U.S. patent application number 14/691002 was filed with the patent office on 2015-10-22 for method to construct and support tube module assemblies for solid particle solar receiver.
The applicant listed for this patent is Babcock & Wilcox Power Generation Group, Inc.. Invention is credited to David T. Wasyluk.
Application Number | 20150300692 14/691002 |
Document ID | / |
Family ID | 54321725 |
Filed Date | 2015-10-22 |
United States Patent
Application |
20150300692 |
Kind Code |
A1 |
Wasyluk; David T. |
October 22, 2015 |
METHOD TO CONSTRUCT AND SUPPORT TUBE MODULE ASSEMBLIES FOR SOLID
PARTICLE SOLAR RECEIVER
Abstract
A solar receiver module includes a front tube sheet with light
apertures, a back plate cooperating with the front tube sheet to
define a sealed gap, and light channeling tubes optically coupled
with the light apertures, extending through the gap and connecting
with the back plate. A flowing heat transfer medium flows in the
gap over exterior surfaces of the light channeling tubes. Slip
joint engagements between light apertures and ends of most or all
of the light channeling tubes accommodate thermal expansion. Each
slip joint may be defined by an inner or outer perimeter of the
light aperture receiving the end of the light channeling tube. A
sub-set of the light channeling tubes may be welded to light
apertures. A module support post may be secured at a center of the
back plate and extend away oppositely from the front tube sheet. A
welded or stamped tube sheet provides a seal between tubes at the
front face of the tube modules. Thermal expansion provides a seal
between adjoining modules at the front face and seal strips provide
a seal at the back face.
Inventors: |
Wasyluk; David T.;
(Mogadore, OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Babcock & Wilcox Power Generation Group, Inc. |
Barberton |
OH |
US |
|
|
Family ID: |
54321725 |
Appl. No.: |
14/691002 |
Filed: |
April 20, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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61981974 |
Apr 21, 2014 |
|
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Current U.S.
Class: |
126/714 ;
126/663; 126/674; 29/402.03; 29/890.033 |
Current CPC
Class: |
F24S 2023/88 20180501;
F24S 80/20 20180501; Y02E 10/40 20130101; F24S 20/20 20180501; F28D
13/00 20130101; Y02E 10/41 20130101; F24S 40/80 20180501 |
International
Class: |
F24J 2/24 20060101
F24J002/24; F24J 2/46 20060101 F24J002/46; F24J 2/26 20060101
F24J002/26 |
Goverment Interests
GOVERNMENT RIGHTS
[0002] The United States Government may have certain rights to this
invention pursuant to contract number DE-AC36-08GO28308 between the
United States Department of Energy and Alliance For Sustainable
Energy, LLC. This invention was developed under subcontract
ZGJ-3-23315-01 between Alliance For Sustainable Energy, LLC. and
Babcock & Wilcox Power Generation Group, Inc. under contract
number DE-AC36-08GO28308.
Claims
1. A solar receiver module comprising: a front tube sheet including
light apertures; a back plate cooperating with the front tube sheet
to define a sealed gap; and light channeling tubes having first
ends optically coupled with the light apertures and extending
through the gap and having second ends connected with the back
plate.
2. The solar receiver module of claim 1 further comprising a
flowing or fluidized heat transfer medium disposed in the gap over
exterior surfaces of the light channeling tubes.
3. The solar receiver module of claim 2 wherein the flowing or
fluidized heat transfer medium comprises a flowing particulate
medium such as silica sand or calcined flint clay.
4. The solar receiver module of claim 1 further comprising slip
joint engagements between light apertures of the front tube sheet
and first ends of most or all of the light channeling tubes.
5. The solar receiver module of claim 4 wherein each slip joint is
defined by an inner or outer perimeter of the light aperture
receiving the first end of the light channeling tube.
6. The solar receiver module of claim 4 wherein each slip joint is
defined by the inner or outer perimeter of a necked down portion of
the light aperture receiving the first end of the light channeling
tube.
7. The solar receiver module of claim 4 comprising slip joint
engagements between light apertures of the front tube sheet and
first ends of all but a sub-set of the light channeling tubes, the
solar receiver further comprising: welds between light apertures
and the first ends of the sub-set of the light channeling
tubes.
8. The solar receiver module of claim 7 wherein the sub-set of the
light channeling tubes consists of one or more light channeling
tubes.
9. The solar receiver module of claim 4 wherein there are slip
joint engagements between light apertures of the front tube sheet
and first ends of all of the light channeling tubes and the solar
receiver module further comprises: tie rods welded between the back
plate and the front tube sheet.
10. The solar receiver module of claim 4 wherein the light
channeling tubes are cantilever-supported by the second ends
connected with the back plate.
11. The solar receiver module of claim 4 wherein the second ends of
the light channeling tubes are connected with the back plate by
threaded studs extending from the second ends of the light
channeling tubes.
12. The solar receiver module of claim 1 wherein the front tube
sheet comprises said light apertures formed from bent sheet metal
and having outer perimeters that are welded together.
