Self-Tracking Radiant Energy Collector

This invention relates to electromagnetic energy collection, and more particularly, to devices useful in the collection and utilization of radiant energy from solar sources. While the invention is described with particular emphasis in respect to its solar energy source collection application, those skilled in the art will recognize the wider applicability of the inventive principles disclosed hereinafter.

The prior art reveals a number of the devices adapted to concentrate available solar energy and convert that energy to perform useful work. In general, the concentrators may be classified as stationary or movable devices. Stationary devices either are moved manually to follow the energy source, or have special physical constructions which enables the device to gather some percentage of the available solar radiation regardless of the position of the sun, without physical movement of the concentrator. In the last mentioned case of the stationary concentrator, rather elaborate and complex reflector or lens designs are necessary in order to permit the stationary concentrator to accomplish its function.

Prior art concentrators which track the sun, on the other hand, as a class generally use complex electrical and mechanical devices to accomplish the tracking function. For example, photo cells and associated circuits and drivers commonly are employed for this purpose. At their present stage of development, known devices for tracking and concentrating the energy of the sun are relatively expensive to manufacture and maintain.

The invention disclosed hereinafter eliminates these prior art deficiencies by providing a low-cost means and method for tracking solar movement. In the preferred embodiment, tracking is provided by a serpentine shaped expanding means, preferably a bimetal, connected to a concentrator and adapted to receive concentrated energy from the concentrator in disaligned positions of the concentrator, so that it expands and drives the concentrator toward alignment with a solar source. At alignment, the concentrated energy is directed toward a suitable energy conversion means. The bimetal shape utilized for tracking, being temperature or radiant energy sensitive, continually interacts with the available energy supply so that the concentrator follows the energy source, once alignment is attained. For the purposes of this specification, the term "serpentine" is defined to mean the shape given an expanding means so that the expanding means gives relatively large movement with relatively small energy input at an aligned point of maximum energy concentration of the concentrator in order to hold the concentrator in alignment with the energy source while using only a small portion of the available energy; the shape of the expanding means at points other than the aligned point of maximum energy concentration being such as to receive energy from the concentrator, thereby causing the expansion means to move the concentrator back toward the aligned point of maximum energy concentration.

One of the objects of this invention is to provide a low-cost energy conversion device.

Another object of this invention is to provide a simplified device for tracking a source of radiant energy.

Still another object of this invention is to provide a source trackable solar concentrator driven by a suitable heat expandable device.

Yet another object of this invention is to provide a predeterminedly formed expansion device operatively connected to a concentrator of solar energy which is adapted to position the concentrator properly with respect to the solar energy source.

Other objects of this invention will be apparent to those skilled in the art in light of the following description and accompanying drawings.

In accordance with this invention, generally stated, an energy concentrator is provided with simplified, temperature or radiant energy responsive positioning means which function to move the concentrator into alignment with a source of radiant energy. In the preferred embodiment, the concentrator is a Fresnel lens pivotally mounted about an energy reception area. The lens is adapted to concentrate radiant energy on the reception area when the lens is aligned properly with an energy source, conventionally the sun. An expansion means is operatively connected to the lens and is positioned so that the lens directs concentrated energy on the expansion means when the lens is not aligned with the energy source. The particular expansion means of the preferred embodiment is predeterminedly shaped so that at alignment, the expansion means may respond to thermal or radiant energy changes, thereby maintaining the aligned position of the lens and the energy source. Pluralities of individual concentrators may be arranged to form energy collectors. The energy made available from both the individual concentrators or the energy collectors can be used directly or it can be converted to another form.

