U.S. patent application number 14/261940 was filed with the patent office on 2014-08-21 for multi-tube solar collector structure.
This patent application is currently assigned to AREVA SOLAR PTY LIMITED. The applicant listed for this patent is AREVA SOLAR PTY LIMITED. Invention is credited to Peter Le Lievre, Graham L. Morrison.
Application Number | 20140230806 14/261940 |
Document ID | / |
Family ID | 34864684 |
Filed Date | 2014-08-21 |
United States Patent
Application |
20140230806 |
Kind Code |
A1 |
Le Lievre; Peter ; et
al. |
August 21, 2014 |
MULTI-TUBE SOLAR COLLECTOR STRUCTURE
Abstract
A collector system (12) is disclosed that comprises a row of
linearly conjoined collector structures (13). The collector system
is arranged to be located at a level above a field of reflectors
(10) and to receive solar radiation reflected from the reflectors
within the field. The collector structure (13) comprises an
inverted trough (16) and, located within the trough, a plurality of
longitudinally extending absorber tubes (30) that, in use, are
arranged to carry a heat exchange fluid. The absorber tubes (30)
are supported side-by-side within the trough and each absorber tube
has a diameter that is small relative to the aperture of the
trough. The ratio of the diameter of each absorber tube to the
trough aperture dimension is of the order of 0.01:1.00 to 0.10:1:00
and, thus, a plurality of absorber tube functions, in the limit,
effectively to simulate a flat plate absorber.
Inventors: |
Le Lievre; Peter; (North
Sydeny, AU) ; Morrison; Graham L.; (Paddington,
AU) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
AREVA SOLAR PTY LIMITED |
SINGLETON |
|
AU |
|
|
Assignee: |
AREVA SOLAR PTY LIMITED
SINGLETON
AU
|
Family ID: |
34864684 |
Appl. No.: |
14/261940 |
Filed: |
April 25, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13182653 |
Jul 14, 2011 |
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14261940 |
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10597966 |
Aug 14, 2006 |
7992553 |
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PCT/AU05/00208 |
Feb 17, 2005 |
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13182653 |
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Current U.S.
Class: |
126/652 ;
126/663; 126/685 |
Current CPC
Class: |
F24S 20/20 20180501;
F24S 2023/834 20180501; Y02E 10/40 20130101; F24S 30/425 20180501;
F24S 40/80 20180501; F24S 23/70 20180501; F24S 10/742 20180501;
F24S 2030/136 20180501; Y02E 10/44 20130101; F24S 10/72 20180501;
Y02E 10/47 20130101; F24S 2023/872 20180501; F24S 80/40 20180501;
F24S 23/77 20180501; F24S 80/525 20180501; F24S 30/40 20180501;
F24S 2023/87 20180501; F24S 10/40 20180501 |
Class at
Publication: |
126/652 ;
126/663; 126/685 |
International
Class: |
F24J 2/05 20060101
F24J002/05; F24J 2/10 20060101 F24J002/10; F24J 2/24 20060101
F24J002/24 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 17, 2004 |
AU |
2004900786 |
Feb 17, 2004 |
AU |
2004900787 |
Feb 17, 2004 |
AU |
2004900788 |
Claims
1. A linear Fresnel collector comprising a stationary collector
structure that is arranged to be located at a level above a field
of reflectors and to receive solar radiation reflected from
reflectors within the field, the collector structure comprising an
inverted trough having an aperture and an enclosing window and,
located within the trough, a plurality of longitudinally extending
absorber tubes that are arranged to carry a heat exchange fluid,
each absorber tube having a diameter that is small relative to the
aperture of the trough through which the tubes are illuminated, and
the absorber tubes being supported side-by-side in coplanar fashion
within the trough with some of said absorber tubes being located
along margins of the inverted trough, wherein the collector
structure is configured such that a portion of heat exchange fluid
within the collector structure and having a lower temperature than
other of the heat exchange fluid within the collector structure is
directed through said tubes located along the margins of the
inverted trough.
2. The collector as claimed in claim 1 wherein the diameter of each
absorber tube to the dimension of the trough aperture has a ratio
in the range of 0.01:1.00 to 0.10:1.00.
3. The collector as claimed in claim 1 wherein the diameter of each
absorber tube to the dimension of the trough aperture has a ratio
of about 0.03:1.00.
