U.S. patent application number 13/855092 was filed with the patent office on 2013-10-03 for solid particle thermal energy storage design for a fluidized-bed concentrating solar power plant.
This patent application is currently assigned to COLORADO SCHOOL OF MINES. The applicant listed for this patent is ALLIANCE FOR SUSTAINABLE ENERGY, LLC. Invention is credited to Zhiwen MA, Ruichong ZHANG.
Application Number | 20130255667 13/855092 |
Document ID | / |
Family ID | 49233201 |
Filed Date | 2013-10-03 |
United States Patent
Application |
20130255667 |
Kind Code |
A1 |
MA; Zhiwen ; et al. |
October 3, 2013 |
SOLID PARTICLE THERMAL ENERGY STORAGE DESIGN FOR A FLUIDIZED-BED
CONCENTRATING SOLAR POWER PLANT
Abstract
A fluidized-bed concentrating solar power plant comprises a
particle receiver configured to contain solid state particles,
wherein the particle receiver heats the solid state particles by
transferring thermal energy from sunlight to the solid state
particles. The plant also comprises a first silo configured to
receive and store heated solid state particles from the particle
receiver; a heat exchanger configured to receive the heated solid
state particles from the first silo and generate a fluidized
mixture comprising the heated solid state particles suspended in a
gas; and a second silo configured to feed cooled solid state
particles to the particle receiver, the cooled solid state particle
extracted from the fluidized mixture. The first silo and the second
silo each comprise a foundation comprising a base supported by a
plurality of micropile units. Each micropile unit comprises a
plurality of micropile columns coupled to a support block which
supports the base.
Inventors: |
MA; Zhiwen; (Golden, CO)
; ZHANG; Ruichong; (Golden, CO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ALLIANCE FOR SUSTAINABLE ENERGY, LLC |
Golden |
CO |
US |
|
|
Assignee: |
COLORADO SCHOOL OF MINES
Golden
CO
|
Family ID: |
49233201 |
Appl. No.: |
13/855092 |
Filed: |
April 2, 2013 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
61715747 |
Oct 18, 2012 |
|
|
|
61619317 |
Apr 2, 2012 |
|
|
|
61715751 |
Oct 18, 2012 |
|
|
|
61715755 |
Oct 18, 2012 |
|
|
|
Current U.S.
Class: |
126/617 ;
165/104.18 |
Current CPC
Class: |
F28D 2020/0047 20130101;
Y02E 10/44 20130101; F24S 60/10 20180501; Y02E 10/40 20130101; Y02E
60/14 20130101; E02D 27/38 20130101; E04H 7/26 20130101; F24S 90/00
20180501; F28C 3/12 20130101; F28D 20/0056 20130101; H02K 7/1823
20130101; F28C 3/10 20130101; F24S 80/20 20180501; F24S 10/80
20180501; F28D 2021/0045 20130101; F03G 6/065 20130101; F28D 13/00
20130101; Y02E 10/46 20130101; F24S 70/10 20180501; F24S 20/20
20180501 |
Class at
Publication: |
126/617 ;
165/104.18 |
International
Class: |
F24J 2/46 20060101
F24J002/46; F24J 2/34 20060101 F24J002/34 |
Goverment Interests
CONTRACTUAL ORIGIN
[0007] The United States Government has rights in this invention
under Contract No. DE-AC36-08G028308 between the United States
Department of Energy and the Alliance for Sustainable Energy, LLC,
the Manager and Operator of the National Renewable Energy
Laboratory.
Claims
1. A fluidized-bed concentrating solar power plant comprising: a
particle receiver configured to contain solid state particles,
wherein the particle receiver heats the solid state particles by
transferring thermal energy from sunlight to the solid state
particles; a first silo configured to receive and store heated
solid state particles from the particle receiver; a heat exchanger
configured to receive the heated solid state particles from the
first silo and generate a fluidized mixture comprising the heated
solid state particles suspended in a gas; a second silo configured
to feed cooled solid state particles to the particle receiver, the
cooled solid state particle extracted from the fluidized mixture;
wherein the first silo and the second silo each comprise: a
foundation comprising a base supported by a plurality of micropile
units, wherein each micropile unit comprises a plurality of
micropile columns coupled to a support block, wherein the base is
supported by the support block of each of the plurality of
micropile units and each of the plurality of micropile columns
extending into the ground under the foundation.
2. The fluidized-bed concentrating solar power plant of claim 1,
wherein each of the plurality of micropile columns is comprised of
a steel reinforcing bar encased within pressurized grout.
