Heliostat dirigible

Abstract

A heliostat dirigible with a fluid containment structure defining a fluid volume configured to contain a lighter than air fluid. A curved reflective surface is supported by the fluid containment structure when the fluid volume contains a lighter than air fluid. The curved reflective surface is configured to reflect and concentrate sunlight at a target. Tethers and / or connections for a plurality of tethers are arranged around the fluid containment structure such that the attitude of the fluid containment structure can be adjusted when it is floating above the ground.

Description

HELIOSTAT DIRIGIBLEPRIORITY CLAIM

[0001] The application claims priority under 35 U.S.C. §119 and all applicable statutes and treaties from prior United States provisional application serial number 63 / 535,104, which was filed August 29, 2023.FIELD

[0002] A field of the invention is heliostats. Systems of the invention are applicable to concentrating solar-thermal power (CSP) plants.BACKGROUND

[0003] Heliostats are sophisticated controlled minors that focus and therefore concentrate sunlight toward a target. One use is in a solar power facility. In such facilities, like the Ivanpah Solar Power Facility in San Bernardino County, California, heliostats are formed by fields of minors that are controlled to track the sun. These minors focus sunlight onto a receiver at the top of a tall tower where the concentrated light heats a working fluid. That fluid is then used to spin a turbine to generate electricity or provide heat to an industrial process, in the same manner that fossil-fuel or nuclear power plants heat a working fluid. The heated fluid can also be stored instead of immediately used to provide work. The stored heated fluid is available to provide energy on-demand.

[0004] The Ivanpah Solar Electric Generating System is the United States’ largest CSP plant. Much of the capital cost of the system is attributable to the mirrored heliostats and the land required to accommodate frames and motors that support the mirrors. The system includes 173,500 heliostats, each built with two mirrors that are supported by a frame from the ground and include motors to move the mirrors to achieve the correct angle of reflection to concentrate. Tracking devices direct movements of the mirrors.

[0005] Maintenance adds cost, as each of the mirrors is large and fixed, and must be cleaned regularly to avoid reducing the efficiency of reflection and concentration. If any min or is damaged, such as by a storm or other object, replacing one of the large minors is expensive.

[0006] The US Department of Energy has a goal of producing power with a CSP at $0.05 per kilowatt-hour for electricity generated by plants with 12 or more hours of thermal energy storage. Cunent CSP like the Ivanpah CSP have an estimated cost of $100 per square meter of heliostats, and that cost needs to be halved to reach the $0.05 per kilowatt- hour goal.SUMMARY OF THE INVENTION

[0007] A prefened embodiment is a heliostat dirigible with a fluid containment structure defining a fluid volume configured to contain a lighter than air fluid. A curved reflective surface is supported by the fluid containment structure when the fluid volume contains a lighter than air fluid. The curved reflective surface is configured to reflect and concentrate sunlight at a target. Tethers and / or connections for a plurality of tethers are arranged around the fluid containment structure such that the attitude of the fluid containment structure can be adjusted when it is floating above the ground.BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1 is a perspective schematic view a preferred concentrating solar-thermal power system including a heliostat dirigible of the invention;

[0009] FIG. 2 is a front view of the preferred heliostat dirigible of FIG. 1;

[0010] FIGs. 3A-3C illustrate details of preferred curved reflective surfaces of the preferred heliostat dirigible of FIGs. 1 and 2;

[0011] FIGs. 3D-3F illustrate details of a modified version curved reflective surfaces of FIGs. 3A-3C; and

[0012] FIG. 4 is an oblique view of the prefened heliostat dirigible of FIGs. 1 and 2.DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] A preferred embodiment is a heliostat dirigible with a curved reflective face, such as paraboloid face, that is configured to reflect and concentrate sunlight at a target. The preferred heliostat dirigible encloses a lighter than air fluid, such as helium or hydrogen. It can therefore be deployed, for example, near and at a common or close to common height of a power tower in a CSP plant. The shorter path between the reflective face and the target for concentration can be more efficient than a conventional ground- based / fixed heliostat used at current state-of-the art CSP plants. A central major axis of the heliostat dirigible, which can have an overall rounded pyramidal shape, can be horizontal or vertical with respect to a ground reference when the heliostat dirigible is floated via the lighter than air fluid.

