Solar Selective Absorber Coating Methods Plasma Processes

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1 Solar Selective Absorber Coating Methods Plasma Processes Paul Gantenbein & Elimar Frank SPF - Institut für Solartechnik University of Applied Sciences Rapperswil (HSR)

2 Optical properties of a selective absorber Optical properties of solar selective absorbers a AM1.5 e T C ( / ) Wien s displacement law: AM 1.5 ideal characteristics Temperature T ( C) Wavelength l max (mm) thermal 100 C visible range Wavelenght l (mm) Thermodynamics: 2. Law 2

Combination - Multilayers - Metal-Dielectric - Solar-transmitting /

3 Design types of selective absorber - Intrinsic selective material - Surface texture / geometrical structure - Semiconductor-Metal Combination - Multilayers - Metal-Dielectric - Solar-transmitting / Blackbody-like Nb on Si Structural absorber with transition wavelength l = 1 mm 3

Structural absorber - morphology Thronton-Diagram Ann. Rev. Mater. Sci 1977: 239-260 (Graph: A. -M.

4 Structural absorber - morphology Thronton-Diagram Ann. Rev. Mater. Sci 1977: (Graph: A. -M. Valente-Feliciano) Physical (parameters) processes establishing structural zones film morphology. 4

5 Substrates for combined absorbers 5

6 Substrates for combined absorber tubes 6

7 Substrates for combined absorber tubes 7

Plasma process for absorber preparation RF/MF Power DC Power Target Plasma Substrate Match Box RF Filter Vacuum Chamber to ESCA Machine Deposition Chamber Sample Holder Sample Stack Magnetron Target

8 Plasma process for absorber preparation RF/MF Power DC Power Target Plasma Substrate Match Box RF Filter Vacuum Chamber to ESCA Machine Deposition Chamber Sample Holder Sample Stack Magnetron Target Sample Heating Magnetron: E B Pressure Control Valve Ar CH 4 / O 2 Process Gases N Experimental 2 / O Setup 2 Vacuum Pumps Reactive Magnetron Sputtering Target Materials: Cr, W, Ti, Ag, Au, Nitrides ) Process Gases: noble gases / reactive gases 8

9 Plasma Process Technology Components Magnetron Technology planar / circular Magnetron Technology: D. Depla et al. Plasma Deposition Processes 9

10 Coating Methods - RF excitation system Plasma Ignition Frequency Electrical Parameters Lindas Pranevicius - Coating Technology Handbook 10

11 Coating Methods Ion Energy / Sputter Yield ev to K: 1eV~1.16*e4K Schematic of a cathodic arc deposition system. Emission characteristics of a cathodic arc source. H. Randhawa - Coating Technology Handbook 11

Coating Methods / Plasma potential Electrical Parameters / Ion Energy floating metal surface (sheet) Ion Energy / Sputter Yield ev to K: 1eV~1.16*e4K Electron cross-section in Argon.

12 Coating Methods / Plasma potential Electrical Parameters / Ion Energy floating metal surface (sheet) Ion Energy / Sputter Yield ev to K: 1eV~1.16*e4K Electron cross-section in Argon. Sputter yield Y as a function of the Ar+ ion energy at normal incidence in a magnetron sputtering process. Schematic illustration of the plasma sheaths which form between a plasma apparatus walls for large anode and small anode. Scott G. Walteon and J. E. Greene Plasma Deposition Processes 12

13 CERMET absorber surface Substrate Bias Voltage Surface roughness optical & stability behaviour SEM AFM Dielectric/Cr 120 nm a-c:h/cr CERMET auf on Si REM-Lab Uni BS R a = R a (U B ) U B Structural absorber with transition wavelength l = 1 mm 13

14 Chemical composition of an absorber coating Process Gas Composition / Substrate Temperature rf-power Structural absorber with transition wavelength l = 1 mm 14

15 Multilayer Absorber Reflection R(l) in function of Wavelength l - sandwich layer layer Schichtdicken thickness C1 (n, Chromanteil k) d= d = d1, d1; d2, d2; d3 d3 (nm) [nm] R(l) no SiO 2 R(l) d1 SiO 2 R(l) d2 SiO 2 R(l) d3 SiO 2 R(l) d4 SiO nm (n L ) (n f ) CERMET Cu (n s ) Multi-layer on IR-Reflector 15

16 Scale up of substrate bias - Plasma Potential variation Absorber film properties depending of the plasma potential / Bias Patentschrift: DE B4 16

17 Multilayer solar selective absorber Cermet / SiO AM 1.5 BB 373 K Reflectance R(l) [-] ) 120 nm 0.2 2) ) a-c:h/cr CERMET C E R - M a-c:h E + T - SiO Wavelength [mm] REM-Lab Uni BS R(l) of three multilayer systems on copper metal sheets. a sol = 95.0 % to a sol = 95.2 % ; e th = 3.1 % to e th = 3.7 %. 18

18 Absorber Coating Process Parameter List (incomplete) Geometry: Substrate Surface Orientation to Plasma Source Vacuum Chamber design Vacuum Chamber: Base Pressure / Rest Gases Vacuum Pump Technology Plasma Ignition: Reactant : Substrate: Time: Frequency (DC, MF, RF, HF) Plasma Generator Technology / Plasma Density Coating Material Educt / Target Material / Process Gases Process Pressure / Plasma Density Material (el. behaviour) Roughness Temperature Speed Coating time 19

19 Tube Absorber Coating Machine Harding G. L.; US Patent (1982) 20

Step 2 L L = length of the coating machine 39m L T = length of the tubes 4m D H = Diameter of the tube holder

20 Tube Coating Machine High Temperature Solar Selective Absorber Coatings Tube Holder (n tubes) D H Step 4 Step 3 Von Ardenne GmbH Postanschrift: Plattleite 19/ Dresden Deutschland L T Step 1 Process Flow Direction Step 2 L L = length of the coating machine 39m L T = length of the tubes 4m D H = Diameter of the tube holder 1.8m D T = Diameter of the Absorber tube 70mm Source: Von Ardenne GmbH Plattleite 19/ Dresden Germany 21

21 Selective absorber - literature CERMET CERMET W-Al Mo-Si 2 O 3 N 4 3 A. R. Antonaia Escobar-Galindo et al. et al. 23

22 Thank you for your attention! 24

Plasma Activated EB-PVD of Titanium and its Compounds by Means of Large Area SAD

AIMCAL 2005 Myrtle Beach, SC, USA, October 19th, 2005 Plasma Activated EB-PVD of Titanium and its Compounds by Means of Large Area SAD E. Reinhold, C. Steuer VON ARDENNE Anlagentechnik GmbH, Dresden, Germany