WO2022011468A1

WO2022011468A1 - Solar energy collector

Info

Publication number: WO2022011468A1
Application number: PCT/CA2021/050970
Authority: WO
Inventors: Robert De Chazal
Original assignee: Sundraco Power Inc.
Priority date: 2020-07-14
Filing date: 2021-07-14
Publication date: 2022-01-20

Abstract

A solar energy collection system includes (a) a solar collection unit comprising an elongate, hemi-parabolic reflector having a focus line; (b) a target conduit heater which lies along the focus line of the reflector; and (c) a subsystem configured to move a heat transfer fluid through the target conduit heater.

Description

SOLAR ENERGY COLLECTOR

Cross-Reference to Related Applications

[0001] The present application claims priority of U.S. Provisional Application No. 63/051,722 filed on July 14, 2020, the entire contents of which are incorporated herein by reference.

Field of the Invention

[0002] The present invention relates generally to systems and methods for collecting heat energy from solar radiation, and delivering it for storage and/or use in electrical power generation, industrial systems, and/or space heating.

Background

[0003] Parabolic troughs are used as solar thermal collectors, which are straight in one horizontal dimension, and curved as a parabola in the other two dimensions. These troughs are symmetrical and sunlight which is directed at the mirror parallel to its plane of symmetry is focussed along a focal line.

[0004] In installations north and south of the tropics, the trough is usually aligned on a north-south axis, and rotated to track the sun as it moves across the sky each day.

[0005] The reflected sunlight is focused on a tube or conduit coincident with the focal line, heating a fluid within the tube. Thermal oil is typically used as a thermal fluid and runs through the tube to absorb the concentrated sunlight. This increases the temperature of the oil to some 400°C. The heat transfer fluid may then be used to heat steam in a standard turbine generator.

[0006] There is a need in the art for collectors of useable energy from the concentration of solar radiation operating at temperatures beyond the limits of current thermal liquids, where significant efficiencies may be achieved, not only in collection, but in storage and use of the product, as well.

Summary of the Invention [0007] In one aspect, the invention may comprise a solar energy collection system comprising:

(a) a solar collector unit comprising a horizontally elongate, hemi- parabolic reflector having a focus line;

(b) a target conduit heater which lies along the focus line of the reflector; and

(c) a subsystem configured to move a heat transfer fluid through the target conduit heater.

[0008] In some embodiments, the hemi-parabolic reflector has a cross-section of a segment of a parabola, which segment is located entirely on one side of the plane of symmetry of said parabola. In some embodiments, the reflector comprises a plurality of rectangular mirrors arrayed in vertical columns and horizontal rows, each mirror has a curved cross-section occupying a unique position of said segment such that collectively the cross-sections of a vertical row of the mirrors complete a trace of said segment of a parabola. The mirrors are supported independently by a common structure, which independent mirror supports permit each mirror to expand and contract without restraint, and to be aligned independently so as to have its focus line fall at a desired location, generally coincident with the focus line of all other mirrors in the reflector.

[0009] In some embodiments, the target conduit heater is a solar to air energy exchanger which defines a central internal passage through which the heat transfer fluid passes. To heat the heat transfer fluid, concentrated solar energy from the reflector is directed into the target conduit heater through a longitudinal entry chamber. In some embodiments, a linear magnifying lens comprised of a series of columnar lens placed end to end further concentrates solar energy directed into the entry chamber. The lenses are mounted and sealed to the target conduit heater.

[0010] In some embodiments, the target conduit heater comprises at least one insulating layer and/or a reflective layer to reduce conductive and radiant heat loss from the central passage.

In some embodiments, a central heat element is positioned within the central passage, which heat element is heated by the incoming solar radiation and which heats the heat transfer fluid within the central passage. The central heat element may comprise a central rod-like structure with attached fins to increase heat transfer surface area.

[0011] In some embodiments, the target conduit heater defines a countercurrent flow in a concentric passage. An outer sleeve defines a return air passage which surrounds an inner element pipe. Relatively cooler air passes through the return air passage, is turned around at one end of the target conduit heater, and enters the central passage of the element pipe within the target conduit heater.

[0012] The heat transfer fluid is a gas, such as nitrogen or air.

