United States Patent Number: 4,046,462, September 6, 1977. 6 pages. Also available from the United States Patent and Trademark Office. Website: http://www.uspto.gov
A tracking three-dimensional solar energy concentrator is provided by a stretched aluminized polymeric membrane supported by a hoop, the polymeric membrane being formed to a desired curvature by differential loading. The loading on the polymeric membrane determines its curvature. The loading can be varied by utilizing a plastic membrane that has a non-uniform radial distribution of thickness with uniform differential pressure or by applying a non-uniform differential pressure on a membrane having uniform thickness. Reflector membranes having a non-uniform radial distribution of thickness can be obtained by selective spraying of a dissolved plastic such as Krylon on the underside of the aluminized membrane. A non-uniform differential pressure is obtained by using a uniform differential pressure in combination with localized electrostatic or magnetic pressure. The membrane concentrator and its supporting equipment is maintained in a slightly pressurized spherical-cap envelope of transparent plastic to protect the concentrator from the elements.