| 1. |
- Strand, Torsten, et al.
(författare)
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On the Significance of Concentrated Solar Power R&D in Sweden
- 2011
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Ingår i: Proceedings of the World Renewable Energy Congress 2011, Linköping.
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Konferensbidrag (refereegranskat)abstract
- Concentrated Solar Power (CSP) is an emerging renewable energy technology that has the potential to provide a major part of European energy needs at competitive cost levels. Swedish industry is strongly involved in CSP-based energy production either in the form of growing providers on the European energy market or as developers and producers of key components for CSP power plants. The growing industrial interest is reflected and accompanied by state of the art research in this field at the Department of Energy Technology at KTH. In the present paper the main challenges and opportunities for CSP R&D are presented and linked to the industrial environment and interests in Sweden. Related to these challenges, an overview of the latest research activities and results at the Department of Energy Technology is given with examples concerning CSP plant operation and optimisation, techno- economic cycle studies and high temperature solar receiver development.
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| 2. |
- Wang, Wujun
(författare)
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Development of an Impinging Receiver for Solar Dish-Brayton Systems
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A new receiver concept utilizing impinging jet cooling technology has been developed for a small scale solar dish-Brayton system. In a typical impinging receiver design, the jet nozzles are distributed evenly around the cylindrical absorber wall above the solar peak flux region for managing the temperature at an acceptable level. The absorbed solar irradiation is partially lost to the ambient by radiation and natural convection heat transfer, the major part is conducted through the wall and taken away by the impingement jets to drive a gas turbine. Since the thermal power requirement of a 5 kWe Compower® micro gas turbine (MGT) perfectly matches with the power collected by the EuroDish when the design Direct Normal Irradiance (DNI) input is 800 W/m2, the boundary conditions for the impinging receiver design in this work are based on the combination of the Compower®MGT and the EuroDish system.In order to quickly find feasible receiver geometries and impinging jet nozzle arrangements for achieving acceptable temperature level and temperature distributions on the absorber cavity wall, a novel inverse design method (IDM) has been developed based on a combination of a ray-tracing model and a heat transfer analytical model. In this design method, a heat transfer model of the absorber wall is used for analyzing the main heat transfer process between the cavity wall outer surface, the inner surface and the working fluid. A ray-tracing model is utilized for obtaining the solar radiative boundary conditions for the heat transfer model. Furthermore, the minimum stagnation heat transfer coefficient, the jet pitch and the maximum pressure drop governing equations are used for narrowing down the possible nozzle arrangements. Finally, the curves for the required total heat transfer coefficient distribution are obtained and compared with different selected impinging arrangements on the working fluid side, and candidate design configurations are obtained.Furthermore, a numerical conjugate heat transfer model combined with a ray-tracing model was developed validating the inverse design method and for studying the thermal performance of an impinging receiver in detail. With the help of the modified inverse design method and the numerical conjugate heat transfer model, two impinging receivers based on sintered α-SiC (SSiC) and stainless steel 253 MA material have been successfully designed. The detailed analyses show that for the 253 MA impinging receiver, the average air temperature at the outlet and the thermal efficiency can reach 1071.5 K and 82.7% at a DNI level of 800 W/m2 matching the system requirements well. Furthermore, the local temperature differences on the absorber can be reduced to 130 K and 149 K for two different DNI levels, which is a significant reduction and improvement compared with earlier published cavity receiver designs. The inverse design method has also been verified to be an efficient way in reducing the calculation costs during the design procedure.For the validation and demonstration of the receiver designs, a unique experimental facility was designed and constructed. The facility is a novel high flux solar simulator utilizing for the first time Fresnel lenses to concentrate the light of 12 commercial high power Xenon-arc lamps. Finally, a prototype of a 253 MA based impinging was experimentally studied with the help of the 84 kWe Fresnel lens based high flux solar simulator in KTH.
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| 3. |
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| 4. |
- Alsved, Malin, et al.
(författare)
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Sources of Airborne Norovirus in Hospital Outbreaks
- 2020
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Ingår i: Clinical Infectious Diseases. - : Oxford University Press (OUP). - 1537-6591 .- 1058-4838. ; 70:10, s. 2023-2028
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Noroviruses are the major cause of viral gastroenteritis. Disease transmission is difficult to prevent and outbreaks in healthcare facilities commonly occur. Contact with infected persons and contaminated environments are believed to be the main routes of transmission. However, noroviruses have recently been found in aerosols and airborne transmission has been suggested. The aim of our study was to investigate associations between symptoms of gastroenteritis and presence of airborne norovirus, and to investigate the size of norovirus carrying particles.METHODS: Air sampling was repeatedly performed close to 26 patients with norovirus infections. Samples were analysed for norovirus RNA by RT-qPCR. The times since the patients' last episodes of vomiting and diarrhoea were recorded. Size separating aerosol particle collection was also performed in ward corridors.RESULTS: Norovirus RNA was found in 21 (24%) of 86 air samples from 10 different patients. Only air samples during outbreaks, or before a succeeding outbreak, tested positive for norovirus RNA. Airborne norovirus RNA was also strongly associated with a shorter time period since the last vomiting episode (odds ratio 8.1, p=0.04 within 3 hours since the last vomiting episode). The concentration of airborne norovirus ranged from 5-215 copies/m3, and detectable amounts of norovirus RNA were found in particles <0.95 µm and >4.51 µm.CONCLUSIONS: The results suggest that recent vomiting is the major source of airborne norovirus and imply a connection between airborne norovirus and outbreaks. The presence of norovirus RNA in submicrometre particles indicates that airborne transmission can be an important transmission route.