[0014] A portion of the heliostat dirigible closest to the ground when the heliostat dirigible is floated can be referred to as the base of the heliostat dirigible. The curved reflective face is preferably inclined toward the central major axis from the base to an opposite end of the heliostat dirigible. The curved reflective surface is inwardly curved in preferred embodiments, such that a midline from the base to the tip is closer to the central major axis than other portions of the curved reflective surface.

[0015] A plurality of tethers is attached to the heliostat dirigible in a preferred heliostat of the invention. The tethers are controlled by motors that adjust the heliostat dirigible based upon the position of the sun to maintain concentration of sunlight toward a target. A fluid source provides and controls the fluid in the heliostat dirigible to maintain a desired height. Some of the tethers are independently controlled such that the inclination of the central major axis can be gradually tilted to follow and collect rays from the sun. A plurality of tethers are preferably attached to the base, the tip and at various portions of a lightweight frame of the heliostat dirigible. This allows control of the pitch, yaw and roll of the curved reflective surface. A ground level motorized capstan can be utilized on a mobile tractor for ground movement flexibility. This system allows for safe deployment and stowage, including stowage for high wind level events. The heliostat dirigible can beplaced on a telescoping column, on which the tethers maintain stability as they do at ground level. The telescoping column can be moved on a mobile tractor as described above.

[0016] In preferred embodiments, the curved reflective surface is formed from a plurality of lightweight reflector modules held in a lightweight frame. An individual reflector module can be formed of a lightweight substrate, such as thin Styrofoam, that supports a thin reflective film, such as aluminized mylar, reflective foil or polytetrafluoroethylene (PTFE). Each individual reflector module is inexpensive and can be easily replaced. In a preferred embodiment, the reflector modules snap-fit into corresponding holders in the frame of the reflective surface. Other forms of removable attachment can also be used, such as clips, spring loaded interference elements in the frame, et.

[0017] A preferred system of the invention is a plurality of heliostat dirigible that are arranged and controlled to concentrate sunlight toward one or more targets. The target(s) can be power towers that are used to heat fluid in a concentrating thermal power plant. Motors on the ground control tethered heliostat dirigibles to direct sunlight toward one or more targets, such as power towers containing fluid to be heated. The curved reflective surface is adjusted by the tethers as the heliostat dirigible floats such that it receives sunlight throughout a day and reflects and concentrates it toward the target(s). In preferred embodiments, a plurality of heliostat dirigibles are floated such the curved surfaces essentially surround each target.

[0018] In the preferred embodiments of the drawings, the substrate of the heliostat is both lightweight and rigid with a Styrofoam® (or equivalent) inset. The reflective surface of this heliostat can be aluminized mylar, reflective foil or polytetrafluoroethylene (PTFE) attached to the Styrofoam® (or equivalent). The lightweight frame, Styrofoam® (or equivalent) inset and reflective material can be removed for replacement.

[0019] The heliostat dirigible can be designed to be deployed in a vertical or horizontal position relative to ground. It can be tethered and controlled by a motor control center (MCC) to reposition the dirigible or stow it to ground (during weather events such as highwind / hail or periodic maintenance). The tether system can be connected to motorized capstans (similar to marine / boat systems) which control lift and stow positioning for dirigible. Motors on ground can be controlled by a MCC to adjust the dirigible for sun position by achieve a particular pitch, yaw and roll of the curved reflective surface.

[0020] The heliostat dirigible shall be filled with lighter than air fluid, such as helium or hydrogen gas via gas tanks located on ground surface. The heliostat dirigible can have a gas pump installed on ground to deliver helium or hydrogen to a gas bag(s) sufficient to lift the dirigible. The gas bag(s) can be within the overall frame of the heliostat, including the shaped side(s) that provide a curved reflection surface. The helium or hydrogen gas can be pumped into or out of the gas bag(s) through the helium or hydrogen tanks storage system on ground.

