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  • 301.
    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.

  • 302.
    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. 

  • 303.
    Grandon, Thomas
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Technical and economical prospective study of the photovoltaics market2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This study presents the result of the internship that the author has conducted inside the Prospective Team at Total New Energies. It examines the development perspectives for the photovoltaic energy market worldwide. According to all projections from different players involved in the energy field, the market for PVs is and will continue to be steadily growing. The installed capacity is expected to be multiplied by at least 10 times in less than 20 years. Low estimations plan for 700 GW installed by 2035, while the most optimistic projections are expecting more than 1000 GW. This tremendous increase is based on several drivers but the main one may be attributed undoubtedly to the rapid decrease of costs.

    Indeed, PV costs have dropped more than expected during the last several years leading to instabilities for the industry and a sharp uprise for the market. However, the price decrease has recently slowed down and the manufacturers have regrouped, making most PV companies profitable again. The situation is likely to change in the next years following the continued huge expansion that is expected to occur. New regions and countries, especially the emerging economies should take an increasing share of the PV market.

    Distributed PV is also expected to keep growing. This will lead to an unprecedented amount of distributed intermittent energy the network is not designed to take in. This will lead to a change in those PV systems. Current distributed PV systems are basically PV panels and an inverter. However, with the need to integrate distributed PV and the changing regulations promoting self-consumption, new components will be included. Home Energy Management Systems and storage systems will help the PV generation and the demand to match. Aggregation and microgrids will also help utilities to manage the integration of those distributed resources.

    Nevertheless, for PV systems developers, most of these components are new. It will thus call upon new competencies. For example, data analytics and algorithms will take a great importance. PV players will have to acquire them or create new relationship to succeed in this new development of the PV systems. At the same time, companies outside of the PV sector or even the energy may take advantage of some of their skills to enter in this field.

  • 304.
    Grassart, Pierre
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Monitoring of the lubrication system of an aircraft engine through a Prognostic and Health Monitoring approach2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 305.
    Gravoille, Pauline
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    CASE STUDY OF ACTIVE FREE COOLING WITH THERMAL ENERGY STORAGE TECHNOLOGY2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    May 25, 2011, Reuters’ headline read: "New York State is prepared for summerelectricity demand". The NY operator forecasts for next summer a peak of 33GW, close to therecord ever reached. With soaring cooling demands, the electricity peak load represents a substantialconcern to the energy system. In the goal of peak shaving, research on alternative solutions based onThermal Energy Storage (TES), for both cooling and heating applications, has been largely performed.This thesis addresses thermal comfort applications with use of active free cooling through implementationof latent heat based TES. Active free cooling is based on the use of the freshness of a source, the outsideair for example, to cool down buildings. This work conceptualizes the implementation of TES basedcooling system with use of Phase Change Material in an in-house-built model. The principle of PhaseChange Material, or Latent Heat TES (LHTES), lies on latent energy which is the energy required for thematerial to change phase. In order to properly size this cooling system, a multi-objective optimization isadopted. This optimization, based on minimization of multi-objective functions, led to optimal designconfigurations. In parallel, the electrical consumption of the system and the volume uptake of the systemwere also considered. Through the obtained optimization studies, we identified non-linearinterdependency between the two objective functions: the cost of the system and the acceptable remainingcooling needs. By remaining cooling needs, we mean the cooling needs that the system cannot meet. As amatter of fact, sizing the system according to these cooling needs would imply a very high cost. It wasfound that for a certain amount of remaining cooling needs, the PCM-based cooling system reveals to bean interesting solution compared to conventional air conditioning in terms of electrical consumption andoverall system cost.

  • 306.
    Grudziecki, Jan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    CFD INVESTIGATION OF THE PURGE AIR INFLUENCE ON THE FLOW STRUCTURE AND BEHAVIOUR OF GAS TURBINE STAGE AND ROTOR-STATOR DISC CAVITY SYSTEM2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Gas turbines operate with medium of very high temperatures, which requires using advanced materials for vanes and blades and sophisticated methods of their cooling. Other parts of the turbine have to be protected from contact with hot gases. Discs that hold vanes and blades are especially exposed to this danger. In order to avoid it certain improvements have to be applied: providing sealing air and adjusting geometry of the hub to make the ingress to the cavity (space between discs)more difficult. This thesis concerns CFD investigation of the influence of the amount of sealing air on sealing efficiency and on the flow in the main annulus.

    The first part concerned literature study. Phenomena of ingress and interaction between main flow and sealing air were described. Different methods of estimating efficiency were shown.

    The second part focused only on the main path of the gas, modeling secondary air as constant and uniform outflow through the opening. The aim was to investigate how the power and reaction rate depend on the secondary air. The results were also exported to be used as boundary condition in the second part of the thesis.

    The last part concerned only the cavity – conditions at the main annulus were taken from the main annulus solution. Pressure in specified locations was measured and used to calculate sealing efficiency. Results were compared with the theoretical equations from the literature study. A structure of the flow inside the cavity was analyzed for several different amounts of the sealing flow.

    A method of unsteady flow analysis was developed and described. It was successfully implemented which proves that the method is promising. However, some improvements are necessary to obtain stable solution and research in this field should be continued.

  • 307.
    Guedez, Rafael
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Implementation And Validation Of Loss Prediction Methods To An Existing One Dimensional Axial Turbine Design Program2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    One of the early steps in axial turbine design is the use of one-dimensional (1D) mean line calculations to predict the turbine performance and estimate the principal geometric parameters, such as radius and blade heights, that will be needed in further computational fluid dynamic (CFD) studies. This 1D analysis is based on the estimation of the aerodynamic losses expressed as a function of simple blade parameters and the velocity triangles. In this regard, there exist different loss correlations widely used in literature to estimate these losses but at the same time there is a lack of information regarding differentiation between them. Thereafter, the objective in this work was to judge and compare the behaviors of the Kacker- Okapuu, Craig-Cox and Denton loss correlations, all of them widely-used in turbine performance prediction.

    Present work shows the implementation of these different loss correlations on an existing 1D mean line numerical tool, LUAX-T. Subsequently, once implemented, the correlations were compared and analyzed by the use of a validation process and performing a parametric study.

    The results show that similar key parameters such as the flow turning, solidity and aspect ratio rule the different loss mechanisms in each correlation. On the other hand, the parametric study shows that the correlations are in agreement with the theory and give similar trends for performance prediction even though they all predict different values of efficiency for the same turbine stage. Moreover, the validation process show the correlations were found to be accurate enough when comparing against two different sets of experimental data. However, it was also proved that the models are only accurate if used within the range of applicability they were developed for, hence a complete knowledge of the limitations of each correlation should be known prior to using them.

    Finally, the extension of the one-dimensional mean line numerical tool LUAX-T will serve to perform further studies related to turbine design, as there are very few non-confidential turbomachinery design tools available for teaching or researching. Furthermore, a parametric study tool was also developed as part of the program. This last extension and the loss implementation codes are described in this work.

  • 308.
    Guedez, Rafael
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Arnaudo, Monica
    Topel, Monika
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Zanino, R.
    Hassar, Z.
    Laumert, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Techno-economic Performance Evaluation of Direct Steam Generation Solar Tower Plants with Thermal Energy Storage Systems Based on High-temperature Concrete and Encapsulated Phase Change Materials2016In: SOLARPACES 2015: INTERNATIONAL CONFERENCE ON CONCENTRATING SOLAR POWER AND CHEMICAL ENERGY SYSTEMS, 2016, article id UNSP 070011Conference paper (Refereed)
    Abstract [en]

    Nowadays, direct steam generation concentrated solar tower plants suffer from the absence of a cost-effective thermal energy storage integration. In this study, the prefeasibility of a combined sensible and latent thermal energy storage configuration has been performed from thermodynamic and economic standpoints as a potential storage option. The main advantage of such concept with respect to only sensible or only latent choices is related to the possibility to minimize the thermal losses during system charge and discharge processes by reducing the temperature and pressure drops occurring all along the heat transfer process. Thermodynamic models, heat transfer models, plant integration and control strategies for both a pressurized tank filled with sphere-encapsulated salts and high temperature concrete storage blocks were developed within KTH in-house tool DYESOPT for power plant performance modeling. Once implemented, cross-validated and integrated the new storage model in an existing DYESOPT power plant layout, a sensitivity analysis with regards of storage, solar field and power block sizes was performed to determine the potential impact of integrating the proposed concept. Even for a storage cost figure of 50 USD/kWh, it was found that the integration of the proposed storage configuration can enhance the performance of the power plants by augmenting its availability and reducing its levelized cost of electricity. As expected, it was also found that the benefits are greater for the cases of smaller power block sizes. Specifically, for a power block of 80 MWe a reduction in levelized electricity costs of 8% was estimated together with an increase in capacity factor by 30%, whereas for a power block of 126 MWe the benefits found were a 1.5% cost reduction and 16% availability increase.