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| 5. |
- Ghaem Sigarchian, Sara, et al.
(författare)
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Modeling and Analysis of a Hybrid Solar-Dish Brayton Engine
- 2012
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Ingår i: Proceedings of the International SolarPACES Conference 2012.
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Konferensbidrag (refereegranskat)abstract
- Small-scale recuperated gas turbines with a highly efficient recuperator would appear to have considerable potential to be used in solar/fossil-fuel hybrid dish systems. The hybrid solar gas turbine can be configured in several different fashions, with the key difference being the relative positions of the solar receiver and burner as well as the operation mode of the burner.Steady state and transient models have been implemented in Engineering Equation Solver and the performance of various configurations are studied and compared. Layouts in which the receiver is located before the turbine (pressurized receivers) demonstrate higher performance compared to the one in which the receiver is located after the turbine (atmospheric receivers). The variation in operation throughout the year is taken into account and the performance of the system analyzed for two different cities (Yechang in China and Bechar in Algeria, with low and high solar insolation respectively). The integration of a solar receiver into a micro gas turbine reduces the yearly fuel consumption by around 15-16% in Yechang and up to 40% in Bechar. This will result in reductions of CO2 emissions as well as leading to lower daily operating costs. The hybrid nature of the Dish-Brayton system guarantees availability of the engine to meet the electricity demand whenever it occurs, allowing the system to supply dispatchable power.
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| 6. |
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| 7. |
- Ragnolo, Gianmarco, et al.
(författare)
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Technoeconomic Design of a Micro Gas-Turbine for a Solar Dish System
- 2014
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Ingår i: Proceedings of the International SolarPACES Conference 2014. Beijing, China. September 16-19. - : Elsevier.
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Konferensbidrag (refereegranskat)abstract
- An integrated approach for the design of a custom-tailored hybrid solar MGT with an integrated solar receiver for the use in a small-scale solar dish unit is presented in order to overcome the inherent limitations of adapting a MGT in the desired power range to solar operation. The resulting MGT-dish equipped with the ‘optimal’ MGT shows a nominal conversion efficiency of 29.6%. Then, a thermoeconomic analysis of the entire system is performed to evaluate and compare the economic and environmental performance of the MGT-dish with a Dish-Stirling system. From an economical point of view the MGT-dish outperforms the dish-Stirling with LCoEs as low as 15.3€cts/kWhel compared to 22.4€cts/kWhel.
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| 8. |
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| 9. |
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| 10. |
- Strand, Torsten, et al.
(författare)
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An Innovative Hybrid Solar Gas-Turbine Power Plant based on the TopCycle Concept
- 2012
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Ingår i: Proceedings of the International SolarPACES Conference 2012, Marrakesh.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The TopCycle is an innovative gas-turbine power plant, in which a supercharger unit is added to a conventional industrial gas-turbine to boost the pressure ratio, and large amounts of steam are injected into the combustion chamber in order to achieve near- stoichiometric combustion. A thermoeconomic simulation model of a hybrid solar version of such a power plant has been developed, allowing determination of its thermodynamic and economic performance, and the results are compared with a more conventional hybrid solar combined cycle power plant. The analysis has shown that a hybrid solar TopCycle power plant can produce electricity with CO2 emissions below 300 kgCO2/MWhe at levelized costs around 60 – 80 €/MWhe, lower than the competing hybrid combined cycle units, and directly competitive with wind power.
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| 11. |
- Wang, Wujun, 1984-, et al.
(författare)
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An inverse design method for a cavity receiver used in solar dish Brayton system
- 2014
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Ingår i: Solar Energy. - : Elsevier. - 0038-092X .- 1471-1257. ; 110, s. 745-755
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Tidskriftsartikel (refereegranskat)abstract
- An inverse design method is developed in order to quickly find possible cavity receiver designs with relative uniform cavity wall surface temperature for a solar dish cavity receiver. In this design method, a heat transfer model of the absorber wall is used for analyzing the main heat transfer process between the cavity wall outer surface, the inner surface and the working fluid. Furthermore, a ray-tracing model based on the parameters of a real dish is utilized for obtaining the solar radiative boundary conditions for the heat transfer model. Impinging jet cooling technology is introduced due to its high heat transfer coefficient in the stagnation area, which can be used for cooling the peak flux on the cavity wall. After applying a well-designed impinging system, the temperature peak on the peak flux region in traditional receiver designs can be mitigated without introducing any over pressure drop problem.