13. The solar receiver module of claim 1 wherein the front tube
sheet comprises single-piece sheet metal having said light
apertures punched into the single-piece sheet metal.
14. The solar receiver module of claim 1 wherein the light
apertures have triangular, circular, square or diamond, regular or
flared hexagonal cross-sections.
15. The solar receiver module of claim 1 wherein the back plate
comprises a metal plate.
16. The solar receiver module of claim 1 wherein the light
channeling tubes comprise drawn tubes, extruded tubes, or bent
sheet metal welded tubes.
17. The solar receiver module of claim 1 further comprising: a
module support post extending away from the back plate on the
opposite side of the back plate from the front tube sheet; wherein
the module support post is secured at a center of the back
plate.
18. A solar receiver comprising a plurality of solar receiver
modules as set forth in claim 1 arranged with adjoining front tube
sheets and adjoining back plates to define the solar receiver with
an outward facing surface defined by the adjoining front tube
sheets and an inward facing surface defined by the adjoining back
plates and further having an annular gap between the outward facing
surface and the inward facing surface.
19. The solar receiver of claim 18 wherein the solar receiver does
not include sealing material interposed between the adjoining front
tube sheets.
20. The solar receiver of claim 18 wherein the front tube sheets
have jagged edges defined by peripheral light apertures with flat
sides, and the jagged edges with flat sides of adjoining front tube
sheets mesh together.
21. The solar receiver of claim 18 further comprising: sealing
strips disposed at interfaces between adjoining back plates.
22. The solar receiver of claim 21 wherein each sealing strip is
attached to only one of any two adjoining solar receiver
modules.
23. A solar power generation system comprising: a solar receiver as
set forth in claim 18; a flowing or fluidized heat transfer medium
disposed in the annular gap over exterior surfaces of the light
channeling tubes of the solar receiver modules; and a fluidized-bed
boiler or heat exchanger arranged to receive heated heat transfer
medium from the solar receiver.
24. A method of operating a solar receiver as set forth in claim
18, the method comprising: disposing a flowing or fluidized heat
transfer medium in the annular gap of the solar receiver over
exterior surfaces of the light channeling tubes of the solar
receiver modules; and operating heliostats to concentrate solar
energy onto the solar receiver wherein the concentrated solar
energy is effective to induce thermal expansion of the solar
receiver modules.
25. The method of claim 24 wherein the solar receiver modules have
slip joint engagements between light apertures of the front tube
sheet and first ends of most or all of the light channeling tubes
that accommodates thermal expansion of the solar receiver
modules.
26. The method of claim 24 wherein each solar receiver module
further comprises a module support post secured at a center of the
back plate and extending inward from the inward facing surface
defined by the adjoining back plates whereby thermal expansion of
the solar receiver modules increases sealing force between
adjoining front tube sheets.
27. A method of performing maintenance on the solar receiver of
claim 18, the method comprising: disconnecting a solar receiver
module support post from the back plate or a support column; and
pulling the disconnected solar receiver module out of the solar
receiver.
28. A method of performing maintenance on the solar receiver module
of claim 1, the method comprising: removing a connection between
the light channeling tubes and the back plate of the solar receiver
module; removing the front tube sheet of the solar receiver module
by operations including disengaging slip joint engagements between
light apertures of the front tube sheet and first ends of light
channeling tubes wherein after removal of the front tube sheet the
light channeling tubes remain cantilever-supported by the
connections of their second ends with the back plate; and removing
a selected light channeling tube by disconnecting the second end of
the selected light channeling tube from the back plate.
29. The method of claim 28 wherein removing the front tube sheet of
the solar receiver module further comprises: breaking welds between
axial support light channeling tubes and the front tube sheet.
30. The method of claim 28 wherein removing the front tube sheet of
the solar receiver module comprises: disconnecting tie rods
connecting the back plate and the front tube sheet.
Description
RELATED APPLICATION DATA
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/981,974 filed Apr. 21, 2014 and titled "Method
to Construct and Support Tube Module Assemblies for Solid Particle
Solar Receiver". U.S. Provisional Application No. 61/981,974 filed
Apr. 21, 2014 is incorporated herein by reference in its
entirety.
BACKGROUND
[0003] The following pertains to the solar power generation arts
and related arts. In a known solar concentration design, a field of
heliostats concentrates solar power onto a (typically
tower-mounted) solar receiver. A flowing heat transfer medium flows
through the solar receiver. This flowing heat transfer medium
absorbs energy from the concentrated light and is thus heated. The
hot flowing heat transfer medium may be variously used, for example
being fed into a fluidized-bed boiler to generate steam for driving
an electrical generator turbine.
[0004] Some such solar concentrators are described, by way of
non-limiting illustrative example, in Ma, U.S. Pub. No.
2013/0257056 A1 published Oct. 3, 2013 which is incorporated herein
by reference in its entirety, and in Ma et al., U.S. Pub. No.