  • 309.
    Guedez, Rafael Eduardo
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Topel, Monika
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Spelling, J.
    Laumert, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Enhancing the profitability of solar tower power plants through thermoeconomic analysis based on multi-objective optimization2015In: INTERNATIONAL CONFERENCE ON CONCENTRATING SOLAR POWER AND CHEMICAL ENERGY SYSTEMS, SOLARPACES 2014, 2015, Vol. 69, p. 1277-1286Conference paper (Refereed)
    Abstract [en]

    Solar tower power plants with integrated thermal energy storage units represent one of the most promising technologies for enhancing the economic viability of concentrating solar power in the short term. Tower systems allow higher concentration ratios to be achieved, which in turn means higher fluid operating temperatures and thus higher power cycle efficiencies. Moreover, the integration of storage allows power production to be shifted from times where there is low demand to periods where electricity prices are higher, potentially enhancing the profitability of the plant despite representing an additional upfront cost. The variable nature of the solar resource and the myriad potential roles that storage can assume, together with the complexity of enhancing the synergies between the three blocks: the solar field, the storage block and power block, make the design of these power plants a challenging process. This paper introduces a comprehensive methodology for designing solar tower power plants based on a thermoeconomic approach that allows the true optimum trade-off curves between cost, profitability and investment to be identified while simultaneously considering several operating strategies as well as varying critical design parameters in each of the aforementioned blocks. The methodology is presented by means of analyzing the design of a power plant for the region of Seville. For this location, results show that similar profits, measured in terms of the internal rate of return, can be achieved from different power plant configurations in terms of sizing and operating strategy, each associated to different investments. In particular, optimum configurations found corresponded to larger power blocks with medium-to-large solar field and storage blocks that allow the plants to operate continuously throughout the day and be shut down during midnight. Moreover, it is shown that for a fixed power block size it can also be economically interesting to consider smaller storage units and adopt instead a peaking strategy, as this can still be profitable whilst representing a lower investment, thus lower risk.

  • 310.
    Guedez, Rafael
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Ferruzza, Davide
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Arnaudo, Monica
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Rodriguez, Ivette
    Perez-Segarra, Carlos D.
    Hassar, Zhor
    Laumert, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Techno-economic Performance Evaluation of Solar Tower Plants with Integrated Multi-layered PCM Thermocline Thermal Energy Storage - A Comparative Study to Conventional Two-tank Storage Systems2016In: SOLARPACES 2015: INTERNATIONAL CONFERENCE ON CONCENTRATING SOLAR POWER AND CHEMICAL ENERGY SYSTEMS, American Institute of Physics (AIP), 2016, article id UNSP 070012Conference paper (Refereed)
    Abstract [en]

    Solar Tower Power Plants with thermal energy storage are a promising technology for dispatchable renewable energy in the near future. Storage integration makes possible to shift the electricity production to more profitable peak hours. Usually two tanks are used to store cold and hot fluids, but this means both higher investment costs and difficulties during the operation of the variable volume tanks. Instead, another solution can be a single tank thermocline storage in a multi-layered configuration. In such tank both latent and sensible fillers are employed to decrease the related cost up to 30% and maintain high efficiencies. This paper analyses a multi-layered solid PCM storage tank concept for solar tower applications, and describes a comprehensive methodology to determine under which market structures such devices can outperform the more conventional two tank storage systems. A detail model of the tank has been developed and introduced in an existing techno-economic tool developed by the authors (DYESOPT). The results show that under current cost estimates and technical limitations the multi-layered solid PCM storage concept is a better solution when peaking operating strategies are desired, as it is the case for the two-tier South African tariff scheme.

  • 311.
    Guedez, Rafael
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Larchet, Kevin
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Dent, Jolyon
    Green, Adam
    Hassar, Zhor
    Laumert, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    A Techno-Economic Analysis Of Hybrid Concentrating Solar Power And Solar Photovoltaic Power Plants For Firm Power In Morocco2016In: Journal of solar energy engineering, ISSN 0199-6231, E-ISSN 1528-8986Article in journal (Refereed)
    Abstract [en]

    The present study evaluates the optimum configurations and operating strategies of hybrid concentrating solar power and solar photovoltaic power plants for minimizing levelized costs of electricity. These configurations were also required to meet specific design objectives as provided by competitive bid tenders, such as power plant size and operating hours, for a suitable location near Midelt, Morocco. A detailed techno-economic model of the hybrid plant was developed at KTH’s in-house optimization tool DYESOPT, which allows power plant evaluation by means of technical and economic performance indicators. Results show that hybrid plants are able to achieve higher capacity factors. It is also confirmed that, under current cost estimates, hybridization enables a lower cost solution for a given high capacity factor objective than what is achievable either with stand-alone concentrating solar power or solar photovoltaic power plants, respectively. The analysis highlights synergies among the technologies and shows the relation and influence between sizing and operation of their critical components. Main challenges for successful hybridization are also raised together with recommendations for addressing them. Lastly, optimum configurations found for different tender conditions are compared and a brief discussion section at the end is introduced to highlight the relevance of adequate policy design and its impact on the work of project developers for proposing the most competitive solutions

  • 312.
    Guedez, Rafael
    et al.
    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.
    Laumert, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Enhancing the Economic Competitiveness of Concentrating Solar Power Plants through an Innovative Integrated Solar Combined-Cycle with Thermal Energy Storage2014In: Proceedings of the ASME TurboExpo 2014, 2014, Vol. 3AConference paper (Refereed)
    Abstract [en]

    The present work deals with the thermoeconomic analysis of an innovative combined power cycle consisting of a molten- salt solar tower power plant with storage supported by additional heat provided from the exhaust of a topping gas- turbine unit. A detailed dynamic model has been elaborated using an in house simulation tool that simultaneously encompasses meteorological, demand and price data. A wide range of possible designs are evaluated in order to show the trade-offs between the objectives of achieving sustainable and economically competitive designs. Results show that optimal designs of the novel concept are a promising cost-effective hybrid option that can successfully fulfill both the roles of a gas peaker plant and a baseload solar power plant in a more effective manner. Moreover, designs are also compared against conventional combined cycle gas turbine power plants and it is shown that, under specific peaking operating strategies, the innovative concept can not only perform better from an environmental standpoint but also economically.

  • 313.
    Guedez, Rafael
    et al.
    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.
    Laumert, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Reducing the Number of Turbine Starts in Concentrating Solar Power Plants through the Integration of Thermal Energy Storage2015In: Journal of solar energy engineering, ISSN 0199-6231, E-ISSN 1528-8986, Vol. 137, no 2Article in journal (Refereed)
    Abstract [en]

    The operation of steam turbine units in solar thermal power plants is very different than in conventional base-load plants. Due to the variability of the solar resource, much higher frequencies of plant start-ups are encountered. This study provides an insight to the influence of thermal energy storage (TES) integration on the typical cycling operation of solar thermal power plants. It is demonstrated that the integration of storage leads to significant reductions in the annual number of turbine starts and is thus beneficial to the turbine lifetime. At the same time, the effects of storage integration on the electricity costs are analyzed to ensure that the designs remain economically competitive. Large storage capacities, can allow the plant to be shifted from a daily starting regime to one where less than 20 plant starts occur annually. Additionally, the concept of equivalent operating hours (EOHs) is used to further analyze the direct impact of storage integration on the maintenance planning of the turbine units.

  • 314.
    Guedez, Rafael
    et al.
    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.
    Laumert, Björn
    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.
    Optimization of Thermal Energy Storage Integration Strategies for Peak Power Production by Concentrating Solar Power Plants2014In: PROCEEDINGS OF THE SOLARPACES 2013 INTERNATIONAL CONFERENCE, 2014, Vol. 49, p. 1642-1651Conference paper (Refereed)
    Abstract [en]

    The integration of thermal energy storage systems in concentrating solar thermal power plants allows power production to be shifted from times where there is low demand to periods where electricity prices are higher. Although increasing the total investment, thermal energy storage can therefore enhance profitability of the solar power plant. The present study presents optimum power plant configurations for a given location considering different price-based grid integration strategies. Such optimum plant configurations were determined using a thermo-economic optimization approach where the operating strategy was set such that electricity was generated once the market price exceeds a given price level, defined as the minimum price selling indicator. Plants were optimized for different indicator values to cover designs from base load and peak power production. For each of these price-operating strategies, optimum plant configurations were found by varying two solar-related design parameters, namely the solar multiple and the storage size, whilst simultaneously evaluating the economic performance of each design. Finally, an economic analysis was performed for each of the optimum power plants, assuming financial conditions throughout the lifetime of the power plant. Results show that the optimum plant configurations vary with respect to the chosen operating strategy. Optimum configurations for peak power production yielded relatively smaller storage units than that of the optimum baseload plants. Furthermore, the study demonstrates that under current cost estimations, and for the specified location, concentrating solar thermal power is not an attractive option for utility-grid investors. However, it is shown that when considering a reduction in investment costs or the possibility of having renewable electricity incentives such as the investment tax credit treasury cash grant, concentrating solar thermal power plants can become an economically viable technology.