[0013] In some embodiments, the target conduit heater defines a central internal passage through which the heat transfer fluid passes and a longitudinal entry chamber which is coincident with the focus line of the solar collector unit, through which focused solar radiation may pass through into the central internal passage. Preferably, the target conduit heater comprises a lens assembly associated with the entry chamber, comprising a plurality of lenses for modulating the solar radiation passing into the entry chamber and central internal passage. The lens assembly may include a removeable lens cap for covering the lens, which lens cap is moved between an open position and a closed position by an actuator operatively connected to a light sensor.

[0014] In some embodiments, the target conduit heater defines a countercurrent flow passage in an outer concentric passage, and a turnaround for directing the heat transfer fluid from the outer concentric passage into the central passage.

[0015] In some embodiments, the target conduit heater further comprises air mixers within the central passage.

[0016] In some embodiments, the solar collection unit is aligned from east to west, and further comprising a subsystem for tracking the elevation of the sun and adjusting the position of the solar collection unit accordingly.

[0017] In some embodiments, the solar collection unit is operatively connected to a control system configured to rotate the solar collection unit to track the elevation of the sun, and/or a subsystem to move a heat transfer fluid through the target conduit heater, the system configured to: (a) rotate the solar collection unit in accordance with the measured or predicted elevation of the sun above the horizon; and/or

(b) control the flow rate of heat transfer fluid through the target conduit heater.

Brief Description of the Drawings

[0018] In the drawings, like elements are assigned like reference numerals. The drawings are not necessarily to scale, with the emphasis instead placed upon the principles of the present invention. Additionally, each of the embodiments depicted is but one of a number of possible arrangements utilizing the fundamental concepts of the present invention.

[0019] Figures 1.1 and 1.2 is a schematic depiction of the solar collection unit(s) of one embodiment. Figure 1.3 is a schematic depiction of the flow of heat transfer fluid through one embodiment of the system.

[0020] Figures 2.1 to 2.4 are views of one embodiment of solar collection unit assemblies.

[0021] Figures 3.1 to 3.3 are views of embodiments of a mirror panel array and a mirror panel.

[0022] Figures 4.1 to 4.4 are views of a supporting structure and features thereof.

[0023] Figures 5.1 to 5.5 are views of a mirror panel and supporting structure.

[0024] Figures 6.1 and 6.2 are views of the solar collection unit in a storage position.

[0025] Figures 7.1 to 7.4 are views of a target conduit heater.

[0026] Figures 8.1 to 8.4 are views of the lens assembly of a target conduit heater.

[0027] Figures 9.1 to 9.5 are views of a central heater element in a target conduit heater.

[0028] Figures 10.1 to 10.3 are views of a coupling connecting adjacent target conduit heaters.

[0029] Figures 11.1 to 11.3 are views of a static mixer.

[0030] Figures 12.1 to 12.5 are views of a coupling hat. [0031] Figures 13.1 to 13.4 are views of a primary pivot and secondary pivot of a solar collection unit.

[0032] Figures 14.1 to 14.3 are views of a base support assembly of a solar collection unit.

[0033] Figures 15.1 to 15.5 are views of a lens cap assembly.

[0034] Figures 16.1 to 16.4 are views of a turnaround attached to an end coupling.

Detailed Description

[0035] As used herein, the terms “vertical” and “horizontal” are used to describe the relative positioning, orientation or direction of certain elements, based on a substantially horizontal array, where the parabolic focal line is substantially horizontal. The present invention is not restricted to any one orientation, however, so these terms are not intended to be absolute limitations.

[0036] The present invention relates to a concentrated solar power collection system 1. One embodiment of a solar collection unit (SCU) 100 is illustrated in Fig 1.1. In Fig 1.2, an array of four groups of SCUs are shown, each comprising a hemi-parabolic reflector, having a horizontal focal line. As used herein, the term "hemi-parabolic" means a segment of a parabola which exists on one side of the full parabola’s line of symmetry. In other words, the hemi-parabolic collectors are asymmetric. Thus, as will be appreciated by those skilled in the art, the SCU reflector has a cross-section in a plane perpendicular to the focal line, which is a segment of a hemi-parabola. Solar radiation directed into the hemi-parabola is reflected onto the focus line.

[0037] By using both parabolic mirrors and lenses, the SCU 100 is capable of concentrating solar irradiation, the energy of which is transferred to a heat transfer fluid. This heat energy may then be used for example, to generate steam for a steam turbine generator, or stored for use in different applications and systems.

