Abstract
A solar receiver and associated components, systems and methods for use with a concentrated solar power plant. The solar receiver including a heat-absorbing solid body, an optical arrangement configured to direct light on to the heat-absorbing solid body, and a heat exchanger cowl proximate the heat-absorbing solid body arranged to provide a flow of working fluid over the rotor. In use, the light from the optical arrangement heats the heat-absorbing solid body which in turn heats the working fluid proximate the heat-absorbing solid body. The heat-absorbing solid body is movable relative to the optical arrangement from a first position to a second position such that the heat-absorbing solid body does not overheat.
Claims
1. A solar receiver for a concentrated solar power station operating at light concentration values of up to 20,000, the solar receiver comprising: a heat-absorbing solid body comprising a material with a melting point in excess of 1500° C., wherein the heat-absorbing solid body is a rotor and is frustoconical in shape; an optical arrangement configured to direct light onto an inner surface of the heat-absorbing solid body; and a heat exchanger cowl arranged to provide a flow of working fluid over the heat-absorbing solid body; wherein the light from the optical arrangement heats the heat-absorbing solid body which in turn heats the working fluid proximate to the heat-absorbing solid body; and wherein the heat-absorbing solid body is movable relative to the optical arrangement.
2. The solar receiver according to claim 1, wherein the heat-absorbing solid body comprises a surface configured to receive and store solar radiation in the form of heat.
3. The solar receiver according to claim 1, wherein at least a portion of one or more surfaces of the heat-absorbing solid body is movable from a first position to a second position, wherein the at least a portion of the one or more surfaces of the heat-absorbing solid body is heated at the first position and is cooled at the second position.
4. The solar receiver according to claim 1, further comprising one or more support structures configured to guide rotation of the heat-absorbing solid body, wherein the heat-absorbing solid body is at least partially mounted upon the one or more support structures.
5. The solar receiver according to claim 1, wherein the heat-absorbing solid body comprises a hollow portion.
6. The solar receiver according to claim 5, wherein the heat exchanger cowl directs at least a portion of the working fluid through the hollow portion of the heat-absorbing solid body such that working fluid flows over an inner surface of the heat-absorbing solid body.
7. The solar receiver according to claim 6, wherein the hollow portion of the heat-absorbing solid body comprises a plurality of conduits.
8. The solar receiver according to claim 7, wherein the plurality of conduits are tubular.
9. The solar receiver according to claim 1, wherein the heat-absorbing solid body comprises a body and a coating, the coating comprising the material, the material having a solar absorptance in excess of 0.8.
10. The solar receiver according to claim 9, further comprising an insulating layer between the body of the heat-absorbing solid body and the coating.
11. The solar receiver according to claim 1, wherein the heat-absorbing solid body comprises: one or more adsorptive tiles configured to receive and store solar radiation; one or more impingement heat shield plates configured to cool the heat-absorbing solid body and protect components of the solar receiver from excess temperatures during use; and a body configured to seat the adsorptive tiles and impingement heat shield plates.
12. The solar receiver according to claim 1, wherein the optical arrangement comprises: a light tube comprising: a casing; a first aperture and a second aperture formed in the casing; and a layer of reflective material arranged inside the casing; wherein the second aperture is spaced apart from the heat-absorbing solid body to provide a clearance therebetween.
13. The solar receiver according to claim 12, wherein the layer of reflective material is configured to direct light from the first aperture toward and/or out of the second aperture and towards the heat-absorbing solid body.
14. The solar receiver according to claim 1, wherein the optical arrangement comprises a compound parabolic concentrator (CPC).
15. The solar receiver according to claim 6, wherein the heat-absorbing solid body comprises an inlet and an outlet, and the heat exchanger cowl is in fluid communication with at least one of an inlet and an outlet of the heat-absorbing solid body.
16. The solar receiver according to claim 1, wherein the heat exchanger cowl comprises: an inlet; an outlet; and one or more fluid channels configured such that working fluid flowing through the inlet will pass across one or more surfaces of the heat-absorbing solid body prior to passing through the outlet.
17. The solar receiver according to claim 15, wherein the inlet and outlet of the heat exchanger cowl are positioned such that the direction of fluid flowing through the heat exchanger cowl is counter-current relative to a direction of movement of the heat-absorbing solid body.
