Inflatable heliostatic solar power collector

Increased utilization of solar power is highly desirable as solar power is a readily available renewable resource with power potential far exceeding total global needs; and as solar power does not contribute to pollutants associated with fossil fuel power, such as unburned hydrocarbons, NOx and carbon dioxide. The present invention provides low-cost inflatable heliostatic solar power collectors, which can be stand-alone units suitable for flexible utilization in small, medium, or utility scale applications. The inflatable heliostatic power collectors use a reflective surface or membrane “sandwiched” between two inflated chambers, and attached solar power receivers which may be of photovoltaic and/or solar thermal types. Modest concentration ratios enable benefits in both reduced cost and increased conversion efficiency, relative to simple prior-art flat plate solar collectors.

BACKGROUND OF THE INVENTION

Increased utilization of solar power is highly desirable as solar power is a readily available renewable resource with power potential far exceeding total global needs; and as solar power does not contribute to pollutants associated with fossil fuel power, such as unburned hydrocarbons, NOx and carbon dioxide. Solar powerplants produce no carbon dioxide that contributes as a greenhouse gas to global warming—in sharp contrast to fossil fuel powerplants such as coal, oil, natural gas, or even biofuel powerplants. Limitations to the widespread deployment of solar power, either solar photovoltaic power or solar thermal power, have largely been a consequence of higher power cost per kilowatt-hour for traditional solar power systems as compared with fossil fuel power systems, driven in large part by the cost to make these solar power systems.

As an enabler for low cost solar power, the idea of using inflatable heliostats (devices that track the Sun's apparent motion), was first proposed in the pioneering U.S. Pat. No. 5,404,868 entitled “Apparatus Using a Balloon Supported Reflective Surface for Reflecting Light from the Sun.”

BRIEF SUMMARY OF THE INVENTION

The present invention provides further inventive development of inflatable heliostat devices, with added novelty in multiple areas. More specifically, the present invention provides for low-cost inflatable heliostatic solar power collectors, which are stand-alone units suitable for use in small, medium, or utility scale applications, as opposed to prior art “power tower” concepts best suited for utility scale application. In one preferred embodiment the inflatable heliostatic power collector uses a reflective surface or membrane “sandwiched” between two inflated chambers, and an elongated solar power receiver which receives solar insolation reflected and concentrated by this reflective surface.

The power receiver may be of photovoltaic and/or solar thermal types, in variant preferred embodiments of the invention. The utilization of modest concentration ratios enables benefits in both reduced cost and increased conversion efficiency, relative to simple prior-art flat plate solar collectors.

In a preferred embodiment the inflatable structure includes inventive application of simple lightweight and low cost frame members, and heliostatic aiming for azimuth and elevation control using simple and low cost motorized control means. The invention provides great flexibility and value in tailored applications using varying numbers of the low-cost inflatable heliostatic power collectors, of varying scalable size designs, for optimal use in applications ranging from (i) one or a few units for private home installations on a rooftop or back-yard, to (ii) estate/farm/ranch/commercial building installations with a small/medium field of units, to (iii) utility scale installations with medium/large/very large field(s) of units.

DETAILED DESCRIPTION

FIG. 1Ashows a left end view of a preferred embodiment of the invention, an inflatable heliostatic solar power collector1that applies an ingenius lightweight inflatable structural design to enable concentrating solar powerplants with elongated solar receivers that can be made at unprecedented low cost—for small, medium and large-scale applications for electricity and/or heat generation from clean, renewable and plentiful solar power coming from the Sun.

An inflatable heliostatic solar power collector1is shown, comprising: a reflection and concentrating surface3for reflecting and concentrating sunrays; a substantially enclosed upper inflatable volume4above said reflection and concentrating surface3, with a transparent surface5above said upper inflatable volume; a substantially enclosed lower inflatable volume6below said reflection and concentrating surface3, with a bottom surface7below said lower inflated volume; support structure8for supporting said solar power collector on a supporting surface10; and heliostatic control means11for aiming said solar power collector as a function of at least one of time and other parameters, such that incoming sunrays14from a sunward direction will be reflected and concentrated by said reflection and concentration surface, onto a structurally connected solar power receiver2proximate to said transparent surface5, at a concentration ratio of at least 2 suns.

The embodiment ofFIG. 1Acan also be described as an inflatable heliostatic solar power collector1, comprising: an elongated solar power receiver2E (elongation axis into the page in this end view); a reflection and concentrating surface3for reflecting and concentrating sunrays; a substantially enclosed elongated upper inflatable volume4above said reflection and concentrating surface3, with a transparent surface5above said upper inflatable volume; a substantially enclosed elongated lower inflatable volume6below said reflection and concentrating surface3, with a bottom surface7below said lower inflated volume; support structure8for supporting said solar power collector on a supporting surface10; and heliostatic control means11for aiming said solar power collector as a function of at least one of time and other parameters, such that incoming sunrays14from a sunward direction will be reflected and concentrated by said reflection and concentration surface, onto said elongated solar power receiver2E at a concentration ratio of at least 2 suns.

With the elongated solar power receiver2E receiving concentrated solar radiation, an optional set of cooling fins24may be provided immediately adjacent to and above the solar power receiver, to prevent any undesirable overheating of the solar power receiver with potential adverse effects on material properties and/or solar receiver efficiency.

InFIG. 1Athe illustrated support structure8includes permanently connected elongated framing members9forming a framework around the upper inflatable volume4and lower inflatable volume6, as well as 2 support legs8L visibly illustrated in this view, out of multiple support legs numbering from 3 to 12 in typical embodiments.FIG. 1Aalso shows that support structure8further includes a front support bar30, a rear support bar32, and a curved connecting bar34connecting the ends of the front support bar30and the rear support bar32; and also further includes a cross-section perimeter enclosing structural ring23which can contribute to restraining the transparent surface5and the bottom surface7against inflation-induced forces arising from inflation of the upper part and the lower part of the inflatable volume (i.e., the upper inflatable volume4and lower inflatable volume6in the illustrated embodiment). In the illustrated embodiment the supporting surface10is an Earth surface10E. While a level Earth or ground surface is shown, in alternate embodiments the invention can be installed on a sloped surface, and surface treatments such as local paving with asphalt or a concrete pad could be optionally used.