In the drawings,

FIG. 1 is a diagrammatic view in perspective, showing one illustrative embodiment of energy concentrator of this invention;

FIG. 2 is a view in side elevation of the energy concentrator of this invention, shown in a disaligned position;

FIG. 3 is a view in side elevation of the concentrator shown in FIG. 1, shown in its aligned position;

FIG. 4 is a view in perspective of one illustrative embodiment of an energy collector;

FIG. 5 is a view in side elevation of the energy collector shown in FIG. 4;

FIG. 6 is a view in perspective of an energy collector element utilizing the energy collector of FIG. 4;

FIG. 7 is a series of diagrammatic views demonstrating the operation of the positioning means utilized with the embodiments of this invention;

FIG. 8 is a view in perspective of one illustrative embodiment of positioning means utilized with the concentrator of FIG. 1;

FIG. 9 is a top plan view of a second illustrative embodiment of an energy collector of this invention; and

FIG. 10 is a sectional view taken along the line 10--10 in FIG. 10.

Referring now to FIG. 1, reference numeral 1 indicates one illustrative embodiment of energy conversion device of this invention. The device 1, shown somewhat diagrammatically in FIG. 1, includes an energy concentrator or concentrating means 2 carried in a frame 3.

The concentrating means 2 preferably is an energy focusing lens, although those skilled in the art will recognize that a reflector focusing element may be utilized in place of the lens focusing device shown, merely by redesigning various structural components of the invention. Preferably, the concentrator 2 is a Fresnel lens of a known, flat panel design. The flat panel design is preferred because it permits the construction of a physically smaller radiant heater 35, shown in FIG. 6 and described in greater detail hereinafter, than permitted with other known lens or reflector designs. However, other concentrators are compatible with the broader aspects of my invention. For example, the concentrator 2 may comprise several panels of Fresnel devices arranged as the sides of a pyramid. Or, the concentrator 2 may comprise a conical Fresnel device which does not have flat panels. Conical Fresnel designs are not as deeply bowed in conical shape as other conical lens designs, but have increased efficiency because of the elimination of shadowing inherent in the flat Fresnel panel constructions.

The concentrator means 2 is mounted within the frame 3 by any convenient method. In the embodiment of FIG. 1, the frame 3 is rectangular in plan, having oppositely opposed side pairs 40, 41 and 46, 47, respectively, surrounding the concentrator means 2. Individual ones of the sides may be joined to one another by any convenient method. Either mechanical interlocking techniques or some form of welding works well, for example. A pair of support arms 4 and 5 are attached to the side 40 of frame 3 along an end 42 and an end 48 of the respective arms 4 and 5. The arms 4 and 5 are mounted for rotation, as generally indicated at pivots 6 and 7, along respective ends 43 and 49 of the arms. A cross member 58 may be used to add structural rigidity between the arms 4 and 5, if desired.

A lower edge 8 of the side 41 of the frame 3 has a pair of supports 10 and 11, respectively, attached to it. A cross member 44 extends between the support pair 10 and 11, on an end of the support pair opposite their attachment with the edge 8. A counter-weight 9 is mounted to the member 44 and functions to counter-balance the weight of the concentrator 2 about the pivots 6 and 7. The counter-weight 9 was used in conjunction with the embodiment of FIG. 1 because the size and weight of the concentrator means 2 tends to cause the concentrator means 2 to drop against a stop 45 with such force as to damage the concentrating means when the energy source passes beyond the movement limits of the device 1. Other embodiments of my invention may not require the use of the counter-weight 9.

The concentrating means 2 has a front face 12 and a focusing axis, indicated generally by the numeral 13 in FIG. 2. Commonly, the axis 13 is normal to the face 12, although the location of the axis 13 with respect to the face 12 has not been found critical in present embodiments of the invention, and other focusing axes arrangements are compatible with the broader aspects of this invention. As indicated above, a Fresnel lens is utilized for the concentrator means 2. The Fresnel lens or Fresnel reflector has the advantage of being essentially flat, thereby permitting the construction of a device having relatively small physical dimensions, although various configurations used in Fresnel designs may require some depth in order to increase the efficiency of the lens or reflector due to the shadowing effect prevalent in flat Fresnel lens constructions.

The concentrating means 2 is adapted to focus incoming radiant energy rays, indicated generally by the numeral 14, toward a concentrating area 15. The concentrating area 15 has a suitable conversion means 16 associated with it. The conversion means 16 converts the radiant energy to another, more useable form. Thus, conversion means 16 may be a pipe carrying a liquid which is heated by the energy rays at the area 15. Or, the conversion means 16 may be a photoelectric device, for example, which converts the incoming energy to electrical energy. In turn, the electrical energy may be stored in suitable storage means, not shown, or it may be used immediately.