  • 315.
    Guedez, Rafael
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Topel, Monika
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Conde, Inés
    Gas Natural Fenosa Engineering.
    Ferragut, Francisco
    Gas Natural Fenosa Engineering.
    Callaba, Irene
    Gas Natural Fenosa Engineering.
    Spelling, James
    IMDEA .
    Hassar, Zhor
    Total New Energies.
    Perez-Segarra, Carlos David
    UPC.
    Laumert, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    A Methodology for Determining Optimum Solar Tower Plant Configurations and Operating Strategies to Maximize Profits Based on Hourly Electricity Market Prices and Tariffs2016In: Journal of solar energy engineering, ISSN 0199-6231, E-ISSN 1528-8986, Vol. 138, no 2, article id 021006Article in journal (Refereed)
    Abstract [en]

    The present study analyzes the influence that market conditions have on determining optimum molten salt solar tower plants with storage that maximizes profits (in terms of plant configuration, sizing, and operation) for a location in South Africa. Three different scenarios based on incentive programs and local wholesale electricity prices are considered. A multi-objective optimization modeling approach was followed, showing the tradeoff curves between minimizing investment and maximizing profits when varying critical size-related parameters (such as nameplate capacity, solar multiple (SM), and storage capacity) together with power-cycle design and operating specifications including dynamic startup curves and different storage dispatchability strategies. Results are shown by means of a comparative analysis between optimal plants found for each scenario, highlighting the value that storage has under the current two-tier tariff scheme and the relevance of designing a suitable policy for technology development. Finally, a final analysis is performed with regard to the indicators used for economic evaluation of power plants, by comparing the differences between optimum designs found when using the levelized cost of electricity (LCoE) solely as performance indicator instead of cash-flows and profit-based indicators, such as the internal rate of return (IRR).

  • 316.
    Gueguen, Steven
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Risk assessment of marine energy projects2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The marine energy technologies (Wave Energy Converters, Tidal Energy Converters and floating wind turbines) are still at an early stage of development since no commercial array exists today. Their development has to face three main issues: the lack of feedback from the field, the great diversity of the existing technologies and the harsh marine environment. This thesis proposes a methodology and a support tool to assess the financial risks linked to a marine energy project based on the reliability of systems.

    The first part of the methodology is a reliability and maintainability assessment which is directly based on the classic FMECA (Failure Modes, Effects and Criticality Analysis) methodology. Then an Excel prediction tool was developed so as to assess the financial risks linked to a marine energy projects. This support tool is based on a Monte-Carlo method and relies on reliability data provided by the FMECA. The whole methodology developed is simple since no accurate data exists. Moreover, the support tool is designed so as to be adapted for a large variety of technologies and maintenance strategies. Finally, all the outputs of this support tool are quantitative. The main outputof the methodology is the LCOE (Levelized Cost Of Energy) since this value is a function of the CAPEX (CAPital EXpenditures), OPEX (OPerational EXpenditures) and the availability of the array.

    To prove the validity of the support tool, this one was tested on several existing WECs thanks to the input parameters provided by the developers. So as to keep the confidentiality of these data, it was decided to develop in this thesis one fictive example including two different WECs. In depth analysis and comparison of technologies are carried out: sensibility analysis on several parameters, optimization of the design for one technology (dry-mate connector Vs. wet-mate connector), optimization of the maintenance strategy for one technology.

    The strength of the methodology developed lies in the ability to really calculate both the OPEX and the availability of the array based on reliability data and without performing an exhaustive analysis of each system. However, the support tool is limited to 13 components per technology. So, if more components need to be taken into account, a functional analysis has to be done in order to gather components in functions. Moreover, because of the lack of data, the FMECA performed is simplified: failure rates are linked to components instead of failure modes.

  • 317.
    Gunarathne, Duleeka
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Optimization of the performance ofdown-draft biomass gasifier installedat National Engineering Research &Development (NERD) Centre ofSri Lanka2012Independent thesis Advanced level (degree of Master (Two Years)), 80 credits / 120 HE creditsStudent thesis
    Abstract [en]

    Using biomass gasification to produce combustible gas is one of the promising sustainable energy optionsavailable for many countries. At present, a few small scale community based power generation systemsusing biomass gasifiers are in operation in Sri Lanka. However, due to the lack of proper knowledge, thesesystems are not being operated properly in full capacity. This stands as an obstacle for further expansionof the use of gasifier technology.The objective of this study was to identify the most influential parameters related to fuel wood gasificationwith a down draft gasifier in order to improve the gasification processes.A downdraft gasifier of 10kW electrical capacity was used to study the effect of equivalent ratio (Actual airfuel ratio to Stoicheometric air fuel ratio: ER) on the specific gas production, the heating value of gasproduced and the cold gas efficiency using three throat diameters (125mm, 150mm and 175mm). Six trialswere carried out for each throat diameter by varying the supply air flow to change the ER. The gassamples were tested for their compositions under steady state operating conditions. Using mass balancesfor C and N, the cold gas efficiencies, calorific values and the specific gas production rates weredetermined.The results showed that with all throat diameters the calorific value of gas reduced with the increase ofER. The cold gas efficiency reduced with ER in a similar trend for all three throat diameters. The specificgas production increased with ER under all throat diameters.Calorific value and specific gas production are changing inversely proportional manner. The ER to beoperated is depends on the type of application of the gas produced and engine characteristics. When alarge heat is required, low ER is to be used in which gas production is less. In the opposite way, when alarge amount of gas is needed, higher value of ER is recommended.

  • 318.
    Gunasekara, Saman Nimali
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Phase Equilibrium-aided Design of Phase Change Materials from Blends: For Thermal Energy Storage2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Climate change is no longer imminent but eminent. To combat climate change, effective, efficient and smart energy use is imperative. Thermal energy storage (TES) with phase change materials (PCMs) is one attractive choice to realize this. Besides suitable phase change temperatures and enthalpies, the PCMs should also be robust, non-toxic, environmental-friendly and cost-effective. Cost-effective PCMs can be realized in bulk blends. Blends however do not have robust phase change unless chosen articulately. This thesis links bulk blends and robust, cost-effective PCMs via the systematic design of blends as PCMs involving phase equilibrium evaluations. The key fundamental phase equilibrium knowledge vital to accurately select robust PCMs within blends is established here. A congruent melting composition is the most PCM-ideal among blends. Eutectics are nearly ideal if supercooling is absent. Any incongruent melting composition, including peritectics, are unsuitable as PCMs. A comprehensive state-of-the-art evaluation of the phase equilibrium-based PCM design exposed the underinvestigated categories: congruent melting compositions, metal alloys, polyols and fats.

    Here the methods and conditions essential for a comprehensive and transparent phase equilibrium assessment for designing PCMs in blends are specified. The phase diagrams of the systems erythritol-xylitol and dodecane-tridecane with PCM potential are comprehensively evaluated. The erythritol-xylitol system contains a eutectic in a partially isomorphous system unlike in a non-isomorphous system as previous literature proposed. The dodecane-tridecane system forms a probable congruent minimum-melting solid solution, but not a maximum-melting liquidus or a eutectic as was previously proposed. The sustainability aspects of a PCM-based TES system are also investigated. Erythritol becomes cost-effective if produced using glycerol from bio-diesel production. Olive oil is cost-effective and has potential PCM compositions for cold storage. A critical need exists in the standardization of methods and transparent results reporting of the phase equilibrium investigations in the PCM-context. This can be achieved e.g. through international TES collaboration platforms.

  • 319.
    Gunasekara, Saman Nimali
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    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.
    Binary Phase Equilibrium Study of the Polyols Blend Erythritol-Xylitol with the T-History Method for Phase Change Materials Design2015In: The 13th International Conference on Energy Storage- Greenstock 2015, 2015Conference paper (Refereed)
    Abstract [en]

    Polyols are emerging PCM with attractive melting temperatures and enthalpies. The binary phase diagram of the system Erythritol-Xylitol is constructed using the Temperature-history method, and evaluated for its PCM-suitability. With blending, lowering of the melting points was expected, also verified with a recent study presenting the system as a simple eutectic. Herein, the tests covered the full compositional range, with thermal cycling around the previously reported eutectic. Some compositions exhibited possible glass transition after the first melting. For these, by seeding the starting material to the supercooled liquid, a preceding melting with heating was achieved. The results show several PCM suitable points in the phase diagram: eutectics and congruent melting compounds. This appears to be a partially isomorphous type, but not simple eutectic type. Microstructural evaluations for phase and miscibility verifications can further clarify this. For some compositions secondary phase changes were observed, indicating probable polymorphs, of solid-solid PCM interest.

  • 320.
    Gunasekara, Saman Nimali
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Kumova, Sofia
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology. Gubkin Russian State University of Oil and Gas, Russia.
    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.
    Experimental phase diagram of the dodecane–tridecane system as phase change material in cold storage: [Diagramme de phase expérimental du système dodécane–tridécane comme matériau à changement de phase pour des applications d'entreposage frigorifique]2017In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 82, p. 130-140Article in journal (Refereed)
    Abstract [en]

    Integrating thermal storage with phase change materials (PCMs) in refrigeration and air conditioningprocesses enables energy performance improvements. Herein, the experimental phase diagram of thealkanes system dodecane-tridecane (C12H26-C13H28) is evaluated to find PCMs for freezing applications.For that, the Temperature-history method was coupled with a Tammann plot analysis. The obtainedC12H26-C13H28 phase diagram indicated a congruent minimum-melting solid solution and polymorphs. Theminimum-melting liquidus and the polymorphs identified here, agree with previous literature. However,the system does not represent a eutectic, as previously was proposed. The minimum-meltingcomposition is here identified within 15-20 mol% C13H28 compositions. The 17.7 mol% C13H28 is thenarrowest minimum-melting composition among those analyzed, melting and freezing between -16 to -12 °C and -17 to -15 °C, with: the enthalpies 185 kJ kg-1 and 165 kJ kg-1; no supercooling; and only minorhysteresis. Hence, this blend has potential as a PCM in freezing refrigeration applications.