4. The collector as claimed in claim 1 wherein there are about ten
to thirty of the absorber tubes supported side-by-side within the
trough.
5. The collector as claimed in claim 1 wherein there are sixteen of
the absorber tubes supported side-by-side within the trough.
6. The collector as claimed in claim 1 wherein each of the absorber
tubes is constituted by a metal tube.
7. The collector as claimed in claim 1 wherein each of the absorber
tubes is coated over at least a portion of its surface with a solar
absorptive material coating.
8. The collector as claimed in claim 1 and incorporating a
longitudinally extending roof, and wherein the inverted trough is
located in spaced relationship below the roof
9. The collector as claimed in claim 8 wherein an insulating
material is located in the space between the inverted trough and
the roof
10. The collector as claimed in claim 1 wherein a window that is
substantially transparent to solar radiation extends across the
aperture of the inverted trough and thereby closes the trough to
create a heat confining cavity within the trough.
11. The collector as claimed in claim 10 wherein the window is
formed from a flexible plastics sheet material that is connected to
marginal side wall portions of the trough.
12. The collector as claimed in claim 11 wherein means are provided
to pressurise the cavity and thereby inflate the window in a
direction away from the absorber tubes.
13. The collector as claimed in claim 10 wherein the inverted
trough has flared sidewalls.
14. The collector as claimed in claim 1 and including flow control
for the heat exchange fluid in the plurality of absorber tubes.
15. The collector as claimed in claim 1 and including flow control
to selectively vary the channeling of the heat exchange fluid into
and through the plurality of absorber tubes whereby the absorption
aperture of the collector structure is, in use, effectively
varied.
16. The collector as claimed in claim 1 and comprising a plurality
of the collector structures, the collector structures being
connected together co-linearly to form a row of the structures.
17. The collector as claimed in claim 16 wherein the row has a
length and each of the absorber tubes extends along substantially
the full length of the row.
18. The collector as claimed in claim 1, wherein the trough is
surmounted by a corrugated roof.
19. The collector as claimed in claim 1, wherein the trough is
surmounted by a roof that is carried by arched structural
members.
20. The collector as claimed in claim 2 wherein the aperture is
about 1100 mm.
21. The collector as claimed in claim 3 wherein the aperture is
about 1100 mm.
22. The collector as claimed in claim 4 wherein the aperture is
about 1100 mm.
23. The collector as claimed in claim 5 wherein the aperture is
about 1100 mm.
24. The collector as claimed in claim 2 wherein a plurality of said
tubes each has an outside diameter of about 33 mm.
25. The collector as claimed in claim 3 wherein a plurality of said
tubes each has an outside diameter of about 33 mm.
26. The collector as claimed in claim 4 wherein a plurality of said
tubes each has an outside diameter of about 33 mm.
27. The collector as claimed in claim 5 wherein a plurality of said
tubes each has an outside diameter of about 33 mm.
28. The collector as claimed in claim 20 wherein a plurality of
said tubes each has an outside diameter of about 33 mm.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Continuation of U.S. patent
application Ser. No. 13/182,653, filed Jul. 14, 2011, and entitled
MULTI-TUBE SOLAR COLLECTOR STRUCTURE, which is a Continuation of
U.S. patent application Ser. No. 10/597,966, filed Aug. 14, 2006,
and entitled MULTI-TUBE SOLAR COLLECTOR STRUCTURE, and now U.S.
Pat. No. 7,992,553, which is an application submitted under 35
U.S.C. 371 as a U.S. National Phase application of International
patent application Number PCT/AU2005/000208, filed Feb. 17, 2005,
which claims priority to Australian Application Serial Number
2004900787, filed Feb. 17, 2004, Australian Application Serial
Number 200400788, filed Feb. 17, 2004, and Australian Application
Serial Number 200400786, filed Feb. 17, 2004, the contents of which
are each hereby incorporated by reference as if recited in full
herein for all purposes.
FIELD OF THE INVENTION
[0002] This invention relates to a solar collector structure that
employs a plurality of absorber tubes that are arranged to be
illuminated by solar radiation from a reflector field and to
transfer absorbed energy to a heat exchange fluid that is, in use
of the structure, carried by the tubes. The invention has been
developed in the context of a so-called compact linear Fresnel
reflector (CLFR) system and is hereinafter described in relation to
such a system. However, it will be understood that the invention
may have broader application.