3. The fluidized-bed concentrating solar power plant of claim 1,
wherein the first silo and the second silo each further comprise: a
hollow cylinder having a height, a width, and a diameter, the
height and the diameter defining a volume for storage of solid
particles; and wherein the foundation is located at a first end of
the hollow cylinder, the foundation comprising the base having a
height, a width, and a diameter; wherein the base is concentric
with the hollow cylinder, and the width of the base being greater
than or equal to the width of the cylinder.
4. The fluidized-bed concentrating solar power plant of claim 3,
wherein at least one of the first silo or the second silo further
comprises a cover located at a second end of the hollow cylinder
and configured to enclose the second end of the hollow
cylinder.
5. The fluidized-bed concentrating solar power plant of claim 3,
wherein the hollow cylinder is comprised of steel-reinforced
concrete, the steel-reinforced concrete comprising: a plurality of
vertical steel reinforcing bars, the plurality of vertical steel
reinforcing bars separated from one another by a first separation
distance, the first separation distance being selected from a range
of approximately 6 inches to approximately 12 inches; and two
columns of horizontal steel reinforcing bars, a first column of the
two columns located on a first side of each of the plurality of
vertical steel reinforcing bars and a second column of the two
columns located on a second side of each of the plurality of
vertical steel reinforcing bars; wherein the first column is
separated from the second column by approximately 5 inches; wherein
the horizontal steel reinforcing bars in the first column are
separated from one another by approximately 6 inches; and wherein
the horizontal steel reinforcing bars in the second column are
separated from one another by approximately 6 inches.
6. The fluidized-bed concentrating solar power plant of claim 3,
wherein the hollow cylinder is comprised of steel-reinforced
concrete, the steel-reinforced concrete comprising: a plurality of
vertical steel reinforcing bars, the plurality of vertical steel
reinforcing bars separated from one another by a first separation
distance, the first separation distance being selected from a range
of approximately 6 inches to approximately 12 inches; and a
plurality of post-tension strand bundles separated vertically from
one another by a vertical separation distance, the plurality of
post-tension strand bundles extending in a direction approximately
perpendicular to the plurality of vertical steel reinforcing bars;
wherein each of the post-tension strand bundles comprises a
plurality of strands; wherein the number of strands in each of the
post-tension strand bundles is dependent on a size of the hollow
cylinder.
7. The fluidized-bed concentrating solar power plant of claim 6,
wherein the vertical separation distance has an initial value near
the first end of the hollow cylinder and increases as a function of
height to a final value near a second end of the hollow
cylinder.
8. The fluidized-bed concentrating solar power plant of claim 7,
wherein the initial value of the vertical separation distance is 12
inches and the final value is 20 inches.
9. The fluidized-bed concentrating solar power plant of claim 6,
wherein the number of strands, per ton of material, in each strand
bundle decreases as a function of the size of the hollow
cylinder.
10. The fluidized-bed concentrating solar power plant of claim 1,
wherein the first silo is configured with a coned bottom and the
second silo is configured with a flat bottom.
11. The fluidized-bed concentrating solar power plant of claim 1,
wherein each of the micropile columns extends into the ground at a
non-zero angle to a plane that is perpendicular to a bottom surface
of the concrete block.
12. The fluidized-bed concentrating solar power plant of claim 1,
wherein the micropile units are separated from one another by at
least 2 feet.
13. A silo structure for a fluidized-bed concentrating solar power
plant, the silo structure comprising: a hollow cylinder having a
height, a width, and a diameter, the height and the diameter
defining a volume for storage of solid particles used for
transferring heat in the fluidized-bed concentrating solar power
plant; and a foundation located at a first end of the hollow
cylinder, the foundation comprising a base and a plurality of
micropile units, the base having a height, a width, and a
wall-centered diameter; wherein the base is concentric with the
cylinder and the width of the base being greater than or equal to
the width of the cylinder; wherein each micropile unit comprises a
plurality of micropile columns and a support block coupled to each
of the plurality of micropile columns, each of the plurality of
micropile columns extending into the ground under the foundation;
wherein the base is supported by the support block of each of the
plurality of micropile units and the first end of the hollow
cylinder is supported by the base.
14. The silo structure of claim 13, wherein each micropile column
is comprised of a steel reinforcing bar surrounded by pressurized
grout.
15. The silo structure of claim 13, further comprising a coned
bottom at the first end of the hollow cylinder.