FIG. 1Afurther illustrates the inflatable heliostatic solar power collector1, wherein the support structure8includes means for fixedly engaging the supporting surface10and further includes bearing-connected means for supporting the combination of the bottom surface7, the reflection and concentrating surface3, the transparent surface5and the solar power receiver2, so as to permit motion of said combination as commanded and controlled by heliostatic control means; wherein the heliostatic control means here includes (i) powered elevation control means11E for orienting said combination in elevation angle, and (ii) powered azimuth control means11A for orienting said combination in azimuth angle.

The transparent surface5could be a flexible transparent sheet made of representative materials such as transparent polycarbonate film or transparent vinyl or polyethylene film. Desired attributes of the transparent sheet include high transparency, tensile strength, low cost, weather resistance, resistance to discoloration from sunlight exposure, temperature resistance, durability, scratch & impact & tear & puncture resistance against wind-blown sand, heavy rain, sleet or hail. In variant embodiments part or all of the transparent surface could also optionally use semirigid or rigid transparent materials such as glass, tempered glass, acrylic or plexiglass, or semirigid or rigid polycarbonate. The bottom surface7could be made of nontransparent or not necessarily transparent sheet material such as “plastic” sheet (e.g., polyester, polycarbonate, polyvinyl, etc.) or artificial or natural fabric material treated to be substantially airtight. Desired attributes of the bottom surface include durability, impact & tear & puncture resistance, ability to maintain an approximate desired shape, and very low cost.

FIG. 1Afurther illustrates the inflatable heliostatic solar power collector1, wherein said reflection and concentrating surface3includes a reflective membrane3R which is reflective on its upper side (e.g., a reflectorized polyester/mylar membrane as an example); and wherein an upwardly concave desired shape of said reflection and concentrating surface3is at least in part maintained by the application of differential inflation pressure between said upper inflatable volume4and said lower inflatable volume6, with an appropriate positive differential pressure contributing to imparting the upwardly concave desired shape. Note that the pressure-induced shape is approximately a circular arc shape, which in turn is an approximation of a perfectly focusing parabolic shape. In variant embodiments substantially rigid shaping elements may be affixed to the lower side of the reflection and concentrating surface, to also contribute to imparting the desired shape, which may be more precisely defined as a near-parabolic shape for embodiments with high concentration ratios of 30 or more. Desired attributes of a reflective membrane include tensile strength, very high reflectivity, smooth surface, ability to maintain the desired shape, temperature resistance, durability, and low cost.

FIG. 1Bshows the same view asFIG. 1A, now illustrating how a representative incoming sunray14I is reflected around a local normal vector15to the reflection and concentrating surface3, to proceed as representative reflected sunray14R to the solar power receiver2. The upwardly concave desired shape of said reflection and concentrating surface3is at least in part maintained by the application of differential inflation pressure between said upper inflatable volume4and said lower inflatable volume6, with an appropriate positive differential pressure contributing to imparting the upwardly concave desired shape. The desired shape will preferably reflect incident sunlight falling on the entire reflection and concentrating surface3onto the solar power receiver2, and preferably also without large local variations in solar energy flux hitting different points on the receiving surface of the solar power receiver.

FIG. 1Cshows an enlarged sectional view on a vertical plane cut, to illustrate in more detail how the preferred embodiment ofFIG. 1Aprovides heliostatic control means including (i) powered elevation control means11E for orienting said combination in elevation angle, and (ii) powered azimuth control means11A for orienting said combination in azimuth angle. The powered elevation control means11E comprises a powered sprocket13engaging an elevation control transmission element selected from the group16consisting of a chain and a cable—here a thin but strong strap with periodic holes that are positively and precisely engaged by the powered sprocket13. The termini of the strap are secured inside an outwardly facing Channel-section (C-section) structural ring23, adjacent to the outer face of the inner web23W of the C-section structural ring and between the two flanges of the C-section. The outward flange edges (with optional lips)23F of the C-section structural ring are also visible in this view. The powered sprocket13precisely executes elevation angle control of the heliostatic solar power collector, including the reflective surface and the solar receiver, by precisely moving the strap, which precisely rotates the structural ring23, which in turn precisely rotates the combination of the bottom surface7, the reflection and concentrating surface, the transparent surface and the solar power receiver, so as to permit motion of said combination as commanded and controlled by the heliostatic control means.

The structural ring23is located relative to a front support bar30by a front support roller31which provides bearing-connected means for the front support bar to support and locate the structural ring, with the front support roller31just fitting into the C-section between the outward flange edges23F and with a rolling contact engagement of the outer face of the inner web23W; and with the rear support roller33also just fitting into the C-section between the outward flange edges23F and with a rolling contact engagement of the outer face of the inner web23W. In alternate embodiments the rolling locating interface between the support bar and the structural rings can utilize any of a variety of track and wheel/roller or slot and wheel/roller interfaces, with the track or slot on either side of the interface, within the spirit and scope of the invention.

The front support bar30is supported on the structural base ring8B by front support bar supporting member30S, which is a panel or wall type member as illustrated, and may be of solid, hollow, or sandwich structural type. Similarly the rear support bar32is supported on the structural base ring8B by rear support bar supporting member32S, which is also a panel or wall type member as illustrated. The entire structural base ring8B is rotatable in azimuth angle by powered azimuth control means11A, with the azimuthal rotation being enabled by the use of bearing-connected means for support legs8L to support the structural base ring8B.

The powered azimuth control means11A comprises at least one of (i) a powered sprocket which engages an azimuth control transmission element selected from the group consisting of a chain and a cable, and (ii) a powered gear below said bottom surface7which powered gear engages and drives a gear element on an azimuth control element selected from the group of a structural base ring portion of said support structure and a base plate portion (here the structural base ring8B) of said support structure. In the illustrated preferred embodiment a powered gear is shown, here comprising a conventional gear type of edge drive gear36D which engages teeth on the outer edge of the structural base ring8B. Note that other gear types or friction engagement means may be used in alternate embodiments of the invention, and that chain/cable driven azimuth control can be provided in still other embodiments, within the spirit and scope of the invention as described and claimed herein.