2013/0255667 A1 published Oct. 3, 2013 which is incorporated herein
by reference in its entirety, and in Maryamchik et al.,
"Concentrated Solar Power Solids-Based System", U.S. Ser. No.
14/250,160 filed Apr. 10, 2014 and published as U.S. Pub. No.
2014/0311479 A1 which is incorporated herein by reference in its
entirety.
BRIEF SUMMARY
[0005] In some aspects disclosed herein, a solar receiver module
comprises a front tube sheet including light apertures, a back
plate cooperating with the front tube sheet to define a sealed gap,
and light channeling tubes having first ends optically coupled with
the light apertures and extending through the gap and having second
ends connected with the back plate. A flowing or fluidized heat
transfer medium, for example a flowing particulate medium such as
silica sand or calcined flint clay, but not limited thereto, is
suitably disposed in the gap over exterior surfaces of the light
channeling tubes. In some embodiments the solar receiver module
further comprises slip joint engagements between light apertures of
the front tube sheet and first ends of most or all of the light
channeling tubes. Each slip joint may be defined by an inner
perimeter of the light aperture receiving the first end of the
light channeling tube. In some such embodiments, each slip joint is
defined by the inner perimeter of a necked down portion of the
light aperture receiving the first end of the light channeling
tube. In some embodiments slip joint engagements are provided
between light apertures of the front tube sheet and first ends of
all but a sub-set of the light channeling tubes, and welds are
provided between light apertures and the first ends of the sub-set
of the light channeling tubes. In some such embodiments, the
sub-set of the light channeling tubes are immediately neighboring
light channeling tubes engaging light apertures that are centrally
located on the front tube sheet. In some embodiments the second
ends of the light channeling tubes are connected with the back
plate by threaded studs extending from the second ends of the light
channeling tubes. In some embodiments a module support post extends
away from the back plate on the opposite side of the back plate
from the front tube sheet, and is secured at a center of the back
plate.
[0006] In some aspects disclosed herein, a solar receiver comprises
a plurality of solar receiver modules as set forth in the
immediately preceding paragraph arranged with adjoining front tube
sheets and adjoining back plates to define the solar receiver with
an outward facing surface defined by the adjoining front tube
sheets and an inward facing surface defined by the adjoining back
plates and further having an annular gap between the outward facing
surface and the inward facing surface. In some solar receiver
embodiments the solar receiver does not include sealing material
interposed between the adjoining front tube sheets. In some solar
receiver embodiments, the front tube sheets have jagged edges
defined by peripheral light apertures and the jagged edges of
adjoining front tube sheets mesh together.
[0007] In further aspects disclosed herein, a solar power
generation system includes a solar receiver as set forth in the
immediately preceding paragraph, a flowing or fluidized heat
transfer medium disposed in the annular gap over exterior surfaces
of the light channeling tubes of the solar receiver modules, and a
fluidized-bed heat exchanger arranged to receive heated heat
transfer medium from the solar receiver. In still further aspects
disclosed herein, a method of operating a solar receiver as set
forth in the immediately preceding paragraph is disclosed. The
method comprises disposing a flowing or fluidized heat transfer
medium in the annular gap of the solar receiver over exterior
surfaces of the light channeling tubes of the solar receiver
modules, and operating heliostats to concentrate solar energy onto
the solar receiver wherein the concentrated solar energy is
effective to induce thermal expansion of the solar receiver
modules. In such a method, slip joint engagements between light
apertures of the front tube sheet and first ends of most or all of
the light channeling tubes suitably accommodates thermal expansion
of the solar receiver modules. Additionally, the central rear
support of the tube modules allows the modules to thermally expand
into one another creating sealing at the front face between
adjoining tube modules.
[0008] These and other non-limiting aspects and/or objects of the
disclosure are more particularly described below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The invention may take form in various components and
arrangements of components, and in various process operations and
arrangements of process operations. The drawings are only for
purposes of illustrating preferred embodiments and are not to be
construed as limiting the invention. This disclosure includes the
following drawings.
[0010] FIG. 1 diagrammatically shows an illustrative solar
concentrator system, with enlarged detail drawings of the solar
receiver shown in insets identified by block arrows.
[0011] FIG. 2 diagrammatically shows a side view of one solar
receiver module of the solar receiver of FIG. 1, with the flow path
of the flowing heat transfer medium indicated diagrammatically by a
shaded block arrow.
[0012] FIGS. 3-6 diagrammatically illustrate aspects of a suitable
assembly of a solar receiver module of the solar receiver of FIG.
1.
[0013] FIG. 7 shows an enlarged view of one light channeling tube
of the solar receiver of FIG. 1.
[0014] FIG. 8 shows a perspective view of the front tube sheet of
the solar receiver of FIG. 1, with the inner perimeter of the
necked-down portion of an aperture shown in an inset.
[0015] FIG. 9 diagrammatically shows thermal expansion experienced
by a solar receiver module as it is brought into operation.
