes. The results of the study are summarized and discussed based on comparisons with other forecasts and feedstock availability projections.The results show that the current situation in each country is very heterogeneous in terms of technologies, volumes, maturity, potential growth and valorization aspects. However, the future holds a promise of a more straightforward trendline: agricultural residues should be used much more as feedstock (in co-digestion with other inputs) and biogas upgrade to biomethane should increase a lot, mainly for injection in existing gas grids. However, market dynamics are and will remain very different from one country to another, because of diverging support schemes set on a national scale.

  • 273. Geraimchuk, I.M
    et al.
    Geraimchuk, M.D
    Kazachkov, I.V
    Fransson, Torsten
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Virtual university environment: Swedish-Ukrainian network for design and implementation of Internet-based education software2010Conference paper (Other academic)
  • 274. Geraimchuk, M.D
    et al.
    Kazachkov, I.V
    Fransson, Torsten
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Development and implementation of multimedia educational systems for universities and schools2007Conference paper (Refereed)
  • 275.
    Gezork, Tobias
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    INVESTIGATION OF A QUASI-3D METHOD FOR OPTIMIZING AERODYNAMIC PERFORMANCE OF GAS TURBINE AIRFOILS2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Over the past few decades the performance of gas turbine airfoils has been improved continually by creating advanced aerodynamic and thermal designs.

    Today often-times optimisation methods are used to handle the increased complexity of such a design, where possible efficiency performance increase is in the order of a fraction of a percentage point. However, optimisation is expensive when performed based on 3D CFD calculations. Therefore, an optimisation strategy based on simpler, less expensive analysis methods is desirable.

    In this thesis a quasi-3D optimization approach to reduce blade profile losses is investigated. The presented quasi-3D setup uses several blade sections that are evaluated with a computationally inexpensive 2D CFD code. The results obtained with the code are then combined to get the overall blade performance, neglecting 3D flow features than are not captured by the 2D calculations. 3D blade design features, such as bow, lean or sweep, are not investigated.

    In the work presented, three test case s are set up and investigated: a second stage stator vane, a fourth stage stator vane and a third stage rotor blade. First, results obtained with the quasi-3D method are compared to results obtained by full 3D CFD calculations in a correlation study.

    Next, quasi-3D optimization is performed for the three test cases and the results of the optimization are evaluated by means of a full 3D CFD calculation and compared to the quasi-3D predictions.

    The results indicate that the method is suitable for optimization and application concepts are presented.

  • 276.
    Gezork, Tobias
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Gutierrez, Mauricio
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Groth, Pieter
    GKN Aerospace Sweden AB.
    Vogt, Damian M.
    Institut für Thermische Strömungsmaschinen und Maschinenlaboratorium, University of Stuttgart.
    Fransson, Torsten
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Unsteady blade force computation sensitivity in a transonic turbine to rotor tip gap, hub and shroud cavity model detail2015In: Proceedings of the 14th International Symposium on Unsteady Aerodynamics, Aeroacoustics & Aeroelasticity of Turbomachines, 2015Conference paper (Refereed)
    Abstract [en]

    The influence of including geometric detailing features on blade forcing predicted by CFD calculations is investigated. Various features such as rotor tip gap, rotor tip shroud cavity with substantial leakage flow and large rotor upstream hub rim cavity are investigated. The test case is based on a single stage transonic test turbine rig in which the unsteady aerodynamics and blade forcing have previously been investigated numerically.

    Including the tip gap and the tip shroud leakage in the computational model resulted in an overall increase in unsteady forcing. The change in forcing is mainly due to a change in secondary flow structure, but also due to a change of the stage flow condition. Conversely, it is shown that including the hub cavity in the computational model, even without the presence of purge-flow, reduces the unsteady force. Lastly, even though there are changes in unsteady blade loading, the blade response amplitude is only changed marginally (maximum 7%) due to forcing variations alone.

  • 277.
    Gezork, Tobias
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Mayorca, M. A.
    Groth, P.
    Vogt, D. M.
    Fransson, Torsten
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Influence of tip shroud cavity detailing on turbine blade forcing calculations2014In: ASME Turbo Expo 2014: Turbine Technical Conference and Exposition, ASME Press, 2014, Vol. 7B, p. V07BT35A021-Conference paper (Refereed)
    Abstract [en]

    Forced response in turbomachinery refers to the vibration of a component due to an excitation originating from another component. Obstacles, such as struts and blade rows in the upstream and downstream flow path of a turbomachine engine lead to engine order (EO) excitations. To be able to predict the severity of these excitations, both aerodynamic and structural calculations are performed. There is a risk of critical high cycle fatigue (HCF) failure when the force acts at a resonance frequency. Customarily, forcing calculations exclude detailing features, such as leakage flows. The current investigation uses a two stage subsonic model steam turbine configuration with shrouded rotor blades to demonstrate the influence of neglecting flow through seal cavities for blade forcing predictions. Upstream and downstream vanes are the excitation sources on the rotor blade. Calculation results are compared for a configuration including and excluding the tip shroud cavity. Computed data is compared to available pressure data from tests in the model turbine. The investigation shows for the first blade passing excitation at design point that the axial and circumferential rotor forcing change by +22%, respectively +4% when including the tip shroud cavity for the investigated configuration. The change in forcing arises from the interaction of the leakage flow with the main stream flow. For highly loaded designs this can be of importance if there is a critical excitation.