The heliostatic control means includes at least one of an electrically powered motor, a linear actuator, and a stepper motor, with a stepper motor12S here illustrated as driving the edge drive gear36D to precisely control the azimuth angle of the structural base ring8B, and thence the azimuth angle of the combination of the bottom surface7, the reflection and concentrating surface, the transparent surface and the solar power receiver, so as to permit azimuthal motion of said combination as commanded and controlled by the heliostatic control means.

The combination of the azimuth control and the elevation control enable heliostatic pointing of the inflatable solar power collector to always face the Sun, and to maximize power collected at any installation location, time of year and time of day. A heliostatic control module40is illustrated, which includes power and computation means such as a microprocessor or computer, to issue azimuth and elevation control commands. The heliostatic control means for aiming said solar power collector as a function of at least one of time and other parameters, preferably performs its aiming function also as a function of at least one of (i) time of day, (ii) time of year, (iii) latitude of the location of installation of said heliostatic solar power collector, (iv) installation orientation of the support structure relative to the supporting surface10, and (v) slope of the supporting surface. The heliostatic control module40may also optionally combine and incorporate power conditioning means for receiving solar power from the solar receiver, conditioning this power as desired (AC vs DC, frequency, phase, voltage and current characteristics, transient smoothing/control, etc), and then transmitting the power to a user, e.g. via an electrical wire or cable.

FIG. 1Dshows a similar view asFIG. 1C, but with the azimuth drive now using an edge drive worm gear36W engaging inclined teeth on the upper outer perimeter of the structural base ring8B. In this illustrated embodiment the worm gear is driven by an electrically powered motor12E, rather than a stepper motor. In variant embodiments alternate combinations of motors (and/or linear actuators) and gears can be used within the sprit and scope of the invention as defined and claimed herein.

FIG. 2Ashows a front view of the preferred embodiment ofFIG. 1AandFIG. 1B.

As illustrated, the inflatable heliostatic solar power collector1includes a solar power receiver2which is a photovoltaic receiver2P in the configuration of a linear solar power collector18.

The geometric configuration of the solar power collector1is seen to include a central portion19with an approximately constant cross-section on planar cuts perpendicular to an axis of elongation20of the elongated solar power receiver2E, and further includes left end closure portion21L and right end closure portion21R on the left and right sides of said central portion, which left and right closure portions serve to provide left and right side enclosure for said upper inflatable volume4and said lower inflatable volume6. The left and right closure portions may use enclosing surfaces which are flexible membranes, semirigid surfaces such as flexible membranes with rigidifying and/or shaping attached members, and/or rigid enclosing surface members. When flexible members are used, they may be either unshaped flexible members which assume a desired shape under inflation pressure, or shaped or tailored flexible members that have a nominal shape that is maintained or reinforced when subject to inflation pressure. An example of prior art use of flat flexible members that take a desired shape under inflation pressure is the use of two flat sheets seamed together at their edges in mylar balloons, which when inflated take an oval or near-ellipsoidal shape, with membrane crinkling at the equatorial seams of the balloon.

FIG. 2Aalso clearly shows that support structure8including permanently connected elongated framing members9forming a framework around the upper inflatable volume4and lower inflatable volume6, further comprises a plurality of cross-section perimeter enclosing structural rings23which can contribute to restraining the transparent surface5and the bottom surface7against inflation-induced forces arising from inflation of the upper part and the lower part of the inflatable volume (i.e., the upper inflatable volume4and lower inflatable volume6in the illustrated embodiment).

Connecting interfaces between various combinations of the reflection and concentrating surface3, the transparent surface5, the bottom surface7, the framing members9and the structural rings23, can be of a variety of many known interface types including mechanical interfaces (e.g., tongue & groove joints, zip-lock type joints etc), fastener connected interfaces (e.g., using bolts, nuts, screws, rivets, zippers etc), heat-welded or laser-welded seams, bonded joints with lap or butt joint interfaces, sealing taped joints, and combination or hybrid joints and interfaces as known from the prior art. A required condition of whatever is the selected interface and joint solution is that the upper inflatable volume4and the lower inflatable volume6must be fully enclosed and sealed to prevent air leakage from these inflated volumes to the atmosphere outside the inflatable heliostatic solar power collector1, using some combination of the surfaces, framing members and structural rings as recited above, along with appropriately sealed interfaces or joints. Selection of specific joint architectures should preferably take into consideration low cost and weight, minimizing leaks, and ease of repair or replacement of surfaces or portions of surfaces in case of damage (scratching etc) or rupture. One option would be to use sealed seams at a perimeter interface line connecting the transparent surface5, reflection and concentration surface3, and bottom surface7, to fully enclose the upper inflatable volume4and the lower inflatable volume6, while connecting outside the inflatables to the framing members. Another option would be to use panels of surface members such as membranes, which connect to adjacent framing members around each panel's perimeter and are sealed at those interfaces (e.g., using a bonded lap joint, a heat-seamed lap joint, or a zipper or zip-locked joint with a covering adhesive sealing tape which is transparent for transparent surface sealing). The use of multiple panels increases the risk of leaks, but eases the ability to replace a single damaged panel if such localized damage should occur.

FIG. 2Bshows the same view asFIG. 2A, but with the upper and lower parts of the inflatable heliostatic solar power collector1separated to more clearly show the component elements. The framing members9are more clearly distinguishable, with a top frame member9T above the upper inflated volume4and adjacent to and contributing to the support of the elongated solar receiver2E; a front frame member9F substantially at the intersection of the front bottom edge of the transparent surface5, the front edge of the reflection and concentrating surface3, and the front top edge of the bottom surface7; and a bottom frame member9B near (but in this example not located exactly at) the bottom of the bottom surface7. Again, the bottom frame member9B may also optionally include some ballast weight to help locate the center of mass of the rotating-in-elevation parts of the device as elevation angle pointing control is executed by the heliostatic control means11.

FIG. 3Ashows a rear view of the preferred embodiment ofFIGS. 1A and 2A.