18. The solar receiver according to claim 16, wherein the heat exchanger cowl further comprises an insulating layer.
19. The solar receiver according to claim 16, wherein the heat exchanger cowl comprises one or more impingement holes configured to provide cooling to the heat-absorbing solid body separate from the working fluid flow.
20. The solar receiver according to claim 1, further comprising a control system and one or more sensors communicably coupled to the control system.
21. The solar receiver according to claim 20, wherein the control system is configured to increase speed of movement of the heat-absorbing solid body in response to detection of an increase in light incident upon the one or more sensors, and/or to decrease the speed of movement of the heat-absorbing solid body in response to the detection of a decrease in incident light upon the one or more sensors.
22. The solar receiver according to claim 1, wherein the material comprises zirconium, zirconium oxide and/or cermets thereof, zirconium bromide and/or cermets thereof, chromium oxide and/or cermets thereof, aluminium oxide and/or cermets thereof, molybdenum, steel, steel alloys, tungsten, high refractive index polymer, high temperature resistant absorptive black paint, silicon carbide, or combinations thereof.
23. The solar receiver according to claim 1, wherein the working fluid is selected from the group consisting of air, helium, carbon dioxide, and any combination thereof.
24. A concentrated solar power station comprising: one or more mirrors, lenses, heliostats and/or reflectors; and a receiving mast comprising a solar receiver comprising: a heat-absorbing solid body comprising a material with a melting point in excess of 1500° C., wherein the heat-absorbing solid body is a rotor and is frustoconical in shape; an optical arrangement configured to direct light onto an inner surface of the heat-absorbing solid body; and a heat exchanger cowl arranged to provide a flow of working fluid over the heat-absorbing solid body; wherein the light from the optical arrangement heats the heat-absorbing solid body which in turn heats the working fluid proximate to the heat-absorbing solid body; and wherein the heat-absorbing solid body is movable relative to the optical arrangement.
25. The concentrated solar power station according to claim 24, further comprising a generation system configured to convert heat energy from the working fluid into electrical energy.
26. A method for converting light into electrical energy, comprising: a) heating a solar receiver comprising: a heat-absorbing solid body comprising a material with a melting point in excess of 1500° C., wherein the heat-absorbing solid body is a rotor and is frustoconical in shape; an optical arrangement configured to direct light onto an inner surface of the heat-absorbing solid body; and a heat exchanger cowl arranged to provide a flow of working fluid over the heat-absorbing solid body; wherein the light from the optical arrangement heats the heat-absorbing solid body which in turn heats the working fluid proximate to the heat-absorbing solid body; and wherein the heat-absorbing solid body is movable relative to the optical arrangement; wherein the heating comprises shining light onto one or more surfaces of the heat-absorbing solid body of the solar receiver; b) moving the heat-absorbing solid body from a first position to a second position; c) exchanging heat between the heat-absorbing solid body and a working fluid; and d) converting the heat energy of the working fluid into electrical energy.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0045] Embodiments of the present invention will now be described with reference to the following drawings, in which:
[0046] FIG. 1 is a top down view of a solar receiver within the scope of the present invention;
[0047] FIG. 2 is a side view of the solar receiver of FIG. 1 omitting the cowling and two of the light tubes;
[0048] FIG. 3 is schematic representation of the heat exchanger cowl of FIG. 1;
[0049] FIG. 4 is a representation of an electricity generation system that may be used in conjunction with a solar receiver of the present invention; and
[0050] FIG. 5 is a representation of an alternative solar receiver with a hollow cylindrical drum configuration.
[0051] FIG. 6 is a representation of an alternative solar receiver with a conical shape.
[0052] FIG. 7 is a cross-sectional view of a solar receiver of the design of FIG. 6.
[0053] FIGS. 8A to 8E are representations of components of a solar receiver for use with the receiver according to FIG. 6 and/or FIG. 7.
[0054] FIG. 9 is a cross-sectional schematic representation of a hollow rotor that may be used with the solar receivers described herein.
[0055] FIG. 10 is a cross-sectional schematic representation of an alternative hollow rotor that may be used with the solar receivers described here.
[0056] FIG. 11 is a schematic perspective view of a further alternative hollow rotor that may be used with the solar receivers described herein.