16. The silo structure of claim 13, wherein each of the micropile
columns extends into the ground at a non-zero angle to a plane that
is perpendicular to a bottom surface of the concrete block.
17. The silo structure of claim 13, wherein the micropile units are
separated from one another by at least 2 feet.
18. The silo structure of claim 13, wherein the hollow cylinder is
comprised of steel- reinforced concrete, the steel-reinforced
concrete comprising: a plurality of vertical steel reinforcing
bars, the plurality of vertical steel reinforcing bars separated
from one another by a first separation distance, the first
separation distance being selected from a range of approximately 6
inches to approximately 12 inches; and two columns of horizontal
steel reinforcing bars, a first column of the two columns located
on a first side of each of the plurality of vertical steel
reinforcing bars and a second column of the two columns located on
a second side of each of the plurality of vertical steel
reinforcing bars; wherein the first column is separated from the
second column by approximately 5 inches; wherein the horizontal
steel reinforcing bars in the first column are separated from one
another by approximately 6 inches; and wherein the horizontal steel
reinforcing bars in the second column are separated from one
another by approximately 6 inches.
19. The silo structure of claim 13, wherein the hollow cylinder is
comprised of steel-reinforced concrete, the steel-reinforced
concrete comprising: a plurality of vertical steel reinforcing
bars, the plurality of vertical steel reinforcing bars separated
from one another by a first separation distance, the first
separation distance being selected from a range of approximately 6
inches to approximately 12 inches; and a plurality of post-tension
strand bundles separated vertically from one another by a vertical
separation distance, the plurality of post-tension strand bundles
extending in a direction approximately perpendicular to the
plurality of vertical steel reinforcing bars; wherein each of the
post-tension strand bundles comprises a plurality of strands;
wherein the number of strands in each of the post-tension strand
bundles is dependent on the diameter of the hollow cylinder.
20. The silo structure of claim 19, wherein the vertical separation
distance has an initial value near the first end of the hollow
cylinder and increases as function of height to a final value near
a second end of the hollow cylinder.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to and the benefit of:
[0002] U.S. Provisional Application No. 61/715,747 entitled "Solid
Particle Thermal Energy Storage Design For A Fluidized-Bed
Concentrating Solar Power Plant" and filed on Oct. 18, 2012,
(Applicant Docket No. NREL PROV/12-73) , which is incorporated
herein by reference in its entirety;
[0003] U.S. Provisional Application No. 61/619,317 entitled
"Gas-Solid Two-Phase Heat Transfer Material CSP Systems and
Methods" and filed on Apr. 2, 2012, (Applicant Docket No. NREL
PROV/11-92) which is incorporated herein by reference in its
entirety;
[0004] U.S. Provisional Application No. 61/715,751 entitled
"Fluidized-Bed Heat Exchanger Designs for Different Power Cycle in
Power Tower Concentrating Solar Power Plant with Particle Receiver
and Solid Thermal Energy Storage", filed on Oct. 18, 2012,
(Applicant Docket NREL PROV/12-74), which is incorporated herein by
reference in its entirety; and
[0005] U.S. Provisional Application No. 61/715,755, entitled
"Enclosed Particle Receiver Design for a Fluidized Bed in Power
Tower Concentrating Solar Power Plant", filed on Oct. 18, 2012,
(Applicant Docket NREL PROV/13-05), which is incorporated herein by
reference in its entirety.
[0006] Attorney Docket No. NREL 12-73 1
BACKGROUND
[0008] Concentrating Solar power (CSP) systems utilize solar energy
to drive a thermal power cycle for the generation of electricity.
CSP technologies include parabolic trough, linear Fresnel, central
receiver or "power tower," and dish/engine systems. Considerable
interest in CSP has been driven by renewable energy portfolio
standards applicable to energy providers in the southwestern United
States and renewable energy feed-in tariffs in Spain. CSP systems
are typically deployed as large, centralized power plants to take
advantage of economies of scale. A key advantage of certain CSP
systems, in particular parabolic troughs and power towers, is the
ability to incorporate thermal energy storage. Thermal energy
storage is often less expensive and more efficient than electric
storage and allows CSP plants to increase capacity factor and
dispatch power as needed--for example, to cover evening or other
demand peaks. Improved plant structural designs are needed,
however, to support improvements in CSP systems utilizing thermal
energy storage.
[0009] The foregoing examples of the related art and limitations
related therewith are intended to be illustrative and not
exclusive. Other limitations of the related art will become
apparent to those of skill in the art upon a reading of the
specification and a study of the drawings.