[0016] FIGS. 10-13 diagrammatically illustrate aspects of a
suitable assembly of adjacent solar receiver modules to construct
the solar receiver of FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0017] A more complete understanding of the processes and
apparatuses disclosed herein can be obtained by reference to the
accompanying drawings. These figures are merely schematic
representations based on convenience and the ease of demonstrating
the existing art and/or the present development, and are,
therefore, not intended to indicate relative size and dimensions of
the assemblies or components thereof.
[0018] Although specific terms are used in the following
description for the sake of clarity, these terms are intended to
refer only to the particular structure of the embodiments selected
for illustration in the drawings, and are not intended to define or
limit the scope of the disclosure. In the drawings and the
following description below, it is to be understood that like
numeric designations refer to components of like function.
[0019] The singular forms "a," "an," and "the" include plural
referents unless the context clearly dictates otherwise.
[0020] A value modified by a term or terms, such as "about" and
"substantially," may not be limited to the precise value
specified.
[0021] It should be noted that many of the terms used herein are
relative terms. For example, the terms "interior", "exterior",
"inward", and "outward" are relative to a center, and should not be
construed as requiring a particular orientation or location of the
structure.
[0022] The terms "horizontal" and "vertical" are used to indicate
direction relative to an absolute reference, i.e. ground level.
However, these terms should not be construed to require structures
to be absolutely parallel or absolutely perpendicular to each
other. For example, a first vertical structure and a second
vertical structure are not necessarily parallel to each other.
[0023] The term "plane" is used herein to refer generally to a
common level, and should be construed as referring to a volume, not
as a flat surface.
[0024] To the extent that explanations of certain terminology or
principles of the solar receiver, boiler and/or steam generator
arts may be necessary to understand the present disclosure, the
reader is referred to Steam/its generation and use, 40th Edition,
Stultz and Kitto, Eds., Copyright 1992, The Babcock & Wilcox
Company, and to Steamlits generation and use, 41st Edition, Kitto
and Stultz, Eds., Copyright 2005, The Babcock & Wilcox Company,
the texts of which are hereby incorporated by reference as though
fully set forth herein.
[0025] With reference to FIG. 1, a solar concentrator power
generation plant includes a field of heliostats 10 disposed over an
area 12 occupied by the plant. The heliostats 10 are
diagrammatically represented in FIG. 1, and typically include
suitable components (not shown) such as beam-forming optics
typically comprising mirrors or other reflectors and beam-steering
apparatus such as multi-axis motorized system that cooperate to
capture solar radiation impinging upon the heliostat and form the
light into energy beams 14 that are directed to a solar receiver
16, with the multi-axis motorized systems of the heliostats 10
operating to track the (apparent) movement of the sun across the
sky to keep the light beams 14 directed to the solar receiver 16
over the course of the day. (As used herein, the terms such as
"light", "solar radiation", and "solar energy" are used
interchangeably, and encompass all energy from the sun that is
captured and concentrated by the heliostats 10 and/or other
referenced system components whether such solar energy is in the
form of visible light, infrared light, or ultraviolet light. In the
case of components that are heated by solar radiation, the term
"energy" or "solar energy" encompasses energy in the form of heat
so generated.) In the illustrated configuration, the solar receiver
16 is mounted in an elevated position on a tower 18 so as to
provide an unimpeded direct line-of-sight between each heliostat 10
in the field and the solar receiver 16. However, other physical
arrangements are contemplated--for example, a tower could include a
top-mounted mirror system that directs light downward to a solar
receiver located at (or even below) ground level (variants not
illustrated).
[0026] With continuing reference to FIG. 1 including its insets,
and with further reference to FIG. 2, the solar receiver 16
comprises an assembly of solar receiver tube modules 20, one of
which is shown in side view in FIG. 2, where it is seen that the
solar receiver tube module 20 includes a front tube sheet 22
defined by adjoining light apertures 24, light channeling tubes 26
connected with respective apertures 24 and extending into the
receiver tube module 20, and a back plate 28 to which "rear" ends
of the light channeling tubes 26 are connected. By way of
non-limiting illustration, the apertures 24 and light channeling
tubes 26 may comprise bent sheet metal (e.g. sheet steel)
components, drawn tubes, or so forth, and the back plate 28 may
comprise a metal plate (e.g. steel plate). For example, the light
channeling tubes can be manufactured by a drawing process or by
stamping two halves and welding with two longitudinal seam welds.
As used herein, the following orientation terms are used: the
"front" side of the solar receiver module 20 is faced by the front
tube sheet 22 where light enters, while the "back" side of the
solar receiver module 20 is the side faced by the back plate 28.
The light channeling tubes 26 are in an approximately horizontal
orientation, although some tilting of the light channeling tubes 26
is contemplated, for example a downward tilt of a few degrees to a
few tens of degrees to up to about 45.degree. is contemplated to
better align with the upward angle of light beams 14 coming from
the heliostats 10. A module support post 30 (for example, a metal
pipe or rod) connects with the back plate 28 and extends rearward.
