Post on 19-Feb-2022
High-Temperature Coating for Solar-Thermal Energy Conversion
Renkun Chen
Associate Professor Department of Mechanical and Aerospace Engineering
Materials Science & Engineering Program University of California, San Diego
Collaborators: Prof. Zhaowei Liu (ECE, UCSD), Prof. Sungho Jin (MatSci, UCSD) Students: Sunmi Shin, Lizzie Caldwell, Conor Riley, Jaeyun Moon (UNLV),
Taekyoung Kim (A123), Bryan vanSaders (Michigan)
Sponsors:
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Concentra)ng Solar Power (CSP)
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3 DOE Report: “2014: The year of CSP”
Concentra)ng Solar Power (CSP)
4 Source: “Technology Roadmap: Solar Thermal Electricity”, IEA
CSP: Cumula)ve Installed Capacity
5 Source: “Technology Roadmap: Solar Thermal Electricity”, IEA
CSP: Thermal Energy Storage
6 DOE Sunshot IniIaIves
Target LCOE in Y2020: 6¢/kWh (cf. 21¢/kWh in Y2010, 13¢/kWh in Y2013)
DOE Sunshot Ini)a)ves on CSP
7 There is an op)mal working temperature for any given concentra)on ra)o
The Quest for High Temperature
Source: “Technology Roadmap: Solar Thermal Electricity”, IEA
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Solar receiver requirements to achieve the target LCOE: -‐-‐ HTF exit temperature ~720oC, Thermal eff. ≥ 90%, Life)me ≥ 10k cycles
DOE Sunshot FOA “APOLLO”
Next-‐Genera)on CSP Systems
Ideal solar selec)ve coa)ng (SSC)
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Figure of Merit (FOM) is determined by absorptance in the solar spectrum and IR emiSance
• FOM depends on solar concentraIon raIo C and absorber surface temperature T • Assuming C=1000 and T=750oC for Solar Towers • For high C (>1000), the infrared emission loss is relaIvely less important.
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R-‐ Calculated reflectance spectrum I-‐ Total solar irradiance, as reported in ASTM G173 C-‐ ConcentraIon factor (raIo of absorber area to mirror collecIon area) B-‐ Planckian black body emission
J. Moon, D. Lu, B. VanSaders, T.K. Kim, S.D. Kong, S. Jin, R. Chen, Z. Liu, Nano Energy 8 (2014) 238-‐246.
Solar Selec)ve Coa)ng
1. High Figure of Merit (Thermal Efficiency): >= 0.90 (90% efficiency) 2. High Temperature Stability and Reliability: at 750 oC under air environment -‐ Oxida)on resistance -‐ Crystal structure stability without decomposi)on -‐ No delamina)on of SSC layer from metal tube substrate 3. Low-‐cost Fabrica)on
-‐ DOE SunShot Project’s Milestone (Y2012-‐2015)
Requirements for Next-‐Gen Solar Receivers
[1] J. Sol-Gel Sci. Tech. 20, 61–83, 2001, [2] LBNL CoolColors Lab.
Cu1.285Fe0.43Mn1.285O4 Film on Al Substrate[1] Copper Chromite [2]
a: without SiO2 binder; b, c: with SiO2 binder
Why spinel oxides? • Suitable op)cal proper)es (also adjustable
with atomic composiIon) • Cheap, abundant • Already oxidized (more stable at high T) • Scalable synthesis (e.g. hydrothermal and sol-‐
gel synthesis)
Spinel Oxides as SSC Materials
Hydrothermal Synthesis: Cu-‐Contained Spinel NanoPar)cles
CuCl2 2H2O 1M Solution(aq) CrCl3 6H2O 1M Soution(aq)
Mixing for 5h at RT
Cu-Cr Hydroxide
Co-Precipitation with 10M NaOH Solution(aq)
Mixing for 2h at RT
Hydrothermal Synthesis at 200oC / 20h
CuCl2 2H2O 1M Solution(aq) FeCl3 6H2O 1M Solution(aq) MnCl2 4H2O 1M Solution(aq)
Mixing for 5h at RT
Cu-Fe-Mn Hydroxide
Co-Precipitation with 10M NaOH Solution(aq)
Mixing for 2h at RT
Hydrothermal Synthesis at 200oC / 20h
Copper Chromites Cu-Fe-Mn Oxides
Centrifuging & Washing
Spinel Metal Oxide NPs
Freeze-Drying
Post-Treatment
Crystallization at 550oC/5h/Air
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Scalable Coa)ng Process
Cu/Cr=1/2
Cu/Cr=1/1
Crystalliza)on: 550oC/5h/Air
Copper Chromites NPs Synthesized with Different Condi)ons
APS< 50 nm
APS< 50 nm 0.3-‐1µm
200-‐600 nm
Crystalliza)on: 750oC/2h/Air
-‐-‐ Copper chromites synthesized with 2 different atomic composiIons. -‐-‐ CrystallizaIon condiIon as a final step of synthesis to be opImized.
Atomic Comp.
