U.S. patent application number 09/850175 was filed with the patent office on 2002-04-25 for parabolic reflectors.
Invention is credited to Yeomans, Allan James.
Application Number | 20020047814 09/850175 |
Document ID | / |
Family ID | 3825806 |
Filed Date | 2002-04-25 |
United States Patent
Application |
20020047814 |
Kind Code |
A1 |
Yeomans, Allan James |
April 25, 2002 |
PARABOLIC REFLECTORS
Abstract
A parabolic reflector assembly (10) comprising a base member
(11) formed of magnetic material and defining a parabolic surface
(12), and a flexible magnet sheet (18) carrying a reflective sheet
(19) magnetically bonded to the parabolic surface to form a
parabolic reflecting surface. A method of manufacturing the
parabolic reflector assembly is also disclosed. The parabolic
reflector assembly typically may be used as a concentrator is solar
energy concentrating apparatus.
Inventors: |
Yeomans, Allan James;
(Surfers Paradise, AU) |
Correspondence
Address: |
WOOD, PHILLIPS, VAN SANTEN
CLARK & MORTIMER
Suite 3800
500 West Madison Street
Chicago
IL
60661
US
|
Family ID: |
3825806 |
Appl. No.: |
09/850175 |
Filed: |
May 7, 2001 |
Current U.S.
Class: |
343/912 ;
343/914 |
Current CPC
Class: |
Y02E 10/45 20130101;
G02B 5/10 20130101; Y02E 10/40 20130101; F24S 23/74 20180501 |
Class at
Publication: |
343/912 ;
343/914 |
International
Class: |
G02B 005/10; H01Q
015/14 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 21, 2000 |
AU |
PR 1769 |
Claims
I claim:
1. A parabolic reflector assembly comprising: a base member formed
of a magnetic material and defining a parabolic surface, at least
one flexible magnet sheet having an inner side and an outer side,
said flexible magnet sheet being magnetically bonded to said base
member with said inner side of said magnet sheet being adjacent
said parabolic surface such that said magnet sheet adopts the
parabolic shape of said parabolic surface, and a reflective
material on said outer side of said magnet sheet and defining a
parabolic reflective surface.
2. A parabolic reflector assembly as claimed in claim 1 wherein
said reflective material is bonded to said outer side of said
magnet sheet.
3. A parabolic reflector assembly as claimed in claim 2 wherein
said reflective material is in the form of or is carried by a
flexible sheet.
4. A parabolic reflector assembly as claimed in claim 3 wherein
said reflective material comprises a laminate of a sheet plastics
material and a reflective film.
5. A parabolic reflector assembly as claimed in claim 3 wherein
said magnet sheet includes on its outer side a self adhesive
material for bonding of said reflective material sheet to said
magnet sheet.
6. A parabolic reflector assembly as claimed in claim 1 wherein
said base member is formed of a sheet of magnetic material.
7. A parabolic reflector assembly as claimed in Clam 6 and
including a parabolic former and wherein said sheet of magnetic
material is held against said parabolic former to form said base
member with said parabolic surface.
8. A parabolic reflector assembly as claimed in claim 1 and
including a layer of flexible highly heat conductive material
between said reflective material and said magnet sheet.
9. A parabolic reflector assembly as claimed in claim 8 wherein
said heat conductive material comprises aluminium sheet.
10. A method of manufacturing a parabolic reflector assembly, said
method including the steps of: providing a base member formed of
magnetic material, said base member having a parabolic surface,
providing at least one flexible magnet sheet, said magnet sheet
having an inner side and an outer side, providing a reflective
material on the outer side of said magnet sheet; and applying said
flexible magnet sheet to said parabolic surface such that said
flexible magnet sheet is magnetically bonded to said base member
with said inner side of said magnet sheet adjacent to said
parabolic surface whereby to cause said reflective material to
define a parabolic reflective surface.
11. A method as claimed in claim 10 and including the step of
forming said base member from a panel of sheet magnetic metal.
12. A method as claimed in claim 11 wherein said base member is
formed by the steps of pressing said panel of sheet magnetic metal
against a parabolic former and securing said panel to said
former.
13. A method as claimed in claim 12 and including the step of
providing a layer of highly heat conductive material between said
reflective material and said magnet sheet.
14. Solar energy collecting apparatus including a solar energy
concentrator for concentrating solar energy on a target wherein
said solar energy concentrator comprises a parabolic reflector
assembly of the type claimed in claim 1.
Description
TECHNICAL FIELD
[0001] This invention relates to parabolic reflectors which may be
used as solar energy concentrators in solar energy collecting
apparatus but which also may be used in other applications. The
present invention also relates to a method of manufacturing
parabolic reflectors.