  • 278.
    Gezork, Tobias
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Petrie-Repar, Paul
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Influence of gap detailing on calculated unsteady non-adjacent blade row aero-forcing in a transonic compressor stageManuscript (preprint) (Other academic)
    Abstract [en]

    Resonant or close to resonant forced response excitation of compressor blades limits component life time, and can potentially lead to high cycle fatigue failure if the excitingforces are large and damping is insufficient. When numerically quantifying the forcing function by means of simulations,simplifications are typically made in the analysis to reducecomplexity and computational cost. In this paper we numerically investigate how the blade forcing function is influencedby the rotor tip gap flow and by flow across gaps in the upstream VIGV row. Unsteady simulations are made using a testrig geometry where a forcing crossing with an excitation froma non-adjacent blade row had previously been measured. Theeffects of the gaps on the forcing function for the first torsionmode are presented for both the non-adjacent blade row excitation (changes compared with a case without gaps indicating a 20% reduction) and an adjacent excitation (changes indicating an80% increase in terms of forcing function amplitude comparing with a case without gaps).

  • 279.
    Gezork, Tobias
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Petrie-Repar, Paul
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Fransson, Torsten
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    A NEW VISUALIZATION METHOD FOR HARMONIC UNSTEADY FLOWS IN TURBOMACHINERY2016In: PROCEEDINGS OF THE ASME TURBO EXPO: TURBINE TECHNICAL CONFERENCE AND EXPOSITION, 2016, VOL 7B, AMER SOC MECHANICAL ENGINEERS , 2016Conference paper (Refereed)
    Abstract [en]

    Understanding unsteady flow processes is key in the analysis of challenging problems in turbomachinery design such as flutter and forced response. In this paper a new visualization method for harmonic unsteady flow is presented. The method illustrates the direction in which unsteady waves are traveling and transporting energy by the direct visualization of the propagating pressure waves in terms of field lines constructed from the wave group velocity. The group velocity is calculated from the unsteady flow solution by assuming that the local unsteady pressure perturbation of interest can be represented by a single harmonic unsteady wave. The applicability of the method is demonstrated for three test cases including a linear cascade of two-dimensional flat plates and a linear cascade of two-dimensional compressor blade profiles.

  • 280.
    Gezork, Tobias
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Völker, S.
    Applicability of quasi-3d blade design methods to profile shape optimization of turbine blades2013In: Proc. ASME Turbo Expo, 2013Conference paper (Refereed)
    Abstract [en]

    The performance of gas turbine airfoils is continually improved by creating advanced aerodynamic and thermal designs. Optimization methods are used to handle the increasing complexity of such a design. However, optimization is expensive when performed based on 3D CFD calculations. Therefore, an optimization strategy based on simpler, less expensive analysis methods is desirable. Oftentimes, a so-called quasi-3D (Q3D) approach is used, where 2D calculations are carried out on multiple, radially stacked meridional blade sections. This paper investigates the applicability of such an approach for optimization with regard to blade profile loss. Obviously, certain physical effects are neglected using this approach, leading to errors in the predicted blade performance. Still, optimization based on Q3D calculations might be possible if the error is consistent, i.e. not random. For this purpose, a design of experiment (DOE) was carried out to compare and correlate loss predictions from Q3D calculations and high-fidelity 3D CFD calculations for gas turbine blades. It is shown that the total pressure loss coefficients found with both the Q3D and 3D calculations correlate well (75-90%) to warrant the use of a Q3D method for profile shape optimization. Subsequently, an optimization is performed to demonstrate the applicability of the method.

  • 281.
    Ghaem Sigarchian, Sara
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Design Optimization of a Complex PolygenerationSystem for a Hospital2018In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 11, no 1071Article in journal (Refereed)
    Abstract [en]

    Small-scale decentralized polygeneration systems have several energetic, economic and environmental benefits. However, using multiple energy sources and providing multiple energy services can lead to complicated studies which require advanced optimization techniques for determining optimal solutions. Furthermore, several parameters can influence the design and performance of a polygeneration system. In this study, the effects of heat load, renewable generation and storage units on the optimal design and performance of a polygeneration system for a hypothetical hospital located in northern Italy are investigated. The polygeneration system shows higher performance compared to the reference system, which is based on the separate generation of heat and power. It reduces fuel consumption by 14–32%, CO2 emissions by 10–29% and annualized total cost by 7–19%, for various studied scenarios. The avoided fuel and electricity purchase of the polygeneration system has a positive impact on the economy. This, together with the environmental and energetic benefits if the renewable generation and use of storage devices, indicate the viability and competitiveness of the system.