[0057] FIG. 12 is a schematic perspective view of a complex rotor design that may be used with the solar receivers described herein.
[0058] FIG. 13 is a flow diagram of a method according to the present invention.
DESCRIPTION
[0059] The following examples present various aspects of the present invention and means of implementing the same. The examples provided are merely exemplary solar receivers and are not intended to limit the scope of the invention.
[0060] FIG. 1 shows a top down view of a solar receiver within the scope of the present invention. The solar receiver 100 includes a substantially cylindrical rotor 1. The rotor includes a substantially cylindrical central rotor body 6 which includes a central axle 4 running through the centre of the cylinder's circular flat surfaces. The central axle 4 allows the rotor to rotate around a central pivot point. The rotor includes a layer of insulating material 2 that covers the curved face of the cylindrical rotor body, and a coating 3. The coating includes any suitable material with a high solar absorbance, high refractive index and a high thermal tolerance (i.e. melting point). In exemplary embodiments, the coating includes a material that approximates a black body.
[0061] Positioned at 90° intervals around the rotor cylinder are four light tubes 10 configured to direct light onto the coating 3 on the curved face of the cylindrical rotor. Each light tube 10 includes an outer casing 12 containing reflective mirror surfaces 11. The casing 12 narrows as it approaches the rotor 1 and arrives at an end aperture 14 at its narrowest point, the aperture facing the coated rotor surface 3. The shape of the casing 12 and the reflective mirror surfaces 11 are configured to direct light through the light tube 10 towards the end aperture 14 of the light tube 10 and onto the coated surface 3 of the rotor 1. As shown in FIG. 2, the clearance 13 between the end of each light tube 10 and the coated surface 3 of the rotor 1 is minimized to reduce leakage or loss of energy as the light leaves the light tube 10. The rotor 1 and the light tubes 10 are not in direct contact to prevent damage to the rotor 1 and/or light tubes 10 when the rotor 1 rotates. The ends of the casing 10 comprise extending portions 15 that extend away from the end aperture 14 approximately parallel to the curved coated surface 3 of the rotor 1. The extending portions further reduce the leakage or loss of energy from the solar receiver 100 by further reducing the spatial area through which light may leave the area between the light tube 10 and the rotor 1. The end aperture 14 of each light tube 10 is rectangular in cross section with a length 16 equivalent to the height 7 of the rotor. The end aperture 14 of each light tube 10 is positioned such that light leaving the light tube 10 will be substantially perpendicular to the portion of the coated surface 3 of the rotor 1 faced by the end aperture 14.
[0062] Returning to FIG. 1, four heat exchanger cowls 20 are arranged around the rotor 1 between each of the four light tubes 10. A schematic representation of one such cowl is shown in FIG. 3. The cowl 20 is shaped such that the edges of the cowl in closest proximity to the rotor 1 are contoured to conform to the curvature of the rotor 1. The cowl 20 is primarily formed from an insulating material and comprises an inlet 23 and an outlet 24 connected by a flow passage 25 that extends through the cowl. A portion of one of the walls of the flow passage 25 is substantially formed by the coated surface 3 of the rotor 1 against which the cowl 20 is positioned. In operation, air flows through the flow passage 25 of the heat exchanger cowl 20 from the inlet 24 to the outlet 25 in a direction 22 that is counter-current to the direction of rotation 5 of the rotor 1. The air entering the cowl via the inlet is at a lower temperature than the rotor 1 and therefore promoted transfer of heat from the coated surface 3 of the rotor 1 to the flow of working fluid air.
[0063] In operation, light incident on the solar receiver 100 is directed towards the rotor 1 via the light tubes 10. The light is absorbed by the coated surface 3 of the rotor and is thereby converted to thermal energy. The thermal energy is then carried around the circumference of the rotor 1 via rotation, and transferred to the air flowing through the heat exchanger cowls positioned around the rotor. As previously described, the light tubes may be accompanied by one or more mirrors, lenses, prisms or alterative optical component that allows light from one or more heliostats to reach the light tubes and thus the rotor of the solar receiver. In some embodiments, the light tubes may be entirely absent in favour of alternative optical arrangements.