DRAWINGS
[0010] Exemplary embodiments are illustrated in referenced figures
of the drawings. It is intended that the embodiments and figures
disclosed herein are to be considered illustrative rather than
limiting.
[0011] FIG. 1 is a diagram of one embodiment of an exemplary
storage silo.
[0012] FIGS. 2A-2D depict exemplary layouts of micropile units
within a foundation base.
[0013] FIG. 3 depicts one embodiment of an exemplary micropile
unit.
[0014] FIG. 4 depicts one embodiment of an exemplary micropile
column.
[0015] FIGS. 5A-5B depict embodiments of exemplary reinforced
concrete.
[0016] FIG. 6 is a cross-section view of an exemplary post-tension
strand bundle.
[0017] FIG. 7 is a block diagram of one embodiment of an exemplary
concentrating solar power plant.
[0018] FIG. 8A is a cross-section view of an exemplary coned bottom
for a silo.
[0019] FIG. 8B is a top view of the exemplary coned bottom in FIG.
8A.
[0020] FIGS. 9A and 9B are cross-section views of exemplary
reinforced concrete for a coned bottom of a silo.
DETAILED DESCRIPTION
[0021] In the following detailed description, reference is made to
the accompanying drawings that form a part hereof, and in which is
shown by way of illustration specific illustrative embodiments.
However, it is to be understood that other embodiments may be
utilized. The following detailed description is, therefore, not to
be taken in a limiting sense.
[0022] FIG. 1 is a diagram of one exemplary embodiment of a storage
silo 100 for storage of solid particles (e.g., sand or ash) used in
a fluidized-bed concentrating solar power plant, such as the power
plant described below with respect to FIG. 7. Silo 100 is
configured to meet the demands of storing solid particles for use
in a fluidized-bed concentrating solar power plant. For example,
the storage silo 100 is configured to store thousands of tons of
sand up to a temperature range of approximately
800.degree.-900.degree. C. Additionally, the storage silo 100 is
configured to accommodate different types of environmental
conditions such as, but not limited to, high wind loads, seismic
activity, and/or varying soil conditions. Additionally, in some
embodiments, the silo 100 is made of concrete with a refractory
liner for heat resistance and insulation using materials known to
one of skill in the art.
[0023] The exemplary storage silo 100 in FIG. 1 is comprised of a
foundation 102 and a hollow cylinder 104. The cylinder 104 has a
height 101 and a diameter 103 which define a volume for storing the
solid particles. The environment of the volume defined by the
cylinder 104 is inert with only hot air in this example. For
instance, there are no combustion gases in this example.
[0024] In the examples described herein, the diameter 103 is
measured from the center of the wall of the cylinder 104. For
example, in this embodiment, the cylinder 104 is comprised of a
wall having a thickness of approximately 12 inches. The diameter
103 is, therefore, measured from a point six inches deep into the
wall of the cylinder 104 in this example. However, it is to be
understood that other thicknesses of the wall can be used in other
embodiments and that the diameter can be measured from an inner
surface or exterior surface of the wall of the cylinder 104. Table
1 provides exemplary values for the height, diameter, and
corresponding storage capacity of solid particles. It is to be
understood that the values in Table 1 are provided by way of
example only and that other dimensions can be used in other
embodiments. For example, in some embodiments, a height-to-diameter
ratio of approximately 3:1 is used in determining the dimensions of
the silo.
TABLE-US-00001 TABLE 1 DIAMETER HEIGHT CAPACITY 45 ft 130 ft 6,250
tons 50 ft 148 ft 12,500 tons 55 ft 165 ft 17,000 tons 65 ft 230 ft
34,000 tons
[0025] In this example, a cover or dome 106 is optionally located
at one end of the cylinder 104 to enclose the volume defined by the
cylinder 104 at the end of the cylinder 104. The cover 106 is
comprised of the same material as the cylinder 104. For example, in
this embodiment, the cover 106 and cylinder 104 are comprised of
steel-reinforced concrete, as described in more detail below. The
foundation 102 is located at the end of the cylinder 104 opposite
from the cover 106. The foundation 102 includes a plurality of
micropile units 108. Each micropile unit 108 includes a plurality
of micropile columns 109 and a footing or block 111 surrounding one
end of the respective micropile columns. The micropile columns 109
have a length 110 which extends into the ground or soil 116. In
this embodiment, the length 110 of the micropile units 108 is 50
feet. However, it is to be understood that the length 110 can be
different in other embodiments. Additionally, all of the micropile
units 108 do not, or may not have the same length in other
embodiments. The micropile units 108 are used to anchor the
foundation 102 and stabilize against seismic and surcharge loads
from the earth as described in more detail below. The foundation
102 also includes a slab or base 112 having a thickness 114 placed
on top of the footings 111.
