Facet development for a faceted stretched-membrane dish by SAIC.

摘要

The concept for a multi-facet stretched-membrane dish concentrator could reduce the cost and weight of solar thermal dish systems. A stretched-membrane mirror facet for such a multi-facet solar dish concentrator has been developed by Science Applications International Corporation (SAIC). Twelve of the 3.7-m diameter facets will be used to form a 115-m(sup 2) dish concentrator, providing 75 kW(sub th) to operate a 25-kW(sub e) Stirling engine for electric power production. The facet SAIC designed is focused using a vacuum system to elastically deform the thin (0.003-inch thick) stainless steel facet membranes. Elastic focusing was chosen over plastically deforming the membrane to a parabolic shape because it results in a simple manufacturing process. The SAIC facet can be focused from infinity to a minimum focal length-to-diameter ratio of about 2.7. Analytical design studies and experimental tests were performed to evaluate stresses in the ring and membranes during operation, the effects of strain cycling on the reflective surface, and to measure the optical quality of the mirror facets. SAIC produced two prototype mirror facets and they were optically tested at the Solar Energy Research Institute and at Sandia National Laboratories. The first facet showed slope errors ranging from 2.95 to 3.3 mrad over the f/d range of 2.7 to 3.0.