[0038] The system comprises a subsystem configured to move a heat transfer fluid through the target conduit heater at a desired rate. As shown in Figure 1.3, an exemplary system is shown schematically, which comprises a heat transfer fluid reservoir, at least one SCU 100 and a steam generating system 101. The heat transfer fluid is pumped through the system using at least one pump. Multiple SCUs may be connected in series and/or in parallel. Various piping, pumps, valves and other equipment necessary for proper circulation of the heat transfer fluid will be apparent to those skilled in the art.

[0039] In preferred embodiments, the heat transfer fluid is a gas. Gases, being less dense than liquids, require much less energy to deal with elevation changes. The use of a gas as a heat transfer fluid thus permits installations with elevation changes, for example, to be built on a hillside to improve collection and the use of land.

[0040] Unlike conventional solar energy collectors, the SCU 100 does not irradiate broadly the outside surface of a receiver, but focuses its collected energy into an elongate, cylindrical target conduit heater.

[0041] Because of its hemi-parabolic configuration, particularly in locations north or south of the Tropic of Cancer or the Tropic of Capricorn respectively, the SCU 100 is preferably oriented in an east-west orientation, with its reflector facing due south in the northern hemisphere, or due north in the southern hemisphere. As such, it always reaches its maximum performance at solar noon, where the solar zenith angle is at a minimum. As the solar zenith angle changes, the system preferably include a subsystem to track the elevation of the sun, either by a sensor or by the predicted position based on date and time. The SCU 100 is then pivoted to maintain the focus line on the target conduit heater. As latitudes of locations become greater than 40 degrees, conventional troughs, which swing to face east to west as the day progresses, begin to perform badly during winter months.

[0042] The description of the present invention has been presented for purposes of illustration and description, but it is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention. Embodiments were chosen and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated. To the extent that this description is of a specific embodiment or a particular use of the invention, it is intended to be illustrative only, and not limiting of the claimed invention. [0043] In different embodiments, the invention may comprise any one or any combination of two or more of the following elements, and any element may itself comprise any one or a combination of two or more features described in respect of the elements below.

The Solar Collection Unit (SCU)

[0044] The solar collection system 1 is modular in the sense that the system may comprise a plurality of SCUs, arrayed in parallel, as shown in Fig 1.2. This modularity is a feature of the invention and provides valuable flexibility in responding to the amount of available insolation in a particular location or installation.

[0045] Each SCU 100 comprises several component assemblies, as seen in Figs 2.1-2.4. Fig 2.1 shows a single SCU 100 with its compound parabolic mirror (CPM) 200, target conduit heater (TCH) 300, swing arm assembly (SAA) 400, and ground support 500. Figs 2.2, 2.3, and 2.4 are exploded views of these assemblies

The Mirror Panel Array

[0046] The CPM 200 reflector comprises a mirror panel array (MPA) 210 comprising a plurality of rectangular mirror panels 211, vertically and horizontally arrayed in a hemi- parabolic shape with a horizontal focal line. The array 210 is supported by a set of parabolic support beams 220, and a support frame 230, which comprises a back brace 231 and adjustable support cables 232. As the CPM 200 is hemi-parabolic, these components are cantilevered and their weight is thus preferably minimized. Adjustable cables rather than struts are used both for that reason and because precise alignment of the CPM 200 as a whole then becomes possible in the field, on a continuing basis.

[0047] As may be seen in Figs. 3.1-3.3, each mirror panel is rectangular in plan, and has a curved cross-section which comprises a parabolic segment appropriate to the panel’s position in the array. Longitudinally, each mirror panel 211 in an array is separated from adjacent panels by a parabolic support beam 220. Furthermore, each panel 211 is separated from its adjacent panel by a narrow gap which allows for thermal expansion of the panels, and free movement of panels with regard to servicing functions. As well, these gaps may also serve to reduce wind loads on the CPM 200. [0048] Fig 3 shows that each mirror panel 211 has four guide-pins, two at the top (213), and two at the bottom (214). The pins are attached to the panel 211 with the aid of a stabilizing end cap 212, shown in Fig 3.2. Each panel 211 comprises several layers: a thin transparent protective layer 215, a reflective layer 216, and a weather-proof backing 218, which may include a metal layer 217. The transparent protective layer 215 may comprise a tough, very thin, transparent coating. As described above, all components of the CPM are preferably fashioned from lightweight materials. For example, the weather-proof backing may be air- filled, whether by virtue of a stiff, foam-like material, a honey-combed core, or the like.