Optionally, insulation and/or lagging 32 is provided on the back
side of the module 20, for example contacting the back plate 28, to
reduce heat loss from the back side of the module 20.
[0027] With reference back to the insets of FIG. 1, solar receiver
modules 20 are assembled to form the solar receiver 16 as a hollow
cylindrical structure having an outward-facing (faceted)
cylindrical surface 42 defined by adjoining planar front tube
sheets 22 of the adjoining solar receiver modules 20, and an
inward-facing (faceted) cylindrical surface 48 defined by adjoining
planar back plates 28 of the adjoining solar receiver modules 20.
The two cylindrical surfaces 42, 48 define an annular gap 50, which
gap 50 is also indicated for the single solar receiver module 20
depicted in FIG. 2. It will be appreciated from FIG. 2 that the
light channeling tubes 26 of the solar receiver modules extend
through the annular gap 50 between the two cylindrical surfaces 42,
48, and that the light beams 14 suitably input light into the light
channeling tubes 26 through the apertures 24 in the outward-facing
cylindrical surface 42. The solar receiver modules 20 are suitably
supported by their respective module support posts 30 on a truss or
other support structure 52 secured to the tower 18.
[0028] With continuing reference to FIGS. 1 and 2, a flowing heat
transfer medium 56 (diagrammatically indicated in FIG. 2 by a
downward shaded block arrow) flows generally downward through the
gap 50 under force of gravity. Additionally or alternatively, the
flowing heat transfer medium can be fluidized with compressed air,
which may improve contact between the heat transfer medium and tube
surfaces to enhance heat transfer. The flowing heat transfer medium
56 thus flows over the exterior surfaces of the light channeling
tubes 26. These tubes 26 are preferably constructed so as to absorb
most of the channeled light, for example by including suitable
absorbing coatings on their inside surfaces, optional faceting to
cause light to scatter within the light channeling tubes 26 so as
to increase the number of opportunities for absorption, or so
forth. Thus, the solar energy channeled through the light
channeling tubes 26 is transferred into heat absorbed by the tubes
26 and then transferred to the flowing heat transfer medium 56. In
this manner, solar energy contained in the light beams 14 is
converted to heat energy contained in the flowing heat transfer
medium 56, and thus the solar energy is contained as heat in the
flowing heat transfer medium 66 that exits the bottom of the solar
receiver 16.
[0029] With particular reference back to FIG. 1, the heated flowing
heat transfer medium 56 exiting the bottom of the solar receiver 16
may be variously used. In the illustrative example, the heated
flowing heat transfer medium 56 exiting the bottom of the solar
receiver 16 feeds into a storage silo 57 and fluidized-bed boiler
or heat exchanger 58 shown diagrammatically in FIG. 1. The storage
silo 57 provides thermal storage capability, as hot particles are
stored in the silo 57 and may for example be used to provide
thermal energy during cloudy days or at night. Thermal storage via
the silo 57 decouples energy collection and power production
thereby allowing dispatchable, continuous power production. The
fluidized-bed boiler or heat exchanger 58 may, for example,
comprise a bubbling fluidized bed (BFB) or circulating fluidized
bed (CFB) boiler or heat exchanger or so forth, in which the heated
flowing heat transfer medium 56 is dispersed on the fluidized bed
so as to heat water (to form steam) or other working fluids such as
air or supercritical CO.sub.2 to drive a power cycle and
turbine-generator (not shown) to produce electrical power or to
perform other useful work.
[0030] The flowing heat transfer medium 56 is typically a flowing
particulate medium such as silica sand or calcined flint clay (e.g.
with average particle size on the order of a few hundred microns),
but is not limited thereto (for example, it is contemplated to
employ air as the flowing heat transfer medium). In typical
embodiments in which the flowing heat transfer medium 56 is a
flowing particulate medium, it is to be understood that this
flowing particulate medium serves as the hot "fluid" which is
dispersed onto the fluidized bed of the fluidized-bed boiler or
heat exchanger 58. Said another way, the term "fluid" as used
herein in reference to the flowing heat transfer medium 56
encompasses flowing particulate media.
[0031] With reference to FIG. 1, the flowing particulate medium is
suitably returned to the top of the solar receiver 16 by any
suitable elevator structure, for example driven by motors, diesel
engines, or so forth. The top inset of FIG. 1 diagrammatically
shows a suitable return structure 60 for this purpose comprising
receiver bucket elevators and a solids distribution hopper.
[0032] With reference to FIG. 2, the front tube sheet 22 and the
back plate 28 define the gap 50 of the solar receiver module 20
through which the flowing heat transfer medium 56 flows over the
exterior surfaces of the light channeling tubes 26. Thus, the front
tube sheet 22 and the back plate 28 should seal against leakage of
the flowing heat transfer medium 56 outside of the module 20.