[0026] In some embodiments, the slab 112 is at least partially
submerged in the soil 116. In addition, the thickness 114, in some
embodiments, is 18 inches. However, other thickness can be used in
other embodiments. The base 112 is concentric with the cylinder
104. As measured from the center of the base 112, the base 112 has
the same wall-center to wall-center diameter as the cylinder 104 in
this example. However, the base 112 may have a wider outside
diameter than the cylinder 104, as shown in this example. The
micropile units 108 are formed in a pattern and are located under
the wall of the cylinder 104. For example, FIGS. 2A-2D depict a top
view of exemplary layouts of micropile units.
[0027] FIG. 2A depicts an exemplary layout of micropile units 208
for a cylinder having a diameter of 45 feet. The circle 204 depicts
the location of the cylinder 104 on the base 212 above the pattern
of micropile units 208. As shown in FIGS. 2A-2D, the cylinder 104
is concentric with the slab 212 and therefore is located at
approximately the center of the slab 212. As mentioned above, the
slab 212 may, however, have an outside diameter that is wider than
the cylinder 104's outside diameter. FIG. 2B depicts an exemplary
layout of micropile units 208 for a cylinder having a diameter of
50 feet, as shown by circle 204. FIG. 2C depicts an exemplary
layout of micropile units 208 for a cylinder having a diameter of
55 feet, as shown by circle 204. FIG. 2D depicts an exemplary
layout of micropile units 208 for a cylinder having a diameter of
65 feet, as shown by the circle 204.
[0028] As can be seen, each exemplary layout includes a plurality
of rows of micropile units 208. The number of rows and the number
of micropile units 208 in each row depends on the maximum load or
weight to be supported by the corresponding silo. Hence, as the
diameter of the corresponding silo and foundation base 212
increases, the maximum load to be supported also increases. Hence,
the number of micropile units 208 is also increased
accordingly.
[0029] For example, in FIG. 2A there are 3 rows of micropile units
208, whereas in FIG. 2D there are 4 rows of mircopile units 208.
Similarly, the total number of micropile units 208 increases with
increasing diameter of foundation base 212. In some embodiments,
each of the micropile units 208 is located at least 2 feet from
another micropile unit 208. Separating each micropile unit 208 by
at least 2 feet helps the micropile units 208 resist surcharges
produced by loading the silo. Table 2 below provides exemplary
values for the number of micropile units 208 to be used based on
the diameter of the foundation base 212 and corresponding silo. It
is to be understood that the number of micropile units in Table 2
are provided by way of example only.
TABLE-US-00002 TABLE 2 Number of Micropile units Diameter 55 45
feet 102 50 feet 136 55 feet 264 65 feet
[0030] FIG. 3 depicts an exemplary embodiment of a micropile unit
308. Micropile unit 308 can be used for each of the plurality of
micropile units 108 in FIGS. 1 and 2. Micropile unit 308 includes a
plurality of micropile columns 309 and a support block 311 which
encases or surrounds one end of the micropile columns 309. The
support block 311 can be comprised of concrete and has a height
331, a width 333, and a depth 335. In one embodiment, the height
331 is approximately 4 feet, the width 333 is approximately 8 feet,
and the depth 335 is approximately 8 feet. In this example, four
micropile columns 309 are used to form micropile unit 308. However,
it is to be understood that more or fewer than four micropile
columns 309 can be used in other embodiments. For example, in one
alternative embodiment, a fifth micropile column is placed in the
center of the other four micropile columns. In addition, the
micropile columns 309 are placed relative to one another so that
they resist loads from all directions. For example, as shown in the
example of FIG. 3, each micropile column 309 is placed near a
corner of the concrete block 311. However, other arrangements of
the micropile columns 309 can be used in other embodiments. Each
micropile column 309, in this example, is placed at a non-zero
angle 339 relative to a plane perpendicular to the bottom of the
block 311. In this example, the angle 339 is 10 degrees. However,
other angles greater or less than 10 degrees can be used in other
embodiments.
[0031] An exemplary micropile column 409 is depicted in FIG. 4. As
shown in FIG. 4, each micropile column is comprised of a column of
grout 413 having a steel reinforcing bar 415 placed within the
grout 413. For example, a column can be dug in the soil. The steel
reinforcing bar 415 is placed in the column and then the grout 413
is placed into the column under pressure. In particular, in this
example, the grout 413 is compressed into the column under 5,000
pounds per square inch (psi), and the steel reinforcing bar 415 is
a #20, 150 Grade steel bar. In other embodiments, other grout
pressures and reinforcing bar materials may be used. A plurality of
centralizers can be used to assure that the bar 415 is centrally
placed in the column in some embodiments. For example, in some
embodiments, centralizers can be placed at 10 foot centers along
each bar 415. Each micropile column 409, in this example, is 50
feet long and has a diameter of 12 inches. In addition, in some
embodiments, more than one steel reinforcing bar 415 is used in
each column 409. For example, in one embodiment, a plurality of
bars 415 can be evenly distributed in a column 409 having a
diameter of 12 inches with a distance between any two bars in the
range of approximately 2.8 inches to approximately 4 inches.
Furthermore, in some embodiments, each individual column 409
includes a steel plate at the top of the column 409. The plate
extends the tributary area of the respective column 409. As the
tributary area increases, the capacity for the respective column
409 to resist direct loading becomes more effective.
[0032] FIGS. 5A and 5B depict exemplary embodiments of reinforced
concrete which can be used in implementing the wall of a silo such
as silo 100. For example, the reinforced concrete described in FIG.
5A or 5B can be implemented in the cylinder 104 and cover 106. In
both FIG. 5A and FIG. 5B, vertical steel reinforcing bars (rebar)
520 are used for vertical reinforcement of the concrete 530. As
used herein, the term `vertical` refers to a direction that is
parallel with the axis of the silo's hollow cylinder. Similarly,
the term `horizontal` refers to a direction that is perpendicular
with the axis of the silo's hollow cylinder.
[0033] In some embodiments, #10 rebar having a diameter of 1.25
inches is used. However, in other embodiments, vertical rebar 520
having other sizes are used. In the examples shown in FIGS. 5A and
5B, the vertical reinforcing bars 520 have an approximately uniform
horizontal separation distance 525 throughout the silo wall. In
some embodiments, the separation distance 525 is selected from the
range of approximately 6 inches to approximately 12 inches.
However, it is to be understood that other values of the separation
distance 525 can be used in other embodiments.
[0034] In FIG. 5A, horizontal reinforcing bars 540 are also placed
horizontally and used for periphery reinforcement of the concrete
530. In particular, as shown in FIG. 5A, two columns 541-1 and
541-2 of horizontal reinforcing bars 540 are used. A first column
541-1 is located on a first side of each of the vertical
reinforcing bars 520 and a second column 541-2 is located on a
second side of each of the vertical reinforcing bars 520. The
horizontal reinforcing bars 540 in each column are separated
vertically by a vertical separation distance 545. In addition, the
columns 541-1 and 541-2 of horizontal reinforcing bars 540 are
separated horizontally from one another by a horizontal separation
distance 547. In some embodiments, the vertical separation distance
545 is approximately 6 inches. Additionally, in some embodiments,
the horizontal separation distance 547 is approximately 5 inches.
However, it is to be understood that other values for vertical
separation distance 545 and horizontal separation distance 547 can
be used in other embodiments. In addition, the vertical separation
distance 545 can increase from a first value near the bottom of the
silo to a second value near the top of the silo, in some
embodiments.
[0035] In FIG. 5B, post-tension strand bundles 560 are used as the
horizontal reinforcement in lieu of horizontal reinforcing bars
540. The post-tension strand bundles 560 extend in a direction
approximately perpendicular to the vertical steel reinforcing bars
520. Each post-tension strand bundle 560 is a bundle of a plurality
of steel strands that is located in a corresponding hole in the
concrete 530 and tightened by pulling on both ends of the bundle
560. For example, in one embodiment, after the concrete 530 is
cured, the strand bundles 560 are tensioned to 270 kilopounds per
square inch (ksi). FIG. 6 is a cross-section view of an exemplary
post-tension strand bundle 660. As shown in FIG. 6, the exemplary
strand bundle 660 includes six strands. Each strand, in some
embodiments, has a diameter of 0.75 inches. However, it is to be
understood that each strand can have a different diameter in other
embodiments. In addition, the number of strands in each strand
bundle 560 is dependent on the size of the corresponding silo. The
size of the silo is represented in Table 3 by the amount of solid
particles which can be stored therein. For example, Table 3 lists
exemplary silo sizes and an exemplary corresponding number of
strands used in each strand bundle 560. However, the silo size can
also be measured in terms of the diameter of the silo, as discussed
above with respect to Table 1. Table 3 also includes an exemplary
total number of strand bundles based on the silo size.
TABLE-US-00003 TABLE 3 SILO SIZE NUMBER OF STRANDS 6,250 tons 5
12,500 tons 6 17,000 tons 7 34,000 tons 12
[0036] As shown in Table 3, as the size of the corresponding silo
increases, the number of strands, per ton of material, in each
strand bundle decreases. For example, the number of strands in each
bundle 560 for a silo size of 6,250 tons is 5. If the same number
of strands, per ton of material, in each strand bundle 560 was used
for a silo size of 12,500 tons, then each strand bundle 560 would
have 10 strands. However, as shown in the exemplary Table 3, the
number of strands, per ton of material, in each strand bundle 560
is 6 for a silo size of 12,500 tons. Thus, the cost for horizontal
reinforcement per ton of material contained decreases as the silo
size increases. As a result, the cost of a post-tension strand
horizontally reinforced silo may be up to 10% lower than the cost
of a steel-rebar horizontally reinforced silo due to savings on the
material.
[0037] Each strand bundle 560 is separated vertically from other
strand bundles 560 by a vertical separation distance 565. In some
embodiments, the vertical separation distance 565 is uniform
throughout the silo. However, in other embodiments, the vertical
separation distance 565 varies as a function of height. That is,
the vertical separation distance 565 has an initial value at the
end of the silo cylinder near the foundation and a second final
value at the opposite end of the silo cylinder. For example, in
some such embodiments, the vertical separation distance 565 between
two strand bundles 560 near the cover of the silo is greater than
the vertical separation distance 565 in the middle of the silo
which, in turn, is greater than the vertical separation distance
565 near the foundation of the silo. In other words, the vertical
separation distance 565 for a given strand bundle 560 increases as
the respective height of the given strand bundle 560 increases. The
vertical separation distance 565 can increase with height in some
embodiments because the load due to the stored solid particles
decreases with height. In some embodiments, the initial vertical
separation distance 565 at the foundation of the silo is
approximately 12 inches and increases with height. For example, in
one embodiment, the separation distance 565 between strand bundles
560 is 12 inches near the bottom of the silo and changes
proportionally to 20 inches near the top.
[0038] The silo structure described above can be implemented in a
concentrating solar power plant, such as the exemplary power plant
700 shown in FIG. 7. The exemplary system 700 includes an array 702
of heliostats 703. Each heliostat 703 includes a mirror 705 which
reflects light from the sun toward a receiver 704. In addition,
each heliostat 703 is configured to turn its respective mirror 705
to compensate for the apparent motion of the sun in the sky due to
the rotation of the earth. In this way, each respective mirror 705
continues to reflect sunlight toward the receiver 704 as the
position of the sun in the sky changes.
[0039] The combined sunlight reflected from the plurality of
heliostats 703 in the array 702 provides temperatures of
approximately 500-1000.degree. C. at the receiver 704. The receiver
704 is configured to transfer the solar heat from the combined
sunlight to a heat transport material adapted to store thermal
energy such as molten salts or other particles. The heated
particles are passed from the receiver 704 to a hot silo 706. The
hot silo 706 is implemented using a silo construction as described
above with respect to FIGS. 1-6. In some embodiments, the hot silo
706 has a cone bottom as shown and described below with respect to
FIG. 8A-9B. A cone bottom helps enable the hot silo 706 to dispense
the stored particles using gravity flow.
[0040] Heated particles from the hot silo 706 are delivered via a
conveyor 708 to a heat exchanger 710 as needed. In this embodiment,
the heat exchanger 710 is implemented as a fluidized-bed heat
exchanger having three stages. In particular, the heat exchanger
710 includes a super heater 711, an evaporator 713, and a
preheater/economizer 715. However, it is to be understood that
other types and configurations of heat exchangers can be
implemented in other embodiments.
[0041] A pump 712 compresses gas and delivers the compressed gas to
the heat exchanger 710 where the pressure of the compressed gas
suspends the heated particles in the gas. The fluidized mixture of
compressed gas and heated particles is moved through the stages of
the heat exchanger 710 to transfer heat from the heated particles
to a working fluid, such as but not limited to water or ammonia. It
is to be understood that, in other embodiments, other working
fluids can be used. For example, other working fluids include, but
are not limited to, hydrocarbons (e.g., butane, propane, propylene,
etc.) and liquid fluorocarbons (e.g., tetrafluoroethane).