BACKGROUND ART
[0002] In solar energy collecting apparatus, parabolic reflectors
are commonly used for concentrating solar energy on solar energy
absorbers. The reflectors which are used are formed of various
materials. For example, the reflectors may comprise metal such as
aluminium which is highly polished to define a reflecting surface,
or glass mirrors. It is important in solar energy collecting
apparatus used in the generation of electrical power that the costs
of the apparatus be such that the unit power generating costs are
competitive with that of conventional power generation systems. The
known reflectors used in solar energy collecting apparatus however
are generally relatively expensive to manufacture resulting in
increased overall costs of the solar energy collecting apparatus.
Further if the reflective surfaces of the reflectors become
damaged, the whole reflectors are usually required to be replaced
which is also costly. Further costs can arise because of loss of
power generating capacity in down time in replacing the
reflectors.
SUMMARY OF THE INVENTION
[0003] The present invention aims to provide a parabolic reflector
which is relatively inexpensive, which may be easily constructed
and which may be easily and rapidly replaced in the event of damage
thereto. The present invention further aims to provide a method of
manufacturing a parabolic reflector of the above type. The present
invention further aims to provide solar energy concentrating
apparatus employing parabolic reflectors of the above type. Other
objects and advantages of the invention will become apparent from
the following description.
[0004] The present invention thus provides in a first aspect, a
parabolic reflector assembly comprising:
[0005] a base member formed of a magnetic material and defining a
parabolic surface,
[0006] at least one flexible magnet sheet having an inner side and
an outer side, said flexible magnet sheet being magnetically bonded
to said base member with said inner side of said magnet sheet being
adjacent said parabolic surface such that said magnet sheet adopts
the parabolic shape of said parabolic surface, and
[0007] a reflective material on said outer side of said magnet
sheet and defining a parabolic reflective surface.
[0008] The reflective material may be in the form of or be carried
by a flexible sheet such as a plastics sheet which may be bonded or
adhered to the outer side of the magnet sheet. The adherence
between the magnet sheet and sheet of reflective material may be
defined by self-adhesive layer on the outer side of the magnet
sheet, on one side of the reflective material sheet or both.
[0009] The reflective material sheet may be formed as a laminate of
sheet plastics material and a reflective film such as a silver film
or aluminium film. A particularly suitable material is that
manufactured by the 3M company and sold under the trademark
Silverlux silver film.
[0010] As an alternative, the reflective material may be defined by
a layer deposited on or otherwise applied to the outer side of the
magnet sheet.
[0011] The flexible magnet sheet may be any form of flexible
permanent magnet and comprise for example a flexible plastic
material such as a thermoplastic material which incorporates a
magnetic powder or magnetic granules and which is known under the
trademark Tromaflex.
[0012] The base member for the formation of a parabolic reflector
assembly which is of a parabolic trough form may comprise a panel
of magnetic sheet metal formed into a parabolic shape to define a
parabolic trough surface to receive the magnet sheet which through
magnetic attraction to the metal sheet conforms closely to the
parabolic trough surface to form a parabolic trough reflector.
Suitably the panel of sheet metal is pressed and held against a
parabolic formed to form the base member with the parabolic
surface. The panel may be secured to the former for example by
welding. The base member however may also comprise a parabolic dish
member defining a parabolic dish surface to which a plurality of
flexible magnet sheets carrying reflective layers or materials may
be magnetically bonded to form a parabolic dish reflector
assembly.
[0013] A layer of a highly heat conducting material may be
interposed between the reflective material and magnet sheet.
Suitably, the heat conducting material is aluminium or other high
heat conducting metal. The highly heat conducting material is used
to dissipate heat generated in the reflector. In parabolic
reflectors of the above type, the optical concentrators can have
imperfect concentrating surfaces which can result in localised
areas of high concentration of solar energy and thus areas of high
temperature. This can cause damage to the components of the
parabolic reflector, particularly the magnet sheet. The use of a
highly heat conducting material interposed between the reflective
material and magnet sheet dissipates the heat and conducts it more
readily through to the parabolic base member. In addition, the
highly heat conducting material adds some stiffness to the
reflective material/magnet sheet combination such that a more
accurate parabolic surface results when the combination is applied
to parabolic base members having imperfect parabolic surfaces, for
example a galvanised sheet metal base member which may define an
imperfect surface due to the galvanising process causing uneven
deposits on the surface.
[0014] The present invention in a further aspect provides a method
of manufacturing a parabolic reflector assembly, said method
comprising the steps of:
[0015] providing a base member formed of magnetic material, said
base member having a parabolic surface, providing at least one
flexible magnet sheet, said magnet sheet having an inner side and
an outer side,
[0016] providing a reflective material on the outer side of said
magnet sheet; and
[0017] applying said flexible magnet sheet to said parabolic
surface such that said flexible magnet sheet is magnetically bonded
to said base member with said inner side of said magnet sheet being
adjacent said parabolic surface whereby to cause said reflective
material to define a parabolic reflective surface.