FIG. 3Ashows an inflatable heliostatic solar power collector1, comprising: a reflection and concentrating surface3for reflecting and concentrating sunrays; a substantially enclosed upper inflatable volume4above said reflection and concentrating surface3, with a transparent surface above5said upper inflatable volume4; a substantially enclosed lower inflatable volume6below said reflection and concentrating surface3, with a bottom surface7below said lower inflated volume6; support structure8for supporting said solar power collector on a supporting surface10; and heliostatic control means11for aiming said solar power collector as a function of at least one of time and other parameters, such that incoming sunrays from a sunward direction (down from the top of the page in the illustrated view) will be reflected and concentrated by said reflection and concentration surface3, onto a structurally connected solar power receiver2proximate to said transparent surface5, at a concentration ratio of at least 2 suns;

wherein said solar power receiver2further comprises means for generating useful electrical power from received solar power (here comprising the solar cell elements included in photovoltaic receiver2P); wherein said solar power receiver2is an elongated solar power receiver2E that has greater length along an axis of elongation20than along any other axis; wherein said reflection and concentrating surface3has greater length along said axis of elongation20than along any other axis; wherein said transparent surface5, said bottom surface7, and said reflection and concentrating surface3each include flexible membrane elements whose shapes are dependant on inflation of said upper inflatable volume4and said lower inflatable volume6; wherein an upwardly concave desired shape of said reflection and concentrating surface3is at least in part maintained by the application of differential inflation pressure between said upper inflatable volume4and said lower inflatable volume6; further comprising an enclosing structural ring23on a plane substantially perpendicular to said axis of elongation20, which enclosing structural ring23can contribute to restraining said transparent surface5and said bottom surface7against inflation-induced forces arising from inflation of the upper part and the lower part of the inflatable volume (i.e., the upper inflatable volume4and lower inflatable volume6respectively); further comprising an elongated structural member (here the top frame member9T) that has greater length along an axis of elongation than along any other axis, which elongated structural member provides structural support to maintain said elongated solar power receiver2E in its desired location and orientation to receive sunrays reflected and concentrated by said reflection and concentrating surface3; further comprising elongated side perimeter structural members (i.e., rear frame member9R visible in this view, and front frame member9F visible in the view shown inFIG. 2B) that have greater length along said axis of elongation than along any other axis, which elongated side perimeter structural members contribute to supporting said reflection and concentrating surface3along at least portions of the perimeter of said reflection and concentrating surface, and which elongated side perimeter structural members also provide perimeter restraint to at least one of said transparent surface5and said bottom surface7; and wherein said heliostatic control means11includes at least one of (i) electrically powered elevation control means11E for orienting the inflatable heliostatic solar power collector1in elevation angle, and (ii) electrically powered azimuth control means11A for orienting the inflatable heliostatic solar power collector1in azimuth angle.

The inflatable heliostatic solar power collector1is here seen with the support structure8including means27for fixedly engaging the supporting surface10, support legs8L, structural base ring8B, rear support bar32, curved connecting bars34, and other components which together comprise bearing-connected means for supporting the combination of the bottom surface7, the reflection and concentrating surface3, the transparent surface5and the solar power receiver2, so as to permit motion of said combination as commanded and controlled by the heliostatic control means.

FIG. 3Bshows the view and embodiment ofFIG. 3A, but further illustrates how representative incoming sunrays14I are reflected around local normal vectors15to the reflection and concentrating surface3, to proceed as representative reflected sunrays14R to the solar power receiver2. The upwardly concave desired shape of the reflection and concentrating surface3is at least in part maintained by the application of differential inflation pressure between the upper inflatable volume4and the lower inflatable volume6, with an appropriate positive differential pressure contributing to imparting the upwardly concave desired shape. Note that the reflection and concentrating surfaces3in the left end closure portion21L and the right end closure portion21R are actually concave along two axes, to reflect light from these portions onto the narrow depth and along the long axis of the elongated solar power receiver2E.

FIG. 4Ashows a top view of the preferred embodiment ofFIGS. 1A,2A and3A.

The inflatable heliostatic solar power collector1is illustrated, further comprising perimeter structural members including font frame member9F, rear frame member9R, bottom frame member9B & optional bottom corner members9BC, top frame member9T, structural rings23, left end frame member9LE and right end frame member9RE, all supporting said reflection and concentrating surface3along at least portions of the perimeter of said reflection and concentrating surface. The perimeter structural members also provide perimeter restraint to at least one of said transparent surface5and said bottom surface (not visible in this view as it lies below the reflection and concentrating surface3).

The inflatable heliostatic solar power collector1comprises a solar power receiver2which is a photovoltaic receiver2P, and further comprises means for cooling said photovoltaic receiver comprising at least one of cooling fins, blown air cooling, liquid cooling, and mixed phase boiling cooling—with cooling fins24shown in the illustrated embodiment. The use of multiple elongated cooling fins24to remove heat and reduce temperature for photovoltaic receiver/solar cell elements takes advantage of a large and distributed heat dissipation area to allow the solar cells to operate at lower temperatures where they are more efficient, especially for silicon solar cells.

FIG. 4Bshows a top view looking “through” the elements illustrated inFIG. 4Awhich are made “invisible” here but located in dotted lines, to more clearly show the supporting structure beneath such as the structural base ring8B and additional support and heliostatic control elements. Six support legs8L are shown in a hexagonal layout, with the rightmost of these also serving as the location of the azimuth control means11A, as described in detail with reference toFIG. 1C. The support legs are connected to each other by optional leg connecting structure8LC, in this hexagonal layout, while each support leg is secured in the supporting surface by means27for fixedly engaging the support surface, such as concrete base imbedding or Earth screws to name two known approaches. Note that in alternate embodiments, alternate numbers of support legs from 3 and up can be used, in lieu of the 6 shown here. The structural base ring8B is supported by the support legs through bearing means that permit it to rotate as commanded to different azimuth orientations. The structural base ring8B supports a front support bar30through front support bar supporting members30S, which here comprise 3 substantially vertical panel-type structural members, but which may utilize truss or post type structural members in alternate embodiments. Similarly, the structural base ring8B supports a rear support bar32through rear support bar supporting members32S, which here also comprise 3 different substantially vertical panel-type structural members, but which may utilize truss or post type structural members in alternate embodiments.

