In concentrating solar power, high-temperature solar receivers can provide heat to highly efficient cycles for electricity or chemical production. Excessive heating of the fused-silica window and the resulting recrystallization are major problems of high-temperature receivers using windows. Excessive window temperatures can be avoided by applying an infrared-reflective solar-transparent coating on the fused-silica window inside. Both glass temperatures and receiver losses can be reduced. An ideal coating reflects part of the thermal spectrum (λ>2.5μm) of the hot absorber (1100°C) back onto it without reducing solar transmittance. Extensive radiation simulations were done to screen different filter types. The examined transparent conductive oxides involve a high solar absorptance, inhibiting their use in high-concentration solar systems. Although conventional dielectric interference filters have a low solar absorption, the reflection of solar radiation, which comes from various directions, is too high. It was found that only rugate filters fulfill the requirements for operation under high-flux solar radiation with different incident angles. A thermodynamic qualification simulation of the rugate coating on a window of a flat-plate receiver showed a reduction of almost 175 K in mean window temperature and 11% in receiver losses compared with an uncoated window. For the configuration of a pressurized receiver (REFOS type), the temperature could be reduced by 65 K with slightly reduced receiver losses. Finally, a 25μm thick rugate filter was manufactured and optically characterized. The measured spectra fitted approximately the design spectra, except for two absorption peaks, which can be avoided in future depositions by changing the deposition geometry and by using in situ monitoring. The issue of this paper is to share the work done on the choice of filter type, filter design, thermodynamic evaluation, and deposition experiments.

1.
Buck
,
R.
,
Bräuning
,
T.
,
Denk
,
T.
,
Pfänder
,
M.
,
Schwarzbözl
,
P.
, and
Téllez
,
F.
, 2002, “
Solar-Hybrid Gas Turbine-Based Power Tower Systems (REFOS)
,”
ASME J. Sol. Energy Eng.
0199-6231,
124
(
1
), pp.
2
9
.
2.
Heller
,
P.
,
Pfänder
,
M.
,
Denk
,
T.
,
Téllez
,
F.
,
Valverde
,
A.
,
Fernandez
,
J.
, and
Ring
,
A.
, 2006, “
Test and Evaluation of a Solar Powered Gas Turbine System
,”
Sol. Energy
0038-092X,
80
(
10
), pp.
1225
1230
.
3.
Karni
,
J.
,
Kribus
,
A.
,
Doron
,
P.
,
Rubin
,
R.
,
Fiterman
,
A.
, and
Sagie
,
D.
, 1997, “
The DIAPR: A High-Pressure, High-Temperature Solar Receiver
,”
ASME J. Sol. Energy Eng.
0199-6231,
119
, pp.
74
78
.
4.
Kribus
,
A.
,
Doron
,
P.
,
Rubin
,
R.
,
Reuven
,
R.
,
Taragan
,
E.
,
Duchan
,
S.
, and
Karni
,
J.
, 2001, “
Performance of the Directly-Irradiated Annular Pressurized Receiver (DIAPR) Operating at 20 Bar and 1200°C
,”
ASME J. Sol. Energy Eng.
0199-6231,
123
, pp.
10
17
.
5.
Röger
,
M.
,
Buck
,
R.
, and
Müller-Steinhagen
,
H.
, 2005, “
Numerical and Experimental Investigation of a Multiple Air Jet Cooling System for Application in a Solar Thermal Receiver
,”
ASME J. Heat Transfer
0022-1481,
127
(
8
), pp.
863
876
.
6.
Röger
,
M.
,
Pfänder
,
M.
, and
Buck
,
R.
, 2006, “
Multiple Air-Jet Window Cooling for High-Temperature Pressurized Volumetric Receivers: Testing, Evaluation, and Modeling
,”
ASME J. Sol. Energy Eng.
0199-6231,
128
(
3
), pp.
265
274
.
7.
Uhlig
,
R.
, and
Röger
,
M.
, 2004, “
Development of a Window Cooling for High Temperature Solar Receivers
,”
22nd CAD-FEM Users’ Meeting 2004, International Congress on FEM Technology With ANSYS CFX & ICEM CFD Conference
, Dresden, Germany, Nov. 10–12.
8.
Imenes
,
A. G.
,
Buie
,
D.
,
Mills
,
D. R.
,
Schramek
,
P.
, and
Bosi
,
S. G.
, 2006, “
A New Strategy for Improved Spectral Performance in Solar Power Plants
,”
Sol. Energy
,
80
, pp.
1263
1269
. 0038-092X
9.
Furman
S. H.
, and
Tikhonravov
,
A. V.
, 1992,
Basics of Optics of Multilayer Systems
,
Editions Frontiers
,
Gif-sur-Yvette, France
.
10.
Lange
,
S.
,
Bartzsch
,
H.
,
Frach
,
P.
, and
Goedicke
,
K.
, 2006, “
Pulse Magnetron Sputtering in a Reactive Gas Mixture of Variable Composition to Manufacture Multilayer and Gradient Optical Coatings
,”
Thin Solid Films
0040-6090,
502
, pp.
29
33
.
11.
Janicki
,
V.
,
Gäbler
,
D.
,
Wilbrandt
,
S.
,
Leitel
,
R.
,
Stenzel
,
O.
,
Kaiser
,
N.
,
Lappschies
,
M.
,
Görtz
,
B.
,
Ristau
,
D.
,
Rickers
,
C.
, and
Vergöhl
,
M.
, 2006, “
Deposition and Spectral Performance of an Inhomogeneous Broadband Wide-Angular Antireflective Coating
,”
Appl. Opt.
0003-6935,
45
, pp.
7851
7857
.
12.
Hottel
,
H. C.
, 1954, “
Radiant-Heat Transmission
,”
Heat Transmission
,
3rd ed.
,
W. H.
McAdams
, ed.,
McGraw-Hill
,
New York
, pp.
55
125
.
13.
Hottel
,
H. C.
, and
Sarofim
,
A. F.
, 1967,
Radiative Transfer
,
McGraw-Hill
,
New York
.
14.
Manara
,
J.
,
Arduini-Schuster
,
M.
, and
Amthor
,
S.
, 2006, “
Determination of the Complex Refractive Index of Glass
,” Report No. ZAE 2-1004-05.
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