  • 321.
    Gunasekara, Saman Nimali
    et al.
    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.
    Chiu, Justin NingWei
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Phase Diagrams as Effective Tools in Thermal Energy Storage (TES) Design using Phase Change Materials (PCM)2013In: ICAE2013, 2013Conference paper (Refereed)
    Abstract [en]

    Phase diagrams are invaluable in the design of thermal energy storage systems using phase change materials (PCM). They provide important information such as the phase change composition and constitution of the system, as well as an understanding of phenomena like incongruent melting, phase segregation, and subcooling. In this work, the significance of phase diagrams to evaluate a chemical system’s behavior and it’s suitability as a candidate PCM is analyzed along with discussing example systems based on salt, paraffin, fatty acid and sugar alcohol. For a binary system, a number of specific phase changing behaviors are found appropriate for a PCM due to their sharp, definite melting temperatures and proper melting/freezing behaviors. For example, isomorphous minimum or maximum melting types and eutectics of immiscible (non isomorphous) or partially miscible types are all suitable. A system’s miscibility distribution thus governs its suitability as a PCM since it determines the type of phase change. For determining miscibility and constructing theoretical phase diagrams the Gibbs free energy derivatives as well as experiments are useful. In conclusion it is here presented that phase equilibrium studies should be included in a derived protocol for determining suitable PCM candidates for the future. 

  • 322.
    Gunasekara, Saman Nimali
    et al.
    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.
    Chiu, Justin NingWei
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Phase equilibrium in the design of phase change materials for thermal energy storage: State-of-the-art2017In: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 73, p. 558-581Article, review/survey (Refereed)
    Abstract [en]

    This paper presents a review of phase equilibrium as a tool for accurately identifying suitable blended phasechange materials (PCMs) to be used for thermal energy storage (TES). PCM storage increases the overall energyefficiency for many applications, however, high cost and complex phase change phenomena in blends oftenundermine the benefits. The study of phase equilibrium as derived from phase diagrams is the key to solve theseissues. It enables the evaluation of PCM-suitability through indication of temperature-composition points, e.g.congruent melting compositions, eutectics and peritectics. To clearly stake out the opportunities of a phaseequilibrium-based design methodology, this paper reviews the state-of-the-art based on findings from fourdecades (1977–2016). On one hand, eutectics, salts-based systems, fatty acids, and alkanes dominate theexisting PCM literature. Here peritectics have often been erroneously praised as suitable PCMs despite the manyproblems depicted from a phase equilibrium point of view. On the other hand, the most PCM-ideal congruentmelting systems, as well as the blends of polyols, fats, metal alloys and organic-inorganic combinations lack fullattention. This work brings forward the knowledge on these insufficiently explored yet extremely suitable phaseequilibrium characteristics. In addition, comprehensive PCM-design thermal properties of these various blendsare presented, as a basis to further extensive explorations, and material category-based predictions.

  • 323.
    Gunasekara, Saman Nimali
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Pan, Ruijun
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology. Department of Chemistry, Ångström Laboratory, Uppsala University, Box 538 75121 Uppsala, Sweden.
    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.
    Polyols as phase change materials for surplus thermal energy storage2016In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 162, p. 1439-1452Article in journal (Refereed)
    Abstract [en]

    Storing low-temperature surplus thermal energy from industries, power plants, and the like, using phasechange materials (PCM) is an effective alternative in alleviating the use of fossil based thermal energyprovision. Polyols; of some also known as sugar alcohols, are an emerging PCM category for thermalenergy storage (TES). A review on polyols as PCM for TES shows that polyols have phase change temperaturesin the range of 15 to 245 C, and considerable phase change enthalpies of 100–413 kJ/kg. However,the knowledge on the thermo-physical properties of polyols as desirable PCM for TES design is presentlysparse and rather inconsistent. Moreover, the phase change and state change behaviors of polyols need tobe better-understood in order to use these as PCM; e.g. the state change glass transition which manypolyols at pure state are found to undergo. In this work preliminary material property characterizationwith the use of Temperature-History method of some selected polyols, Erythritol, Xylitol andPolyethylene glycol (PEG) 10,000 were done. Complex behaviors were observed for some of the polyols.These are: two different melting temperatures, 118.5–120 C and 106–108 C at different cycles and anaverage subcooling 18.5 C of for Erythritol, probable glass-transition between 0 and 113 C for Xylitol,as well as a thermally activated change that is likely an oxidation, after three to five heating/coolingcycles for Xylitol and Erythritol. PEG 10,000 had negligible subcooling, no glass-transition nor thermallyactivated oxidation. However a hysteresis of around 10 C was observed for PEG 10,000. Therefore thesematerials require detailed studies to further evaluate their PCM-suitability. This study is expected to be an initiation of an upcoming extensive polyol-blends phase equilibrium evaluation.

  • 324.
    Gunasekara, Samman Nimali
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    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.
    Hedström, Peter
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    The Experimental Phase Diagram Study of the Binary Polyols System Erythritol-Xylitol2017In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 174, p. 248-262Article in journal (Refereed)
    Abstract [en]

    A comprehensive phase diagram for the binary polyols system erythritol-xylitol has been mapped with a transparent characterization approach. Here, the phase equilibrium of the system has been studied experimentally using a combination of methods: Temperature-history (T-history), X-Ray Diffraction (XRD), and Field-Emission Scanning Electron Microscopy (FESEM), and linked to Tammann plots. Existing literature has previously shown the system to be a non-isomorphous type forming a simple eutectic, by combining experimental data with theoretical modelling. The present investigation shows that the system’s phase diagram is a partially isomorphous type forming a eutectic, but not a non-isomorphous type forming a simple eutectic. Here, the eutectic was found within 25-30 mol% erythritol and at 77 °C, which differs from the previous studies identifying the eutectic respectively at 25 or 36 mol% erythritol and at 82 °C. The reasons for the differences are hard to deduce since the research approach is not presented as fully transparent from the past studies. In the present study, only the temperature-composition plot of the first melting (of the two components in a physical mix, but not of a single blend) indicated the shape of a simple eutectic in a non-isomorphous system. The cycles after the first melting in contrast started from the real blend, and displayed eutectic and solid-solid phase changes in T-history. These were verified as forming solid solutions with XRD and FESEM. This eutectic melts at a temperature suitable for low-temperature solar heating, but displayed glass transition, supercooling, and thermally activated degradation, thus affecting its practical aspects as a PCM.

  • 325.
    Gunasekara, Samman Nimali
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Ignatowicz, Monika
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    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.
    Thermal conductivity measurement of erythritol, xylitol, and their blends for phase change material design: A methodological study2019In: International journal of energy research (Print), ISSN 0363-907X, E-ISSN 1099-114X, Vol. 43, no 5, p. 1785-1801Article in journal (Refereed)
    Abstract [en]

    This work presents and discusses a detailed thermal conductivity assessment of erythritol, xylitol, and their blends: 25 mol% erythritol and 80 mol% erythritol using the transient plane source (TPS) method with a Hot Disk Thermal Constants Analyzer TPS‐2500S. Thereby, the thermal conductivities of xylitol, 25 mol% erythritol, 80 mol% erythritol, and erythritol were here found for respectively in the solid state to be 0.373, 0.394, 0.535, and 0.589 W m−1 K−1 and in the liquid state to be 0.433, 0.402, 0.363, and 0.321 W m−1 K−1. These obtained results are comprehensively and critically analyzed as compared to available literature data on the same materials, in the phase change materials (PCMs) design context. This study clearly indicates that these thermal conductivity data in literature have considerable discrepancies between the literature sources and as compared to the data obtained in the present investigation. Primary reasons for these disparities are identified here as the lack of sufficiently transparent and repeatable data and procedure reporting, and relevant standards in this context. To exemplify the significance of such transparent and repeatable data reporting in thermal conductivity evaluations in the PCM design context, here focused on the TPS method, a comprehensive measurement validation is discussed along various residual plots obtained for varying input parameters (ie, the heating power and time). Clearly, the variations in the input parameters give rise to various thermal conductivity results, where choosing the most coherent result requires a sequence of efforts per material, because there are no universally valid conditions. Transparent and repeatable data and procedure reporting are the key to achieve comparable thermal conductivity results, which are essential for the correct design of thermal energy storage systems using PCMs.