  • 282.
    Ghaem Sigarchian, Sara
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Modeling and Analysis of a Hybrid Solar-Dish Brayton Engine2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 283.
    Ghaem Sigarchian, Sara
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Small-Scale Decentralized Energy Systems: optimization and performance analysis2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Small-scale polygeneration energy systems, providing multiple energy services, such as heating, electricity, cooling, and clean water, using multiple energy sources (renewable and non-renewable) are considered an important component in the energy transition movement. Exploiting locally available energy sources and providing energy services close to the end users have potential environmental, economic, and societal benefits. Furthermore, integration of thermal and electro-chemical storages in the system can decrease fossil fuel consumption, particularly when applying a long-term perspective.

    Despite their promising potential, the global share of power generation by these systems, including the combined heat and power (CHP) systems, is relatively low in the current energy market. To investigate the applicability of these systems, their competitiveness in comparison with conventional energy solutions should be carefully analyzed in terms of energy, economy, and the environment. However, determining whether the implementation of a polygeneration system fulfills economic, energetic, and environmental criteria is a challenging process. Additionally, the design of such systems is a complex task, due to a system design with various generation and storage modules, and the continuous interaction between the modules, load demand fluctuations, and the intermittent nature of renewable energy sources.

    In this research study, a method to identify the optimal size for small-scale polygeneration systems and suitable operating strategies is proposed. Based on this method, a mathematical model is developed that can optimize the design in terms of energy, economy, and the environment relative to a reference system for a given application. Moreover, the developed model is used to investigate the effects of various parameters on the performance of the system, including, among others, the selected operating strategy and load characteristics as well the climate zones through a number of case studies. It is concluded that the application of a small-scale polygeneration energy system potentially has considerable energetic and environmental benefits. However, its economic feasibility varies from case to case. The concluding remarks are primarily intended to provide a general perception of the potential application of a polygeneration system as an alternative solution. It also provides a general understanding of the effects of various parameters on the design and performance of a complex polygeneration system.

    The results from various case studies demonstrate that the developed model can efficiently identify the optimal size of a polygeneration system and its performance relative to a reference system. This can support engineers and researchers as well as investors and other decision makers to realize whether a polygeneration system is a good choice for a specific case.

  • 284.
    Ghaem Sigarchian, Sara
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    The choice of operating strategy for a complex polygeneration system: A case study for a residential building in Italy2018Manuscript (preprint) (Other academic)
    Abstract [en]

    The operating strategy can affect the optimal solution and performance of a polygeneration energy system. In this study, the effect of operating strategies: following thermal load; following electric load; and modified baseload on the optimal solution of a polygeneration system for a residential building complex in the northern part of Italy is investigated. For the optimal solutions, a comparative analysis is carried out considering the techno-economic and environmental performance of the system. The result elaborates on how the benefits achieved in a polygeneration system are influenced by the choice of operating strategy. In the building complex, implementation of the operating strategies shows considerable energetic, economic and environmental benefits compared to conventional separate heat and power generation. The ranges of annualized total cost reduction of 17–19%, carbon dioxide emission reduction of 35–43% and fuel consumption reduction of 30–38% are achieved for the various operating strategies. However, each of the operating strategies has its own advantages and drawbacks which emphasizes the importance of post-processing of the results in order to make the right choice. For example, the following thermal load shows the advantage of a higher carbon dioxide emission reduction. On the other hand, one drawback is its lower self-sustainability in terms of electric power compared to the other strategies.

  • 285.
    Ghaem Sigarchian, Sara
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology. European Institute of Innovation and Technology, Sweden.
    Malmquist, Anders
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Fransson, Torsten
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Modeling and control strategy of a hybrid PV/Wind/Engine/Battery system to provide electricity and drinkable water for remote applications2014In: Energy Procedia: 2013 ISES Solar World Congress, Elsevier, 2014, Vol. 57, p. 1401-1410Conference paper (Refereed)
    Abstract [en]

    In this paper a small-scale energy system called emergency container is presented. This container has lots of applications and can be designed as stationary solution in remote areas such as rural electrification and a mobile solution for disaster situation, military purposes and exploration teams. In this study the container is a hybrid PV/wind/engine energy system that is designed to provide electricity and drinkable water for 1000 person in disaster situations. A transient model implemented in Transient Simulation System (TRNSYS) program is developed and performance of the system during one-year operation for two locations (Nairobi in Kenya and Nyala in Sudan) with relatively high solar insolation is analyzed. The result of the model is significantly important in order to choose the right size of the different components. Due to the fluctuations of solar and wind energy as well as the importance of the battery life cycle, there is a need to have a smart power management and an appropriate fast response control system. In order to achieve it and to fulfill the energy demand as much as possible through renewable energies, a dispatch strategy is introduced and a control algorithm is applied to the model. This control algorithm has increased system reliability and power availability. The transient simulation shows that the share of power generation by solar energy is 63% and 80% and the share of wind power is 27% and 12% in Nairobi and Nyala respectively. It means that most of the energy demand (around 90%) can be covered by renewable energy. This results in significant mitigation of environmental issues compared to using only diesel engine that is a common solution in disaster situations.