A cross bar 18 is connected between the supports 10 and 11 and is attached thereby by any convenient method at some predetermined point along the longitudinal length of the supports 10 and 11, between the concentrating area 15 and the concentrator means 2. An expansion means 17 is operatively connected between the concentrating area 15 and the cross bar 18. The expansion means 17 preferably is constructed from a bimetallic material. However, other suitable expansion devices are compatible with the broader aspects of this invention.

The expansion means 17 has a first end 20, a second end 50, and a generally serpentine design therebetween. The overall design of the expansion means 17 includes a curved portion 19 near the end 20, which is important in the overall tracking ability of the device 1. The end 20 of the expansion means 17 is attached to the device 1 at the concentrating area 15, while the end 50 is attached to the cross bar 18. As indicated, the particular shape of the expansion means 17 is important, as is later described in greater detail.

Operation of the concentrating means 2 is relatively simple and may be best understood with reference to FIG. 7. The device 1 is positioned so that it faces a source of radiant energy 21 which conventionally is the sun. As the sun or energy source 21 comes above the horizon, as illustrative radiant energy ray 14 impinges the face 12 of the concentrating means 2. The use of a single energy ray 14 is a simplification made for the purpose of explanation. As indicated above, when the ray 14 is aligned, that is, parallel to the axis 13, the ray 14 passes through the concentrator 2 and is directed at the concentrating area 15, and in particular, towards the conversion means 16. Whenever the ray 14 is not aligned with the axis 13, the concentrating means 2 directs concentrated energy towards the expansion means 17. A non-aligned position is illustrated in FIGS. 2 and 7a. As the concentrated energy strikes the expansion means 17, it begins to expand. Since the end 20 of the expansion means 17 is fixed at the concentrating area 15, expansion of the expansion means 17 exerts an upward force on the device 1 because of the interconnection of the end 50 at the cross bar 18, upward being referenced to FIG. 7. That force drives the device 1 counterclockwise, again referenced to FIG. 7, about the pivots 6 and 7. The energy ray 14 continues to move or walk along the curved portion 19 until it passes over the top of the curved portion 19. At that point, the energy ray 14 strikes the conversion means 16.

I have found that some hunting takes place at the initial capture of the energy source 21 by the device 1. That is to say, the expansion means 17 continues to expand after the energy ray 14 passes over the top of the curved portion 19, so that the expansion means 17 begins to contract, lowering the concentrating means 2 until the energy ray 14 again strikes the expansion means 17. This process repeats itself until an equilibrium position is reached. At equilibrium, the energy ray 14 is approximately tangent to the curved portion 19 of the expansion means 17, so that it strikes the concentrating area 15 but still enables the expansion means 17 to expand at a rate sufficient to permit the device 1 to track the energy source 21. Stops, not shown, may be used, if desired, to restrict device 1 movement in any given direction.

A variation of the device 1 construction is shown in FIGS. 4 and 5. As there illustrated, an energy collector or concentrator 62 has a triangular shape in cross section. The concentrator 62 includes a frame 23 having a pair of triangular end sections 51 and 53, respectively. The sections 51 and 53 are identical, and only a single section 51 is described in detail. The section 51 is constructed from a plurality of legs 24, 25 and 26. The legs 24, 25 and 26 of the section 51 are joined to corresponding legs of the section 53 by a plurality of longitudinally extending sides 27, 28 and 29. The sides 27 and 29 are adapted to receive a concentrating means 22 and mount it to the frame 23. The concentrating means 22 has a front face 30. The face 30 preferably is a Fresnel lens configuration of the type described in conjunction with the concentrator embodiment of FIG. 1. A vertex 31 defined by the frame 23 along the side 28 delimits a concentrating area 32. Again, the concentrating area 32 may have a suitable energy conversion means associated with it. A liquid carrying conduit 52 is shown in FIG. 4 for that purpose.