[0064] FIG. 4 shows one way through which the solar receiver 100 of FIG. 1 may be utilized to generate electrical energy. In the system of FIG. 4, the hot working fluid air 42 leaving the outlets 24 of the heat exchanger cowls 20 of solar receiver 100 is carried through an insulated pipe 50 lined with insulating material 41. The hot air is passed through a conventional plate heat exchanger 44. The exhaust air 43 leaving the plate heat exchanger 44 via exhaust pipe 49 is returned to the heat exchanger cowls 20 of the solar receiver 100 for additional energy collection. The hot steam produced in the plate heat exchanger 44 is then passed to a Rankine turbine systems including a turbine 46 and associated generator 48 which generates electrical energy. The hot gases leaving the turbine 46 are then passed through several supplementary heat exchangers 45 before entering condenser 47 and being returned to the plate heat exchanger 44 as cool air/steam. Although FIG. 4 is described with reference to the solar receiver of FIG. 1, the system of FIG. 4 may be used with any solar receiver within the scope of the invention that gives rise to a heated working fluid during operation.
[0065] FIG. 5 shows an angled top-down representation of an alterative example of a solar receiver with a hollow cylindrical drum configuration. Hollow cylindrical rotor 51 is housed inside a series of four heat exchanger cowls 20 positioned at 90° intervals around the rotor cylinder. Between each heat exchanger cowl is a slot 53 which exposes a surface of the rotor 51. The inner surface of the rotor 51 is coated with a layer of coating 52. In operation, solar radiation is focussed upon one or more surfaces of the rotor coating 52 exposed by the one or more slots 53 between the heat exchanger cowls 20. One or more optical arrangements (not shown) are configured to direct and concentrate solar radiation onto the exposed rotor surface on the inside of the hollow cylinder. The rotor 51 and coating 52 rotate in a direction 5 which allows the inner coated surface of the rotor to become exposed to the incident solar radiation over the course of one 360° rotation event. Heat exchanger cowl 20 is stationary during use. Working fluid flows into one or more of the heat exchanger cowls 20 through an inlet 23 and passes over the heated rotor coating surface 52 in a counter-current direction 22. The heated working fluid then leaves the heat exchanger cowl 20 via outlet 24 and is passed to an electrical generation means such as that shown in FIG. 4 and/or to an alternative system desirous of heat energy. The outer surface 54 of the one or more heat exchanger cowls may include one or more impingement holes to allow cooling of the uncoated side of the rotor during use.
[0066] The hollow cylinder system of FIG. 5 may be adapted for use in place of the rotor shown in FIG. 1. In this alternative example (not shown), the rotor coating may instead be positioned on the outside surface of the hollow cylindrical rotor and one or more optical arrangements and/or light tubes may be used to direct solar radiation onto the coated outer surface of the rotor. The position of the working fluid inlet, outlet and flows passages would, in this alternative example, be positioned in the portion of the heat exchanger cowls proximal to the coated rotor surface to allow heat exchange to occur.
[0067] FIG. 6 shows a further configuration of a solar receiver within the scope of the present invention. The solar receiver of FIG. 6 is frustoconical, or substantially conical, in shape. The receiver includes a heat exchanger cowl 20, a shaft 62, a rotor 61, slot 53, inlet 23 and outlet 24. The rotor 61 and cowl 20 are positioned on and around shaft 62, configured such at least rotor 61 may rotate freely around the shaft 62. At least one portion of cowl 20 is absent to form slot 53 which exposes one or more surfaces of the rotor 61 beneath. In operation, solar radiation 101 is focussed towards the exposed portion of the rotor 61 within the slot 53. The exposed portion of rotor 61 absorbs the solar radiation 101 and stores it as heat energy. The frustoconical shape of the receiver allows light to be more easily directed towards the inner surface of the rotor. The rotor 61 rotates via bearing arrangements 63, the rotation driven by a motor and drive belt arrangement (not shown) that cause rotor 61 to rotate while the heat exchanger cowl 20 remains stationary. Cowl 20 is affixed to shaft 62 by any suitable fixing means such as screws or bolts. Working fluid enters the heat exchanger cowl 20 via inlet 23 inside the shaft 62. The working fluid circulates around the heat exchanger cowl 20 across the surface of the rotor 61 before leaving the solar receiver via outlet 24 positioned internal to the shaft 62. The cowl 20 and/or rotor 61 may be at least partially lined with insulating or refractory material. The heat exchanger cowl may further include one or more sealing lips to prevent loss of working fluid through residual gaps formed between the rotor 61 and cowl 20. An additional sealing lip may also be present at the base of the cone/bowl arrangement in proximity to the shaft 62 to prevent further loss of heat.