  • 286.
    Ghaem Sigarchian, Sara
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Malmquist, Anders
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Martin, Viktoria
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Design optimization of a small-scale polygeneration energy system in different climate zones in Iran2018In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 11, no 5, article id 1115Article in journal (Refereed)
    Abstract [en]

    Design and performance of polygeneration energy systems are highly influenced by several variables, including the climate zone, which can affect the load profile as well as the availability of renewable energy sources. To investigate the effects, in this study, the design of a polygeneration system for identical residential buildings that are located in three different climate zones in Iran has been investigated. To perform the study, a model has previously developed by the author is used. The performance of the polygeneration system in terms of energy, economy and environment were compared to each other. The results show significant energetic and environmental benefits of the implementation of polygeneration systems in Iran, especially in the building that is located in a hot climate, with a high cooling demand and a low heating demand. Optimal polygeneration system for an identical building has achieved a 27% carbon dioxide emission reduction in the cold climate, while this value is around 41% in the hot climate. However, when considering the price of electricity and gas in the current energy market in Iran, none of the systems are feasible and financial support mechanisms or other incentives are required to promote the application of decentralized polygeneration energy systems.

  • 287.
    Ghaem Sigarchian, Sara
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Malmquist, Anders
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Martin, Viktoria
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Optimal planning and design method for complex polygeneration systems: A case study for a residential building in ItalyManuscript (preprint) (Other academic)
    Abstract [en]

    Polygeneration energy systems using multiple energy sources (e.g., wind, biomass, solar) and delivering multiple energy services (i.e., heating, cooling, and electricity) have potential economic and environmental benefits over traditional energy generation systems. However, for maximized benefits, such systems must be the correct size and have a suitable operating strategy implemented. In this study, an optimization model is proposed to identify the optimal design and operating strategy of a complex polygeneration system. The system includes photovoltaic modules, solar thermal units, wind turbines, combined heat and power units, energy storages (hot, cold, and electric), vapor compression and absorption chillers, and a boiler. The interactions between these units are managed based on the integrated operating strategies: following thermal load, following electric load and modified base load. A particle swarm optimization is used as an optimization algorithm and the objective function is defined to minimize the annualized total cost, fuel consumption, and carbon dioxide emissions using a weighting factor method. The careful incorporation of the realistic operation of the CHP is considered in the theoretical model. This includes the effects of the part-load operation and outdoor temperature on the efficiency and power output of the CHP. In addition, the size dependency of the unit cost of the chillers and CHP units over the search space is taken into account. With this approach, the achieved results would be as close to real conditions as possible. Six configuration scenarios are examined for a case study in a residential building complex located in northern Italy. It is concluded that implementation of the optimized polygeneration system has energetic, economic, and environmental conservation benefits in all these scenarios. The annualized cost and fuel consumption of the optimal solutions decreased by 3–19% and 10–37%, respectively, for the various scenarios compared to the separate generation system.

  • 288.
    Ghaem Sigarchian, Sara
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Paleta, Rita
    Malmquist, Anders
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Pina, André
    Feasibility study of using a biogas engine as backup in a decentralized hybrid (PV/wind/battery) power generation system: Case study Kenya2015In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 90, no 2, p. 1830-1841Article in journal (Refereed)
    Abstract [en]

    In this study, a hybrid power system consisting of PV (Photovoltaics) panels, a wind turbine and a biogas engine is proposed to supply the electricity demand of a village in Kenya. The average and the peak load of the village are around 8kW and 16.5kW respectively.The feasibility of using locally produced biogas to drive a backup engine in comparison to using a diesel engine as backup has been explored through a techno-economic analysis using HOMER (Hybrid Optimization Model for Electric Renewables). This hybrid system has also been compared with a single diesel based power system.The results show that the hybrid system integrated with the biogas engine as backup can be a better solution than using a diesel engine as backup. The share of power generation by PV, wind and biogas are 49%, 19% and 32%, respectively. The LCOE (Levelized Cost of Electricity) of generated electricity by this hybrid system ($0.25/kWh) is about 20% cheaper than that with a diesel engine as backup ($0.31/kWh), while the capital cost and the total NPC (Net Present Cost) are about 30% and 18% lower, respectively.Regarding CO2 emissions, using a biogas engine as backup saves 17 tons of CO2 per year compared to using the diesel engine as backup.

  • 289.
    Ghaem Sigarchian, Sara
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Strand, Torsten
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Spelling, James
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Malmquist, Anders
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Modeling and Analysis of a Hybrid Solar-Dish Brayton Engine2012In: Proceedings of the International SolarPACES Conference 2012, 2012Conference paper (Refereed)
    Abstract [en]

    Small-scale recuperated gas turbines with a highly efficient recuperator would appear to have considerable potential to be used in solar/fossil-fuel hybrid dish systems. The hybrid solar gas turbine can be configured in several different fashions, with the key difference being the relative positions of the solar receiver and burner as well as the operation mode of the burner.