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XRD and Thermal Stability of CuCr2O4 NPs
* O. CroSaz, F. Kubel, H. Schmid, J. Mater. Chem. 7 (1997) 143-‐146. (PDF 01-‐079-‐5380)
-‐ Crystal informaIon: Tetragonal System Lajce: Body-‐centered Cell Parameters: a 6.030, c 7.782 Main plane: (211) at 2θ=35.19 o
-‐ CuCr2O4 can be confirmed. -‐ Thermally stable at 750oC: a. Aler thermal test, new phase was not seen. b. ParIcle size grown by sintering effect at high temperature.
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Crystalliza)on Condi)on Op)miza)on for CuFeMnO4 NPs
(a) Crystallized at 550oC/5h/air
APS 100-‐200 nm APS 100-‐400 nm
(b) Crystallized at 750oC/2h/air
-‐-‐ Cu-‐Fe-‐Mn Oxide NPs synthesized with Cu/Fe/Mn=1/1/1 (a/a). -‐-‐ OpImized crystallizaIon condiIon: 550 oC / 5h /air, to obtain smaller NPs.
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XRD and Thermal Stability of CuFeMnO4 NPs
* PDF 00-‐020-‐0358.
-‐ CuFeMnO4 can be confirmed. -‐ Thermally stable at 750oC: a. Aler thermal test, new phase was not seen. b. ParIcle size grown by sintering effect at high temperature.
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First we tried mixing both compounds….
…. then we layered both compounds.
Max FOM= 0.894
Max FOM= 0.902
SSC Layers with Mixtures of CuCr2O4 and CuFeMnO4
UCSD’s Black Oxide Coa)ng -- Typical absorptivity of 97 – 98% in the visible to NIR regime. [For power tower type applications with concentration factor of ~1,000, the absorptivity dominates the solar to heat Figure-of-Merit (FOM), with the blackbody emissivity effect being negligible.]
-- CFM/CuCr: highest FOM (0.902) -- Pyromark 2500 : FOM of 0.889
250 500 750 1000 1250 1500 1750 2000
0.03
0.06
0.09
0.12
0.15
Reflectan
ce
Waveleng th (nm)
C F M dens e la yer (C F M-‐H 1) : F 0 .8911 C u2C r2O 5 layer (C C 1) : F 0 .883 C F M(porous top)/C u2C r2O 5 (C F MH1-‐C u1) : F 0 .903 C F M(porous top)/C o3O 4 (C F MH1-‐C o1) : F 0 .8904 C F M(porous top)/C F M (C F MH1-‐C F MH1) : F 0 .8931 P yro la yer (P 1) : F 0 .8896
Pyromark
UCSD Black Oxide Porous CuFeMnO4 top layer& dense CuCr2O4 borom layer; FOM: 0.902
Reflectance vs wavelength for various SSC layer materials
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DOE Report: “2014: The year of CSP”
Solar-‐Thermoelectrics Trough Collectors
G. Chen et al., Nature Mater. (2011)
For low C (e.g., ~100 for troughs), the infrared emission loss is important è Need to improve the selecIvity
High-‐Temperature Spectrally Selec)ve Coa)ng
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Black Oxide
Transparent Conduc)ve Oxide (TCO)
Vis/NIR (< 1-‐2 um)
Tran
smiran
ce
Wavelength
IR (> 1-‐2 um)
• We use Al-‐doped ZnO (AZO) as the TCO • Low cost (compared to ITO) • Adjustable cutoff wavelength • Scalable synthesis
Black Oxide + TCO for High Selec)vity
[1]Kim, J.; Naik, G. V.; Emani, N. K.; Guler, U.; Boltasseva, A. IEEE J. Sel. Topics Quantum Electron. 2013, 19. [2]Jia et.al Thin Solid Films 559 (2014) 69–77 [3]Riley et. al. Small, accepted
Deposi)on Method
µ (cm2/Vs) (at n=~1x1021cm-‐3)
ε''
Scalability
Conformality
Pulsed Laser DeposiIon[1] 47 0.5 Poor Fair SpuSer[2] 8 -‐ Good Good
Atomic Layer DeposiIon[3] 9.8 0.47 Good Excellent
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• Self-‐limiIng surface reacIons • “Monolayers” are deposited by diethly zinc,
water and trimethylaluminum pulses • Chemical composiIon controlled by the raIo of
chemical pulses • Thickness controlled on the angstrom scale • Extremely high conformality
Atomic Layer Deposi)on (ALD) of AZO
AZO (1um) Axer Annealing AZO (1um) Glass
Selec)ve Transmission of AZO
• We have developed solar absorbing coaIng based on nanostructured black oxides – Thermal efficiency (FOM) > 90% – Stable at high temperature – Scalable synthesis and coaIng process – Suitable for next-‐generaIon solar towers.
• On-‐field evaluaIon of the black oxide coaIng • Black oxide + TCO for high-‐temperature selecIve coaIng • IntegraIon into high-‐temperature solar-‐thermal systems
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Summary and Future Direc)ons