[0018] The method may include the further step of providing a
highly heat conductive material between the magnet sheet and the
reflective material.
[0019] The method may additionally include the step of forming the
base member from a panel of sheet magnetic metal. The panel of
sheet magnetic metal may be formed into a parabolic shape by
pressing it against a parabolic former and securing it to the
former. The panel may be secured to the former by welding.
[0020] The present invention in yet a further aspect provides a
solar energy collecting apparatus including a solar energy
concentrator for concentrating solar energy on a target wherein the
solar energy concentrator comprises a parabolic reflector assembly
of the above described type.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] In order that the invention may be more readily understood
and put into practical effect, reference will now be made to the
accompanying drawings which illustrate a preferred embodiment of
the invention and wherein:
[0022] FIG. 1 illustrates in exploded view the components of the
parabolic reflector assembly according to an embodiment of the
invention prior to assembly;
[0023] FIG. 2 illustrates the manner in which a metal sheet may be
formed into a parabolic trough shape to form the base member for
the reflector assembly;
[0024] FIG. 3 is a plan view of the formed parabolic base
member;
[0025] FIG. 4 is a perspective view of the assembled parabolic
reflector assembly according to the invention;
[0026] FIG. 5 is a side view of the assembled parabolic reflector
assembly; and
[0027] FIG. 6 is an enlarged view of the region A of FIG. 6.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0028] Referring to the drawings and firstly to FIG. 1, there is
illustrated the components of a parabolic reflector assembly 10
according to an embodiment of the invention comprising a parabolic
base member 11 formed by a metal sheet of magnetic material,
typically sheet steel. Where the parabolic reflector assembly 10 is
to be used externally as in solar energy collecting apparatus, the
parabolic base member 11 may be formed of galvanised sheet metal to
reduce corrosion.
[0029] A rectangular panel of sheet metal may be formed into a
parabolic trough shape in the manner shown in FIGS. 2 and 3 to form
the base member 11. As illustrated, a planar panel 12 of thin sheet
metal may be arranged centrally of a supporting metal rib or fm 13
which has an edge 14 accurately cut to a parabolic form. The edge
14 typically may be laser cut to achieve the required accuracy. The
panel 12, when urged in the direction of the arrow of FIG. 2 into
position against the rib or fin 12, will, as shown in dotted
outline in FIG. 2, deform and adopt the parabolic shape of the edge
14 of the rib or fm 13. The panel 12 may be simply held in position
by tack welds 15 at spaced positions on either side of the rib or
fm 13 such that the panel 12 defines an accurate parabolic surface
16. The fm or rib 13 may as illustrated be provided with a curved
slot 17 for the purposes of mounting and guiding of the formed
parabolic reflector assembly 10 to track movement of the sun as
described in my U.S. Pat. No. 5,592,932, the contents of which are
herein incorporated by reference. Whilst the above described
arrangement illustrates one method for forming a parabolic base
member 11, it will be appreciated that the parabolic base member 11
may be formed by many different methods such as by pressing the
sheet 12 into the required parabolic shape.
[0030] The reflector assembly 10 further includes a rectangular
flexible magnet sheet 18 which is usually formed of a flexible
plastic such as thermoplastics incorporating a magnetised powder or
granules. The magnet sheet 18 preferably has a length and width
substantially the same as that of the panel 12 which forms the
parabolic base member 11 so as to substantially occupy the full
parabolic surface 16 when applied to the base member 11 as
described further below.
[0031] The reflective surface of the parabolic reflector assembly
10 is defined by a laminate of a rectangular flexible sheet 19
formed of plastics material and incorporating a layer or film 20 of
silver or other highly reflective material, the sheet 19 being of a
size and shape to match the magnet sheet 18. A particular suitable
laminate for this purpose comprises a product known under the trade
mark Silverlux manufactured by the 3M company which incorporates a
silver film. The reflective layer or film 20 may be covered with a
plastic protective sheet 21 which may be removed after formation of
the reflector assembly 10 to expose the reflective layer or film
20.
[0032] Most suitably, the flexible magnet sheet 18 has, or is
provided with, on one side 21, a self-adhesive material or layer
which enables the reflective sheet 19 to be conveniently adhered to
the magnet sheet 18. Alternatively, the reflective sheet 19 may
include on its reverse side, that is, its side opposite the layer
or film 20, a self-adhesive layer or material to permit it to be
adhered to the flexible magnet sheet 18. In yet an alternative
arrangement, a separate adhesive may be provided to adhere the
reflective sheet 19 to the flexible magnet sheet 18.