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| 12. |
- Wang, Wujun, et al.
(författare)
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Conjugate heat transfer analysis of an impinging receiver design for a dish-Brayton system
- 2015
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Ingår i: Solar Energy. - : Elsevier. - 0038-092X .- 1471-1257. ; 119, s. 298-309
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Tidskriftsartikel (refereegranskat)abstract
- An impinging receiver design has been developed for a small scale solar dish-Brayton system. A numerical conjugate heat transfer model combined with a ray-tracing model, based on the boundary conditions of the micro gas turbine and the EuroDish system, has been used for studying the thermal performance of an impinging receiver. According to the results of the preliminary estimation by an inverse design method, four possible impinging nozzle arrangements have been studied by the numerical model based on a 240 mm diameter and 3 mm wall thickness cavity. The inverse design method has been verified to be an efficient way in reducing the calculation costs during the design procedure. Furthermore, the impacts of the cavity diameter and the wall thickness have also been studied.
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| 13. |
- Wang, Wujun, 1984-, et al.
(författare)
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Experimental demonstration of a load flexible combustor for hybrid solar Brayton applications
- 2023
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Ingår i: Energy Conversion and Management. - : Elsevier BV. - 0196-8904 .- 1879-2227. ; 283, s. 116904-
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Tidskriftsartikel (refereegranskat)abstract
- A novel load flexible combustor has been developed for hybrid solar Brayton applications with any solar share. In this combustor design, the fuel is split into a pilot and a main fuel. The pilot flame is designed for re-igniting the main fuel at any workload in the range of 0-100%. Bypass cooling airflows are innovatively introduced for protecting the fuel flows from unpredictable auto-ignition and undesirable flashback. To evaluate the performances, the combustor has been experimentally demonstrated at its 30% workload with the help of the KTH high flux solar simulator, the KTH dual-flow choked nozzle based gas turbine simulator and an impinging solar receiver. By suddenly turning off the solar simulator and increasing the fuel injection, its performances under hybrid operation have been studied in detail. The results show that the combustor outlet air temperature can be successfully maintained in the range of 914.5 +/- 10 degrees C through the whole hybrid operation test without flashback by adjusting the main fuel injection manually after turning off the solar simulator. The temperature peak on the combustor liner of this test appears at the thermocouple TC3 with a value of 958.1 degrees C, which is significantly lower than the allowable working temperature of the material. The pressure drop across the combustor is within the range of 17.4 +/- 2.5 mbar, which is equivalent to approximately 0.58% of its working pressure.
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| 14. |
- Wang, Wujun, 1984-, et al.
(författare)
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Integrated Design of a Hybrid Gas Turbine-Receiver Unit for a Solar Dish System
- 2014
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Ingår i: Proceedings of the International SolarPACES Conference 2014. Beijing, China. September 16-19, 2014. - : Elsevier BV.
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Konferensbidrag (refereegranskat)abstract
- An integrated design concept of a 25 KWel hybrid gas turbine-receiver unit is introduced in this paper. In this design, hot section; receiver, combustor and turbine, is integrated and located in the center of the unit in order to achieve a compact structure with low heat loss and cooling requirement. A ray tracing model is developed for analyzing the focal plane of the potential parabolic dish design and predicting the radiative flux boundary conditions of the receiver. An impinging cavity receiver, with a cylindrical absorber wall and a semi-spherical bottom, is chosen as the receiver for this hybrid unit. The cooling capacities of different impinging arrangements are calculated to determine the thermal boundary conditions on the cooling side. Finally, the optimal dimensions of the receiver are chosen as well as the impingement cooling design. A ‘single ring’ impinging array was found to be optimal for cooling down the wall temperature of the peak flux region to 1200 °C and provide a receiver exit temperature of 840 °C.
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| 15. |
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| 16. |
- Wang, Wujun, 1984-, et al.
(författare)
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The effect of the cooling nozzle arrangement to the thermal performance of a solar impinging receiver
- 2016
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Ingår i: Solar Energy. - : Elsevier. - 0038-092X .- 1471-1257. ; 131, s. 222-234
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Tidskriftsartikel (refereegranskat)abstract
- The effect of the multi-row nozzle arrangement to the thermal performance of an impinging solar receiver is studied, and new governingequations are introduced for modifying the earlier introduced inverse design method. With the help of the modified inverse designmethod and a numerical conjugate heat transfer model, an impinging receiver based on stainless steel 253 MA material has been designedfor the combination of a micro gas turbine and the EuroDish collector system. At a DNI level of 800 W/m2, the average air temperatureat the outlet and the thermal efficiency can reach 1071.5 K and 82.7%. Furthermore, the temperature differences on the absorber can bereduced to 130 K and 149 K for two different DNI levels respectively. This represents a greatly improvement compared with other publishedcavity receiver designs.
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