    Steady state and transient models have been implemented in Engineering Equation Solver and the performance of various configurations are studied and compared. Layouts in which the receiver is located before the turbine (pressurized receivers) demonstrate higher performance compared to the one in which the receiver is located after the turbine (atmospheric receivers). The variation in operation throughout the year is taken into account and the performance of the system analyzed for two different cities (Yechang in China and Bechar in Algeria, with low and high solar insolation respectively). The integration of a solar receiver into a micro gas turbine reduces the yearly fuel consumption by around 15-16% in Yechang and up to 40% in Bechar. This will result in reductions of CO2 emissions as well as leading to lower daily operating costs. The hybrid nature of the Dish-Brayton system guarantees availability of the engine to meet the electricity demand whenever it occurs, allowing the system to supply dispatchable power.

  • 290.
    Giramondi, Nicola
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Multi-energy well kinetic modeling of novel PAH formation pathways in flames2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Polycyclic Aromatic Hydrocarbons (PAHs) are harmful by-products formed during combustion of hydrocarbons under locally fuel-rich conditions followed by incomplete combustion. PAHs act as precursors during the formation of soot. PAHs and soot are harmful for human health and legislation limits the emission of unburned hydrocarbons and soot. Consequently, other measures are necessary in order to limit the production of PAHs and soot in internal combustion engines applications, entailing a possible decrease of fuel efficiency and higher technical requirements for automotive manufactures. The combustion chemistry of PAHs is not fully understood, which prompts the need of further investigations. The chemical dynamics shown by novel pathways of PAH formation involving vinylacetylene addition to the phenyl radical opens up new horizons for the potential contribution to PAH formation through this class of reactions. In the present work novel pathways of the formation of naphthalene and phenanthrene are investigated for a laminar premixed benzene flame and a laminar ethylene diffusion flame. The purpose is to improve the prediction of the aromatic species concentration in the flames. A pathway chosen due the high potential aromatic yield is assessed through preliminary flame calculations relying on simplifying assumptions concerning reaction rates. Certain isomerisation steps of the pathway occur within a time-scale characteristic of thermal relaxation processes. Therefore, the solution of the energy grained master equation is necessary in order to calculate the phenomenological reaction rates resulting from a non-equilibrium kinetic modeling. Quantum chemical calculations are performed in order to calculate molecular properties of the species involved. These properties are subsequently processed to determine the rate constants of the sequence of multi-energy well reactions. Moreover, the chemical dynamics of the pathway is analyzed and the effect of temperature and pressure on the kinetic parameters is investigated. Despite of the potential yield demonstrated through the preliminary flame calculations, the computed rate constants show that the studied reactions are insignificant for the formation of naphthalene and phenanthrene in the studied flames. An effort is put on evaluating if the non-equilibrium kinetic modeling adopted for the calculation of the kinetic parameters is consistent with the kinetic modeling used in the flame calculations. The current work provides an efficient method to compute rate constants of multi-energy well reactions at different thermodynamic conditions, characteristic of flames and of combustion in commercial devices or in internal combustion engines. Pathways with a slightly different chemical dynamics should be tested applying the current methodology. Moreover, further studies should be aimed at overcoming possible limits of the kinetic modeling of multi-energy well reactions occurring in combustion environments.

  • 291. Gkoutzamanis, V. G.
    et al.
    Chiu, Justin Ning Wei
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Martin, Guillaume
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Kalfas, A. I.
    Thermal energy storage in combined cycle power plants: Comparing finite volume to finite element methods2019In: E3S Web of Conferences: SUPEHR19 Sustainable PolyEnergy generation and Harvesting, EDP Sciences, 2019, Vol. 113Conference paper (Refereed)
    Abstract [en]

    The research in thermal energy storage (TES) systems has a long track record. However, there are several technical challenges that need to be overcome, to become omnipresent and reach their full potential. These include performance, physical size, weight and dynamic response. In many cases, it is also necessary to be able to achieve the foregoing at greater and greater scale, in terms of power and energy. One of the applications in which these challenges prevail is in the integration of a thermal energy storage with the gas turbine (GT) compressor inlet conditioning system in a combined cycle power plant. The system is intended to provide either GT cooling or heating, based on the operational strategy of the plant. As a contribution to tackle the preceding, this article describes a series of 3-dimensional (3D) numerical simulations, employing different Computational Fluid Dynamics (CFD) methods, to study the transient effects of inlet temperature and flow rate variation on the performance of an encapsulated TES with phase change materials (PCM). A sensitivity analysis is performed where the heat transfer fluid (HTF) temperature varies from -7°C to 20°C depending on the operating mode of the TES (charging or discharging). The flow rate ranges from 50% to 200% of the nominal inflow rate. Results show that all examined cases lead to instant thermal power above 100kWth. Moreover, increasing the flow rate leads to faster solidification and melting. The increment in each process depends on the driving temperature difference between the encapsulated PCM and the HTF inlet temperature. Lastly, the effect of the inlet temperature has a larger effect as compared to the mass flow rate on the efficiency of the heat transfer of the system.

