| 1. |
- Aichmayer, Lukas
(författare)
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Solar receiver development for gas-turbine based solar dish systems
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Small-scale concentrating solar power plants such as micro gas-turbine based solar dish systems have the potential to harness solar energy in an effective way and supply electricity to customers in remote areas. In such systems, the solar receiver transfers the power of concentrated solar radiation to the working fluid of the power conversion cycle. It is one of the key components as it needs to operate at high temperatures to ensure a high power cycle efficiency and under high flux densities to ensure a high receiver efficiency. In order to address these challenges and to ensure efficient and reliable operation innovative designs are needed.This research work focuses on the complete development of a novel solar receiver applying a new systematic design and analysis methodology. Therefore, a comprehensive receiver design and experimental evaluation process were developed and implemented. The design process includes the identification of technical specifications and requirements, the development of receiver design tools of different investigation levels coupled with multi-objective optimization tools, the evaluation of scaling effects between tests in the KTH high-flux solar simulator and the full-scale solar dish system. As a result of the design process a representative final receiver was established with material temperatures and stresses below critical limits while respecting the design specification.The experimental evaluation includes the enhancement of the KTH high-flux solar simulator to provide stable and reliable operating conditions, the precise characterization of the radiative boundary conditions, the design of a receiver test bed recreating the operating behavior of a gas-turbine, and the final receiver testing for multiple operating points. It was shown that the prototype reaches an efficiency of 69.3% for an air outlet temperature of 800°C and a mass flow of 29.5 g/s. For a larger mass flow of 38.4 g/s a receiver efficiency of 84.8% was achieved with an air outlet temperature of 749°C.The measurement results obtained were then used for a multi-point validation of the receiver design tools, resulting in a high level of confidence in the accuracy of the tools. The validated models were then harnessed to calculate the performance of a full-scale solar receiver integrated into the OMSoP solar dish system. It was shown that a solar receiver can be designed, which delivers air at 800°C with a receiver efficiency of 82.2%.Finally, the economic potential of micro gas-turbine based solar systems was investigated and it was shown that they are ideally suited for small-scale stand-alone and off-grid applications.The results of the receiver development highlight the feasibility of using volumetric solar receivers to provide heat input to micro gas-turbine based solar dish systems and no major hurdles were found.
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| 2. |
- Akbari, Keramatollah, 1961-
(författare)
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Simulation of Indoor Radon and Energy Recovery Ventilation Systems in Residential Buildings
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This study aims to investigate the effects of ventilation rate, indoor air temperature, humidity and using a heat recovery ventilation system on indoor radon concentration and distribution.Methods employed include energy dynamic and computational fluid dynamics simulation, experimental measurement and analytical investigations. Experimental investigations primarily utilize a continuous radon meter and a detached house equipped with a recovery heat exchanger unit.The results of the dynamic simulation show that the heat recovery unit is cost-effective for the cold Swedish climate and an energy saving of about 30 kWh per floor area per year is possible, while it can be also used to lower radon level.The numerical results showed that ventilation rate and ventilation location have significant impacts on both radon content and distribution, whereas indoor air temperature only has a small effect on radon level and distribution and humidity has no impact on radon level but has a small impact on its distribution.
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| 3. |
- Aslanidou, Ioanna, et al.
(författare)
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Teaching gas turbine technology to undergraduate students in Sweden
- 2018
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Ingår i: Proceedings of the ASME Turbo Expo. - : American Society of Mechanical Engineers (ASME). - 9780791851128
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Konferensbidrag (refereegranskat)abstract
- This paper addresses the teaching of gas turbine technology in a third-year undergraduate course in Sweden and the challenges encountered. The improvements noted in the reaction of the students and the achievement of the learning outcomes is discussed. The course, aimed at students with a broad academic education on energy, is focused on gas turbines, covering topics from cycle studies and performance calculations to detailed design of turbomachinery components. It also includes economic aspects during the operation of heat and power generation systems and addresses combined cycles as well as hybrid energy systems with fuel cells. The course structure comprises lectures from academics and industrial experts, study visits, and a comprehensive assignment. With the inclusion of all of these aspects in the course, the students find it rewarding despite the significant challenges encountered. An important contribution to the education of the students is giving them the chance, stimulation, and support to complete an assignment on gas turbine design. Particular attention is given on striking a balance between helping them find the solution to the design problem and encouraging them to think on their own. Feedback received from the students highlighted some of the challenges and has given directions for improvements in the structure of the course, particularly with regards to the course assignment. This year, an application developed for a mobile phone in the Aristotle University of Thessaloniki for the calculation of engine performance will be introduced in the course. The app will have a supporting role during discussions and presentations in the classroom and help the students better understand gas turbine operation. This is also expected to reduce the workload of the students for the assignment and spike their interest.
