Dr. Julius E. Yellowhair Profile

Dr. Julius E. Yellowhair

Principal Optical Engineer

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Author

Publications (13)

SPIE Press Book | 12 August 2020

Field Guide to Solar Optics

Julius Yellowhair

KEYWORDS: Solar energy, Sun, Mirrors, Receivers, Solar radiation, Reflectivity, Geometrical optics, Solar concentrators, Glasses, Atmospheric optics

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Proceedings Article | 2 November 2016 Presentation

Metamaterial-based high efficiency absorbers for high temperature solar applications (Conference Presentation)

Julius Yellowhair, Hoyeong Kwon, Andrea Alù, Robert Jarecki, Subhash Shinde

Proceedings Volume 9937, 99370B (2016) https://doi.org/10.1117/12.2249813

KEYWORDS: Solar energy, Receivers, Absorption, Thermal efficiency, Thermography, Optical properties, Tungsten, Solar thermal energy, Visible radiation, Infrared radiation

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Operation of concentrated solar power receivers at higher temperatures (<700°C) would enable supercritical carbon dioxide (sCO2) power cycles for improved power cycle efficiencies (<50%) and cost-effective solar thermal power. Unfortunately, radiative losses at higher temperatures in conventional receivers can negatively impact the system efficiency gains. One approach to improve receiver thermal efficiency is to utilize selective coatings that enhance absorption across the visible solar spectrum while minimizing emission in the infrared to reduce radiative losses. Existing coatings, however, tend to degrade rapidly at elevated temperatures. In this paper, we report on the initial designs, fabrication, and characterization of spectrally selective metamaterial-based absorbers for high-temperature, high-thermal flux environments important for solarized sCO2 power cycles. Metamaterials are structured media whose optical properties are determined by sub-wavelength structural features instead of bulk material properties, providing unique solutions by decoupling the optical absorption spectrum from thermal stability requirements. The key enabling innovative concept proposed is the use of structured surfaces with spectral responses that can be tailored to optimize the absorption and retention of solar energy for a given temperature range. In this initial study we use Tungsten for its stability in expected harsh environments, compatibility with microfabrication techniques, and required optical performance. Our goal is to tailor the optical properties for high (near unity) absorptivity across the majority of the solar spectrum and over a broad range of incidence angles, and at the same time achieve negligible absorptivity in the near infrared to optimize the energy absorbed and retained. To this goal, we apply the recently developed concept of plasmonic Brewster angle to suitably designed nanostructured Tungsten surfaces. We predict that this will improve the receiver thermal efficiencies by at least 10% over current solar receivers.

Proceedings Article | 5 September 2015 Paper

Testing and optical modeling of novel concentrating solar receiver geometries to increase light trapping and effective solar absorptance

Julius Yellowhair, Clifford Ho, Jesus Ortega, Joshua Christian, Charles Andraka

Proceedings Volume 9559, 95590A (2015) https://doi.org/10.1117/12.2186647

KEYWORDS: Receivers, Solar energy, Solar radiation models, Attenuators, Coating, Photography, Additive manufacturing, Infrared cameras, Prototyping, Thermal efficiency

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Proceedings Article | 5 September 2015 Presentation + Paper

Coupled optical-thermal-fluid and structural analyses of novel light-trapping tubular panels for concentrating solar power receivers

Jesus Ortega, Joshua Christian, Julius Yellowhair, Clifford Ho

Proceedings Volume 9559, 955909 (2015) https://doi.org/10.1117/12.2188235

KEYWORDS: Receivers, Thermal efficiency, Coating, Structural analysis, Solar thermal energy, Thermal modeling, Ray tracing, Holmium, Computational fluid dynamics, Thermography

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Proceedings Article | 7 October 2014 Paper

Reduction of radiative heat losses for solar thermal receivers

Clifford Ho, Joshua Christian, Jesus Ortega, Julius Yellowhair, Matthew Mosquera, Charles Andraka

Proceedings Volume 9175, 917506 (2014) https://doi.org/10.1117/12.2063152

KEYWORDS: Receivers, Solar radiation models, Thermal efficiency, Solar thermal energy, Stars, Performance modeling, Solar radiation, Solar energy, Thermal modeling, Structural design

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Proceedings Article | 7 October 2014 Paper

