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  • 1.
    Aichmayer, Lukas
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Garrido, Jorge
    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.
    Performance Improvements of the KTH High-Flux Solar Simulator2017In: AIP Conference Proceedings 1850, American Institute of Physics (AIP), 2017, Vol. 1850, article id 150001Conference paper (Refereed)
    Abstract [en]

    This paper presents the performance improvements implemented in the KTH high-flux solar simulator to deliver a total power on target closer to the working conditions of real CSP systems. Therefore, additional rectifiers were installed in the power conversion unit of the high-power lamps as well as the back reflector was coated providing more favorable spectral reflectance properties. The results of a single lamp/lens-combination show that the power on target in an aperture of 280mm in diameter was increased from 831W to 1446W while the peak flux was increased from 675kW/m² to 905kW/m².

  • 2.
    Aichmayer, Lukas
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Garrido, Jorge
    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.
    Scaling effects of a novel solar receiver for a micro gas-turbine based solar dish system2018In: International Journal of Solar Energy, ISSN 0142-5919, E-ISSN 1477-2752, Vol. 162, p. 248-264Article in journal (Refereed)
    Abstract [en]

    Laboratory-scale component testing in dedicated high-flux solar simulators is a crucial step in the developmentand scale-up of concentrating solar power plants. Due to different radiative boundary conditions available inhigh-flux solar simulators and full-scale power plants the temperature and stress profiles inside the investigatedreceivers differ between these two testing platforms. The main objective of this work is to present a systematicscaling methodology for solar receivers to guarantee that experiments performed in the controlled environmentof high-flux solar simulators yield representative results when compared to full-scale tests. In this work theeffects of scaling a solar air receiver from the integration into the OMSoP full-scale micro gas-turbine based solardish system to the KTH high-flux solar simulator are investigated. Therefore, Monte Carlo ray-tracing routines ofthe solar dish concentrator and the solar simulator are developed and validated against experimental characterizationresults. The thermo-mechanical analysis of the solar receiver is based around a coupled CFD/FEManalysislinked with stochastic heat source calculations in combination with ray-tracing routines. A geneticmulti-objective optimization is performed to identify suitable receiver configurations for testing in the solarsimulator which yield representative results compared to full-scale tests. The scaling quality is evaluated using aset of performance and scaling indicators. Based on the results a suitable receiver configuration is selected forfurther investigation and experimental evaluation in the KTH high-flux solar simulator.

  • 3.
    Aichmayer, Lukas
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Wang, Wujun
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Garrido, Jorge
    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.
    Experimental evaluation of a novel solar receiver for a micro gas-turbine based solar dish system in the KTH high-flux solar simulator2018In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 159, p. 184-195Article in journal (Refereed)
    Abstract [en]

    This work presents the experimental evaluation of a novel pressurized high-temperature solar air receiver for the integration into a micro gas-turbine solar dish system reaching an air outlet temperature of 800°C. The experiments are conducted in the controlled environment of the KTH high-flux solar simulator with well-defined radiative boundary conditions. Special focus is placed on providing detailed information to enable the validation of numerical models. The solar receiver performance is evaluated for a range of operating points and monitored using multiple point measurements. The porous absorber front surface temperature is measured continuously as it is one of the most critical components for the receiver performance and model validation. Additionally, pyrometer line measurements of the absorber and glass window are taken for each operating point. The experiments highlight the feasibility of volumetric solar receivers for micro gas-turbine based solar dish systems and no major hurdles were found. A receiver efficiency of 84.8% was reached for an air outlet temperature of 749°C. When using a lower mass flow, an air outlet temperature of 800°C is achieved with a receiver efficiency of 69.3%. At the same time, all material temperatures remain below permissible limits and no deterioration of the porous absorber is found.