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| 4. |
- Aslanidou, Ioanna, et al.
(författare)
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Towards an Integrated Approach for Micro Gas Turbine Fleet Monitoring, Control and Diagnostics
- 2018
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Konferensbidrag (refereegranskat)abstract
- Real-time engine condition monitoring and fault diagnostics results in reduced operating and maintenance costs and increased component and engine life. Prediction of faults can change the maintenance model of a system from a fixed maintenance interval to a condition based maintenance interval, further decreasing the total cost of ownership of a system. Technologies developed for engine health monitoring and advanced diagnostic capabilities are generally developed for larger gas turbines, and generally focus on a single system; no solutions are publicly available for engine fleets. This paper presents a concept for fleet monitoring finely tuned to the specific needs of micro gas turbines. The proposed framework includes a physics-based model and a data-driven model with machine learning capabilities for predicting system behaviour, combined with a diagnostic tool for anomaly detection and classification. The integrated system will develop advanced diagnostics and condition monitoring for gas turbines with a power output under 100 kW.
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| 5. |
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| 6. |
- Campillo, Javier, 1982-, et al.
(författare)
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Open-Source Modelling and Simulation of Microgrids and Active Distribution Networks
- 2015
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Ingår i: Sustainable Places 2015, Conference Proceedings. - : Sigma Orionis. - 9791095345008 ; , s. 91-99
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Konferensbidrag (refereegranskat)abstract
- Distributed generation, and active distribution networks constitute an economic and technically viable alternative for reducing green house gases emissions and increase the use of renewable energy sources in local distribution grids. These active networks allow replacing large generators, usually located far from the consumption loads, thus considerably minimizing distribution losses and increase renewable energy penetration. However, designing and successfully controlling these complex networks, becomes a great engineering challenge; most computational modeling and simulation tools available for these systems are either focused on the individual generation components themselves, or the economic dispatch of multiple generators. Moreover, these tools often rely on closed source commercial software that use manufacturers' data for predefining the parameters of the models' components. This approach does not provide enough flexibility to users, since often is not possible to adjust these parameters. This paper presents object- oriented, component-based, open software components for simulating and optimizing the operation of active distribution networks, including multiple distributed generators and energy using the Modelica open-source modeling language.
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| 7. |
- Da Silva, Edna, et al.
(författare)
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Preliminary design optimization of an organic Rankine cycle radial turbine rotor
- 2017
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Ingår i: PROCEEDINGS OF THE ASME TURBO EXPO: TURBINE TECHNICAL CONFERENCE AND EXPOSITION, 2017, VOL 3. - : American Society of Mechanical Engineers (ASME). - 9780791850831
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Konferensbidrag (refereegranskat)abstract
- The present study describes the application of a preliminary design approach for the optimization of an organic Rankine cycle radial turbine. Losses in the nozzle the rotor have initially been modelled using a mean-line design approach. The work focuses on a typical small-scale application of 50 kW, and two working fluids, R245fa (1,1,1,3,3,-pentafluoropropane) and R236fa (1,1,1,3,3,3-hexafluoropropane) are considered for validation purposes. Real gas formulations have been used based on the NIST REFPROP database. The validation is based on a design from the literature, and the results demonstrate close agreement the reference geometry and thermodynamic parameters. The total-to-total efficiencies of the reference turbine designs were 72% and 79%. Following the validation exercise, an optimization process was performed using a controlled random search algorithm with the turbine efficiency set as the figure of merit. The optimization focuses on the R245fa working fluid since it is more suitable for the operating conditions of the proposed cycle, enables an overpressure in the condenser and allows higher system efficiency levels. The R236fa working fluid was also used for comparison with the literature, and the reason is the positive slope of the saturation curve, somehow is possible to work with lower temperatures. Key preliminary design variables such as flow coefficient, loading coefficient, and length parameter have been considered. While several optimized preliminary designs are available in the literature with efficiency levels of up to 90%, the preliminary design choices made will only hold true for machines operating with ideal gases, i.e. typical exhaust gases from an airbreathing combustion engine. For machines operating with real gases, such as organic working fluids, the design choices need to be rethought and a preliminary design optimization process needs to be introduced. The efficiency achieved in the final radial turbine design operating with R245fa following the optimization process was 82.4%. A three-dimensional analysis of the flow through the blade section using computational fluid dynamics was carried out on the final optimized design to confirm the preliminary design and further analyze its characteristics.