For clarity, the full elevation control system is not shown inFIG. 4B, but the group16consisting of a chain and a cable is shown, lying along a path corresponding to the center of the three structural rings23. In alternate embodiments, the elevation control can be accomplished through chain/cable means or gear means, acting on any or all of the 3 structural rings shown; and in still other variant embodiments with other numbers of structural rings implemented, acting on any or all of that number of structural rings.

FIG. 4Cshows a top view of an embodiment very similar to that ofFIG. 4A, but with fan forced cooling rather than cooling by the cooling fins24with no forced airflow implementation. Thus this variant embodiment provides means for cooling the photovoltaic receiver2P comprising at least one of cooling fins, blown air cooling, liquid cooling, and mixed phase boiling cooling—specifically blown air cooling in this particular illustration. The air is blown by front and rear fans43which may be electrically powered fans using a small fraction of the electric power generated by the photovoltaic receiver2P. The electric fan motor is not shown, but any number of motors known from the prior art could be used, and drive the fans either through a single connecting shaft as shown (with fans blade pitch and twist set to produce flow in opposite directions) or through alternate drivetrain means. There is also an airflow tube44with left and right sides covering the cooling fins24, so if the fans are blowing outwards air is sucked in from the left and right ends of the airflow tube and forced along the length of the cooling fins until it is blown outwards near the center of the cooling fin assembly. In alternate embodiments the fans may blow inward rather than outward. The walls of the airflow tube may be transparent, to allow incident sunlight to pass through the airflow tube to the reflection and concentrating surface3, with reduced shadowing losses.

FIG. 4Dshows a variant embodiment similar toFIG. 4C, with means for cooling the photovoltaic receiver comprising at least one of cooling fins, blown air cooling, liquid cooling, and mixed phase boiling cooling; wherein the illustrated cooling fins24serve dual purposes of (i) removing heat from the photovoltaic receiver2P to enable a lower temperature and higher efficiency of the photovoltaic receiver (e.g., for many silicon based solar cells, temperatures below around 55 to 70 degrees C.); and (ii) adding that heat to a solar thermal engine and powerplant integrated into this variant solar power collector1.

FIG. 4Dshows the inflatable heliostatic solar power collector1, wherein the solar power receiver is a combined photovoltaic receiver and solar thermal receiver; and wherein incoming sunrays from a sunward direction will be reflected and concentrated by said reflection and concentration surface onto said photovoltaic receiver, and wherein waste heat from said photovoltaic receiver is conducted as a heat flow to an adjacent solar thermal receiver on the opposite side of said photovoltaic receiver as the light receiving side of the photovoltaic receiver.

Thus the embodiment ofFIG. 4Dprovides an inflatable heliostatic solar power collector1, wherein a solar thermal receiver utilizes solar thermal heat flow to power a thermodynamic cycle engine comprising at least one of a Brayton cycle engine, a Rankine cycle engine, a Sterling cycle engine and an Otto cycle engine—in the illustrated embodiment a Brayton cycle engine with air flowing in through a compressor46, being heated by the heat from the cooling fins24, then flowing out through turbines45, which in turn drive a drivetrain and generator48which both produces solar thermal electricity and drives the compressor. This embodiment thus produces both photovoltaic power and solar thermal power in a hybrid and integrated device, with the solar thermal part using a gas turbine engine with heat provided by “waste heat” from the photovoltaic receiver, as opposed to combustion processes in conventional gas turbine engines such as aircraft jet engines or gas turbine powered electric generators used in certain electric power utility installations.

The solar thermal generator can optionally be run “backwards” to start the compressor and turbines rotating when the solar thermal powerplant is just started up, as in morning or after recovering from a period of cloud cover back into sunshine conditions. Also, an axial compressor configuration is shown, while in alternate embodiments a centrifugal or combined centrifugal+axial compressor could be used. Finally, a single stage turbine is shown, while in alternate embodiments multi-stage turbines could be used.

FIG. 5Ashows a similar view of an alternate embodiment similar to that shown inFIG. 1B, but with a noncircular inflatable cross-section, where the upper inflatable volume4is now taller than it is wide, in this view. The sectional shape of the transparent surface5is now oval or elliptical rather than circular in shape. The reflection and concentrating surface3has a less sharply concave upward shape than the embodiment ofFIG. 1B, to achieve a similar concentration function onto the solar receiver2, which is now at a greater focal distance from the reflective surface.

FIG. 5Aalso illustrates the inflatable heliostatic solar power collector1, wherein said heliostatic control means includes at least one of an electrically powered motor, a linear actuator, and a stepper motor—wherein the illustrated embodiment shows a linear actuator12A. This particular linear actuator installation may also have a supplementary angular actuator (such as the illustrated rotary actuator) to command the direction of orientation of the linear actuator as it goes through “bottom dead center”.

FIG. 5Billustrates an inflatable heliostatic solar power collector1, further comprising means for performing inflation control50including at least one of means for increasing, means for maintaining, means for decreasing, and means for controllably adjusting inflation pressure, in at least one of said upper inflatable volume4and said lower inflatable volume6. The illustrated means for performing inflation control further includes at least one of an inflation valve, a deflation valve, and an air pump.

FIG. 5Bfurther illustrates an inflatable heliostatic solar power collector1, wherein the reflection and concentrating surface3is contacted by at least one of adjacent shaping means for contributing to a desired shape of said reflection and concentrating surface, and damping means for damping undesirable motions of said reflection and concentrating surface—here comprising viscoelastic damping material52on the nonreflective underside of the reflection and concentrating surface3.

FIG. 5Balso shows the use of screw anchors27S, as means for fixedly engaging the supporting surface10, here an Earth surface10E.

FIG. 5Cshows another embodiment similar to that ofFIG. 5B, but now with a substantially parabolic “semirigid” shaped reflection and concentrating surface3as well as a semirigid or rigid transparent surface5. The substantially parabolic shape is here achieved by the use of a substantially rigid mirror element3M with a parabolic shape reflective surface, and with reflective membrane3R on either side of the mirror element, with shaping means53here comprising membrane shaping ribs on the bottom, nonreflective sides of the reflective membranes, to impart an approximately parabolic shape to the reflective membrane portions of the reflection and concentrating surface3.