BACKGROUND OF THE INVENTION
[0003] Prior art solar collector structures of the type with which
the present invention might be compared may be categorized
generally as falling within two groups; a first group that employs
effectively a single absorber tube that extends along the focal
line of a non-inverted trough-type reflector and a second group
that employs a single absorber tube that extends along the focal
line of an inverted trough-type reflector. Collector systems of the
first group suffer the disadvantages that the absorber tube
collects incident solar energy from one only reflector element and
requires complex mounting and fluid coupling arrangements.
Collector systems of the second group largely avoid the
disadvantages of the first group but suffer the disadvantage of
losses occasioned by the need for multiple reflections, firstly
from ground-mounted reflectors and then from the inverted trough
reflectors. Moreover, collector systems of the second group (if not
both groups) suffer a relatively high emissivity-to-absorptance
ratio as a consequence, in part, of the surface area-to-aperture
ratio attributable to the relatively large diameter tube required
of a single-tube collector system. Furthermore, as a secondary
issue, collector systems of both the first and second groups suffer
loss of operating efficiency due to movement of unconfined heated
air from the interior of the trough-like reflectors. Still further,
as a tertiary issue, to the extent that the collector systems of
the first and second groups employ a single absorber tube, those
collector systems are not capable of providing for a variable
absorption aperture.
SUMMARY OF THE INVENTION
[0004] The present invention provides a collector structure that is
arranged to be located at a level above a field of reflectors and
to receive solar radiation reflected from reflectors within the
field. The collector structure comprises an inverted trough and,
located within the trough, a plurality of longitudinally extending
absorber tubes that, in use, are arranged to carry a heat exchange
fluid. The absorber tubes are supported side-by-side within the
trough and each absorber tube has a diameter that is small relative
to the aperture of the trough.
[0005] The ratio of each absorber tube diameter to the trough
aperture dimension may, for example, be in the range of 0.01:1.00
to 0.10:1.00 and typically may be of the order of 0.03:1:00. With
this arrangement the plurality of tubes will, in the limit,
effectively simulate a flat plate absorber.
[0006] The expressions "aperture of the trough" and "trough
aperture" are both intended to be understood as defining,
effectively, the opening of the trough through which incident
radiation may pass to impinge on the absorber tubes.
[0007] A plurality of the collector structures as above defined may
be connected together co-linearly to form a row of the structures
and, in such case, each of the absorber tubes will extend along the
full row, either as a single length of tubing or as conjoined
lengths of tubing.
OPTIONAL FEATURES OF THE INVENTION
[0008] The absorber tubes may be constituted by metal tubes and
each tube may, if required, be coated over at least a portion of
its surface with a solar absorptive coating. In an alternative
arrangement, each absorber tube may comprise a glass or metal
tubular component that is coated with a solar selective surface
coating and a surrounding glass tubular component, with the space
between the two tubular components being evacuated.
[0009] The inverted trough may (but need not necessarily) be
located in spaced relationship below a longitudinally extending
roof and, in such case, an insulating material may be located in
the space between the trough and the roof.
[0010] A window that is substantially transparent to solar
radiation may be employed to close (the aperture of) the trough
and, in so doing, create a heat confining cavity within the trough.
The window may be formed from a rigid material such as glass or it
may, for example, be formed from a flexible plastics sheet material
that is connected to marginal side wall portions of the trough. In
this latter case the cavity may be pressurized to an extent
sufficient to inflate the window in a direction away from the
absorber tubes.
[0011] The heat exchange fluid may in use of the collector
structure be controlled to flow in parallel, unidirectional streams
through the plurality of absorber tubes. Alternatively, means may
be provided for selectively varying the channeling of the heat
exchange fluid into and through the plurality of absorber tubes
whereby the absorption aperture of the collector structure may, in
use, effectively be varied.
[0012] The invention will be more fully understood from the
following description of an exemplary embodiment of the solar
collector structure.