Optical and adhesive properties of dust deposits on solar mirrors and their effects on specular reflectivity and electrodynamic cleaning for mitigating energy-yield loss

Malay Mazumder, Julius Yellowhair, Jeremy Stark, Calvin Heiling, John Hudelson, Fang Hao, Hannah Gibson, Mark Horenstein

Proceedings Volume 9175, 91750K (2014) https://doi.org/10.1117/12.2066328

KEYWORDS: Electrodes, Particles, Atmospheric particles, Mirrors, Solar energy, Reflectivity, Specular reflections, Dielectrics, Reflection, Electrodynamics

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Proceedings Article | 16 September 2014 Paper

Solar optical codes evaluation for modeling and analyzing complex solar receiver geometries

Julius Yellowhair, Jesus Ortega, Joshua Christian, Clifford Ho

Proceedings Volume 9191, 91910M (2014) https://doi.org/10.1117/12.2062926

KEYWORDS: Receivers, Systems modeling, Performance modeling, Convolution, Thermography, Thermal modeling, Computational fluid dynamics, Optimization (mathematics), Solar thermal energy, Optical design

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Proceedings Article | 25 July 2008 Paper

Optical surface measurements for very large flat mirrors

J. Burge, P. Su, J. Yellowhair, C. Zhao

Proceedings Volume 7018, 701817 (2008) https://doi.org/10.1117/12.790048

KEYWORDS: Mirrors, Autocollimators, Error analysis, Prisms, Optical testing, Monte Carlo methods, Phase shifting, Monochromatic aberrations, Polarization, Metrology

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SPIE Journal Paper | 1 February 2008

Measurement of optical flatness using electronic levels

Julius Yellowhair, James Burge

OE, Vol. 47, Issue 02, 023604, (February 2008) https://doi.org/10.1117/12.10.1117/1.2831131

KEYWORDS: Mirrors, Monochromatic aberrations, Optical testing, Error analysis, Zernike polynomials, Optical engineering, Surface finishing, Monte Carlo methods, Spherical lenses, Polishing

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Proceedings Article | 14 September 2007 Paper

Fabrication and testing of large flats

Julius Yellowhair, Peng Su, Matt Novak, Jim Burge

Proceedings Volume 6671, 667107 (2007) https://doi.org/10.1117/12.736775

KEYWORDS: Mirrors, Polishing, Surface finishing, Manufacturing, Glasses, Optical fabrication, Fizeau interferometers, Zerodur, Computer simulations, Optics manufacturing

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Proceedings Article | 29 October 2001 Paper

Selective intermixing of InGaAs/GaAs/AlGaAs quantum wells with spin-on-glass/MgF2 grating caps

Yan-Rui Zhao, Julius Yellowhair, Jinhyun Lee, Shuang Zhang, Alex Raub, Ronghua Wang, Petros Varangis, Abdel-Rahman El-Emawy, Mauro Vilela, Marek Osinski

Proceedings Volume 4594, (2001) https://doi.org/10.1117/12.446541

KEYWORDS: Gallium, Quantum wells, Magnesium fluoride, Diffusion, Annealing, Dielectrics, Chemical species, Photonic integrated circuits, Lithium, Gallium arsenide

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Proceedings Article | 8 September 1998 Paper

Ground demonstration of an optical control system for a space-based sparse aperture telescope

David DeYoung, James Dillow, Stephen Corcoran, Edwina Andrews, Julius Yellowhair, Kevin DeVries

Proceedings Volume 3381, (1998) https://doi.org/10.1117/12.323937

KEYWORDS: Space telescopes, Control systems, Telescopes, Mirrors, Image segmentation, Visibility, Modulation transfer functions, Process control, Tolerancing, Actuators

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Proceedings Article | 28 August 1998 Paper

Ground demonstration of an optical control system for a space-based sparse-aperture telescope

David DeYoung, James Dillow, Stephen Corcoran, Edwina Andrews, Julius Yellowhair, Kevin DeVries

Proceedings Volume 3356, (1998) https://doi.org/10.1117/12.324516

KEYWORDS: Control systems, Space telescopes, Telescopes, Mirrors, Image segmentation, Visibility, Modulation transfer functions, Process control, Tolerancing, Actuators

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Showing 5 of 13 publications

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