    The full text will be freely available from 2020-02-22 10:37
  • 326.
    Gunasekara, Samman Nimali
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Ignatowicz, Monika
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    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, Applied Thermodynamics and Refrigeration.
    Thermal Conductivity Measurement of Erythritol, Xylitol and Their Blends for Phase Change Materials Design: a Methodological Study2018In: The 14th International Conference on Energy Storage, Adana, Turkey: IEA ECES , 2018, p. 364-378, article id 82Conference paper (Refereed)
    Abstract [en]

    This work presents and discusses a detailed thermal conductivity assessment of erythritol, xylitol and their blends: 25 mol% erythritol and 80 mol% erythritol using the Transient Plane Source (TPS) method with a Hot Disk Thermal Constants Analyzer TPS-2500S. Their thermal conductivities were here found to be respectively: 0.59; 0.37; 0.39 and 0.54 W/(m·K) in the solid state, and to be 0.32; 0.43; 0.40 and 0.36 W/(m·K) in the liquid state. These obtained results are comprehensively and critically analyzed as compared to available literature data on the same materials, in the phase change materials (PCMs) design context. This study clearly indicates that the literature has considerable discrepancies among their presented thermal conductivities, and also as compared to the values found through the present investigation. Primary reason for these disparities are identified here as the lack of sufficiently transparent and repeatable data and procedure reporting, and relevant standards in this context. To exemplify the significance of such transparent and repeatable data reporting in thermal conductivity evaluations in the PCM design context, here focused on the TPS method, a comprehensive measurement validation is discussed along various residual plots obtained for varying input parameters (i.e., the heating power and time). Clearly, the variations in the input parameters give rise to various thermal conductivity results, where choosing the most coherent result requires a sequence of efforts per material, but there are no universally valid conditions. Transparent and repeatable data and procedure reporting is the key to achieve comparable thermal conductivity results, which are essential for the correct design of thermal energy storage systems using PCMs.

  • 327.
    Gunasekara, Samman Nimali
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Kumova, Sofia
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology. Gubkin Russian State University of Oil and Gas, Russia.
    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.
    Experimental Phase Equilibrium Study of Dodecane-Tridecane System for Phase Change Materials Design for Thermal Energy Storage2016Conference paper (Other academic)
  • 328.
    Gunasekara, Samman Nimali
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Bigdeli, Sedigheh
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    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.
    Thermodynamic Assessment of Binary Erythritol-Xylitol Phase Diagram for Phase Change Materials DesignManuscript (preprint) (Other academic)
    Abstract [en]

    Here, the experimental phase equilibrium data of the erythritol-xylitol system were thermodynamically optimized, to explore compositions suitable as phase change materials (PCMs) for thermal energy storage (TES). A previous experimental study revealed that erythritol-xylitol was a partially isomorphous system with a eutectic. In the thermodynamic evaluation, the CALPHAD method was employed coupling the phase diagram and thermodynamic property information. There, both unary and binary systems’ experimental data were taken into account, and all phases were described using the substitutional solution model. Finally, a self-consistent thermodynamic description for the erythritol-xylitol system was achieved. The calculated eutectic point is at 76.7 °C and 26.8 mol% erythritol, agreeing well with the experimental data. The calculated phase diagram better-verifies the systems’ solidus and the solvus, disclosing the stable phase relations. Based on the Gibbs energy minimization, phase diagrams can be predicted for the binary and higher order systems, provided the component subsystems are thermodynamically assessed beforehand. In conclusion, to move forward beyond e.g. non-isomorphous simple eutectic systems, methods using Gibbs free energy minimization from a fundamental point-of-view such as CALPHAD are essential.

  • 329.
    Gunasekara, Samman Nimali
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Stalin, Joseph
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Marçal, Mariana
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Delubac, Regis
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology. University of Pau and Pays de l'Adour, France.
    Karabanova, Anastasiya
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology. Gubkin Russian State University of Oil and Gas, Russia.
    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.
    Erythritol, Glycerol, their Blends, and Olive Oil, as Sustainable Phase Change Materials2017In: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 135, p. 249-262Article in journal (Refereed)
    Abstract [en]

    In searching for new candidates to be used in latent heat storage, it is desirable to explore food-grade materials of renewable origin. Here, erythritol, glycerol, and olive oil have been characterized as PCMs. An assessment of the production process of erythritol (melting between 117-120 °C with an enthalpy around 300 kJ/kg) indicates its renewable aspects as a PCM. In addition, a simplified cost assessment of high-purity erythritol production, using glycerol, indicates a potential cost reductions up to 130-1820 times lower than the current laboratory-grade prices. Glycerol already is cost-effective. However, the glycerol-erythritol system, evaluated using the Temperature-history (T-history) method, did not exhibit phase change suitable for PCMs. Glycerol, and up to 30 mol% erythritol compositions had no phase change due to glass transition; the remainder froze but with large supercooling; and the system underwent thermally activated change. Hence, to realize glycerol or the glycerol-erythritol system as PCMs, further research is needed primarily to device fast-crystallization. Olive oil is a cost-effective food commodity, with potential for further cost reductions by mass-production. An olive oil sample, containing the fatty acids: linoleic, palmitic, oleic, margaric, and stearic was evaluated using the T-history method. This olive oil melted and froze between -4.5 to 10.4 °C and -8 to -11.9 °C respectively, with the respective enthalpies 105 and 97 kJ/kg. As the specific heat (cp) profiles of olive oil displayed two peaks, the composition adjustment of olive oil could yield a eutectic or confirm a polymorph. In either case, olive oil has a potential to be a PCM e.g. in chilling applications, while its properties such as thermal conductivity need to be determined. As a whole, this study exemplifies the potential of renewable organic materials, in pure and blend forms, as sustainable PCMs, making TES with PCMs sustainable.

  • 330.
    Gunawan Gan, Philipe
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Concentrated Solar Thermal Plant for Future Fuels Production2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Concentrated Solar Thermal technology (CST) is a very promising renewable energy technology and has a broad range of use. Conventionally, CST systems are mostly used for power generation according to the Rankine cycle and thus often referred to as Concentrated Solar Power (CSP). In this present study, the solar heat is utilized to drive a thermochemical redox cycle of a metal-oxide in order to produce synthetic gas, a combination of hydrogen and carbon monoxide. Later, the synthetic gas is converted into usable liquid fuel whereas the production pathway is CO2 free. This thesis focuses on the process modeling and economic evaluation of solar-driven future fuels production plants. Four future fuels have been selected and modeled using commercial simulation software Aspen Plus®. These 4 future fuels are syngasoline, syndiesel, ethanol and methanol where they can be seen as a very good substitute for current transportation fuels. The heat required at high temperature is delivered using concentrated solar thermal technology with tower configuration for which the heliostat field is designed using in-house software HFLCAL developed by DLR. Syngas is converted into aforementioned fuels using either Fischer-Tropsch or plug-flow reactor. The reactor is modeled taking into account the kinetic of reaction for each fuel, while in case of the absence of kinetic, a stoichiometric approach is implemented. To analyze the hourly plant’s performance, a quasi-steady state analysis is done within MATLAB® environment. The metric used to evaluate the plants are production cost in €/L and overall thermal efficiency. The results show that aforementioned conversion pathway yields higher production costs compared to current market while the lowest production cost is obtained for Methanol at 1.42 €/L. It is shown that solid to solid heat exchanger (STS) efficiency plays a major role in order to make the plant more economically viable. Combining electricity supply of Photovoltaic (PV) and CSP is also shown to be one way to reduce the production cost. If the plant combines PV-CSP is used as the electricity source, syngasoline emerges to be the closest proposed plant to current market fuel production cost with a production cost of 5.99 €/L at the base case scenario which corresponds to 622% relative difference with current market’s production cost and 2.87 €/L at the best case scenario which corresponds to 245% relative difference with current market’s production cost. At the base case scenario, the highest overall thermal efficiency is obtained for the syngasoline plant (4.05%) and at the best case scenario for the ethanol plant (9.2%).

  • 331.
    Gupta, Sunay
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Guédez, Rafael
    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.
    Market potential of solar thermal enhanced oil recovery-a techno-economic model for Issaran oil field in Egypt2017In: SOLARPACES 2016: International Conference on Concentrating Solar Power and Chemical Energy Systems, American Institute of Physics (AIP), 2017, article id 190001Conference paper (Refereed)
    Abstract [en]

    Solar thermal enhanced oil recovery (S-EOR) is an advanced technique of using concentrated solar power (CSP) technology to generate steam and recover oil from maturing oil reservoirs. The generated steam is injected at high pressure and temperature into the reservoir wells to facilitate oil production. There are three common methods of steam injection in enhanced oil recovery - continuous steam injection, cyclic steam stimulation (CSS) and steam assisted gravity drainage (SAGD). Conventionally, this steam is generated through natural gas (NG) fired boilers with associated greenhouse gas emissions. However, pilot projects in the USA (Coalinga, California) and Oman (Miraah, Amal) demonstrated the use of S-EOR to meet their steam requirements despite the intermittent nature of solar irradiation. Hence, conventional steam based EOR projects under the Sunbelt region can benefit from S-EOR with reduced operational expenditure (OPEX) and increased profitability in the long term, even with the initial investment required for solar equipment. S-EOR can be realized as an opportunity for countries not owning any natural gas resources to make them less energy dependent and less sensible to gas price fluctuations, and for countries owning natural gas resources to reduce their gas consumption and export it for a higher margin. In this study, firstly, the market potential of S-EOR was investigated worldwide by covering some of the major ongoing steam based EOR projects as well as future projects in pipeline. A multi-criteria analysis was performed to compare local conditions and requirements of all the oil fields based on a defined set of parameters. Secondly, a modelling approach for S-EOR was designed to identify cost reduction opportunities and optimum solar integration techniques, and the Issaran oil field in Egypt was selected for a case study to substantiate the approach. This modelling approach can be consulted to develop S-EOR projects for any steam flooding based oil fields. The model was developed for steam flooding requirements in Issaran oil field using DYESOPT, KTH's in-house tool for techno-economic modelling in CSP.

