GB2511516A

GB2511516A - Radiation reflector using tensioned metallised sheets

Info

Publication number: GB2511516A
Application number: GB1303885.6A
Authority: GB
Inventors: David Andrew Johnston
Original assignee: Individual
Current assignee: Individual
Priority date: 2013-03-05
Filing date: 2013-03-05
Publication date: 2014-09-10
Also published as: GB201303885D0

Abstract

A reflector comprises a metallised sheet 1 held in shape due to tension provided by a framework of semi-rigid wires 2, 3 or rigid rods. The reflector may in the form of a paraboloid or a hyperboloid. The framework may comprise a set of radial wires and may further include a set of concentric circular wires. Alternatively, the framework may be square or rectangular and comprise rigid rods (9, figure 4) separated by extendable members (10). The reflector may form part of a solar concentrator energy system for providing high intensity solar radiation for electrical power generation or process heat for chemical and other manufacturing processes.

Description

Radiation reflector using tensioned metallised sheets Solar concentrator energy systems are used to provide high intensity solar radiation for a range or purposes -electrical power generation, process heat for chemical and other manufacturing processes, etc. In all such cases, the large power required necessitates a large collecting area, for instance, an input power of 1 MW requires a collecting area of approx. 1000 m2. The large area of the primary collector means that the mirrors required generally constitute the largest singlc cost for the system -in some cases over 50% of the total cost. In order to reduce the cost of solar energy, mirrors are required, which can be produced at low cost. Low weight is also advantageous, as it reduces the mechanical load on tracking systems, thus potentially reducing the cost of these systems.

To meet these design objectives, the present invention proposes a reflector consisting of a metallised sheet held in shape (flat or curved) due to tension provided by a framework of semi-rigid wires or rigid rods. These reflectors may be used individually or as part of a larger array. A number of possible configurations are possible, as described below, and with reference to the accompanying drawings.

Figure 1 shows a parabolic dish reflector.

Figure 2 shows a parabolic dish reflector with an energy converting device placed at the prime focus.

Figure 3 shows a parabolic dish reflector with a secondary mirror placed at the prime focus.

Figure 4 shows a flat reflector.

Figure 5 shows an are of flat reflectors.

In figure 1, the parabolic dish reflector consists of metallised sheet 1 and a framework of semi-rigid Wires 2, 3. The framework consist of radial wires 2 held in a parabolic curve by the tension of the metallised sheet 1, and concentric circular wires 3 which improve the curvature of the metallised sheet 1. The metallised sheet 1 is held in tension by the framework of semi-rigid wires 2,3.

In some cases, the energy converting device 5 (solar heater, etc) is placed at the prime focus of the reflector 6, as shown in figure 2. Alternatively, a secondary mirror 7 may be installed at this position, as shown in figure 3. This mirror may be flat or curved, and may be a tensioned metallised sheet 1 and a framework of semi-rigid wires 2, 3, or of an alternative construction. If the secondary mirror 7 is curved, it will be hyperbolic rather than parabolic. However, a hyperbolic reflector can be constructed from metallised sheet 1 and a framework of semi-rigid wires 2, 3, similar to the parabolic dish reflector 6. If the secondary mirror is flat 7, and constructed from metallised sheet 1 and a framework of semi-rigid wires 2, 3, it can be similar in form to the flat reflector described below. The secondary mirror 7 may in turn reflect radiation onto further optical components 8, some of which may be mirrors. These mirrors may also be a tensioned metallised sheet 1 and a framework of semi-rigid wires 2, 3, or of an alternative construction.

In figure 4, the flat reflector consists of metallised sheet 1 and a square or rectangular framework of rigid rods 9. Extendable members 10 at the rear of the reflector increase the separation distance between opposite pairs of rigid rods, thus providing the tension on the metallised sheet 1.

In a heliostat array, the individual flat reflectors 11 are arranged in concentric arcs, a section of one such arc being shown in figure 5. Each reflector requires an independent tracking mechanism to maintain alignment of the reflected beam with the collector, as the sun moves across the sky during the day.

Claims

Claims 1. A reflector consisting of a metallised sheet held in shape due to tension provided by a framework of semi-rigid wires or rigid rods.
2. A reflector, as claimed in Claim 1, wherein the semi-rigid wires are held in shape due to tension provided by the nietallised sheet.
3. A reflector, as claimed in Claim I and Claim 2, wherein the reflector is in the form of a paraboloid.
4. A reflector, as claimed in Claim 1 and Claim 2, wherein the reflector is in the form of a hyperboloid.
5. A reflector, as claimed in Claim 1 and Claim 2, and Claim 3 or Claim 4, wherein the framework of semi-rigid wires consists of a set of radial wires.
6. A reflector, as claimed in Claim 1 and Claim 2, and Claim 3 or Claim 4. and Claim 5, wherein the framework of semi-rigid wires additionally includes a set of concentric circular wires.
7. A reflector, as claimed in Claim 1, wherein extendable members apply a separating force to the rigid rods, which thus apply tension to the metallised sheet, keeping it in the required shape.