WO2007016723A1

WO2007016723A1 - Solar collector

Info

Publication number: WO2007016723A1
Application number: PCT/AU2006/001101
Authority: WO
Inventors: Robert W G Macdonald
Original assignee: PURE SOLAR POWER (IP) Pty Ltd
Current assignee: PURE SOLAR POWER (IP) Pty Ltd
Priority date: 2005-08-08
Filing date: 2006-08-04
Publication date: 2007-02-15
Anticipated expiration: 2008-02-08

Abstract

This invention relates to a solar collector (1 ) for heating air. The solar collector includes a chamber (6) defined by an absorber (2) and a cover (3). The cover (3) is spaced from the absorber (2) so as to define the stagnant zone. A fluid zone is located to the underside of the absorber (2). Heat energy is conducted through the absorber and transferred to air in the fluid zone.

Description

SOLAR COLLECTOR

This invention relates to a solar collector for heating air, and to an installation of a plurality of solar collectors. The collector has a particular commercial application in relation to using the heated air to generate air currents, and it will be convenient to hereinafter describe the invention with reference to this application. It ought to be appreciated however that the invention has other applications including heating for residential and commercial buildings.

The solar collector to which the invention relates is of the kind having a substantially planar absorber for absorbing solar radiation. Solar collectors of the foregoing kind tend to be referred to as solar panels and it ought to be understood that the invention includes, but is not limited to solar panels.

A solar collector known to the applicant is described in the Australian patent specification AU 51484/85, and includes a base absorber plate, a panel body having side and end walls and a transparent cover plate on top. The absorber plate is designed to absorb solar radiation by conduction throughout the plate and transfer the heat energy to the air by radiation and then convection. When in use the heated air is transferred from the collector to the application by fans or natural convection.

The efficiency of such a collector could be improved.

The above discussion of documents, acts, materials, devices, articles and the like is included in this specification solely for the purpose of providing a context for the present invention. It is not suggested or represented that any of these matters formed part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application.

It is an object of this invention to improve the efficiency of existing solar collectors used for heating air. According to one aspect of this invention there is provided a solar collector for heating air, the collector includes; a chamber defined by walls, an absorber forming a base of the chamber for absorbing radiant energy, a cover of transparent material covering the absorber and being spaced from the absorber so that the chamber defines a stagnant zone where in use convection and radiation from the absorber is suppressed, the collector having a fluid zone located to the underside of the absorber where in use radiation and convection are not suppressed, wherein fluid in the fluid zone is air and in use the heat energy conducted through the absorber is transferred to air in the fluid zone.

Suppressing convection encourages the absorber to absorb the energy and conduct the energy through the absorber rather than transferring the energy back towards the cover. Also, suppressing radiation from the absorber to the cover encourages the absorber to retain and conduct energy through the absorber into the relative fluid zone located to the underside of the absorber. This makes for a more efficient transfer of the heat energy. The space in between the cover and absorber is preferably minimised to suppress convection in the stagnant zone and yet large enough to suppress re-radiation. The spacing is preferably less than 30mm, and most preferably between 1 1 mm and 15mm.

The cover is preferably formed from glass, however other transparent materials may also be suitable. The cover is preferably substantially planar and of relatively uniform thickness.

The absorber preferably includes a plate having a surface to receive the radiant energy. The surface of the plate is spaced from the cover in accordance with the said spacing. The surface of the plate preferably extends substantially parallel to the cover.

The surface area of the absorber interfacing with the fluid zone is preferably greater than the surface area interfacing the stagnant zone to facilitate transfer of the energy from the absorber to the air in the fluid zone. It is preferred that the absorber includes at least one fin extending from the rear of the plate so as to increase the surface area of the absorber interfacing the fluid zone. The fins are preferably arranged substantially perpendicular to the plate. The fins may be formed integrally with the plate or formed as a separate component and subsequently attached to the plate.

The solar collector preferably includes an insulation member which combines with the absorber to define the fluid zone. The insulation member may facilitate the control of air flow and minimise heat energy loss.

According to another aspect of this invention there is provided a solar collector installation including a plurality of solar collectors as herein before defined, each collector being retained in position by a frame, the installation including flow induction means for inducing the heated air from the convective zone to flow in a preferred direction.