[0049] Figs 4.1 to 4.4 illustrate certain aspects of the parabolic support beams (PSB) 220. Fig 4.3 shows a detailed portion of a mirror constraint beam 225 and the main load-bearing beam 221, as well as the swing arm attachment notch 223, and an anchor 233 to which the adjustable support cables may attach. The main beam 221 preferably has a box construction for strength, as is shown in Fig 4.4 cross-section of the PSB 220.

[0050] Fig. 5 shows structures of a mirror constraint beam 225. The mirror panels 211 attach to the mirror constraint beam 225 as it is configured with guide pin slots 227, 226, which allow adjustment and replacement of any of the mirror panels 211. The top guide-pins 213 of each panel 211 slide into a J-slot 226, while the bottom guide pins 214 are held within the straight slot 227, where it is constrained there by a guide pin lock 240, and bolt 241. Thermal expansion and contraction of the panels 211 are freely permitted by the mirror expansion/contraction allowances 229, shown in Fig 5.4, and by the gap provided between the panel 211 and the mirror constraint beam 225, as shown in Fig 5.5.

[0051] This configuration allows the CPM 100 to avoid the various optical distortions of the reflectors that occur in conventional tightly constrained reflectors which are fixed rigidly to support structures.

[0052] The resting position of each top pin 213 is governed by the precise configuration and location of the J-slot 226. The J-slot 226 is a curved channel, which allows the panel to be secured simply by gravity, which will tend to pull the top pins 213 into the end of the J-slot 226.

[0053] The straight slot 227 and guide pin lock 240 accommodates a U-shaped shim 228 which permits the panel's focus line to be precisely positioned. The shim 228 arms may have slightly different thickness, which alters the pin 214 position depending on the choice and/or positioning of the shim.

[0054] This configuration permits the panels 211 to be partly released, as may be seen in Fig 6.1 and 6.2, which shows one column of panels 211 released by their locks and hanging for installation, maintenance, or removal. If the guide pin locks are part of a common release mechanism (not shown) rather than being bolted, all panels 211 may be quickly released, removed, and stored, for example to prevent damage in severe weather. This function may not only keep the mirrors’ surfaces from being damaged, it reduces the wind load on the CPM structure as a whole, thus also lessening the potential for damage. Repairs or maintenance on other components of the CPM would already be more easily and quickly accomplished with the panels 211 out of the way.

Target Conduit Heater (TCH) and Concentration Techniques

[0055] A cylindrical target conduit heater (TCH) 300 receives the reflected energy from the mirror panel array and heats the heat transfer fluid. Concentration of solar insolation averages about 70 times in conventional, low-temperature solar concentration troughs. This limit is largely imposed by the design of their receiver and the nature of the thermal oil heat transfer fluid. Use of a gas as the heat transfer fluid, combined together with the design of the collector, may allow the SCU 100 concentration levels - and therefore operating temperatures - to be significantly higher than prior art configurations.

[0056] The TCH 300 defines a linear entry chamber 307 for directing the focused solar radiation from the mirror panel array (MPA) into the interior of the TCH. The TCH 300 comprises an element pipe 301 coated or surrounded by a thin reflective wall 302, which in turn is surrounded by a insulation layer 303. An outer concentric shell layer supported by structural ribs 305 forms a return air sleeve (RAS) 304. A lens cradle 330 attaches to the exterior of the TCH. Preferably an additional insulation layer is provided around the RAS, as shown in Fig 7.2. The double walls of the RAS and its structural ribs 305, combined with the bridging effect of the lens cradle 300, provide the TCH 300 with considerable structural strength.

[0057] Lenses 331 modulate the direction and concentration of the solar radiation passing into the entry chamber and central internal passage. A high concentration level is first achieved with the CPM by taking the effective collector aperture width of insolation and focusing that light on a set of magnifying lenses 331 positioned on the focal line, as shown in Figure 7.4. The lenses 331 then focus that light further, through the insolation entry chamber 307, and onto a central heater element 350. The natural aura of light around the solar disc and the dispersive action of the atmosphere on its insolation is somewhat compensated for by the action of magnifying lenses 331 and by the action of the reflective sides 308 of the entry chamber 307 which deliver dispersed irradiation into the element pipe 301 by way of additional reflections.

[0058] The configuration of the TCH 300 concentrates the light energy into the element pipe, while also creating thermal barriers to reduce heat loss. Radiation within the element pipe 301 is reflected back toward the central heater element by the thin reflective wall 302, while the insulating layers will prevent heat from conducting outwards.