Moreover, the connections of the light channeling tubes 26 to the
front tube sheet 22 should also seal against leakage of the flowing
heat transfer medium 56 into either the apertures 24 or the light
channeling tubes 26, since any such leakage will introduce blockage
into the light channeling tubes 26 and/or result in egress of the
flowing heat transfer medium 56 outside of the solar receiver
module 20. Moreover, it will be appreciated that interfaces between
adjoining modules 20 should be similarly sealed. That is, the
interfaces between adjoining front tube sheets 22 of outward-facing
cylindrical surface 42 and the interfaces between adjoining back
plates 28 of the inward-facing cylindrical surface 48 should seal
against leakage of the flowing heat transfer medium 56, so as to
seal against leakage from the annular gap 50 of the solar receiver
16.
[0033] Another consideration is that the solar receiver 16
undergoes substantial thermal cycling during startup, shutdown,
cloud transients and emergency trips. In some contemplated
embodiments intended to operate a fluidized bed boiler or heat
exchanger, the flowing heat transfer medium 66 is to be heated to a
temperature of order 800.degree. C. (1470.degree. F.). Accordingly,
the solar receiver 16 should be robust against thermal cycling over
a range of 0.degree. C.-800.degree. C. in some embodiments, and
over even larger temperature ranges in other contemplated
embodiments.
[0034] With reference to FIGS. 3-8, a suitable approach for
assembling the solar receiver module 20 to address these design
factors (provide a low stress thermal expansion) is described.
FIGS. 3, 5, and 6 illustrate diagrammatic perspective views of
assembly operations. FIG. 4 diagrammatically shows suitable welds
used in the operation depicted in FIG. 3. FIG. 7 shows an enlarged
a diagrammatic side sectional view of one light channeling tube 26
of the assembled solar receiver module. FIG. 8 shows a diagrammatic
perspective view of the front tube sheet 22, with the inner
perimeter of the necked-down portion of an aperture shown in an
inset.
[0035] FIG. 3 shows a diagrammatic perspective view of a first
assembly operation in which a small number (illustrative four)
light channeling tubes 26 are welded to their respective
corresponding apertures 24 of the front tube sheet 22. The welded
light channeling tubes 26 are optionally chosen to be centrally and
adjacently located so as to minimize differential thermal expansion
amongst the welded light channeling tubes 26, although other
selections of the light channeling tubes 26 to be welded are also
suitable. FIG. 4 illustrates a suitable welding approach for the
operation depicted in FIG. 3. In this approach, each tube to be
welded is force-fitted onto or into the mating opening of the front
tube sheet 22, and fillet welds 70 are formed by a suitable welding
process. Some interior surfaces 72 may not be accessible for
welding in the case of immediately neighboring welded tubes as
shown in FIGS. 3 and 4 (although some of these surfaces could be
accessible for welding if welding is performed before inserting
adjacent tubes). In an alternative approach, the welded tubes are
chosen to be spaced apart in the array, so that symmetrical and/or
additional welds can be made on each tube in order to provide
additional support/rigidity of the front tube sheet to resist wind
loads for example.
[0036] FIG. 5 depicts a diagrammatic perspective view of a next
operation in which the remaining light channeling tubes 26 are
inserted into their corresponding apertures 24, but are not welded.
To this end, as seen in FIGS. 7 and 8 the back side of each
aperture 24 of the front tube sheet 22 includes a necked-down
portion 74 that defines an inside perimeter 76 facing the end of
the light channeling tube 26. As seen in FIG. 7, the outer
perimeter of the light channeling tube 26 is sized slightly smaller
than the matching inside perimeter 76 of a necked-down portion 74
of the aperture 24, and the insertion of the tube end into the
necked-down portion 74 of the aperture 24 forms a slip joint 80
(labeled in FIG. 7) between the end of the tube 26 and the aperture
24. Other slip joint configurations are contemplated. For example,
the tube can have a larger diameter than the necked-down portion of
the aperture, in which case the necked down portion of the aperture
fits inside the tube end. It is noted here that the light
channeling tubes 26 may have various perimeter shapes, such as
triangular, circular, square or diamond, regular or flared
hexagonal, or so forth. In the illustrative example of FIGS. 3-8,
the light channeling tubes 26 have regular hexagonal perimeters and
accordingly the inner perimeter 76 of the necked-down portion 74 of
the aperture 24 is correspondingly hexagonal, as seen in the inset
of FIG. 8.
[0037] In the illustrative example of FIG. 8, the apertures 24 also
have hexagonal perimeters at the front side of the front tube sheet
22, with the necking of each aperture 24 leading to the light input
(i.e. front) side of the aperture 24 being flared outward or
approximately conically expanding. This enhances light collection
efficiency by the aperture 24. Additionally, by making the
apertures 24 with hexagonal perimeters at the front side of the
front tube sheet 22, they can form a honeycomb structure as seen in
FIG. 8, which maximizes the collection area of the front tube sheet
22 that collects light into the light channeling tubes 26. Other
geometries can be used, such as circular apertures, but such
geometries will result in added "dead area" between the circular
apertures that does not lead into the light channeling tubes thus
reducing the efficiency of the receiver.