  • 292.
    Glodic, Nenad
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Sensitivity of Aeroelastic Properties of an Oscillating LPT Cascade2013Licentiate thesis, monograph (Other academic)
    Abstract [en]

    Modern turbomachinery design is characterized by a tendency towards thinner, lighter and highly loaded blades, which in turn gives rise to increased sensitivity to flow induced vibration such as flutter. Flutter is a self-excited and self-sustained instability phenomenon that may lead to structural failure due to High Cycle Fatigue (HCF) or material overload. In order to be able to predict potential flutter situations, it is necessary to accurately assess the unsteady aerodynamics during flutter and to understand the physics behind its driving mechanisms. Current numerical tools used for predicting unsteady aerodynamics of vibrating turbomachinery components are capable of modeling the flow field at high level of detail, but may fail in predicting the correct unsteady aerodynamics under certain conditions. Continuous validation of numerical models against experimental data therefore plays significant role in improving the prediction accuracy and reliability of the models.

     

    In flutter investigations, it is common to consider aerodynamically symmetric (tuned) setups. Due to manufacturing tolerances, assembly inaccuracies as well as in-service wear, the aerodynamic properties in a blade row may become asymmetric. Such asymmetries can be observed both in terms of steady as well as unsteady aerodynamic properties, and it is of great interest to understand the effects this may have on the aeroelastic stability of the system.

     

    Under certain conditions vibratory modes of realistic blade profiles tend to be coupled i.e. the contents of a given mode of vibration include displacements perpendicular and parallel to the chord as well as torsion of the profile. Current design trends for compressor blades that are resulting in low aspect ratio blades potentially reduce the frequency spacing between certain modes (i.e. 2F & 1T). Combined modes are also likely to occur in case of the vibration of a bladed disk with a comparatively soft disk and rigid blades or due to tying blades together in sectors (e.g. in turbines).

     

    The present investigation focuses on two areas that are of importance for improving the understanding of aeroelastic behavior of oscillating blade rows. Firstly, aeroelastic properties of combined mode shapes in an oscillating Low Pressure Turbine (LPT) cascade were studied and validity of the mode superposition principle was assessed. Secondly, the effects of aerodynamic mistuning on the aeroelastic properties of the cascade were addressed. The aerodynamic mistuning considered here is caused by blade-to-blade stagger angle variations

     

    The work has been carried out as compound experimental and numerical investigation, where numerical results are validated against test data. On the experimental side a test facility comprising an annular sector of seven free-standing LPT blades is used. The aeroelastic response phenomena were studied in the influence coefficient domain where one of the blades is made to oscillate in three-dimensional pure or combined modes, while the unsteady blade surface pressure is acquired on the oscillating blade itself and on the non-oscillating neighbor blades. On the numerical side, a series of numerical simulations were carried out using a commercial CFD code on a full-scale time-marching 3D viscous model. In accordance with the experimental part the simulations are performed using the influence coefficient approach, with only one blade oscillating.

     

    The results of combined modes studies suggest the validity of combining the aeroelastic properties of two modes over the investigated range of operating parameters. Quality parameters, indicating differences in mean absolute and imaginary values of the unsteady response between combined mode data and superposed data, feature values that are well below measurement accuracy of the setup.

     

    The findings of aerodynamic mistuning investigations indicate that the effect of de-staggering a single blade on steady aerodynamics in the cascade seem to be predominantly an effect of the change in passage throat. The changes in steady aerodynamics are thereby observed on the unsteady aerodynamics where distinctive effects on flow velocity lead to changes in the local unsteady pressure coefficients. In order to assess the overall aeroelastic stability of a randomly mistuned blade row, a Reduced Order Model (ROM) model is introduced, allowing for probabilistic analyses. From the analyses, an effect of destabilization due to aero-asymmetries was observed. However the observed effect was of moderate magnitude.

  • 293.
    Glodic, Nenad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Bartelt, Michael
    Vogt, Damian
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Fransson, Torsten
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Aeroelastic Properties of Combined Mode Shapes in an Oscillating LPT Cascade2009Conference paper (Refereed)
  • 294.
    Glodic, Nenad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Vogt, Damian
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Fransson, Torsten
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Experimental and numerical investigation of mistuned aerodynamic influence coefficients in an oscillating LPT cascade2012In: Proceedings of the ASME Turbo Expo, New York: American Society of Mechanical Engineers , 2012, p. 1355-1367Conference paper (Refereed)
    Abstract [en]

    The effect of aerodynamic mistuning on the aerodynamic damping in an oscillating Low-Pressure Turbine (LPT) cascade is investigated. The considered aerodynamic mistuning is caused by blade-to-blade stagger angle variations. The study is carried out experimentally and numerically by employing the influence coefficient method. On the experimental side a sector cascade is used where one of the blades is made oscillating in three orthogonal modes. The unsteady blade surface pressure is acquired on the oscillating blade and two neighbour blades and reduced to aeroelastic stability data. By gradually de-staggering the oscillating blade, aerodynamically mistuned influence coefficients are acquired. On the numerical side full-scale time-marching RANS CFD simulations are performed using nominal and de-staggered blades. The study shows that variations in blade-to-blade stagger angle affect the aerodynamic influence coefficients and as a consequence overall aeroelastic stability. Whereas discrepancies are found in the exact prediction of mistimed influence coefficients compared to measured, the overall magnitude and trends are well captured.