  • 332.
    Gutierrez, Mauricio
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Gezork, Tobias
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Yang, Shu
    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.
    Andersson, C.
    Vogt, D. M.
    Forced response analysis of a transonic turbine using a free interface component mode synthesis method2015In: 11th European Conference on Turbomachinery Fluid Dynamics and Thermodynamics, ETC 2015, European Conference on Turbomachinery (ETC) , 2015Conference paper (Refereed)
    Abstract [en]

    Assessing forced response is crucial during the design phase of turbomachines. Since the analyses are computationally expensive and time-consuming when using full models, Reduced Order Models (ROM) are utilized to decrease the number of Degrees Of Freedom (DOF) and consequently analysis time and cost. The ROM used in the current analysis belongs to the component mode synthesis (CMS) method with a free-interface approach known as Craig-Chang. A transonic high pressure turbine is investigated featuring large ranges of disk and blade dominated modes depending in the Nodal Diameter (ND). The free-interface approach will be assessed in the disk and blade dominated regions with a detailed study of the frequencies and mode shapes. In addition, a forced response analysis within the blade dominated region is evaluated in the paper. Moreover, a study of the amount of modes required in the basis for the reduced order transformation matrix is presented.

  • 333.
    Gutierrez, Mauricio
    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.
    Kielb, Robert E.
    Duke Univ, Dept Mech Engn, Durham, NC 27708 USA..
    Key, Nicole L.
    Purdue Univ, Sch Mech Engn, Zucrow Labs, Purdue, IN 47907 USA..
    A Mistuned Forced Response Analysis of an Embedded Compressor Blisk Using a Reduced-Order Model2019In: Journal of engineering for gas turbines and power, ISSN 0742-4795, E-ISSN 1528-8919, Vol. 141, no 3, article id 032505Article in journal (Refereed)
    Abstract [en]

    Accuracy when assessing mistuned forced response analyses is still a major concern. Since a fully coupled analysis is still very computational expensive, several simplifications and reduced-order models (ROMs) are carried out. The use of a reduction method, the assumptions and simplifications, generate different uncertainties that challenge the accuracy of the results. Experimental data are needed for validation and also to understand the propagation of these uncertainties. This paper shows a detailed mistuned forced response analysis of a compressor blisk. The blisk belongs to the Purdue Three-Stage (P3S) Compressor Research Facility. Two different stator-rotor-stator configurations of 38 and 44 upstream stator vanes are taken into consideration. Several loading conditions are analyzed at three different speed lines. A ROM known as subset nominal mode (SNM), has been used for all the analyses. This reduction takes as a basis a set of modes within a selected frequency spectrum. It can consider a complete family of modes to study the disk-blade modal interaction. A detailed comparison between the predicted and measured results has been performed, showing a good agreement for the high loading (HL) conditions.

  • 334.
    Gutierrez Salas, Mauricio
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Development of Accurate Reduced Order Models in a Simulation Tool for Turbomachinery Aeromechanical Phenomena2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Modern gas turbines are still vulnerable to vibrations when operated at certain speeds. This unstable environment can lead to high cycle fatigue (HCF) and damage several of the components inside the turbine. Since engineers are striving to increase the turbines’ efficiency with thinner and more complex blade shapes, these critical speeds will always be present. For these reasons, aeromechanical analyses that is the study of structural and aerodynamic forces need to be assessed with a high level of accuracy. Since this type of analysis are very computational expensive, reduced order models (ROMs) are utilized to decrease the degrees of freedom (DoF) for a faster computation without compromising the accuracy. The present work focuses on cyclic and noncyclic ROMs implemented in an already existing aeroelastic tool, with different characteristics in their condensation and ease of usage depending on the analysis.

     

    The AROMA (Aeroelastic Reduced Order Model Analysis) tool has been previously developed to predict the fatigue life of turbomachinery blades with the use of ROMs. The aim of this work has been to improve the tool in terms of accuracy, flexibility and speed, by employing additional reduction methods capable to predict forced responses analysis of large industrial-size models.

     

    The understanding of an aeroelastic phenomena would not be complete if mistuning is not considered in the analysis. A mistuned bladed-disk means that all its sectors do not share the same mass and stiffness properties, which in reality this is the case. Mistuning can be addressed as probabilistic, taking into account the manufacturing tolerances and wear of the bladed disk, or it can be assessed as deterministic, also known as intentional mistuning.

     

    The latter is achieved to increase the flutter stability by breaking the circumferential traveling waves modes due to energy confinement, and also to have a certain understanding of the forced response amplitude, which helps in designing for worst and best case scenarios.

     

    The ROMs that have been incorporated in the AROMA tool are known as the component mode synthesis (CMS) and subset nominal mode (SNM) approaches. The CMS is split into two branches, these are the fixed- and freeinterface methods known as Craig-Bampton (CB) and Craig-Chang (CC), respectively. An intensive study with numerical and experimental validation has been performed for these three reduction methods. The outcome of the study is that each of these methods have their own drawbacks and benefits depending on the aeromechanical analysis problem. The SNM showed that it produces fast computations, with high level of accuracy when the mistuning level is low. On the other hand, a novel and unique approach, Craig-Chang multisubstructuring (CCMS), demonstrated fast computations and high accuracy when the mistuning level is high.

  • 335.
    Gutierrez Salas, Mauricio
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Validation of detailed CFD simulation of cascade flutter2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Throughout the years, some of the forces of nature within the gas turbine engines have been hidden due to the great amount of stiffness and low loading airfoils used as design drivers. Nowadays, these design key factors on the airfoils have been changing towards a less rigid and high loading blades to achieve a higher power to weight ratio and improve the performance. These new concepts have stimulated other physics that underlie the blades behavior. One example is flutter, which is a new challenge that engineers are facing today. The phenomenon it is still unclear in many aspects where the need of experimental test is always necessary for a better understanding.

     The present work deals with the complex flutter phenomenon in an annular section turbine cascade located at KTH(Royal Institute of Technology). A detailed CFD (Computational Fluid Dynamics) simulation process with Volvo Aero’s software tool, Volsol, is used to understand and validate the results with experimental data taken from the KTH facility.

     Four operating points are studied, where two of the cases represent an off-design condition. In addition, two different mesh grids will be used for different approaches. One approach is to compare the steady simulations of these four operating points by using Volsol against Ansys CFX. The other that implies an optimized mesh is to run the steady plus the unsteady aerodynamic simulations. For every case, the solutions of the steady state or mean flow will be taken as initial conditions for the unsteady simulations. The outcome of the latter analyses will be post-processed to address flutter with four different reduced frequencies. Another parameter to contemplate is the orthogonal rigid body modes of the blade, which could be axial, torsional and circumferential. The results from the unsteady are post-processed to obtain the complex unsteady pressure coefficients, the phase lag between the motion and complex unsteady pressures and assess flutter with the stability curve.

  • 336.
    Gutierrez Salas, Mauricio
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Bladh, R.
    Martensson, H.
    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.
    Vogt, D. M.
    Forced response analysis of a mistuned compressor blisk comparing three different reduced order model approaches2016In: Proceedings of the ASME Turbo Expo, ASME Press, 2016Conference paper (Refereed)
    Abstract [en]

    Accurate structural modeling of blisk mistuning is critical for the analysis of forced response in turbomachinery. Apart from intentional mistuning, mistuning can be due to the manufacturing tolerances, corrosion, foreign object damage and in-service wear in general. It has been shown in past studies that mistuning can increase the risk of blade failure due to energy localization. For weak blade to blade coupling, this localization has been shown to be critical and higher amplitudes of vibration are expected in few blades. This paper presents a comparison of three reduced order models for the structural modeling of blisks. Two of the models assume cyclic symmetry while the third model is free of this assumption. The performance of the reduced order models for cases with small and large amount of mistuning will be examined. The benefits and drawbacks of each reduction method will be discussed.

  • 337.
    Gutierrez Salas, Mauricio
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Bladh, Ronnie
    Martensson, Hans
    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.
    Vogt, Damian M.
    Forced Response Analysis of a Mistuned, Compressor Blisk Comparing Three Different Reduced Order Model Approaches2017In: Journal of engineering for gas turbines and power, ISSN 0742-4795, E-ISSN 1528-8919, Vol. 139, no 6, article id 062501Article in journal (Refereed)
    Abstract [en]

    Accurate structural modeling of blisk mistuning is critical for the analysis of forced response in turbomachinery. Apart from intentional mistuning, mistuning can be due to the manufacturing tolerances, corrosion, foreign object damage, and in-service wear in general. It has been shown in past studies that mistuning can increase the risk of blade failure due to energy localization. For weak blade to blade coupling, this localization has been shown to be critical and higher amplitudes of vibration are expected in few blades. This paper presents a comparison of three reduced order models (ROMs) for the structural modeling of blisks. Two of the models assume cyclic symmetry, while the third model is free of this assumption. The performance of the reduced order models for cases with small and large amount of mistuning will be examined. The benefits and drawbacks of each reduction method will be discussed.

