Embed Size (px)
Citation preview
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:
1
Concentra)ng Solar Power (CSP)
2
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
8
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)
!"# =1− ! ! !(!)!"!
! − 1! 1− !(!) !(!,!)!"!
!
!(!)!"!!
!!!!!!
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.
9
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
12
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.
14
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.
15
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.
16
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.
17
18
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
19
20
!"# =1− ! ! !(!)!"!
! − 1! 1− !(!) !(!,!)!"!
!
!(!)!"!!
!!!!!!
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
21
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
22
• 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
24
Summary and Future Direc)ons