[0021] Preferred embodiments provide a lightweight dirigible for a heliostat (solar concentrator) application. The design is not only significantly less weight than traditional “glass / metal” heliostats, the capital cost for installation is 90% less than aforementioned traditional heliostats. The maintenance cost of this design will be a fraction of traditional heliostats.

[0022] Preferred embodiments of the invention will now be discussed with respect to experiments and drawings. Broader aspects of the invention will be understood by artisans in view of the general knowledge in the art and the description of the experiments that follows.

[0023] FIG. 1 is a not-to-scale schematic view of a preferred concentrating solarthermal power system 100 including a preferred heliostat dirigible 102. A curved reflective surface 104 is shaped, preferably concave, to concentrate power toward a focal point 106 that receives concentrated light. The focal point 106 in a preferred embodiment is tall tower where the concentrated light heats a working fluid, and the heated fluid can spin a turbine. The concentrated light can also be directed to another target such as a focal point 106 that then distributes the concentrated light to one or more solar cells. The curvedreflective surface 104 can be configured to direct the concentrated light to a small point, or over a broader focal area such as a solar panel.

[0024] The reflective surface 104, in an example implementation can have an approximate total surface area range of several hundred to several thousand square feet. Such areas are many times the surface area of conventional heliostats. Generally, the size of the reflective surface 104, components of the reflective surface 104, and the heliostat dirigible 102 is readily scalable to suit particular applications.

[0025] The heliostat dirigible 102 includes an outer segmented frame 108 that holds a plurality of individual reflective elements 110. Tethers 112 include ground-based controlled motors 114 to adjust the attitude and / or altitude of the heliostat dirigible. By retracting, extending or moving the tethers 112 with respect to each other, the controlled motors 1 14 can control the pitch, yaw and roll of the curved reflective surface 104. Motors 114 are preferably mobile motorized capstans as have been used in marine applications and can be controlled via wireless connection. Within the frame 108 is a fluid membrane 116 that defines a fluid containment structure defining a fluid volume configured to contain a lighter than air fluid. The fluid membrane 116 (e.g., a gas bag) can be a separate structure from the frame 108, as in FIG. 1, or can be integral with an interior or the frame 108. A ground-based gas source and pump 120 can supply, maintain and regulate the lighter-than- air fluid in the fluid membrane via a supply hose 122. The gas source and pump 120 can also be mobile and controlled wirelessly.

[0026] FIG. 2 front view shows the curved reflective surface 104. The segmented frame 118 is attached to a base 202 of the heliostat dirigible 102. Segments of the frame 118 and individual reflective elements 110 are arranged such that the curved reflective surface 104 is inclined toward the central major axis 204 from the base 202 to an opposite end tip 206 of the heliostat dirigible 102. The curved reflective surface 104 is preferably inwardly curved such that a midline (that is on the central major axis 204) from the base to the tip is closer to the central major axis 204 than other portions of the curved reflective surface. The segments of the frame 118 and individual reflective elements 110 are also arranged toform a paraboloid reflective surface, which can effectively concentrate reflected light toward the focal point 106.

[0027] FIGs. 3A-3C show a portion of the frame 118 and one of the individual reflective elements 110. Multiple portions of the frame 118 together form part of the curved reflective surface 104 as shown in FIG. 3A. FIG. 3B shows that the frame provides an opening 302 that is preferably closely sized to an individual reflective element 110 show in FIG. 3C. This can provide a friction or interference fit, and a backing 304 of the frame 118 can provide a surface for an adhesive to provide adherence between the frame 118 and the reflective element 110. Each of the reflective elements 110 preferably includes a lightweight and rigid substrate 306 that is coated with or attached to a reflective material 308. A suitable substrate is made from closed-cell extruded polystyrene foam, such as Styrofoam® brand material. Other materials that can form a suitable lightweight and rigid substrate include com-based materials, molded fibers and molded pulps. Thin wood materials and others will be apparent to artisans.