ThusFIG. 5Cprovides an inflatable heliostatic solar power collector1, wherein said reflection and concentrating surface3includes at least one of (i) a reflective membrane which is reflective on its upper side and (ii) a mirror element—in the illustrated embodiment mirror element3M. The illustrated embodiment also shows an inflatable heliostatic solar power collector1, wherein said reflection and concentrating surface3is contacted by adjacent shaping means53for contributing to a desired shape of said reflection and concentrating surface.

FIG. 5Dshows a left side cross-sectional view of another embodiment of the invention. In this embodiment the reflection and concentrating surface has no pressure differential across it, but is shaped in part by the effect of shaping tension elements53T such as tethers, in part by fabrication of an inherent shape into the membrane, and in small part by gravitational forces. The reflection and concentrating surface3is a reflective membrane3R, supported around its perimeter by a reflective surface perimeter ring54. The perimeter ring54is in turn supported by perimeter ring positioning elements55, which may be tether, rod or trusswork elements.

FIG. 5Dthus shows an inflatable heliostatic solar power collector1, comprising: an inflatable volume with a substantially constant cross-section58; a solar power receiver2at the top of said cross-section when the Sun is directly overhead (as shown with incoming vertical sunrays14); a reflection and concentrating surface3traversing said cross-section and dividing said inflatable volume into an upper part4P and a lower part6P; a transparent surface5above said upper part; a bottom surface7below said lower part; end cap means56for closing the two ends of said inflatable volume outward from the end planes bounding the constant cross-section portion of the inflatable heliostatic solar power collector1; and heliostatic control means11for aiming said solar power collector as a function of at least one of time and other parameters, such that incoming sunrays14from a sunward direction will be reflected and concentrated by said reflection and concentration surface3, onto said solar power receiver2at a concentration ratio of at least 2 suns. Note that while the upper part4P and lower part6P of the inflated volume with substantially constant cross-section58are connected in the illustrated embodiment, in alternate embodiments they may be separate and distinct, unconnected parts in the sense that air could not move freely between these two parts.

The inflatable heliostatic solar power collector1ofFIG. 5Dfurther comprises a plurality of cross-section perimeter enclosing structural rings23(one seen in this view) which can contribute to restraining said transparent surface5and said bottom surface7against inflation-induced forces arising from inflation of the upper part4P and the lower part6P of said inflatable volume.

The heliostatic control means11includes elevation control means11E for engaging and precisely rotating at least one of said structural rings23to effect elevation angle control of said solar power collector; and powered elevation control means are provided which comprise a powered gear (here the elevation angle control worm gear38W) engaging and driving a gear element on (the outer face of) a structural ring23engaging said transparent surface5and said bottom surface7and enclosing a region which includes portions of said upper inflatable volume4P and said lower inflatable volume6P. The structural rings23and inflatable skins5and7are connected to and supported by the end cap means56in this illustrated embodiment, with elevation rotation bearings between the end cap means56and the end cap support bars57.

FIG. 5Dfurther illustrates the inflatable heliostatic solar power collector1, wherein said reflection and concentrating surface3is contacted by adjacent shaping means53for contributing to a desired shape of said reflection and concentrating surface3and wherein said adjacent shaping means53comprises connected shaping tension elements.

FIG. 6Ashows a left side view of an embodiment of the invention with a solar thermal receiver that receives concentrated reflected solar radiation and utilizes that solar power to boil water pumped by a recirculation pump72through transport tubes and through boiling tubes70with light absorbing lower surfaces, such as black painted metal. The water is boiled in the boiling tubes, and the resulting steam is transported through other transport tubes71(possibly concentric with the incoming water tubes) either directly to an end user or customer which desires heat (e.g., for home heating or building heating or swimming pool heating or industrial process heat); or optionally through a steam turbine module45S connected to a steam turbine driven power generator69. The use of an elongated solar thermal receiver2T enables boiling of water flowing in the boiling tubes even with lower levels of incoming solar radiation, as heat is added to the flowing water over an elongated flow path. Depending on levels of solar radiation, appropriate steam generation and heat and temperature profiles along the boiling tubes can be achieved by varying flow rate through these boiling tubes, and by use of different size boiling tubes for potential different locale applications with different average levels of solar insolation.

FIG. 6Ashows an inflatable heliostatic solar power collector1, wherein the solar power receiver is a solar thermal receiver2T, and further comprising means for conveying thermal power (transport tubes71) from said solar power collector to a destination for the beneficial use of said thermal power.

The optional steam turbine module45S in conjunction with the recirculation pump72, transport tubes, and boiling tubes70at the solar thermal receiver2T, together comprise thermodynamic engine means for converting a portion of the output of the solar thermal receiver2T into motion (at the steam turbine shaft output), and further comprise optional electrical power generation means for converting a portion of said motion into electrical power (in the steam turbine driven power generator69). The inflatable heliostatic solar power collector1, has a solar thermal receiver2T that utilizes solar thermal heat flow to power a thermodynamic cycle engine comprising at least one of a Brayton cycle engine, a Rankine cycle engine, a Sterling cycle engine and an Otto cycle engine—specifically a Rankine or steam cycle engine in the illustrated embodiment.

FIG. 6Bshows a variant embodiment to that ofFIG. 6A, with a combined photovoltaic and solar thermal receiver and powerplant. This embodiment features means for cooling the photovoltaic receiver comprising mixed phase boiling cooling; wherein the illustrated boiling tubes70serve dual purposes of (i) removing heat from the photovoltaic receiver2P to enable a lower temperature (e.g., typically around 100 deg C. or the boiling point of water, for advanced material concentrating solar cells) and potentially higher efficiency of the photovoltaic receiver; and (ii) adding that heat to a solar thermal engine and powerplant integrated into this variant solar power collector1.