  • 295.
    Glodic, Nenad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Vogt, Damian
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Fransson, Torsten
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Influence of Tip Clearance Modelling in Predictions of Aeroelastic Response in an Oscillating LPT Cascade2012Conference paper (Refereed)
    Abstract [en]

    The present study investigates the influence of tip clearance modelling in predictions of the aeroelastic response in an oscillating Low-Pressure Turbine (LPT) cascade. The study was carried out through validation of different numerical models against experimental data. On the experimental side a sector cascade was used, where one of the blades was oscillated in axial bending mode. Unsteady pressure measurements were performed at several spanwise positions on the non-oscillating blades and at mid-span of the oscillating blade. On the numerical side full-scale time-marching RANS CFD simulations were performed employing models with and without tip clearance. The study showed that the model without tip clearance provides reliable result up to 70%. In the near-tip region difference induced due to the absence of tip clearance in the model amounts to about 25% of minimum stability value, relative to the nominal tip clearance model. It has also been shown that the resolution of the tip clearance mesh in spanwise direction of the gap might have a considerable impact of prediction accuracy. Imposed small variations in the tip clearance size have not led to substantial changes in predicted aeroelastic response of the cascade.

  • 296.
    Godawitharana, Sampath
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Rajaratne, Rohitha
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Technical and Financial Viability of Utilizing Waste Heat for Chilled Water Production and Biomass for Heating Applications in Hospitality Industry2012Independent thesis Advanced level (degree of Master (Two Years)), 80 credits / 120 HE creditsStudent thesis
    Abstract [en]

    The purpose of the thesis is to determine the potential of lessening the high energy cost in the hospitality industry so that the industry could stay alive after a three decades of civil war in Sri Lanka. The hospitality industry is a significant contributor to the country’s economic growth. Tourism industry has much hope of recovering in the year 2010. Improved tourism would also benefit larger part of Sri Lankan population as they are directly and indirectly employed to serve the tourism industry.

    Sri Lanka has a high electricity production cost as it depends heavily on the imported fossil fuel. Survival of hospitality industry would depend on the manner in which the energy cost - the second highest overhead in hotels is managed. If the industry survives, Sri Lanka would receive more foreign exchange and thereby improve country’s foreign currency reserve which could contribute to high growth rate. As electricity production is mainly depending on thermal, the volatility of world crude oil prices is directly affecting the country’s electricity prices. However, low dependence on the grid would help the hospitality industry to mitigate the energy cost.

    As the electricity and diesel costs -the highest and the next - are considerable portions in energy cost in hospitality industry, the study aims to discuss the possible ways of mitigating such costs. Measurements done by the presenters found that the usage of electricity for air conditioning system does constitute most of the electricity consumption for a hotel whilst most of the diesel consumption is for thermal applications. If Air Conditioning (AC) can be operated without electricity and thermal applications could be operated using abundantly available alternative energy sources then the overall energy costs of hospitality industry could be reduced thereby making higher profits. This would ensure industry survives and country gets more foreign exchange. 

    Study and calculations done by the presenters proved that operating of generators only for electricity production is not viable, due to high fossil fuel cost, however if its high exhaust temperature which is wasted otherwise, could be utilized for operation of absorption chillier then the dependence of grid electricity for air conditioning could be minimized. Further studies also revealed that if water cooled generator is used for such purpose instead of air cooled, and then the hot water requirement of hotel also could be fulfilled, thus mitigating the dependence of fossil fuel which is used otherwise for hot water production.

    Study also revealed that if thermal energy could be fed with biomass- Sri Lanka being a tropical country is blessed with abundantly available biomass - then the dependency on the fossil fuel for thermal applications could be avoided. This would not only mitigate the second highest energy cost for hotels but also create less carbon foot print, more environmental friendly and produce less noxious exhaust gases thereby creating an advertisement to attract tourists who longing to support green hotels

  • 297.
    Gonzalez Salazar, Miguel Angel
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    System analysis of waste heat applications with LNG regasification2008Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The combination of the continuously growing demand of energy in the world, the depletion of oil and its sharp price increase, as well as the urgent need for cleaner and more efficient fuels have boosted the global trade of liquefied natural gas (LNG). Nowadays, there is an increasing interest on the design philosophy of the LNG receiving terminals, due to the fact that the existing technologies either use seawater as heating source or burn part of the fuel for regasifying LNG, thus destroying the cryogenic energy of LNG and causing air pollution or harm to marine life. This investigation addresses the task of developing novel systems able to simultaneously regasify LNG and generate electric power in the most efficient and environmentally friendly way. 