It is preferred that the frame be configured to angle the plate of the absorber relative to a horizontal plane, so that the plate rises in the direction of flow.

Each collector preferably includes at least one turbulence inducer located to the underside of the absorber to discourage laminar flow in the preferred direction. It is further preferred that the turbulence inducer induce turbulence in the flow of air which encourages convection of the heat away from the absorber. The turbulence inducer is preferably angled substantially transverse to the preferred direction of flow, and preferably extending from the absorber so as to deflect the flow away from the absorber. The preferred angle depends on the velocity of the air flow. The turbulence inducer is preferably curved and presents a curved surface to the approaching flow of air. Alternatively or additionally the turbulence inducer may extend from the insulation member.

The flow induction means may take any form. It can be a controlled or uncontrolled aperture. It will be convenient to hereinafter describe the invention in detail with reference to the attached drawings which illustrate a preferred embodiment of a collector according to the invention. It ought to be appreciated however that the generality of the preceding portion of the specification is not to be superseded by the specifics of the following description.

Figure 1 illustrates a plan view of a preferred embodiment of solar collector according to the invention.

Figure 2 illustrates a cross section of the solar collector from Figure 1 .

Figure 3 illustrates an isometric view from the under side of a portion of the solar collector.

Figure 4 illustrates a side view of the solar collector showing the preferred direction of flow.

Figure 5 illustrates an alternative embodiment of the solar collector in cross section.

Referring firstly to Figure 1 which illustrates the preferred embodiment of the solar collector 1 to be substantially rectangular in shape. It ought to be appreciated that the solar collector 1 may have a different shape to that shown in Figure 1 , and the shape shown is merely preferred. For example where the collector 1 is to form part of a circular or semi-circular array, it may be preferable for the collector to be shaped as a trapezium.

Referring now to Figure 2 which illustrates in cross section the solar collector 1 from Figure 1. In summary Figure 2 illustrates an absorber 2, a cover 3 and a pair of side walls 4, which combine with end walls 5 (see Figure 1 ) to define a chamber 6. The function of the chamber 6 will be described later in the specification. The absorber 2 as shown in Figure 2 is formed from a plate 7 with a plurality of fins 8 extending from a rear of the plate 7. The fins 8 may be formed integrally with the plate 7, or subsequently attached thereto. The absorber 2 illustrated is connected to the side walls 4.

The side walls 4 illustrated in Figure 2 include a rebate 9 formed in an upper surface thereof for accommodating the cover 3. The collector 1 illustrated includes an edge capping 10 which caps the upper surface of the side and end walls 4,5 for capturing the cover 3 within the rebate 9. It is preferred that the edge capping 10 be detachable from the side and end walls 4,5 to facilitate removal of the cover 3. This will facilitate replacement of the cover 3, particularly when the cover 3 has been damaged.

When in use the collector 1 is preferably spaced from a support surface such as the ground. In order to achieve the spacing a frame 1 1 of any suitable configuration may be used. The frame 1 1 shown in Figure 2 is merely for illustrative purposes only.

When in use radiant energy passes through the transparent cover 3 and is absorbed by the plate 7 of the absorber 2. The heat energy is conducted through the plate 7 and to a lesser extent through the fins 8 connected to the plate 7. The heat energy is then transferred to the air at the underside of the plate 7 by radiation and convection. Forced convective currents are developed to move the heated air away from the plate 7 and fins 8.

The dimensions of the chamber 6, and in particular the spacing between the cover 3 and plate 7 are such as to suppress the development of convective currents and suppress radiation so as to establish a relatively stagnant zone within the chamber. This encourages the chamber 6 to act as an insulative layer to the plate 7 to encourage conduction of the energy through the plate 7, rather than back to the cover 3 and/or into the air located in the chamber 6. Referring now to Figure 3 which shows the under side of the collector 1 including 2 turbulence inducers 12. Each inducer 12 illustrated is located in the fluid zone extending from the rear of the plate 7.