An expansion means 33 extends between the concentrating area 32 and the side 29 of the frame 23. The expansion means 33 has a first end 65 and a second end 66. The end 66 is attached to the side 29 of the frame 23, while the end 65 is fixed, for example, either to a suitable enclosure for the concentrator 62, or to the side 28 adjacent the concentrating area 32. The expansion means 33 includes a curved portion 36 which functions in a manner similar to the curved portion 19 of the concentrating means 2. The side 28 of the frame 23 is pivotally mounted at 34 to permit rotation of the concentrator 62.

As shown in FIG. 6, a multiplicity of the concentrators 62 may be arranged serially in an energy collector element 38 to define the radiant heater 35. The heater 35 includes a plurality of the concentrators 62 arranged to permit a coil 37 to extend through a series of the concentrating means 62, individual ones of which are arranged parallelwise with respect to one another. The concentrator 62 plurality may be mounted in a suitable enclosure 55. Enclosure 55 is conventional and is not described in detail.

Operation of the concentator 62, individually or with respect to the energy collector element 38, is substantially similar to that described in conjunction with the concentrating means 2. That is, the radiant energy source 21 will direct a ray 14 toward the curved portion of the expansion means 33. As the temperature of the expansion means increases, it expands, rotating the concentrator about its pivot point and aligning the axis of the concentrating means 22 with the energy source 21. Thereafter, the expansion means 33 enables the concentrating means 22 to track the source 21 continuously between suitable, preselected limits.

The embodiments of FIGS. 1 through 8 are designed for single axis tracking of the energy source. The width, thickness, location and number of expanding means used with the embodiments illustrated in those figures, depends on the forces required to lift the concentrating means, which in turn depends upon the size and weight of the concentrating means itself, and whether a counter-weight is utilized with any particular embodiment.

FIGS. 9 and 10 illustrate a concentrating means 80 capable of dual axis tracking of an energy source. The concentrating means 80 includes a support structure 81 having a support arm 82 extending upwardly from it. The support structure 81 also has a concentrating area 88 associated with it. The arm 82 has a first end pivotally mounted along the support 81, and a second end attached to a focusing lens 87. The concentrating means 80 also includes a cylindrical side wall portion 84 having a bottom edge 85 and a top edge 86. The top edge 86 supports the focusing lens 87 which preferably is of a flat Fresnel lens construction. The lens 87 is mounted along the edge 86 of the side wall 84 by any convenient method. The concentrating area 88 has a suitable energy conversion device associated with it, which may be similar to those described in conjunction with the embodiment of FIGS. 1-8.

An expansion device 89 is operatively connected between the support structure 81 and the edge 85 of the side wall 84. Expansion device 89 is a spoke arrangement having a plurality of legs 90 extending radially outwardly from the centrally located concentrating area 88 of the support structure 81. Each of the legs 90 includes a curved portion 91. As with the embodiment of FIGS. 1-8, the individual legs 90 of the expansion device 89 are intended to pass concentrated energy from an energy source tangentially along the curved portion 91 in aligned positions of the concentrating means 80, and to direct energy toward respective ones of the legs 90 in disaligned positions of the energy source. In the particular embodiment of FIGS. 9 and 10, the expansion device 89 has six of the legs 90 extending outwardly from the pivotal mounting of the support arm 82 so that the support 82, and consequently the lens 87, has 2.degree. of freedom, enabling the concentrating means 80 to follow energy source movement for both declinational and diurnal movement.

Numerous variations, within the scope of the appended claims, will be apparent to those skilled in the art in light of the foregoing description and accompanying drawings. Thus, the design silhouette of the device may vary considerably in other embodiments of this invention, as may the enclosure containing the concentrating means. While a counter-weight was utilized with the embodiment of FIG. 1, the invention does not require use of a counter-weight in all of its intended forms. Although a lens is the preferred form of concentrating means, those skilled in the art will recognize that a reflector system may be used to accomplish similar results. In like manner, lens arrangements other than Fresnel constructions are compatible with the invention. These variations are merely illustrative.