[0068] FIG. 7 shows a cross section of a solar receiver conforming to the design of FIG. 6. The rotor of FIG. 7 includes a rotor body 67 upon which is seated absorptive tiles 64 and impingement heat shield plates 65. In operation, the absorptive tiles 64 are exposed to solar radiation through slot 53. The solar tiles 64 absorb the solar radiation as heat energy prior to its transfer to the working fluid flowing from the inlet 23 to the outlet 24. The absorptive tiles 64 may be formed from refractory material or any absorptive material previously described as suitable for a rotor or rotor coating. The absorptive tiles 64 rest upon impingement heat shield plates 65 which are configured to both protect the rotor body 67 from exposure to excessive heat and to allow the passage of air to cool the rotor body 67 and/or absorptive tiles 64. Although FIG. 7 shows a plurality of absorptive tiles 64 and a plurality of impingement heat shield plates 65, it is envisaged that either or both the absorptive tiles 64 and the impingement heat shield plates 65 may be present in the form of a single article around the inner surface of the rotor body 67 or alternatively in segmented form as shown. Additional insulating and/or refractory material (not shown) may be present between the absorptive tiles 64, impingement heat shield plates 65 and/or rotor body 67 as required.
[0069] With additional reference to FIG. 8A, impingement heat shield plates 65 have one or more impingements holes 70 therethrough. The impingement holes 70 allow the passage of cooling air or other fluid through the impingement heat shield plates to facilitate the cooling or temperature regulation of the rotor body 67 and/or absorptive tiles 64. Where a plurality of impingement holes 70 are present, the holes may be arranged in any suitable pattern or orientation. The impingement holes may be positioned or angled to guide the flow of air along a particular path, or across specific portions of the solar receiver, as desired. FIG. 8B shows a representation of absorptive tiles 64. The tiles 64 are designed to be interlocking when arranged upon the rotor body 67. In practice, a compliance gap 71 may be provided between tiles to account for thermal expansion, manufacturing defects, etc.
[0070] FIG. 8C shows the rotor body 67 of the rotor 61 in isolation. The rotor body 67 includes one or more support ribs 66 that extend outward from the inner surface of the rotor body 67. The impingement heat shield plates 65 and absorptive tiles 67 rest upon the support ribs 66 to provide a ‘cooling gallery’ void space 68 between the rotor body 67 and tiles/plates (64, 65). When the absorptive tiles are at least partially formed from a porous material, the working fluid may be passed through the absorptive tiles to the cooling gallery from where it may be further directed to the outlet 24. The rotor body 67 may further include radiative elements (not shown) such as fins to facilitate transfer of heat to the working fluid. Optionally, the support ribs 66 may be configured to function as radiative elements. To facilitate rotation, the rotor body 67 includes a drive belt groove 69 to allow a motor and drive belt (not shown) to rotate the rotor 61 as required.
[0071] FIG. 8D shows a schematic of shaft component 62. In operation, rotor body 67 sits atop shaft 62, supported at least in part upon support lip 73. The inlet 23, outlet 24 and fixing points 72 are exposed through the centre gap 74 of the rotor body 67 to allow fixing of the cowl 20 to the shaft. FIG. 8E shows a cross section of the cowl 20 across inlet 24. Passages 77 are shown in the cowl 20 to allow screws or bolts to interact with fixing points 72 on the shaft. When affixed to the shaft 62, the inlet and outlet working fluid channels of the cowl 20 will align with the inlet 23 and outlet 24 of the shaft to allow working fluid to flow across the surface of the rotor 61. One or more voids 76 in the cowl 20 allow passage of working fluid from the inlet 23 to the rotor and ultimately from the rotor to the outlet 24. In the examples shown, the inlet and outlet passages are positioned either side of the cowl slot 53. Sealing lips 75 prevent the escape of hot air from between the rotor 61 and the cowl 20.