[0028] FIGs. 3D-3F show a variation of the portion of the frame 118 and the individual reflective elements 110 in FIGs. 3A-3C. The lightweight and rigid substrate 306 includes a diagonal fold line 318 (formed e.g. via partial cut through the material of the substate 306). The fold line 318 creates more curvature, and the example shows angles with respect to vertical and horizontal edges that establish a smooth curvature for the reflective surface 104. Additional fold lines and different angles can be used to create a desired focus point or area depending upon the overall size of the reflective surface 104 and the size of the individual reflective elements 110.

[0029] The reflective material can be formed from aluminized mylar or polytetrafluoroethylene (PTFE). Other materials include aluminum foils, though aluminum foils are less reflective than aluminized mylar. Reflective fabrics can also be used.

[0030] FIG. 4 shows that the curved reflective surface 104 of the heliostat dirigible 102 forms a concave paraboloid from a convex cut. The control achieved through the tethers112 and the fluid allows the FIG. 1 system to adjust the position of the curved surface while the sun changes position during the day and efficiently collect the sunlight, concentrate it, and direct it at the focal point 106.

[0031] While specific embodiments of the present invention have been shown and described, it should be understood that other modifications, substitutions and alternatives are apparent to one of ordinary skill in the art. Such modifications, substitutions and alternatives can be made without departing from the spirit and scope of the invention, which should be determined from the appended claims.

[0032] Various features of the invention are set forth in the appended claims

Claims

CLAIMS1. A heliostat dirigible comprising: a fluid containment structure defining a fluid volume configured to contain a lighter than air fluid; a curved reflective surface supported by the fluid containment structure when the fluid volume contains a lighter than air fluid, wherein the curved reflective surface is configmed to reflect and concentrate sunlight at a target; and tethers and / or connections for a plurality of tethers arranged around the fluid containment structure such that the attitude of the fluid containment structure can be adjusted when it is floating above the ground.

2. The heliostat dirigible of claim 1, wherein the fluid containment structure comprises fluid membrane within a frame.

3. The heliostat dirigible of claim 2, wherein the frame comprises a plurality of curved sections in an area of the curved reflective surface, and a plurality of individual reflectors are held in the plurality of curved sections.

4. The heliostat dirigible of any previous claim, wherein the curved reflective surface is formed from plurality of individual reflectors.

5. The heliostat dirigible of claim 4, wherein the individual reflectors each comprise a lightweight substrate that supports a reflector.

6. The heliostat dirigible of claim 5, wherein the substrate comprises a diagonal fold line.

7. The heliostat dirigible of claim 5, wherein the substrate is rigid.

8. The heliostat dirigible of claims 6 or 7, wherein the substrate comprises or consists of a closed-cell extruded polystyrene foam.

9. The heliostat dirigible of any previous claim, wherein the reflective surface comprises aluminized mylar or polytetrafluoroethylene (PTFE).

10. The heliostat dirigible of any previous claim, wherein the curved reflective face is inclined toward the central major axis from the base to an opposite end of the heliostat dirigible.

11. The heliostat dirigible of any previous claim, wherein the curved reflective surface is inwardly curved such that a midline from the base to the tip is closer to the central major axis than other portions of the curved reflective surface.

12. A CSP plant comprising a plurality of heliostat dirigibles of any previous claim deployed and controlled to concentrate sunlight toward one or more targets containing fluid to be heated.

13. A heliostat system comprising a heliostat dirigible of any previous claim, tethers and controllers to adjust the attitude and / or altitude of the heliostat dirigible.

14. The heliostat system of claim 13, wherein the controllers control the pitch, yaw and roll of the reflective surfaces.

15. The heliostat system of claim 13, wherein the controllers comprise capstan motors.

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