FIG. 6Bthus shows the inflatable heliostatic solar power collector1, wherein the solar power receiver2is a combined photovoltaic receiver2P and solar thermal receiver; and wherein incoming sunrays from a sunward direction will be reflected and concentrated by said reflection and concentration surface3onto said photovoltaic receiver2P, and wherein waste heat from said photovoltaic receiver is conducted as a heat flow to an adjacent solar thermal receiver utilizing boiling tubes70on the opposite side of said photovoltaic receiver as the light receiving side of the photovoltaic receiver.

Thus the embodiment ofFIG. 6Bprovides an inflatable heliostatic solar power collector1, wherein a solar thermal receiver utilizes solar thermal heat flow to power a thermodynamic cycle engine comprising at least one of a Brayton cycle engine, a Rankine cycle engine, a Sterling cycle engine and an Otto cycle engine—in the illustrated embodiment a Rankine or steam cycle engine with steam from boiling tubes70flowing in out through steam turbines45S, which in turn drive a drivetrain and generator48which both produces solar thermal electricity and drives the recirculation pump71. This embodiment thus produces both photovoltaic power and solar thermal power in a hybrid and integrated device, with the solar thermal part using a steam engine with heat provided by “waste heat” from the photovoltaic receiver. Hybrid installations where the steam engine continues to run using heat from a fossil fuel or other nonsolar boiler during periods of night or cloud cover, are also possible with known adaptations of this embodiment. While mixed phase boiling is shown, in alternate embodiments Rankine cycles can be used with superheated steam as the working fluid.

FIG. 6Cshows another embodiment with combined photovoltaic and solar thermal receiver elements, but this time with photovoltaic elements on either side of a solar thermal element.

The inflatable heliostatic solar power collector1, features a solar power receiver2which is a combined photovoltaic receiver2P and solar thermal receiver2T, and wherein the elongated solar power receiver includes an elongated solar thermal receiver portion with elongated photovoltaic receiver portions disposed on either side of the elongated solar thermal receiver portion, as illustrated (axis of elongation into the page in this view).

The Inflatable Heliostatic Solar Power Collector of Claim7,

FIG. 6Calso shows means for cooling the photovoltaic receivers2P comprising at least one of cooling fins, blown air cooling, liquid cooling, and mixed phase boiling cooling, with cooling fins24illustrated but any of the other cooling options being possible in variant embodiments. With this layout of photovoltaic receiver elements straddling on either side of a solar thermal receiver, another conducive option would be to run cooling tubes with liquid, e.g. water from the recirculation pump, over the photovoltaic receiver to provide liquid cooling, while preheating the water before it runs through the boiling tube70for the solar thermal part of the receiver.

FIG. 7Ashows a rear view of another embodiment of an inflatable heliostatic solar power collector1, wherein the support structure8includes permanently connected elongated framing members forming a framework9PF around the upper inflatable volume4and lower inflatable volume6. This embodiment has a less wide constant cross-section portion than the corresponding embodiment ofFIG. 3B.

FIG. 7Bshows an embodiment similar toFIG. 7A, but with flat end caps rather than domed end caps. The flat end cap means56here comprise the left end frame member9LE and right end frame member9RE, which are rigid flat pressure bulkheads.

FIG. 7Cshows a front view of an embodiment wherein the inflatable heliostatic power collector1is in the approximate shape of an ellipsoid, with ends truncated by end cap means56connected through elevation angle change permitting hinge means to end cap support bars57. The solar power receiver2is still an elongated member, but curved to follow along the crown line of the ellipsoid and with a front to back (into the page) depth that increases near the center of the receiver. A single central structural ring23is provided, with the elevation control means11E engaging this structural ring23. The structural ring23can be a single piece or a multipiece ring, and made of metallic, plastic, composite or hybrid material construction. The upper inflatable volume4is bounded above by a transparent surface5, and bounded below by the reflection and concentration surface3, which now has appropriate curvature in two axes to appropriately reflect and focus incident sunlight onto the solar power receiver2. The lower inflatable volume6is bounded on top by the underside of the reflection and concentrating surface3, and bounded below by the bottom surface7.

The end cap support bars57are connected to and supported by a structural base ring8B, which in turn is supported by ground plate means8GP via azimuth control means11A, which rotate and control the base plate8B in azimuth angle.

FIG. 8shows an embodiment of an inflatable heliostatic solar power collector1, wherein the support structure8includes detachably connected elongated framing members9D forming a framework around the upper inflatable volume4and lower inflatable volume6. The detachably connected elongated framing members9D can have any of numerous known detachable connection means, including fastener means such as nut and bolt connectors, detachable adhesive-connected joints, nesting tube joints, tongue and groove joints, etc. Note also that the embodiment ofFIG. 8provides an inflatable heliostatic solar power collector1which is wider and has more reflective area than the embodiment ofFIG. 3B, through the use of staggered upper outboard framing members relative to their lower outboard framing member counterparts, with corner fittings transferring load across the staggered frame geometry. The combination of the elongated framing members and the corner fittings provide for a rigid, truss-like and cage-like structure connected to the flexible or membranous inflatable structure members, together to be able to resist wind loads and precipitation loads. Note that the embodiment ofFIG. 8also has a nonlinear geometry for the cooling fins24, and noncircular air holes in these cooling fins, to enable needed heat dissipation in the higher heat load central region of the elongated solar power receiver2E.

FIG. 9Ashows a top view of an embodiment similar to that shown inFIG. 4B, but with the structural base ring8B replaced by a structural base plate8BP. Adjustable support legs8LA are shown, which allow precise adjustment of the base plane of the inflatable heliostatic solar power collector; calibration via a calibration computer or microprocessor; and adjustment for sloping surface installation such as on a pitched roof surface of a building.

FIG. 9Bshows a top view of an arrangement of inflatable heliostatic solar power collectors1similar to the embodiment shown inFIG. 4B, in a rectangular array as illustrated on a supporting surface such as a ground surface or a building roof. Note that siting on a building roof is very feasible for these lightweight inflatable heliostatic solar power collectors1, as they do not put much of a weight load on that surface. In alternate embodiments the spacing along the different axes of the array can be varied, to balance objectives of higher density of installation to maximize solar power generated per unit surface area of ground or roof, versus reduced occurrences of shadowing of collectors by other collectors and as a function of latitude, surface slope, North orientation and possibly other parameters. In still other alternate embodiments, triangular, hexagonal, arc and spoke, or other regular or irregular arrays or arrangements of inflatable heliostatic solar power collectors can be used, within the spirit and scope of the invention.