[0059] Generally, relatively cool heat transfer fluid flows down the RAS 304, absorbing some heat by conduction from the element pipe 301, and upon reaching the end of the TCH 300, is redirected in a turnaround 600, to flow back through the central passage of the element pipe 301 and the entry chamber 307, where it will be heated by the solar radiation and conduction from the central heater 350.

[0060] Very high temperature differentials will occur radially within the TCH 300 creating challenges in managing thermal expansion and contraction where one SCU 100 joins another. Two design elements mitigate this issue. Firstly, the thin reflective wall 302 may expand and crumple with little to no loss in efficiency of performance, and little to no axial pressure applied to adjacent components. By contrast, the RAS will maintain a relatively low and even temperature throughout as it is insulated on either side (303). This allows the remaining axial thermal expansion issues to be dealt with relatively easily, as will be shown.

[0061] Fig. 8.2 is an exploded detail view of the lens cradle 330, which comprises a structural framework comprised of angle members 333 and cross bolts 339, held in place by side gaskets 335, a lens retention strip 337 and screws 338. Rivets 334 or other fasteners connect the angle members 333 to the RAS 304. Separating each lens from an adjacent lens are pairs of reflective lens end gaskets 336. Each lens 331 is beveled at either end (Fig 8.4) which allows the angled gaskets 336 to divert incoming, concentrated insolation away from the cross bolts. The combination of end and side gaskets 336 comprise an air seal around each lens. The seal need not be perfect as any loss of the heat transfer gas will be small and non-polluting.

The Focal Line heater element

[0062] Figs 9.1-9.5 show the focal line heater element 350, which is comprised of element segments 351. Each segment 351 comprises a central tube 352 bearing a plurality of radially projecting fins 353. The segments are connected to one another and supported in place by support wheels 355 at each end of the segment.

[0063] The fins 353 each have members 354 designed to introduce turbulence in the fluid stream and to provide surface area to transfer heat to the surrounding heat transfer fluid.

These members may comprise louvers 354, as may be seen in Fig 9.4. Air deflectors may also be attached to any portion of each support wheel 355. Each support wheel 355 has a circumferential gap in the vicinity of the entry chamber 307, as in Fig 9.4, so as to prevent thermal expansion distortions arising from the incoming concentrated insolation. This configuration allows the focal line heater element 350, as a whole, to be loaded and removed from either end of the TCH 300 for assembly and maintenance.

[0064] The heater element will experience significant thermal expansion, depending on the choice of material used in for the central tube 352. Where two central tubes 352 abut each other, the support wheel 355 may comprise an expansion hub 358 to allow for such expansion, as may be seen in Fig 9.5.

Coupling

[0065] Target conduit heaters 300 of adjacent SCUs 100 are connected longitudinally by means of a coupling 401, which is part of a swing arm assembly 400 as shown in Fig 2.2 and others.

[0066] As shown in Figs. 10.1-10.3, the coupling 401 provides smooth flow of heat transfer fluid in the RAS and in the central passage from one TCH 300 to the next, while permitting thermal expansion of the TCH elements. Also, the coupling 401 is locked rotationally to the TCH and to the pivot arm assembly, such that the TCH is rotated in unison with the SCU, when the SCU is rotated to provide for precise tracking of the sun elevation. It is preferred to avoid the direct impact of concentrated irradiation from the CPM 200 arriving along the continuous focus line and also to avoid contact with the CPM when the latter is folded while not in operation.

[0067] Coupling 401 comprises a central drum and two coupling flanges 409 as pictured in Fig 10. Cross-section Fig 10.2 shows how the drum mirrors the structure of the TCH 300 with its own coupling hot air pipe 402, insulation ring 403, and a coupling return air sleeve (RAS) 404. The flanges define several holes, each of which, with its own bolts, spacers, washers, and locking nuts, allows the attachment of various devices (to be described in later sections), while some also provide a strengthening link between the flanges of their couplings.

[0068] Figs 10.1 and 10.2 show the coupling 401 defines female coupling joints 405 which receive a male coupling joint 309 formed on the end of a TCH. Gaskets 406 lie within the coupling . The protrusion of the males 309 and the depth of the females 405 are such that, when cool, the thermal contraction of the return air sleeves 304 will not permit full separation of the joints, while at high temperatures, the thermally expanded males will press against the gaskets sufficiently to provide a tight seal, but not so much as to allow buckling of the TCH 300.