[0038] FIG. 6 depicts a next operation in which the back plate 28
is attached to the back ends of the light channeling tubes 26 by
fasteners 82, which may by way of illustrative example be
washer/nut fasteners that connect with threaded studs 84 extending
from the back ends of the light channeling tubes 26 (see FIG. 5).
With particular reference to FIG. 7, in one configuration an end
cap 86 including the threaded stub 84 is welded to the back end of
the light channeling tubes 26.
[0039] In the solar receiver module 20 fabricated in accord with
the process described with reference to FIGS. 3-8, each light
channeling tube 26 is supported in cantilevered fashion from the
back plate 28 by way of the fastener 82, 84. The front end of the
light channeling tube 26 is laterally restrained by the slip joint
80, but is free to expand or contract in the axial direction (that
is, in the direction of the tube axis). This allows independent
thermal expansion due to tubes operating at different temperatures
and thus expanding to different lengths. In the case of the welded
light channeling tubes 26 (those of FIGS. 3-4), the thermal
expansion of the tubes is not accommodated by a slip joint but
rather has the effect of moving the front tube sheet 22 outward
(during thermal expansion) or inward (during thermal contraction)
in response to heating or cooling, respectively, of the solar
receiver module 20. The slip joints of the remaining (large
majority) of light channeling tubes accommodates any differences in
thermal expansion amongst the array of light channeling tubes 26.
The front tube sheet 22 is supported by all the light channeling
tubes 26, but is secured in the tube-axial direction only by the
welded tubes of FIGS. 3-4.
[0040] In an alternative embodiment, it is contemplated to employ
separate designated tie rods (not shown) welded between the back
plate 28 and the front tube sheet 22 to provide the tube-axial
direction support, rather than obtaining this axial support by
welding designated light channeling tubes 26 as in the operation of
FIGS. 3-4. This alternative approach employing tie rods has the
advantage of employing the slip joints 74 for all of the light
channeling tubes 26 (as none are welded to the front tube sheet 22
in this alternative embodiment), but perhaps at the cost that some
light receiving area is lost (i.e. select tubes removed to make
room for tie rods) to accommodate the designated tie rods.
Additionally, the impact of the tie rods on the flow paths of the
flowing heat transfer medium 56 should be taken into account in
performing numerical thermal analyses.
[0041] With particular reference to FIGS. 7 and 8, the front tube
sheet 22 provides the front seal between tubes within a module for
the gap 50 (see FIG. 2). To this end, the hexagonal aperture
perimeters at the front side of the front tube sheet 22 which form
the honeycomb structure seen in FIG. 8 are joined to create the
seal. In one contemplated approach, the front tube sheet 22 is
formed by punching hexagonal openings corresponding to the
apertures 24 into a single metal sheet (e.g. single steel sheet)
and then working the openings using sheet metal forming tooling to
define the necked-down portion 74.
[0042] With reference to FIG. 7, in another contemplated approach,
each hexagonal aperture 24 is separately formed from sheet metal,
with the six sides of the hexagonal perimeter being flat sides 87.
The flat sides 87 of each pair of adjoining apertures are then
welded together to assemble the front tube sheet 22. Other
approaches are contemplated. For example, in a variant approach the
sides are flat on one to four of the segments of the hexagonal
perimeter around the perimeter of the module and straight on the
remaining segments where two apertures adjoin. In this case, only
the edges of each adjoining apertures are welded together to
assemble the front tube sheet 22. As yet another variant, it is
contemplated to employ separate or integral tube cap pieces that
are welded to the back end of the tube or formed as part of the
tube to facilitate making good seals.
[0043] The illustrative solar receiver module assembly approach
described with reference to FIGS. 3-8 addresses both flow sealing
and thermal expansion design considerations within the module.
[0044] With reference to FIGS. 9-13, approaches are described for
assembling the solar receiver modules 20 to form the overall solar
receiver 16 while addressing both flow sealing and thermal
expansion design considerations between adjoining modules. FIG. 9
illustrates a diagrammatic perspective view of a solar receiver
module 20 in isolation, with thermal expansion directions indicated
diagrammatically by arrows. (Note that in FIG. 9 the apertures are
omitted in depicting the front tube sheet 22). FIG. 10 illustrates
a diagrammatic side sectional view of a portion of the solar
receiver 16 including four solar receiver modules 20 mounted by
their respective module support posts 30 to a support column 88,
for example using bolted connections or other fastening methods.
The support column 88 may, for example be a vertical column of the
truss or other support structure 62 (see FIG. 1). Because each
module is mounted via the module support post 30 which is centrally
located (see FIGS. 2 and 10), the thermal expansion of the module
in the height and width direction is reduced compared to a top,
bottom, or side supported module during heating of the solar
receiver module 20 (FIG. 9), which makes it easier to seal between
adjoining modules because they thermally expand from their central
support point. Individual module support posts also eliminate the
need for a buckstay system of the type employed with top supported
modules to resist wind and earthquake loads.