[0033] After joining of the reflective sheet 19 to the flexible
magnet sheet 18, the joined sheets 18 and 19 are applied to the
parabolic base member 11 to form the 30 parabolic reflector
assembly 10 shown in FIGS. 4 to 6. This may simply be achieved by
positioning the joined sheets 18 and 19 in alignment with the
parabolic base member 11 and pushing the sheets 18 and 19 inwardly
towards the base member 11. The flexible magnet sheet 18 will be
magnetically attracted to the magnetic parabolic base member 11 and
seat firmly on the surface 16 to thereby form the reflective sheet
19 and surface 20 into a true parabolic shape defined by the base
member 11. The face-to-face mating between the inner side of the
magnet sheet 18, that is the side opposite the side 12, and the
parabolic surface 16 will ensure that the magnet sheet 18 carrying
the reflective sheet 19 is securely held in position to resist
detachment in the event of high winds, rain or other adverse
weather conditions. If however, the reflective sheet 19 or
reflective layer 20 becomes damaged, the magnet sheet 18 may be
simply detached from the parabolic base member 11 and replaced by a
new assembly of magnet sheet 18 and reflective sheet 19.
[0034] In a modification, a further sheet 23 of flexible highly
heat conducting material (shown in dotted outline in FIG. 1) of
similar peripheral dimensions to the sheets 18 and 19 may be
interposed between the reflective sheet 19 and magnet sheet 18 and
adhered thereto. The sheet 23 which typically may be of 0.5 mm in
thickness but which may be of other thicknesses will provide some
stiffness to the assembly of reflective sheet 19 and magnet sheet
18 and further serve to dissipate heat and conduct it to the
parabolic base member 11. Thus heat which is developed in localised
areas of the reflector assembly 10 due to imperfect optical
characteristics of the reflective sheet 19 will be dissipated and
conveyed rapidly by the heat conducting sheet 23 to the underlying
parabolic base 11 to minimise the possibility of damage to the
reflective sheet 19 and/or magnet sheet 18. Further the additional
stiffness in the assembly will ensure that any imperfections in the
parabolic surface 16 of the base member 11 will have minimal effect
on the parabolic reflecting characteristics of the reflector
assembly 10.
[0035] The sheet 23 may be adhered on opposite sides to the magnet
sheet 18 and the reflective sheet 19 by any suitable adhesives or
alternatively via self adhesive layers on the magnet sheet 18
and/or reflective sheet 19. Alternatively, the reflective sheet 19
may be provided with the heat conducting sheet 23 adhered thereto
in a composite laminate.
[0036] The present invention thus provides an arrangement whereby a
parabolic trough reflector may be manufactured accurately, quickly
and inexpensively and which allows rapid repair in the case of
damage to the reflective surface. Parabolic reflectors according to
the present invention can be used in many different applications
but typically are used in solar energy concentrating applications
where solar energy is concentrated by the parabolic reflector onto
a target. Thus in the embodiment of FIGS. 4 and 5, the parabolic
reflector assembly 10 may be used in solar energy collecting
apparatus as a parabolic concentrator with the formed parabolic
reflective surface 20 concentrating energy on a suitable target for
example a tubular member carrying an energy transfer medium which
is arranged at the focus of the parabolic reflector assembly. Such
apparatus is defined in my aforesaid U.S. Pat. No. 5,592,932.
[0037] The embodiment described relates to a parabolic trough
reflector of a particular shape and configuration however it will
be appreciated that the parabolic trough reflector may be of any
shape desired with the magnet sheet 18 and reflective sheet 19
simply cut or provided in a size to fit the parabolic trough
surface. Of course, the parabolic trough surface may carry a
plurality of magnet sheets 18 carrying reflective sheets 19
sufficient to cover the parabolic trough surface 16 or cover the
surface 16 to the extent required. For example the trough surface
16 may be covered in a pair of end-to-end abutting sheets 18
carrying reflective sheets 19, the join between abutting sheets 18
being arranged centrally of and extending transversely of the base
member 11.
[0038] It also should be appreciated that the invention may be
applied to the formation of a parabolic dish reflector or
concentrator in which case a plurality of magnet sheets 18 carrying
the reflective sheets 19 may be magnetically bonded to the
parabolic dish surface in abutting end-to-end or side-to-side
relationship to form a composite parabolic reflecting dish
concentrator.
[0039] Whilst the above has been given by way of illustrative
embodiment of the invention, all such variations and modifications
thereto as would be apparent to persons skilled in the art are
deemed to fall within the broad scope and ambit of the invention as
defined in the appended claims.
* * * * *