PETAL (Parabolic Energy Transformation and Astrophysics Laboratory) is a large multipurpose dish-shaped concentrator, located at Sede Boqer. Its 2-axis tracking paraboloidal surface, with aperture area in excess of $400m2,$ is constructed from 216 adjustable mirror panels. The very large aperture and high concentration ratio of PETAL render the direct characterization of its optical performance a nontrivial task. We have applied a variety of methods in order to assess PETAL’s optical quality. These include imaging the full moon and Jupiter at night, and analysis of the 3-D caustic image produced by the scattering of focused sunlight off particles in the air. The main results of these studies, together with the preliminary results of measurements on 36 individual panels, are presented here. Among the three measurements that look at objects of the same angular size (i.e. the sun and moon), the average image size (i.e. radius of circle containing 90% of the intensity) is $0.247±0.012m,$ demonstrating a 5% spread about the mean for three different methods. This result is in agreement with 0.22 m for the Jupiter image. Successful application of these methods for characterization of PETAL proves their applicability to more commonly used solar dishes of smaller sizes but with similar or better concentration ratios.

1.
Blackmon
,
J.
,
1985
, “
Development and Performance of a Digital Image Radiometer for Heliostat Evaluation at Solar One
,”
ASME J. Sol. Energy Eng.
,
107
, pp.
315
321
.
2.
Mancini
,
T.
,
1991
, “
Analysis and Design of Two Stretched-Membrane Parabolic Dish Concentrators
,”
ASME J. Sol. Energy Eng.
,
113
, pp.
180
187
.
3.
Johnston
,
G.
,
1995
, “
Flux Mapping the 400m2 “Big Dish” at the Australian National University
,”
ASME J. Sol. Energy Eng.
,
117
, pp.
290
293
.
4.
Ballestrin
,
J.
,
2002
, “
A Non-Water-Cooled Heat Flux Measurement System Under Concentrated Solar Radiation Conditions
,”
Sol. Energy
,
73
(
3
), pp.
159
168
.
5.
Ulmer
,
S.
,
Reinalter
,
W.
,
Heller
,
P.
,
Lupfert
,
E.
, and
Martinez
,
D.
,
2002
, “
Beam Characterization and Improvement with a Flux Mapping System for Dish Concentrators
,”
ASME J. Sol. Energy Eng.
,
124
, pp.
182
188
.
6.
Wendelin, T., Jorgensen, G., and Wood, R., 1991, “SHOT: A Method for Characterizing the Surface Figure and Optical Performance of Point Focus Solar Concentrators,” ASME-JSES-JSME International Solar Energy Conference, Reno, NV, pp. 555–560.
7.
Grossman, J., 1994, “Development of a 2f Optical Performance Measurement System,” Proceedings of the ASME International Solar Engineering Conference, pp. 25–32.
8.
Shortis
,
M.
, and
Johnston
,
G.
,
1996
, “
Photogrammetry: An Available Surface Characterization Tool for Solar Concentrators, Part I: Measurements of Surfaces
,”
ASME J. Sol. Energy Eng.
,
118
, pp.
146
150
.
9.
Wendelin, T., and Grossman, J., 1995, “Comparison of Three Methods for Optical Characterization of Point Focus Concentrators,” ASME-JSES-JSME International Solar Energy Conference, Maui, Hl, pp. 775–780.
10.
Johnston, G., 1997, “Focal Region Modeling and Characterization of Paraboloidal Dish Solar Concentrators,” PhD Thesis, Australian National University, Canberra.
11.
Walraven
,
R.
,
1978
, “
Calculating the Position of the Sun
,”
Sol. Energy
,
20
(
5
), pp.
393
397
.
12.
Kaneff, S., 1991, “The White Cliffs Project, Overview for the period 1979–1989,” Office of Energy, Sydney 1991, ISBN 0 7305 6954 3 91/113.
13.
Rabl, A., 1985, Active Solar Collectors and Their Applications (Oxford University Press, New York).