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- Martinez-Manuel, Leopoldo, et al.
(författare)
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A comprehensive analysis of the optical and thermal performance of solar absorber coatings under concentrated flux conditions
- 2022
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Ingår i: Solar Energy. - : Elsevier BV. - 0038-092X .- 1471-1257. ; 239, s. 319-336
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Tidskriftsartikel (refereegranskat)abstract
- Solar Absorber Coatings (SACs) are widely used materials for improving thermal efficiencies of solar receivers. Traditionally, these SACs are investigated using heat treatments to test their optical-thermal properties; however, tests under concentrated flux conditions are still required. In this work, the thermal efficiency of different SACs is experimentally evaluated and compared. The analyzed SACs are: (1) Pyromark®2500, (2) Solkote®, (3) Thurmalox®250, (4) Comex® and (5) a new Soot from Forest Biomass (SFB) based coating. To assess the SACs performance, a High Flux Solar Simulator along with a calorimetric test bench are implemented under a well-controlled indoor environment applying two levels of concentrated irradiance of 100 ± 3 kW/m2 and 415 ± 12 kW/m2 named low and high flux level, respectively. Results show that, for a low flux level, the analyzed coatings present thermal efficiencies in a range from 91.74% to 83.24%, exhibiting a slightly close performance in most of the cases. Correspondingly, for a high flux level, the efficiencies range from 88.69% to 72.69%, with Pyromark®2500 being the most efficient in both cases. In addition, variations in the optical properties are reported for the experimental campaign with the high flux level, observing slight changes in the spectral absorptance and emittance. From these results, Pyromark presents the highest drop in solar absorptance of 1.22%, which is attributed to microcracks observed through the Scanning Electron Microscope (SEM). Thus, the presented approach can provide valuable information about the effects that concentrated flux levels can have in the optical-thermal performance of the analyzed samples.
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| 2. |
- Martinez-Manuel, Leopoldo, et al.
(författare)
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Numerical analysis on the optical geometrical optimization for an axial type impinging solar receiver
- 2021
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Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 216
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Tidskriftsartikel (refereegranskat)abstract
- Solar cavity receivers are key components in point-focus concentrating solar power technologies due to their benefits of high efficiency and operating temperature. Accordingly, the enhancement of the optical performance can yield to significant improvements in the whole thermal power system. In this study, a geometrical optimization of an axial type impinging receiver for a solar dish Brayton system was analytically accomplished through Monte Carlo ray tracing method. By modeling a reference cylindrical cavity, optical surface properties and geometrical parameters were analyzed by dividing the cavity into three zones: front wall, middle wall and back wall. Simulation results show that the light flux peaking on the cylindrical wall can be significantly reduced when the cavity front wall is modified by changing the inclination angle; the light flux distribution over the absorber surface can be flattened by increasing the cavity radius; the irradiance distribution over the absorber can be efficiently adjusted by modifying the cavity back wall. After the cavity geometry optimization, the optical efficiency of the receiver can be enhanced by 3.34%, the material volume can be reduced by 20.1% and the peak flux on the cavity wall can be reduced by 38.6%, from 30 to 18.4 kW/m(2).
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