     

    Existing and proposed technologies for integrated LNG regasification and power generation were identified and simple, efficient, safe and compact alternatives were selected for further analysis. A baseline scenario for integrated LNG regasification and power generation was established and simulated, consisting of a cascaded Brayton configuration with a typical small gas turbine as topping cycle and a simple closed Brayton cycle as bottoming cycle. Various novel configurations were created, modeled and compared to the baseline scenario in terms of LNG regasification rate, efficiency and power output. The novel configurations include closed Rankine and Brayton cycles for the bottoming cycle, systems for power augmentation in the gas turbine and combinations of options. A study case with a simple and compact design was selected, preliminarily designed and analyzed according to characteristics and costs provided by suppliers. The performance, costs and design challenges of the study case were then compared to the baseline case. The results show that the study case causes lower investment costs and a smaller footprint of the plant, at the same time offering a simple design solution though with substantially lower efficiencies.

  • 298.
    González Morales, César Augusto
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    CHARACTERIZATION OF HEAT TRANSFER AND EVAPORATIVE COOLING OF HEAT EXCHANGERS FOR SORPTION BASED SOLAR COOLING APPLICATIONS2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The content of this Master thesis is the characterization of three different cross unmixed flow heat exchangers. All of the heat exchangers have different inner geometries and dimensions. In order to perform the characterization of these heat exchangers, measurements of heat transfer were done under different conditions: five different temperatures at the inlet of the sorption side, different mass flow for both inlet sides of the heat exchangers.The heat transfer measurements were done with and without applying indirect evaporative cooling in order to find out the influence of indirect evaporative cooling. This research was done with the objective to find out which heat exchanger presents the best performance. The purpose is to install the heat exchanger in the novel solar driven open air SorLuKo system. This system was developed in Fraunhofer ISE and works under the same principe as the ECOS system. The main objective of the SorLuKo system is to dehumidify and cool a dwelling or small office.

  • 299.
    Gosselin, Gaëlle
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Thermodynamic study of oxygen-enhanced combustion: analysis of different techniques of oxidant production2013Student paper second term, 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Thermal energy is an important resource for many industrial processes and is usually produced by combustion of hydrocarbon fuels with air. These processes could beneficiate from the use of oxygen-enhanced combustion (OEC), whose benefits (pollutants emissions reduction, fuel savings, productivity increase and volumes reduction) are already known. However, low costs oxygen production is still a challenge as the currently most used technique, cryogenics, is very energy consuming and costly. So, the present work proposes the thermodynamic analysis of two different techniques for production of oxidant required for the OEC process, the first one including air separation by polymeric membrane and the second one by PSA. Both systems were simulated on the software EES. Results show an increase of the energetic efficiency in both of the systems (from 22% to 58% in the membrane case and 66% in the PSA case) and of the exergetic efficiencies (from 18% to 48.5% and 54% respectively). A reduction of more than 60% of specific pollutants emissions was shown. The assessed techniques were shown to be energetically more attractive than cryogenics for small plants, the size limit depending on operating conditions.

  • 300.
    GOYAL, ABHINAV
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Impact Assessment Study of Adding RES into the Operational Dispatch of Ghana’s Electricity System2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In the context of a consultancy service contract Lahmeyer International is currently working on the “Renewable Energy Rollout Plan” in the Electricity System of the Republic of Ghana. In this rollout plan the impacts of adding Renewable Energy Systems (RES) to the Ghana Electricity System on the dispatch of the thermal plants as well as associated fuel consumptions, emissions and generation costs are analysed. In the present study one specific question has been addressed, the impact of RES (approx. 7% static penetration) on the operational dispatch of Ghana’s conventional power plant fleet (large share hydro + thermal plants).

     

    The analysis has been conducted by developing a computer based mixed integer linear programming (MILP) optimization model using Microsoft Solver foundation service and programmed on Visual Basic. The model is capable of solving unit commitment and economic dispatch problem, by taking into account various operational characteristics of RES like variability and unpredictability, minimum and maximum energy generation range for hydro power plants and minimum uptime and downtime, technical minima and maxima, spinning reserve and differentiated part load behavior of thermal units. Various dispatch strategies are followed with respect to analysis with and without renewable and the impacts thereof on the electricity system.

     

    The analysis of the results suggests that in 2011 there are not much reserves in the electricity system, since the available capacity of the generating units is quite close to the electricity system requirement (sum of spinning reserve and demand load). In 2016, with additional power plants installed relative to the peak demand load, it is seen to be more economical to switch on diverse plants keeping significant reserves online. This means for the RES integration: In 2011 it would have been infeasible to integrate a large amount of RES and on the other hand in 2016 the integration of the 160 MW RES is feasible as it does not impact the electricity system stability due to the large reserves. 

3456789 251 - 300 of 944
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf