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.

Description

BACKGROUND

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.

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

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.

FIG. 1 is a diagram of one embodiment of an exemplary storage silo.

FIGS. 2A-2D depict exemplary layouts of micropile units within a foundation base.

FIG. 3 depicts one embodiment of an exemplary micropile unit.

FIG. 4 depicts one embodiment of an exemplary micropile column.

FIGS. 5A-5B depict embodiments of exemplary reinforced concrete.

FIG. 6 is a cross-section view of an exemplary post-tension strand bundle.

FIG. 7 is a block diagram of one embodiment of an exemplary concentrating solar power plant.

FIG. 8A is a cross-section view of an exemplary coned bottom for a silo.

FIG. 8B is a top view of the exemplary coned bottom in FIG. 8A.

FIGS. 9A and 9B are cross-section views of exemplary reinforced concrete for a coned bottom of a silo.

DETAILED DESCRIPTION

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.

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°-900° 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.

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.

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 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

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.

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.

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.

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.

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 2
Number of Micropile units Diameter
55                        45 feet
102                       50 feet
136                       55 feet
264                       65 feet

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.

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.

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.

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.

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.

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 3
SILO SIZE   NUMBER OF STRANDS
6,250 tons  5
12,500 tons 6
17,000 tons 7
34,000 tons 12

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.

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.

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.

The combined sunlight reflected from the plurality of heliostats 703 in the array 702 provides temperatures of approximately 500-1000° 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.

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.

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).

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.

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.

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.

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.

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.

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.

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; andwherein 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; andtwo 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; andwherein 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; anda 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; anda 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; andtwo 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; andwherein 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; anda 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.