[0013] The description is provided, by way of example, with
reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] In the drawings
[0015] FIG. 1 shows a largely diagrammatic representation of a CLFR
system that comprises a field of ground mounted reflectors that are
arrayed in rows and collector systems that are constituted by rows
of aligned collector structures;
[0016] FIG. 2 illustrates schematically the reflection of solar
radiation from four reflectors to two collector systems within the
CLFR system;
[0017] FIG. 3 shows an aerial view of a portion of a field of
reflectors and a single collector structure positioned adjacent one
edge of the field;
[0018] FIG. 4 shows a perspective view (from above) of a terminal
end of a collector structure of the type shown in FIG. 3;
[0019] FIG. 5 shows a sectional end view of the collector structure
of FIG. 4;
[0020] FIG. 6 shows a portion of the collector structure which is
encircled by circle A in FIG. 5;
[0021] FIG. 7 shows a portion of the collector structure which is
encircled by circle B in FIG. 5;
[0022] FIG. 8 shows diagrammatically a fluid flow control
arrangement for a collector system that comprises a row of four
interconnected collector structures; and
[0023] FIGS. 9A, 9B and 9C show alternative fluid channeling
arrangements that provide for different effective absorption
apertures.
DETAILED DESCRIPTION OF THE INVENTION
[0024] As shown in FIGS. 1 to 3, the CLFR system comprises a field
of ground mounted reflectors 10 that are arrayed in rows 11 and
further comprises parallel collector systems 12, each of which is
constituted by aligned collector structures 13. A complete CLFR
system might occupy a ground area within the range 5.times.10.sup.1
m.sup.2 to 25.times.10.sup.6 m.sup.2 and the system as illustrated
in FIG. 1 may be considered as a portion only of a larger CLFR
system.
[0025] The reflectors 10 may be of the type described in co-pending
International patent applications numbered PCT/AU2004/000883 and
PCT/AU2004/000884, filed 1 Jul. 2004 by the present Applicant, and
the disclosures of these patent applications are incorporated
herein by reference.
[0026] The reflectors 10 are driven collectively or regionally, as
rows or individually, to track movement of the sun (relative to the
earth) and they are orientated to reflect incident radiation to
respective ones of the collector systems 12, as shown schematically
and by way of example in FIG. 2. Also, some or all of the
reflectors 10 may be driven so as to reorientate, when required, to
change the direction of reflected radiation from one collector
system 12 to another.
[0027] In the system as illustrated in FIG. 1, and as may typically
be the case, each collector system 12 receives reflected radiation
from twelve rows of reflectors 10. Thus, each collector system 12
receives reflected radiation from six rows at one side of the
collector system and from six rows at the other side, although (as
indicated in FIG. 2) the reflecting rows that are associated with
any one receiving collector system need not necessarily be located
immediately adjacent that receiving collector system.
[0028] Each row 11 of reflectors 10 and, hence, each collector
system 12 might typically have an overall length of 300 metres, and
the parallel collector systems 12 might typically be spaced apart
by 30 to 35 metres. The collector systems 12 are supported at a
height of approximately 11 metres by stanchions 14 which are stayed
by ground-anchored guy wires 15, although other similar support
arrangements might be employed.
[0029] As indicated previously, each of the collector systems 12
comprises a plurality of collector structures 13 that are connected
together co-linearly to form a row of the structures. Each of the
collector structures might typically have a length of the order of
12 metres and an overall width of the order of 1.4 metres.
[0030] Each collector structure 13 comprises an inverted trough 16
which might typically be formed from stainless steel sheeting and
which, as best seen in FIG. 5, has a longitudinally extending
channel portion 17 and flared side walls 18 that, at their margins,
define an aperture of the inverted trough. The trough 16 is
supported and provided with structural integrity by side rails 19
and transverse bridging members 20, and the trough is surmounted by
a corrugated steel roof 21 that is carried by arched structural
members 22.
[0031] The void between the trough 16 and the roof 21 is filled
with a thermal insulating material 23, typically a glass wool
material, and desirably with an insulating material that is clad
with a reflective metal layer. The function of the insulating
material and the reflective metal layer is to inhibit upward
conduction and radiation of heat from within the trough.
[0032] A longitudinally extending window 24 is provided to
interconnect the side walls 18 of the trough. The window is formed
from a sheet of material that is substantially transparent to solar
radiation and it functions to define a closed (heat retaining)
longitudinally extending cavity 25 within the trough.
[0033] The window 24 may be formed from glass but it desirably is
formed from a transparent heat resistant plastics material having a
thickness of the order of 60.times.10.sup.-6 m. As shown in FIG. 7,
side margins of the window may be welded to a wire or other heat
resistant rope core 26 and the window may be held in position by
slideably locating the cored side margins in fluted side connectors
27.