  • 4.
    Aichmayer, Lukas
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Wang, Wujun
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Garrido, Jorge
    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.
    Experimental Flux Measurement of a High-Flux Solar Simulator using a Lambertian Target and a Thermopile Flux Sensor2016In: AIP Conference Proceedings 1734, American Institute of Physics (AIP), 2016, Vol. 1734, article id 130001Conference paper (Refereed)
    Abstract [en]

    A measurement system for the experimental determination of the flux distribution at the focal plane of the KTH high-flux solar simulator was designed and implemented. It is based on a water-cooled Lambertian target and a thermopile flux sensor placed close to the focal point of the solar simulator. Correction factors to account for systematic effects were determined and an uncertainty analysis was performed. The measurement system was successfully used to evaluate the flux distribution of a single lamp/lens-arrangement with a peak flux of 675kW/m².

  • 5.
    Garrido Galvez, Jorge
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Wang, Wujun
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Nilsson, Martin
    Cleanergy Company.
    Laumert, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    A Detailed Radiation Heat Transfer Study of a Dish-Stirling Receiver: the Impact of Cavity Wall Radiation Properties and Cavity Shapes2015In: SOLARPACES 2015: INTERNATIONAL CONFERENCE ON CONCENTRATING SOLAR POWER AND CHEMICAL ENERGY SYSTEMS / [ed] Rajpaul, V; Richter, C, American Institute of Physics (AIP), 2015Conference paper (Refereed)
    Abstract [en]

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

  • 6.
    Garrido, Jorge
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Abou-Taouk, A.
    Laumert, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Characterization of a Stirling cavity receiver performance in the KTH high-flux solar simulator and comparison with real Dish-Stirling data2018In: AIP Conference Proceedings, American Institute of Physics Inc. , 2018Conference paper (Refereed)
    Abstract [en]

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

  • 7.
    Garrido, Jorge
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Aichmayer, Lukas
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Abou-Taouk, Abdallah
    Cleanergy, Regnbagsgatan 6, S-41755 Gothenburg, Sweden..
    Laumert, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Experimental and numerical performance analyses of a Dish-Stirling cavity receiver: Geometry and operating temperature studies2018In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 170, p. 913-923Article in journal (Refereed)
    Abstract [en]

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

  • 8.
    Garrido, Jorge
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Aichmayer, Lukas
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Abou-Taouk, Abdallah
    Azelio, Regnbagsgatan 6, S-41755 Gothenburg, Sweden..
    Laumert, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Experimental and numerical performance analyses of Dish-Stirling cavity receivers: Radiative property study and design2019In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 169, p. 478-488Article in journal (Refereed)
    Abstract [en]

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

  • 9.
    Garrido, Jorge
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Aichmayer, Lukas
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Wang, Wujun
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Laumert, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Characterization of the KTH high-flux solar simulator combining three measurement methods2017In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 141, p. 2091-2099Article in journal (Refereed)
    Abstract [en]

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

  • 10.
    Garrido, Jorge
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Sjöqvist, R.
    Laumert, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Mechanical coupling behavior of a dish-Stirling receiver: Influence on the absorber tube stresses2019In: AIP Conference Proceedings, American Institute of Physics (AIP), 2019, Vol. 2126, article id 050003Conference paper (Refereed)
    Abstract [en]

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

  • 11.
    Wang, Wujun
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Aichmayer, Lukas
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Garrido, Jorge
    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.
    Development of a Fresnel lens based high-flux solar simulator2017In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 144, p. 436-444Article in journal (Refereed)
    Abstract [en]

    In this paper, a Fresnel lens based high flux solar simulator (HFSS) is developed for concentrating solar power research and high temperature material testing. In this design, each commercially available 7 kW(e) xenon-arc lamp is coupled with a silicone-on-glass Fresnel lenses as the optical concentrator, and 12 lamp-lens units are distributed in a circular array. In total, the power of the solar simulator can reach 84 kWe. A ray tracing model has been developed based on the real arc-emitter shape and the Fresnel lens optics for predicting the optical performance of the HFSS design. The testing result shows that the ray tracing model can predict the flux distribution on the focal plane accurately but a bit conservative in the center region. The flux distribution on the focal plane appears axisymmetric with a peak flux of 7.22 MW/m(2), and 19.7 kW of radiative power in total is delivered on a 280 mm diameter target. (C) 2017 Elsevier Ltd. All rights reserved.

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