  • 338.
    Gutierrez Salas, Mauricio
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Petrie-Repar, Paul J.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Mårtensson, Hans E.
    Bladh, Ronnie
    Vogt, Damian
    Forced Response Analysis of a Mistuned Blisk Using Noncyclic Reduced-Order Models2018In: Journal of Propulsion and Power, ISSN 0748-4658, E-ISSN 1533-3876, Vol. 34, no 3, p. 565-577Article in journal (Refereed)
    Abstract [en]

    The importance of mistuning analysis lies on understanding the distribution of the vibrational energy around the blisk. The large vibration amplitudes of individual blades inherent in mistuned blisks reduces the high cycle fatigue margin significantly. It is therefore important to perform mistuning analyses at a high accuracy while keeping the computational cost at an acceptable level. Because numerous analyses with large amount of degrees of freedom models are commonly performed, it is frequent to employ reduced-order models such as to reduce the computational effort. In this paper, a unique way to address the reduced-order model is presented, where each blisk sector is attached as individual substructures with the free-interface approach known as Craig-Chang. This implementation is compared against a fixed-interface approach known as Craig-Bampton in terms of accuracy for disk- and blade-dominated modes. Neither of these approaches applies cyclic symmetry, making them more accurate in the presence of mistuning when the harmonic patterns are destroyed. Results show the high benefits of using the free-interface approach for a mistuned forced response analysis.

  • 339.
    Guédez, Rafael
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    A Techno-Economic Framework for the Analysis of Concentrating Solar Power Plants with Storage2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Concentrating solar power plants can integrate cost-effective thermal energy storage systems and thereby supply controllable power on demand, an advantage against other renewable technologies. Storage integration allows a solar thermal power plant to increase its load factor and to shift production to periods of peak demand. It also enables output firmness, providing stability to the power block and to the grid. Thus, despite the additional investment, storage can enhance the performance and economic viability of the plants.

    However, the levelized cost of electricity of these plants yet remains higher than for other technologies, so projects today are only viable through the provision of incentives or technology-specific competitive bid tenders. It is the variability of the solar resource, the myriad roles that storage can assume, and the complexity of enhancing the synergies between the solar field, the storage and the power block, what makes the development of adequate policy instruments, design and operation of these plants a challenging process.

    In this thesis a comprehensive methodology for the pre-design and analysis of concentrating solar power plants is presented. The methodology is based on a techno-economic modeling approach that allows identifying optimum trade-off curves between technical, environmental, and financial performance indicators. A number of contemporary plant layouts and novel storage and hybridization concepts are assessed to identify optimum plant configurations, in terms of component size and storage dispatch strategies.

    Conclusions highlight the relevance between the sizing of key plant components, the operation strategy and the boundaries set by the location. The interrelation between critical performance indicators, and their use as decisive parameters, is also discussed. Results are used as a basis to provide recommendations aimed to support the decision making process of key actors along the project development value chain of the plants. This research work and conclusions are primarily meant to set a stepping stone in the research of concentrating solar power plant design and optimization, but also to support the research towards understanding the value of storage in concentrating solar power plants and in the grid.

  • 340.
    Guédez, Rafael
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Ferragut, F.
    Hassar, Z.
    Topel, Monika
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Callaba, I.
    Pérez-Segarra, C. D.
    Buezas, I. C.
    Spelling, J.
    Laumert, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    A methodology for determining optimum solar tower plant configurations and operating strategies to maximize profits based on hourly electricity market prices and tariffs2015In: ASME 2015 9th International Conference on Energy Sustainability, ES 2015, collocated with the ASME 2015 Power Conference, the ASME 2015 13th International Conference on Fuel Cell Science, Engineering and Technology, and the ASME 2015 Nuclear Forum, ASME Press, 2015Conference paper (Refereed)
    Abstract [en]

    The present study analyses the influence that market conditions have on determining optimum molten salt solar tower plants with storage that maximize profits (in terms of plant configuration, sizing and operation) for a location in South Africa. Three different scenarios based on incentive programs and local wholesale electricity prices are considered. A multi-objective optimization modeling approach was followed, showing the trade-off curves between minimizing investment and maximizing profits when varying critical sizerelated parameters (such as nameplate capacity, solar multiple and storage capacity) together with power-cycle design and operating specifications including dynamic start-up curves and different storage dispatchability strategies. Results are shown by means of a comparative analysis between optimal plants found for each scenario, highlighting the value that storage has under the current two-tier tariff scheme, and the relevance of designing a suitable policy for technology development. Lastly, a final analysis is performed with regards of the indicators used for economic evaluation of power plants, by comparing the differences between optimum designs found when using the levelized cost of electricity solely as performance indicator instead of cash-flows and profit-based indicators, such as the internal rate of return.

  • 341.
    Guédez, Rafael
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Garcia, Jose Angel
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Martin, Fernando
    AF Aries Energia, Paseo Castellana 130,3th Floor, Madrid 28046, Spain..
    Wiesenberg, Ralf
    AF Aries Energia, Paseo Castellana 130,3th Floor, Madrid 28046, Spain..
    Laumert, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Integrated Solar Combined Cycles vs Combined Gas Turbine to Bottoming Molten Salt Tower Plants - A Techno-economic Analysis2018In: INTERNATIONAL CONFERENCE ON CONCENTRATING SOLAR POWER AND CHEMICAL ENERGY SYSTEMS (SOLARPACES 2017) / [ed] Mancilla, R Richter, C, AMER INST PHYSICS , 2018, article id 180006-1Conference paper (Refereed)
    Abstract [en]

    The present work deals with the techno-economic analysis of a novel combined power cycle consisting of a molten-salt solar tower power plant with storage supported by additional heat provided from the exhaust of a topping gas-turbine unit. A detailed model has been elaborated using in house simulation tools that simultaneously encompass meteorological, demand and required dispatch data. A range of possible designs are evaluated for a suitable location with both good solar resource and vast natural gas resources in order to show the trade-offs between the objectives of achieving low carbon-intensive and economically competitive designs. These were compared against more conventional integrated solar combined cycles of equivalent capacity factors. It is shown that the novel concept is worth further investigating as it is able to outperform the more conventional cycle while simultaneously offering additional flexibility to grid-operators.

  • 342.
    Guédez, Rafael
    et al.
    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.
    Laumert, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Enhancing the Economic Competitiveness of Concentrating Solar Power Plants Through an Innovative Integrated Solar-Combined Cycle With Thermal Energy Storage2015In: Journal of engineering for gas turbines and power, ISSN 0742-4795, E-ISSN 1528-8919, Vol. 137, no 4, article id 041701Article in journal (Refereed)
    Abstract [en]

    The present work deals with the thermo-economic analysis of an innovative combined power cycle consisting of a molten-salt solar tower power plant with storage supported by additional heat provided from the exhaust of a topping gas-turbine unit. A detailed dynamic model has been elaborated using an in house simulation tool that simultaneously encompasses meteorological, demand and price data. A wide range of possible designs are evaluated in order to show the trade-offs between the objectives of achieving sustainable and economically competitive designs. Results show that optimal designs of the novel concept are a promising cost-effective hybrid option that can successfully fulfill both the roles of a gas peaker plant and a baseload solar power plant in a more effective manner. Moreover, designs are also compared against conventional combined cycle gas turbine (CCGT) power plants and it is shown that, under specific peaking operating strategies (P-OSs), the innovative concept cannot only perform better from an environmental standpoint but also economically.

  • 343.
    Guédez, Rafael
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Spelling, James
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Laumert, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Thermoeconomic Optimization of Solar Thermal Power Plants with Storage in High-Penetration Renewable Electricity Markets2013In: Energy Procedia, 2013, Vol. 57Conference paper (Refereed)
    Abstract [en]

    Unlike most of renewable energy technologies, solar thermal power plants with integrated thermal energy storage are able to store heat from the sun and thereby supply electricity whenever it is needed to meet the demand. This attribute makes concentrating solar power ideally suited to compensate for fluctuations in other renewable energy sources. In order to analyze this market role, three scenarios were modeled, with low, medium and high penetrations of non- dispatchable renewables (i.e. wind and solar photovoltaics). The demand that cannot be met by these variable sources is met by a solar thermal power plant with heat provided either by a solar field and storage system or a back-up gas burner. For each scenario, the size of the solar field and storage were varied in order to show the trade-off between the levelized generation costs of the system, the annual specific CO2 emissions and the share of renewable electricity generation. The results show that, regardless of the scenario, there exist optimum plant configurations with viable costs whilst simultaneously ensuring a considerable reduction in CO2 emissions. Furthermore, it is shown that the limited flexibility of the power block prevents the system from reaching higher levels of sustainability. Lastly, the results were compared with an equivalent combined cycle power plant, showing that solutions involving solar thermal power can be justified in environmental terms only if large storage units are integrated into the plants.