[0034] FIG. 4 shows a collector structure 13 that is intended to be
located at a terminal end of a row 12 of the collector structures,
and it is provided with an end wall 28 to which is mounted a motor
driven blower 29. The blower is provided in use to maintain a
positive air pressure within the cavity 25 (relative to the ambient
atmospheric pressure) and so to inflate the window in a direction
away from absorber tubes 30 within the inverted trough 16.
[0035] In the collector structure as illustrated, sixteen
longitudinally extending stainless steel absorber tubes 30 are
provided for carrying heat exchange fluid (typically water or,
following heat absorption, water-steam or steam). However, the
actual number of absorber tubes may be varied to suit specific
system requirements, provided that each absorber tube has a
diameter that is small relative to the dimension of the trough
aperture between the side walls 19 of the trough, and the collector
system might typically have between ten and thirty absorber tubes
30 supported side-by-side within the trough.
[0036] The actual ratio of the absorber tube diameter to the trough
aperture dimension may be varied to meet system requirements but,
in order to indicate an order of magnitude of the ratio, it might
typically be within the range 0.01:1.00 to 0.10:1.00. Each absorber
tube 30 might have an outside diameter of 33 mm. and, with an
aperture dimension of, for example, 1100 mm, the ratio of the
absorber tube diameter to the aperture dimension will be
0.03:1.00.
[0037] As indicated previously, with the above described
arrangement the plurality of absorber tubes 30 will, in the limit,
effectively simulate a flat plate absorber, as compared with a
single-tube collector in a concentrating trough. This provides for
increased operating efficiency, in terms of a reduced level of heat
emission from the upper, non-illuminated circumferential portion of
the absorber tubes. Moreover, by positioning the absorber tubes in
the inverted trough in the manner described, the underside portion
only of each of the absorber tubes is illuminated with incident
radiation, this providing for efficient heat absorption in absorber
tubes that carry steam above water.
[0038] As illustrated in FIG. 6, the absorber tubes 30 are freely
supported by a series of parallel support tubes 31 which extend
orthogonally between side walls 32 of the channel portion 17 of the
inverted trough, and the support tubes 31 are carried for
rotational movement by spigots 33. This arrangement accommodates
expansion of the absorber tubes and relative expansion of the
individual tubes. Disk-shaped spacers 34 are carried by the support
tubes 31 and serve to maintain the absorber tubes 30 in spaced
relationship.
[0039] Each of the absorber tubes 30 is coated, along its length
and around a (lower) portion of its circumference that is exposed
to incident solar radiation, with a solar absorptive coating. The
coating may comprise a solar selective surface coating that remains
stable under high temperature conditions in ambient air or it may
comprise a black paint that is stable in air under high-temperature
conditions.
[0040] FIG. 8 of the drawings shows diagrammatically a flow control
arrangement for controlling flow of heat exchange fluid into and
through four in-line collector structures 13 of a collector system.
As illustrated, each of the fluid lines 30A, B, C and D is
representative of four of the absorber tubes 30 as shown in FIG.
5.
[0041] Under the controlled condition illustrated in FIG. 8,
in-flowing heat exchange fluid is first directed along forward line
30A, along return line 30B, along forward line 30C and finally
along and from return line 30D. This results in fluid at a lower
temperature being directed through tubes that are located along the
margins of the inverted trough and a consequential emission
reduction when radiation is concentrated over the central region of
the inverted trough. An electrically actuated control device 35 is
provided to enable selective control over the channeling of the
heat exchange fluid.
[0042] Alternative fluid flow conditions may be established to meet
load demands and/or prevailing ambient conditions, and provision
may effectively be made for a variable aperture collector structure
by closing selected ones of the absorber tubes. Thus, variation of
the effective absorption aperture of each collector structure and,
hence, of a complete collector system may be achieved by
controlling the channeling of the heat exchange fluid in the
alternative manners shown in FIGS. 9A to 9C.
[0043] It is to be understood that the embodiment of the invention
as described with reference to the drawings is presented solely as
an example of one possible form of the invention. Thus, variations
and modifications may be made in the embodiment of the invention as
described without departing from the spirit and scope of the
invention as defined in the appended claims.
* * * * *