[0072] The solar receivers of the present invention may utilize any suitable rotor design suffice that light may be directed to one or more surfaces of the rotor such that the rotor becomes heated, and that the rotor may move or rotate such that the heated portion of the rotor may be cooled by exchanging heat between the rotor surface and a suitable working fluid. Consequently, many alternative rotor designs are envisaged. FIG. 9 shows a cross-sectional schematic representation of a hollow rotor 80 that may be used with the solar receivers described herein. The rotor 80 is formed from two body portions 81, 82 which are substantially discoidal in shape. The body portions 81, 82 are substantially hollow such that working fluid may flow into the first body portion 81 via inlet 83 in the first body portion and out of outlet 84 in the second body portion 82. Positioned between the first body portion 81 and the second body portion 82 are a plurality of conduits 85. The conduits may be any suitable shape including, but not limited to square or rectangular in cross section, tubular with a circular or oval cross section, or more complex cross sectional shapes as desired. The conduits are arranged around the outer circumferential periphery of the circular faces of the discoidal body portions 81, 82, such that the conduits 85 connect the first body portion 81 to the second body portion 82. The resulting configuration approximates the shape of a cylindrical cage with the inlet 83 and the outlet 84 extending out from the respective first and second body portions 82, 83 on the opposite side of each body portion from the side to which the conduits 85 are connected. The conduits 85 are substantially hollow and are in fluid communication with the hollow region of each of the first and second body portions 81, 82. In use, working fluid may therefore flow into the rotor via the inlet 83 into the hollow part of the first body portion 81, through the plurality of conduits 85 into the hollow part of the second body portion 82 and then out through the outlet 84. Solar radiation 86 may be directed towards the surface of one or more of the plurality of conduits 85. In an example, the solar radiation may pass through a slot (not shown) such that the light incident upon the rotor 80 is directed towards a surface area equivalent to, or less than, the surface area of one side of a single conduit 85. Solar radiation 86 incident upon the surface of a conduit 85 will cause the surface of the conduit to become heated. In use, rotor 80 rotates in a direction 87 such that each of the plurality of conduits 85 will becomes exposed to the solar radiation, and thus heated, in turn. Working fluid is passed through the rotor 80 and over the heated internal surfaces of the plurality of conduits 85 such that heat is transferred from the rotor surfaces to the working fluid cooling the rotor and heating the working fluid. Once cooled, each of the plurality of conduits 85 will eventually be carried back to a position at which it is subjected to further heating via the incident solar radiation 86 due to the rotational movement of the rotor 80. The conduits may be positioned in any suitable arrangement. In an example, the conduits may be positioned such that when the rotor is rotating and the incident solar radiation would pass between two conduits on the near side of the rotor, a further conduit will be exposed to the solar radiation on the far side of the rotor due to the light passing through the gap between the two conduits nearest the source of the solar radiation. In this manner, incident solar radiation will be unable to pass through the entirety of the rotor without contacting at least one conduit. Additional conduits may be positioned away from the circumferential periphery of the discoidal rotor bodies and proximate to the centre of the circular surfaces of the bodies as desired. In other examples, solar radiation may be directed towards the rotor 80 from multiple directions via any suitable means such as those shown in the solar receiver of FIG. 1.
[0073] FIG. 10 shows a cross-sectional schematic representation of an alternative hollow rotor 90. Rotor 90 is similar in concept to the rotor of FIG. 9 but has replaced the plurality of conduits with a hollow cylindrical wall 95 that extends around and between the circumferential periphery of the discoidal first body portion 91 and the second body portion 92. In a similar manner to the rotor of FIG. 9, the rotor 90 of FIG. 10 has an inlet 93 in the first body portion 91. In use, working fluid may flow into the hollow part of the first body portion 91 through the inlet and into the hollow part of the cylindrical wall 95. The cylindrical wall 95 is in fluid communication with both the hollow part of the first body portion 91 and the hollow part of the second body portion 92 such that the working fluid will flow over the inner surfaces of the cylindrical wall 95, into the second body portion 92 and out through outlet 94. In operation, the rotor 90 will rotate in a direction 97 such that the outer surface of the cylindrical wall 95 will become exposed to incident solar radiation 96 over the course of one 360° rotation event. The incident light 96 will heat the surface of the cylindrical wall 95 such that it becomes heated. Working fluid passing through the rotor 90 will pass over the inner surface of the hollow cylindrical wall such that heat is transferred from the cylindrical wall 95 to the working fluid. As each heated portion of the surface of the cylindrical wall 95 is carried away from the incident solar radiation 96 it becomes cooled. In this manner, no individual part of the rotor is exposed to the focussed solar radiation for an extended period of time. It is envisaged that solar radiation may be directed towards the rotor 90 from multiple directions via any suitable means suffice that the flow of working fluid may cool each heated portion of the rotor to an suitable temperature between each exposure of that portion of the surface to incident solar radiation.