  • 344.
    Guédez, Rafael
    et al.
    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.
    Laumert, Björn
    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.
    Reducing the Number of Turbine Starts in Concentrating Solar Power Plants through the Integration of Thermal Energy Storage2013In: Proceedings of the ASME TurboExpo 2013, 2013Conference paper (Refereed)
    Abstract [en]

    The operation of steam turbine units in solar thermal power plants is very different than in conventional base-load plants. Due to the variability of the solar resource, much higher frequencies of plant start-ups are encountered. This study provides an insight to the influence of thermal energy storage integration on the typical cycling operation of solar thermal power plants. It is demonstrated that the integration of storage leads to significant reductions in the annual number of turbine starts and is thus beneficial to the turbine lifetime. At the same time, the effects of storage integration on the electricity costs are analyzed to ensure that the designs remain economically competitive. Large storage capacities, can allow the plant to be shifted from a daily starting regime to one where less than 20 plant starts occur annually. Additionally, the concept of equivalent operating hours is used to further analyze the direct impact of storage integration on the maintenance planning of the turbine units.

  • 345.
    Habib, Faraz
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Validation of 3D CFD Simulations of Downwind NREL Wind Turbine using CFD code OpenFOAM: NREL Phase VI Experiment- Baseline Case2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis project is inside a Fraunhofer institute of Wind Energy and Energy System Technology (IWES) downwind turbine project which is three-dimensional (3D) unsteady aerodynamics experiment of horizontal axis wind turbine of phase VI baseline case of NREL (National Renewable Energy Laboratory-USA) and part of WP4 experiment of IEA (International Energy Agency) task number 29. The objective of this thesis project is to validate the simulations of downwind turbine using CFD (computational fluid dynamics) code OpenFOAM (open source field operation and manipulation). The turbine with tower and nacelle is to be simulated using RANS and URANS (Unsteady Reynolds-averaged Navier-Stokes). GGI (General Grid Interface) is used to integrate rotating mesh with stationary mesh. Detailed CAD modeling of blade (aerofoil NREL S809), nacelle, hub and tower of wind turbine has been developed using Autodesk Inventor Professional and CATIAV5. Refined surface hybrid mesh is generated through STL (STereoLithography) surface files using OpenFOAM pre-processing utilities, blockMesh and snappyHexMesh respectively. Cases for Steady simulations using GGI as a interface to integrate moving mesh with stationary is prepared using OpenFOAM dictionaries and libraries. Results from steady simulation are mapped on transient simulation using GGI as an interface. Steady and unsteady simulations are investigated using OpenFOAM standard numerical solvers MRFSimpleFOAM and pimpleDymFOAM respectively. A 3rd party software ParaView 4.0.1 is used which a graphical interface for visualizing and comparing the results obtained from conducted CFD simulations using OpenFOAM toolbox. Local Angle of attack, Axial Induction factor, relative velocity, components of normal and tangential forces are calculated for 3D rotating blade using post processing utilities within OpenFOAM toolbox and ParaView. Results are compared and validated with experimental data. Discussion about 3D tower-blade interaction, rotational effects, boundary layer transitions and stall phenomenon has been done within this research work. 

  • 346.
    Hagström, Peter
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Evaluation of the Biomass potential for Heat, Electricity and Vehicle Fuel in Sweden2005Conference paper (Other academic)
    Abstract [en]

    This paper summarizes some results of a thesis, where the objective was to show how far a biomass quantity, equal to the annual potential produced within the Swedish borders, could reach to cover the present energy needs inSwedenwith respect to ecological circumstances. Three scenarios were studied where the available biomass was converted to different energy carriers; heat, electricity and vehicle fuel. Two levels of biomass supply were studied for each scenario: 1) potential biomass quantities available for energy conversion received from forestry, non-forest land, forest industry and municipality; 2) the same quantities as in case 1 plus the potential biomass quantities available for energy conversion received from agriculture.

    It was indicated that it may be possible to produce as much as 209.4 PJ (58.2 TWh) of electricity via gasification of the Swedish potential of biomass assortments available for energy conversion (i.e. case 2 of biomass supply). The maximum amounts of hydrogen or methanol which may be produced via gasification of the same biomass amounts excluding black liquor were 241.5 PJ/year (67.1 TWh/year) or 197.2 PJ/year (54.8 TWh/year) respectively.

  • 347.
    Hagström, Peter
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Hur stor är den svenska bioenergipotentialen?2006In: Fakta Skog - Om forskning vid Sveriges lantbruksuniversitet, ISSN 1400-7789, no 1, p. 1-4Article, review/survey (Other academic)
    Abstract [sv]

    Med ny omvandlingsteknik skulle den fysiska biomassapotentialen i Sverige kunna stå för ca 40 % av den svenska elproduktionen eller drygt 90 % av all drivmedelsanvändning.

    Produktionskostnaderna för elektricitet eller transportarbete via omvandling av biomassa blir jämförbara med dagens fossilbaserade energisystem.

    Emergianalyser visar att bioenergisystem är resurskrävande, vilket medför att utbytet av totala resurser till samhället blir litet jämfört med alternativa (både fossilbaserade och förnyelsebara) energisystem.

  • 348.
    Hagström, Peter
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Nilsson, Per Olov
    Emergy Evaluation of the Swedish Economy since the 1950s2004In: Proceedings of the Third Biennial Emergy Conference / [ed] Mark Brown, Gainesville, FL: University of Florida, 2004, , p. 18p. 335-344Conference paper (Refereed)
    Abstract [en]

    The aim of this work was to analyze the change in resource basis of the Swedish economy from the 1950s until the present time and to establish indices for solar emergy per Swedish krona (sej/SEK) to be used in further studies. During the period 1956 to 2002, the population increased from 7.3 to 8.9 million. Total emergy use increased from 146.1 x 1021 to 369.5 x1021 solar emjoules per year, largely due to increasing imports of oil and uranium and an expanding service sector. Total imports increased from 85.6 x 1021 to 305.7 x 1021 sej/year and exports increased from 60.8 x 1021 to 262.5 x 1021 sej/year. The fraction of indigenous resources for the total economy decreased from 41.4% to 17.3% in emergy terms. Based on income statistics and consumer price indices the standard of living measured as gross national product per person, corrected for inflation, increased threefold whereas emergy use increased twofold, indicating an efficiency increase of 50% in solar emergy use per real wealth output. The renewable part of solar emergy use decreased from 31.0% to 12.2% during the period, showing a substantial increase in dependence on non-renewable sources.

  • 349.
    Hallberg, Maria
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Hallme, Elin
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Introducing a central receiver system for industrial high-temperature process heat applications: A techno-economic case study of a large-scale CST plant system in a South African manganese sinter plant2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The objective of this thesis was to investigate the potential for introducing a concentrating solar thermal (CST) central receiver plant system based on flexible heliostats - HelioPods - to provide high-temperature process heat in industrial applications. A CST plant system was designed in MATLAB, optically simulated for three design days in the ray-tracing software Tonatiuh and further analyzed in MATLAB by interpolating the results for each hour of the year. A case study was made on introducing a CST plant system based on HelioPods in a South African manganese sinter plant. The study included an investigation of the profitability of up- and downsizing the heliostat field annually with fluctuating heat demand. A circular heliostat field was modelled for the chosen location. The final field had a radius of 53 meters with the receiver located 60% from the field centre. The storage size was 16 demand hours and 17 plants were required. The results showed that 88% of the annual heat demand could be covered by solar heat in the design year. The marketing approach used for the following years was that the heat demand covered by solar heat should never be below the share at the first year, despite the predicted fluctuations in demand. Thus, a minimum solar share of 88% was used as a strategy for annual up- and downsizing of the fields throughout the investigated period of 25 years. That resulted in a field radius differing between 52 and 55 meters.

    The payback period of the final system was 4.35 years, the NPV was 54.33 MUSD over a period of 25 years and the LCOH was 35.39 USD/MWht. However, it was found that the profitability of the system was sensitive to the different scenarios for predicted future diesel prices, this since the pricing of the solar heat was set to 90% of the diesel price. The results in this thesis show that a CST plant system based on HelioPods is a suitable solution to supply high-temperature process heat to industrial applications. It also shows that the HelioPods can unlock potential for flexibility with changing production patterns in the industry of implementation. The results from the study can be used also for other industries with similar temperature range and heat demand. Thus, it could be argued that the implementation of a HelioPod based CST plant system also can be suitable for other industries located in high-DNI areas with dependency on conventional fuels and steady production throughout the whole day.

  • 350.
    Hammer, Steffen
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    3D Flutter Analysis of Space Turbines2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The trend in gas turbine engines towards lighter and more efficient design is increasing. Due to high costs the necessity for good tools in early stages of the design process is therefore tremendous. Especially in the preliminary design flutter simulation is performed in 2D to get fast results. The fast evaluation of new designs, including profile and disk variation, is the driving component in the field.

    The project deals with the development of a method to assess space turbines for flutter susceptibility in 3D. Several parameterized scripts have been created to perform a complete flutter analysis. The ability of performing a modal analysis of the model is herein a key parameter.

    The method is tested on two turbines of a space engine for seven operating points respectively and compared to the 2D simulation. A profile variation is then performed to find an indicator how to stabilize one of the turbines.

    The results of the method are in good agreement with 2D computation. The fast implementation and analysis of different blade profiles is proven. When comparing different blade profiles designed for the same duty, a significant difference in flutter characteristics appears. The results suggest a further, more detailed study on the influence of blade shape variation on the flutter susceptibility.

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