The turbulence inducers 12 are used to encourage the air in the convective zone to move away from the rear of the plate 7. As can be seen in Figure 4 the heated air is encouraged to move in the direction of the arrow X. When the air hits the curved surface of the turbulence inducer 12 it induces turbulence in the air and moves the turbulent air away from the rear of the plate 7.

Referring now to figure 5 which shows the general arrangement of the collector with an insulation member in the form of a panel 13 is attached. The panel 13 can be attached at the underside of the collector to control the induction of mass air flow. Turbulence inducers 14 may also be affixed to the panel 13 as a means of optimising the transfer of heat energy by convention into the convective zone. The inducers 14 are spaced in the longitudinal dimension of the collector.

A plurality of the solar collectors 1 as hereinbefore described can be arranged into an array to feed heated air towards a device such as a solar tower (not shown). The solar tower could use the heated air to drive turbines thus generating electricity. Clearly other uses are possible.

The solar collector 1 as hereinbefore described has the advantage of the relatively non-convective and non-radiative zone positioned adjacent the absorber 2 to encourage the radiant energy to be transferred through the plate 7 by conduction. This is considered to provide a more efficient means of transferring the heat energy to the relatively convective zone at the rear of the plate 7.

Various alterations, modifications and/or additions may be introduced into the constructions and arrangements of parts previously described without departing from the spirit of ambit of the invention.

Claims

1 . A solar collector for heating air, the collector includes; a chamber defined by walls, an absorber forming a base of the chamber for absorbing radiant energy, a cover of transparent material covering the absorber and being spaced from the absorber so that the chamber defines a stagnant zone where in use convection and radiation from the absorber is suppressed, the collector having a fluid zone located to the underside of the absorber where in use radiation and convection are not suppressed, wherein fluid in the fluid zone is air and in use the heat energy conducted through the absorber is transferred to air in the fluid zone.

2. A solar collector according to claim 1 wherein the space in between the cover and absorber is less than 30mm.

3. A solar collector according to claim 2 wherein the space is between 1 1 mm and 15mm.

4. A solar collector according to any one of the preceding claims wherein the cover is formed from glass.

5. A solar collector according to any one of the preceding claims wherein the cover is preferably substantially planar and of relatively uniform thickness.

6. A solar collector according to any one of the preceding claims wherein the absorber includes a plate having a surface to receive the radiant energy, the surface of the plate is spaced from the cover and extends substantially parallel to the cover.

7. A solar collector according to claim 6 wherein the surface area of the absorber interfacing with the fluid zone is greater than the surface area interfacing the stagnant zone so as to facilitate transfer of the energy from the absorber to the air in the fluid zone.

8. A solar collector according to claim 7 wherein the absorber includes at least one fin extending from the rear of the plate so as to increase the surface area of the absorber interfacing the fluid zone.

9. A solar collector according to claim 8 wherein the fins are arranged substantially perpendicular to the plate.

10. A solar collector according to claim 9 wherein the fins are formed integrally with the plate.

1 1 . A solar collector according to any one of the preceding claims including an insulation member which combines with the absorber to define the fluid zone.

12. A solar collector installation including a plurality of solar collectors as herein before defined in any one of claims 1 to 1 1 , each collector being retained in position by a frame, the installation including flow induction means for inducing the heated air from the convective zone to flow in a preferred direction.

13. A solar collector installation according to claim 12 wherein the frame is configured to angle the plate of the absorber relative to a horizontal plane, so that the plate rises in the preferred direction.

14. A solar collector installation according to claim 12 or 13 wherein each collector preferably includes at least one turbulence inducer located to the underside of the absorber to discourage laminar flow in the preferred direction and to induce turbulence in the flow of air which encourages convection of the heat away from the absorber

15. A solar collector installation according to claim 14 wherein the turbulence inducer is angled substantially transverse to the preferred direction of flow, and extending from the absorber so as to deflect the flow away from the absorber.

16. A solar collector installation according to claim 15 wherein the angle selected is dependant upon the velocity of the air flow.

17. A solar collector installation according to any one of claims 14 to 16 wherein the turbulence inducer is curved and presents a curved surface to the approaching flow of air.

18. A solar collector installation according to claim 17 wherein the turbulence inducer extends from the insulation member.