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| 8. |
- Dahlquist, Erik, 1951-, et al.
(författare)
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Comparison of Gas Quality from Black Liquor and Wood Pellet Gasification Using Modelica Simulation and Pilot Plant Results
- 2017
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Ingår i: 8th International Conference on Applied Energy, ICAE 2016; Beijing; China; 8 October 2016 through 11 October 2016. - Amsterdam : Elsevier. ; 105, s. 992-998, s. 992-998
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Konferensbidrag (refereegranskat)abstract
- There is a potential to integrate biomass gasification with pulp & paper and CHP plants in order to complement the existing systems with production of chemicals, such as methane, hydrogen, and methanol etc. To perform system analysis of such integration, it is important to gain knowledge of relevant input data on expected synthesis gas composition by gasifying different types of feed stock. In this paper, the synthesis gas quality from wood pellets gasification (WPG) has been compared with black liquor gasification (BLG) through modeling and experimental results at pilot scale. In addition, the study develops regression models like Partial Least Squares (PLS) made from the experimental data. The regression models are then combined with dynamic models developed in Modelica for the investigation of dynamic energy and material balances for integrated plants. The data presented in this study could be used as input to relevant analysis using e.g. ASPEN plus and similar system analysis tools.
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| 9. |
- Dahlquist, Erik, 1951-, et al.
(författare)
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Experimental and numerical investigation of pellet and black liquor gasification for polygeneration plant
- 2017
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Ingår i: Applied Energy. - : Elsevier Ltd. - 0306-2619 .- 1872-9118. ; 204, s. 1055-1064
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Tidskriftsartikel (refereegranskat)abstract
- It is vital to perform system analysis on integrated biomass gasification in chemical recovery systems in pulp and paper and heat and power plants for polygeneration applications. The proposed integration complements existing pulp and paper and heat and power production systems with production of chemicals such as methane and hydrogen. The potential to introduce gasification-based combined cycles comprising gas turbines and steam turbines to utilize black liquors and wood pellets also merits investigation. To perform such analysis, it is important to first build knowledge on expected synthesis gas composition by gasifying at smaller scale different types of feed stock. In the present paper, the synthesis gas quality from wood pellets gasification has been compared with black liquor gasification by means of numerical simulation as well as through pilot-scale experimental investigations. The experimental results have been correlated into partial least squares models to predict the composition of the synthesis gas produced under different operating conditions. The gas quality prediction models are combined with physical models using a generic open-source modelling language for investigating the dynamic performance of large-scale integrated polygeneration plants. The analysis is further complemented by considering potential gas separation using modern membrane technology for upgrading the synthesis gas with respect to hydrogen content. The experimental data and statistical models presented in this study form an important literature source for future use by the gasification and polygeneration research community on further integrated system analysis.
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| 10. |
- Dahlquist, Erik, et al.
(författare)
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Modeling of Black Liquor Gasification
- 2016
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Ingår i: Proceedings of 2016 9th EUROSIM Congress on Modelling and Simulation. - : Linköping University Electronic Press. - 9789176853993
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Konferensbidrag (refereegranskat)abstract
- The energy situation in both process industries andpower plants is changing. It is becoming interesting toperform system analysis on how to integrate gasificationinto chemical recovery systems in the pulp & paperindustry and into the CHP systems in power plantapplications to complement with production ofchemicals aside of heat and power. The potentialchemicals are methane, hydrogen, and methanol. It isalso interesting to estimate the potential to introducecombined cycles with gas turbines and steam turbinesusing both black liquors and other type of biomass likepellets, wood chips etc. To perform such type ofanalysis, it is vital to have relevant input data on whatgas composition we can expect from running differenttypes of feedstock. In this paper, we focus on blackliquors as feedstock for integrated gasification systems.The experimental results are correlated into partial leastsquares models to predict major composition of thesynthesis gas produced under different conditions.These quality prediction models are then combined withphysical models using Modelica for the investigation ofdynamic energy and material balances for completeplants. The data can also be used as input to analysisusing e.g. ASPEN plus and similar system analysistools
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