[0042] The transfer of heat to the working fluid vaporizes the
working fluid. The vaporized working fluid is passed to a vapor
turbine 714. The pressure of the vapor turns the vapor turbine 714,
which is coupled to and drives the generator 716 to produce
electricity. The vaporized working fluid is then expelled from the
vapor turbine 714 and condensed again in condenser 718. In
particular, the remaining heat from the vaporized working fluid is
transferred to a cooler 720 coupled to the condenser 718. The
removal of heat from the vaporized working fluid causes the working
fluid to condense to a liquid state. A pump 722 is then used to
move the working fluid back into the heat exchanger 710 where it is
vaporized by the transfer of heat from the heated particles
occurring in the heat exchanger 710.
[0043] After the particles pass through the heat exchanger 710, the
resulting fluidized mixture is then passed to a cyclone 724 (also
referred to as a particle separator). In the cyclone 724, the solid
state particles are separated from the gas particles. The solid
particles are then stored in a cold silo 726 for later use. The
cold silo 726 is also constructed using the silo structures
discussed above with respect to FIGS. 1-6. In some embodiments, the
cold silo 726 has a flat bottom as opposed to a coned bottom. An
elevator or conveyer 728 then moves the solid particles as needed
from the cold silo 726 to the receiver 704 where the solid
particles are again heated.
[0044] FIG. 8A depicts a cross-section side view of one example of
a coned bottom 800 for a silo, such as silo 100. FIG. 8B depicts a
top view of the exemplary coned bottom 800. As shown in FIGS. 8A
and 8B, the coned bottom 800 has a first diameter 850 at a first
end and a second diameter 852 at a second end. In addition, the
walls of the coned bottom 800 have a width 856 and are formed at an
angle 854 to a horizontal plane parallel with the bottom of the
coned bottom 800. In this example, the first diameter 850 is 50
feet and the second diameter 852 is 3 feet. In addition, in this
example, the angle 854 is 45 degrees and the width 856 is 2 feet.
However, it is to be understood that other diameters and angles can
be used in other embodiments. The height of the coned bottom 800 is
dependent on the values for the first diameter 850, the second
diameter 852, and the angle 854.
[0045] FIG. 9A is a cross-section view of a segment of an exemplary
reinforced concrete wall 900 for a coned bottom of a silo. As shown
in FIG. 9A, in this example, the wall 900 has a thickness 962 and
includes a plurality of vertical reinforcement bars 972. Each
vertical bar 972 has a diameter 970. In some embodiments, the
vertical reinforcement bars 972 are implemented using #10 bars.
Thus, the diameter 970 is 1.25 inches in such embodiments, as
discussed above. The wall 900 also has embedded within it a
plurality of post-tensioned strand bundles 974 in the horizontal
direction. In some embodiments, the post-tensioned strand bundles
974 are tensioned to 270 ksi. The vertical bars 972 are evenly
displaced in the wall 900 and separated from one another by a
distance 964. In some embodiments, the distance 964 is 1 foot. The
strand bundles 974 are located at a distance 968 such that they are
placed approximately in the center of the wall 900 in this example.
For example, in some embodiments, the thickness 962 is 2 feet and
the distance 968 is 1 foot. The strand bundles 974 are also
separated from one another by a distance 966. In some embodiments,
the distance 966 is 1 foot.
[0046] FIG. 9B is a cross-section view of the segment of the
exemplary reinforced concrete wall 900. The view in FIG. 9B has
been rotated from the view of FIG. 9A as indicated by the change in
the coordinate axes shown with the respective figure. As shown in
FIG. 9B, rows of vertical bars 972 are evenly spaced throughout the
wall 900 by a distance 980. In some embodiments, the distance 980
is 4 inches. For purposes of explanation, FIG. 9B depicts one of
the vertical bars 972 without the surrounding concrete. However, it
is to be understood that each of the vertical bars 972 is embedded
within the wall 900.
[0047] While a number of exemplary aspects and embodiments have
been discussed above, those of skill in the art will recognize
certain modifications, permutations, additions and sub combinations
thereof. It is therefore intended that the following appended
claims and claims hereafter introduced are interpreted to include
all such modifications, permutations, additions and
sub-combinations as are within their true spirit and scope.
* * * * *