FIG. 10Ashows a top view of an embodiment similar to that shown inFIG. 4A. This embodiment further illustrates an inflatable heliostatic solar power collector1, wherein the heliostatic control means for aiming said solar power collector, further comprises calibration means including calibration sensor and microprocessor62, for at least one of (i) adjusting aiming angles of said solar power collector (as for example by commanding incremental angular commands to the elevation control means11E and the azimuth control means11E shown inFIG. 1A) and (ii) adjusting shape of the reflection and concentrating surface3(as for example by commanding an incremental pressure differential to the means for performing inflation control50ofFIG. 5B), to optimize reception of sunrays reflected and concentrated by said reflection and concentration surface, on an elongated solar power receiver2E.

FIG. 10Afurther illustrates an inflatable heliostatic solar power collector1, further comprising electrical power conditioning means80for conditioning electrical power from the photovoltaic receiver2P. The electrical power conditioning means80may perform one or more of electrical power conditioning functions known from the prior art, such as DC to or from AC conversion, voltage changing, voltage and/or current stabilizing, phase control or changing, and/or other electrical power conditioning functions as are known from the prior art.

FIG. 10Afurther illustrates an inflatable heliostatic solar power collector1, wherein power output from the solar power collector1is further acted upon by at least one of electrical power conditioning means80for conditioning electrical power, wire transmission means81for transmitting electrical power, storage means82for storing energy obtained from a time integration of power from said solar power collector and for retransmitting power from said storage means when desired, and grid-engagement means84for permitting said power output to feed back into an electrical power grid85and at least one of slow, stop and reverse an electrical meter measuring net power flow from or to said electrical power grid85. The storage means82may utilize any of many known prior art technologies for storing energy, including battery, chemical, flywheel, and water pump & hydroelectric generator means for storing energy.

FIG. 10Bshows a left side view of an embodiment similar to that shown inFIG. 6A, illustrating an inflatable heliostatic solar power collector1, wherein the heliostatic control means11includes at least one of aiming processor means63for algorithmically computing and commanding desired orientation of said heliostatic solar power collector, stow processor means64for computing and commanding protective stow position of said solar power collector, and diagnostic processor means65for identifying at least one of nonoptimal and faulty operation of said heliostatic solar power collector. The various processor means may of course be combined into one or more multifunction processors, microprocessors or computers, in variant embodiments of the invention, with appropriate connectivity to sensors, controls, displays or annunciation means, and effectors and/or actuators. The aiming processor means63will preferably issue azimuth angle and elevation angle commands to the azimuth control means11A and the elevation control means11E respectively. The aiming processor means may also optionally issue concavity commands to control focusing concavity of a reflective membrane3R. The stow processor means64may be connected to a wind sensor, a precipitation sensor, and/or a potentially damaging particulate sensor (e.g., to sense sand in a sandstorm, and/or sleet and/or hail), and when the transparent surface5is in danger of being damaged, the stow processor means may command the inflatable heliostatic solar power collector1to an orientation which will eliminate or minimize damage to the transparent surface5, e.g., a downward orientation and/or a downwind orientation. Alternately, the stow processor means may annunciate a dangerous condition to an operator, and request installation of a covering tarp to protect the transparent surface. Alternate embodiments with self-deploying reel-out tarps are also possible. The diagnostic processor means65will receive diagnostic signals from appropriate sensors, to enable it to diagnose nonoptimal and/or faulty operation such as nonoptimal/faulty pointing, nonoptimal/faulty reflective surface shaping, and/or optical faults with the transparent surface5and/or with the reflection and concentrating surface3(as for example caused by dirt, deposits or scratches on these surfaces). If the transparent surface is dirty enough as to degrade performance, the diagnostic processor may annunciate this to an operator, who can then hose off the transparent surface5to clean it, or wash with a cleaning solution such as soap solution or a dirt solvent solution. The diagnostic processor may also diagnose pressure leaks or pressure control faults, and/or solar receiver and/or heat system and/or electrical system faults.

FIG. 10Balso illustrates the use of a hybrid power generation system, with the steam turbine module45S driven either by steam from the boiling tubes70and transport tubes71, and/or steam from a fuel-driven steam boiler74, such as a fossil fuel powered unit, to make this a hybrid powerplant with both renewable solar power and nonrenewable fuel-driven source power, to permit all-weather (e.g., including periods of cloud cover or rain) and night operation of the powerplant.

FIG. 10Cshows a rear view of a variant of the embodiment shown inFIG. 3A, with the structural rings23hingedly attached to the rest of the framing members9so as to enable the inflatable heliostatic solar power collector to be deflated and folded into a shorter height profile, to enable transport of stacks of the upper portions with the structural rings angled as shown, and other stacks of the base part including the structural base ring8B and the rear support bar32as shown, on a flatbed trailer77. The illustrated embodiment has two stacks each of upper portions and lower portions, seven high, to enable carriage of 14 complete inflatable heliostatic solar power collectors on the flatbed trailer, in this embodiment. Many variations are possible within the spirit and scope of the invention as defined.

FIG. 10Dshows transport of a very large complete inflatable heliostatic power collector1, inflated with lifting gas (such as helium or hydrogen) in the upper inflatable volume4and lower inflatable volume6, to enable air transport of this very large device from a place of manufacture to a place of siting. A tow aircraft78is shown pulling the device via a tow bar or cable79. The illustrated tow aircraft78is a helicopter, but alternate embodiments could use an airship, blimp, or hybrid heavier-than-air airship with supplementary propulsive or aerodynamic lift.

FIGS. 11 and 12show views corresponding to those ofFIGS. 1A and 3A, of an alternate embodiment with a different support structure8arrangement, as shown.

While certain preferred embodiments of the invention have been described with reference to the attached Figures, it should be understood that further variations and alternate embodiments of the invention are possible within the spirit and scope of the invention as defined in the attached Claims.