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Electronic Resource
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SAND Report: SAND90-7036, July 1991.
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ABSTRACT:
Solar Kinetics, Inc., successfully designed and constructed the optical element of a 7-meter diameter stretched-membrane dish as Task 2 of the second phase of a contract directed by Sandia National Laboratories. Earlier work on this project defined the configuration of the optical element
1. The technique of large-scale membrane forming was shown to be predictable, accurate, and repeatable. Three 7-meter membranes were formed without any contoured tooling.
2. A tensioned hub-and-spoke structure was demonstrated to be practical to fabricate. This innovative structure, like a bicycle wheel, was shown to be very stiff. Optical effects from ring distortion were not apparent.
3. The use of field-replaceable, unattached polymer reflective membrane was demonstrated. This approach allows for the practical field replacement of the reflective membrane when it has degraded due to weathering.
4. A technique was developed and demonstrated to ship the formed membranes from the factory to the dish-installation site. This allows the critical forming of the membrane to be performed in a controlled factory
environment, and the membrane then to be shipped using standard dimension shipping containers. This development further reduces manufacturing and installation costs of the completed dish.
This effort indicates that the stretched-membrane dish concept is a promising approach for solar concentration. The prototype optical element is a significant step in the development of the complete, full-sized dish.
Solar Kinetics, Inc., successfully designed and constructed the optical element of a 7-meter diameter stretched-membrane dish as Task 2 of the second phase of a contract directed by Sandia National Laboratories. Earlier work on this project defined the configuration of the optical element
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and demonstrated the membrane-forming process on 1.4- and 3.7-meter diameter membranes. In Task 2, the membrane- forming process was successfully scaled to 7-meters in diameter, and an innovative hub-and-spoke structure optical element was fabricated. The slope error, as measured with Solar Kinetics’ laser-ray-trace system, was within 3.6 mrad of a perfect parabola. Four major technical issues were successfully addressed in this work:1. The technique of large-scale membrane forming was shown to be predictable, accurate, and repeatable. Three 7-meter membranes were formed without any contoured tooling.
2. A tensioned hub-and-spoke structure was demonstrated to be practical to fabricate. This innovative structure, like a bicycle wheel, was shown to be very stiff. Optical effects from ring distortion were not apparent.
3. The use of field-replaceable, unattached polymer reflective membrane was demonstrated. This approach allows for the practical field replacement of the reflective membrane when it has degraded due to weathering.
4. A technique was developed and demonstrated to ship the formed membranes from the factory to the dish-installation site. This allows the critical forming of the membrane to be performed in a controlled factory
environment, and the membrane then to be shipped using standard dimension shipping containers. This development further reduces manufacturing and installation costs of the completed dish.
This effort indicates that the stretched-membrane dish concept is a promising approach for solar concentration. The prototype optical element is a significant step in the development of the complete, full-sized dish.
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