[0045] In addition, this approach enables the use of smaller tube
modules, which results in smaller solar heat flux gradients across
the face of the module, more uniform operating metal temperatures,
lower thermal stresses and reduced potential for thermal distortion
compared to larger modules with larger face areas.
[0046] With reference to FIG. 11 which shows a diagrammatic
perspective view of the front tube sheet 22 and light channeling
tubes 26 of five modules 20, the hexagonal apertures 24 of
neighboring modules are arranged so that jagged edges 90 of
adjoining solar receiver modules 20 mesh together, that is, with
"slots" of one jagged edge receiving "bumps" of the other jagged
edge. The adjoining modules 20 are designed to fit snugly together
at non-operational temperature (typically room temperature) to form
a seal without employing a sealant material. When brought up to
operating temperature, the isotropic thermal expansion of the
modules 20 about their respective centrally located module support
posts 30 causes the snug fit to become tighter at operational
temperature. The aperture perimeters at the jagged edges 90 include
the flat sides to increase contact area to create a seal.
[0047] While using the foregoing approaches is expected to provide
suitable sealing between adjoining modules 20 at their front sides,
it is additionally or alternatively contemplated to employ a high
temperature sealant material. However, interposing sealing material
between the modules reduces the active area and thus efficiency of
the solar receiver 16 for collecting and channeling light.
[0048] With reference to FIGS. 12 and 13 which show diagrammatic
perspective and diagrammatic back views, respectively, of a portion
of the solar receiver 16 including a 4.times.2 array of modules 20,
the sealing between adjoining modules 20 at the back side is also
required. In illustrative FIGS. 12 and 13 the back plates 28
include contoured edges 92 (e.g. sawtooth at top and bottom and
pumpkin tooth edges at sides to match the contour of the tubes)
that mesh together but with clearance in the non-operating
condition to allow thermal expansion and prevent interference of
back plates 28 between adjoining modules in the operating
condition. As shown in FIG. 13, the gap between back plates 28
along the edges and corners are then sealed with seal strips 94 and
corner seal plates 96 respectively that are bolted to one but not
both adjoining modules as shown to allow free thermal expansion of
the back plates 28. Unlike the case for the front side, however,
there is no concern about additional sealing features blocking
light at the back side.
[0049] An advantage of the disclosed solar receiver modules 20 is
that individual modules are readily removed for repair or
replacement. At non-operating temperature the modules 20 have
thermally contracted to their smallest configuration, and an
individual module can be removed by disconnecting its module
support post 30 from the column 88 (see FIG. 10, or more generally
by disconnecting the support post from the module back plate) and
pulling the module out. This is facilitated if no sealing material
is employed at interfaces between adjoining modules. To facilitate
such removal, in the embodiment of FIG. 13 each sealing strip 94 is
removable and is attached by fasteners to only one of the two
adjoining modules 20, and at meeting corners a removable corner
cover sealing plate 96 is attached to one of the sealing strips 94.
This reduces the number of sealing strips that must be removed to
pull out an individual module. Additionally, by securing each
sealing element 94, 96 to only one module, a slip joint is
effectively formed so that thermal expansion is accommodated.
Repair and replacement of individual light channeling tubes 26 is
similarly simplified by the disclosed assembly. To replace a light
channeling tube 26, the center support tubes are unbolted from the
back plate. These are the light channeling tubes that are welded to
the front tube sheet 22 as described with reference to FIGS. 3 and
4. (In alternative embodiments in which separate tie rods are
employed, these are unbolted from the back plate). The front tube
sheet 22 is thereby released so that the slip fitted tubes 26 can
unbolted and removed and replaced. To replace one of the support
tubes which is welded to the front tube sheet 22, some of the
surrounding support tubes may need to be removed to gain access to
break the welds to the tube sheet.
[0050] In similar fashion, it is contemplated to modularize the
insulation and/or lagging 32 (FIG. 10) on the back side of the
module 20, for example by employing a piece of insulation/lagging
for each module, or for each set of four neighboring modules, or so
forth. The insulation/lagging 32 does not perform any sealing
function, and may for example be blanket-type insulation with ship
lapped edges to reduce heat loss.
[0051] Illustrative embodiments including the preferred embodiments
have been described. While specific embodiments have been shown and
described in detail to illustrate the application and principles of
the invention and methods, it will be understood that it is not
intended that the present invention be limited thereto and that the
invention may be embodied otherwise without departing from such
principles. In some embodiments of the invention, certain features
of the invention may sometimes be used to advantage without a
corresponding use of the other features. Accordingly, all such
changes and embodiments properly fall within the scope of the
following claims. Obviously, modifications and alterations will
occur to others upon reading and understanding the preceding
detailed description. It is intended that the present disclosure be
construed as including all such modifications and alterations
insofar as they come within the scope of the appended claims or the
equivalents thereof.
* * * * *