[0074] FIG. 11 shows a schematic perspective view of a further alternative hollow rotor 100 that may be used with the solar receivers described herein. Rotor 100 operates in a manner comparable to the rotor of FIG. 9 with the main difference in configuration being that rotor 100 is frustoconical in shape in contract to the cylindrical shape of rotor 80. Rotor 100 includes a first discoidal body portion 101 and a second discoidal body portion 102. An inlet 103 extends from one circular face of the first body portion 101 while an outlet extends from one circular face of the second body portion 102. For the avoidance of doubt, the inlet may instead extend from the second body portion 102 and the outlet from the first body portion 101 if desired. In the embodiment shown, the first body portion 101 is smaller in diameter than the second body portion 102 resulting in a rotor with a general frustoconical shape. A plurality of conduits 105 connect the outer circumferential periphery of the first body portion 101 and the outer circumferential periphery of the second body portion 102. Each of the plurality of conduits 105 is hollow such that the inlet 103 and outlet 104 are in fluid communication via a hollow part (not shown) of each of the first and second body portions 101, 102 and the hollow interior (not shown) of each of the plurality of conduits 105. In operation, solar radiation 106 is directed towards one or more surfaces of the rotor 100. The rotor 100 rotates in a direction 107 such that each of the plurality of conduits 105 will be gradually exposed to the incident solar radiation 106 as the rotor 100 rotates. When the solar radiation 106 contacts the surface of one of the plurality of conduits 105, the conduit will become heated. Working fluid flowing in through the inlet 103 and into the hollow part of the plurality of conduits 105 will flow over the internal heated surfaces of the conduits 105 such that heat energy is transferred from each heated conduit to the working fluid. The heated working fluid then flows into the hollow part of the second body portion 102 and through the outlet 104.
[0075] Additional complex rotor shapes may also be used in the solar receivers of the present invention. More complex rotor shapes may be selected to impart particular advantages to the solar receivers in which they are used. For example, a rotor shape may be selected to influence the specific interaction of solar radiation with the surface of the rotor. FIG. 12 shows an example of one such complex rotor 110. Rotor 110 is in the shape of a truncated cone with sides that increasingly diverge from the absent point of the cone as the sides extend away from the absent point. The resultant shape approximates the bell portion of a trumpet. Rotor 110 may be used in a solar receiver that approximates the configuration shown in FIGS. 6 to 8. Rotor 110 is formed from absorptive tiles 114 resting upon rotor body 115. The absorptive tiles 114 are curved and interlocking to provide a substantially continuous absorptive surface on the interior of the rotor. In use in an appropriately shaped solar receiver, the rotor 110 will rotate in a direction 111. Solar radiation 113 will be directed onto the surface of the absorptive tiles 114 through a slot (not shown) in a similar manner to the configuration shown in FIG. 7. Working fluid may then be passed across one or more surfaces of the rotor to cool the rotor and carry the heat away for further use such as electrical generation.
[0076] The solar receivers described herein may be used with the method shown in FIG. 13. The method of FIG. 13 shows a flowchart describing the main method steps of the present invention. The method 200 includes: heating a solid body by shining light onto one or more surfaces of the solid body 210; exchanging heat between the solid body and a working fluid 220; and converting the heat energy of the working fluid into electrical energy 230.
[0077] The features of the examples provided may be generally be combined in any technically appropriate manner consistent with methods and solar receivers of the present invention. Additional modifications within the scope of the invention will be apparent to those skilled in the art with the benefit of this disclosure and the appended claims.
