CA2237882A1

CA2237882A1 - Means of causing a plane mirror to function as a heliostat of adjustable focal length

Info

Publication number: CA2237882A1
Application number: CA002237882A
Authority: CA
Inventors: D. Fraser Symington; P. Tracy Symington; A. Fraser Symington
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-07-02
Filing date: 1998-07-02
Publication date: 2000-01-02

Abstract

Method of systematically deforming a plane mirror to function as a focusing heliostat of adjustable focal length. A plane mirror is made to deform through the application of force at a number of peripheral points which is opposed by the application of force to the centre area of the mirror. The resulting complex topology functions as a solar mirror capable of concentrating incident sunlight on a distant focal point. By adjusting the degree and location of the forces applied to the mirror, the focal length and degree of concentration of sunlight on the focal point can be adjusted.

Description

MEANS OF CAUSING A PLANE MIRROR TO FUNCTION AS A HELIOSTAT OF

This invention relates to a method of concentrating the energy of the sun on a small area to create high-grade heat. Such a device may be used singly or as a module of a compound reflective area.
In combination with other devices, it is a means of accurately and economically placing solar 20 energy under the degree of control required for numerous industrial and domestic applications.
Various forms of device for carrying the invention into practice are illustrated by way of example in the accompanying drawings. It is to be understood that the specific details of the apparatus disclosed are provided as examples only and not by way of limitation of the broad scope 25 of the invention, which scope is defined in the appended claims.
~ Figure 1 is a cross sectional view of the device: a backing plate, compressible and expansible interface, a sheet of plane mirror, and tensioning screws.
30 ~ Figure 2 is an perspective view of the device, showing the mirror under tension.
~ Figure 3 is an exploded perspective view of the reflective module.
Refernng to Figure 3, the reflective module will be seen to consist of a sheet of plane glass 35 mirror 2 of lateral dimensions substantially greater than the thickness of the mirror, which is caused to adhere to interface 3 which consists of compressible and expansible material of smaller lateral and vertical dimensions than the mirror. The interface is in turn made to adhere to backing plate 1.
40 Referring to figure l, force is exerted against the mirror at several peripheral points by screws 4, and countervailing force is supplied by interface 3, resulting in distortion of the mirror to irregular concave form capable of concentrating the rays of the sun in a manner comparable to the action of a heat-moulded or ground parabolic mirror. The focal length may be adjusted by increasing or decreasing the force exerted by screws 4. The spatial relationship of the number and 45 position of pressure points in combination with the shape and dimensions of the interface determine the focal length and degree of concentration of sunlight at the focal point. A typical -. , effective radius of curvature that may be achieved by this method is 8 or more times the lateral dimensions of the mirror, with a focal area of one twentieth the area of the mirror.
Concentrations of twenty times normal solar intensity may therefore be achieved with this 50 method.
Solar minors made in this fashion are less costly to manufacture than ground or moulded parabolic or spherical glass mirrors and more resistant to weathering and abrasion than aluminized plastic.
In another form, the interface 3 is replaced by screws affixed to the mirror sheet 2 which protrude through holes in the backing plate 1 permitting tensioning by nuts or other devices which apply pulling force against the backing plate. In this form, the peripheral screws 4 may be replaced by fixed posts of appropriate length. By tightening the pull-screws, distortion of the mirror 2 is effected comparable to that achieved by use of an interface and peripheral screws.
In yet another version studs or posts of suitable length are affixed to a backing plate, and the mirror is set on them and placed under pressure to distort it and simultaneously glue or cement the central portion of the mirror to the central portion of the backer plate.
Some of the advantages which accrue from the above and other characteristics are as follows:
1. The cost of plane minor glass is substantially lower than the cost of moulded or ground concave mirrors.

2. Replacement of plane minors in the event of breakage while in use in remote area is much quicker and less costly.

3. Packing, shipping and insurance costs for plane mirrors are lower than for shaped minors.

4. Mirrors distorted in this manner concentrate the sunlight they reflect, whereas plane minors reflect light in a beam which becomes larger in cross section in proportion to the distance of the target from the minor, due to the parallax effect.

Claims

The embodiments of the invention to which exclusive property or privilege is claimed are defined as follows:

1. A device for systematically distorting plane mirror glass to concentrate the energy derived from the sun and reflected from said mirror, comprising:
a) A plane stiff or rigid plate with several screws passing through threaded holes at peripheral points, a sheet of plane glass mirror of equal or similar size, and an interface of smaller dimension made of compressible and expansible material; the above being glued or cemented together as a sandwich whereof the periphery of the mirror may be bent away from the rigid plate by force exerted by said screws, so as to concentrate the reflected rays of the sun in a manner comparable to a parabolic mirror.
b) A plane stiff or rigid plate similarly fitted with peripheral screws, and a mirror to which several screws are affixed in a pattern conforming generally to the periphery of the interface which they replace, and which exert pull against the push of the peripheral screws, thereby distorting the mirror into a complex topology capable of concentrating sunlight.
c) A device similar to the above, but with studs or posts replacing the peripheral scews.
d) A device similar to the above, without pull-screws attached to the mirror, but in which the mirror is distorted by force against its central portion, and while distorted is cemented to the central portion of the stir or rigid plate.