[0069] Locking of all rotating components is achieved by narrow ridges in the coupling’s RAS wall, male rotation lock 407, grooves in the TCH’s RAS, and female rotation lock 306, as seen in Figs 10.1 and 10.2.

Air Flow Inverter (AFI) 360

[0070] The couplings 401 may each comprise a static mixer 370 which disturbs the natural, radial segregation of air currents that will take place within the element pipe 301 central passage. In operation, without any further interference of the fluid flow, air moving through the element pipe 301 will tend to separate into two distinct streams with a mixing boundary between them. The central flow will be hot and turbulent to a degree dependent on the configuration of the central heater element 350, while the outer flow along the element pipe circumference will be cooler, faster and more laminar with no strong tendency to mix with the hot central flow. As this pattern would result in rapid and potentially destructive overheating of the heater element as a whole, the coupling 401 is configured with the static mixer to the air flow within the element pipe.

[0071] The static mixer 370 comprises a number of inverter tubes 371, each with a helical divider 372, and beaks 376 which capture air from and deliver air to the central region of the central passage, as pictured in Fig 11.3. The effect of the device is to flip central hot air 374 entering the static mixer at its centre to the outside, while doing the reverse with cool air flow 373 around the periphery. Some of that outer, cooler air slips through the inverter cool air bypass 375. This combination significantly increases the transfer of heat to the gas.

Coupling Hat

[0072] The CPM 200 reflects incoming solar insolation and concentrates it along a focus line on or near the TCH lenses 331. It is preferred to shield the coupling 401 from this focused solar energy to avoid thermal discrepancies across the coupling 401. Thus, the coupling may comprise a coupling hat 430 which has reflective surfaces 425 for deflecting the insolation 325 away from the coupling, and into through the adjacent lenses 331. The hat 430 is anchored to the coupling flanges 409 through attachments 432 as shown, which, by the use of spacers and bolts mentioned previously, contributes to the overall rigidity of the couplings.

Compound Parabolic Mirror (CPM) Deployment, Tracking, and the Compound Parabolic Mirror Stop

[0073] A CPM 200 may be pivoted between a deployed position shown in Figure 13.1 and the storage position shown in Figure 13.4, by rotation of the couplings 401. The CPM is rigidly attached to the couplings by means of swing arm assemblies 420, as shown in Figs. 13.1 and 13.2. A first pivot axis is provided with the coupling 401 and a second pivot axis is provided with the CPM pivot 435 at the distal end of the swing arm 421. The CPM pivot 435 which attaches to the swing arm attachment notch 223 at the lower end of a parabolic support beam. When the CPM is fully deployed and in collecting mode, as it is in Fig 13.1, rotation of the coupling 401 and swing arm 421 provides the solar elevation tracking function of the system.

[0074] The secondary rotation about the CPM pivot 435, combined with the primary rotation of the coupling 401, allows the CPM mirror panel array 210 to be stored when not in use, or to be positioned for installation and maintenance, as it is in Fig 13.4 and Fig 6. As such, the CPM’s reflective surfaces may not be directly exposed to heavy winds or precipitation. This protective capability allows the mirror’s transparent protective layer 215 (Fig 3.3) to be thin and light-weight, which may be important because of the cantilevered design of the CPM.

[0075] A stop arm 423 is attached to the swing arm assembly 420 and aligned with a parabolic support beam 220. When the MPA is rotated to its storage position, the stop arms 423 contact the parabolic support beam s to support the MPA, as shown in Fig. 13.4. The stop arm is secured to the coupling 401 with standard bolts and spacers, which also provide extra stability to the coupling 401.

Solar Collector Unit Support Assembly 500

[0076] Each SCU 100 in the system is supported at both ends by base support assembly 500. Each coupling 401 is retained within a retaining ring 503, which can be opened to permit assembly or disassembly, as seen in Fig 14.2. Roller bearings 504 within the retaining ring confine the coupling 401. A base 501 firmly embedded or attached to the ground, supports support posts 502. Main retention cables 504 attach between main pulley 507 mounted on support post 502 and the upper end of parabolic support beam 220, passing over rollers externally attached to the retaining ring 503.

[0077] Optionally, photovoltaic (PV) panels (not shown) may be attached to the angled support posts 502, which naturally directs the PV panel generally towards the sun. The electricity generated by the PV panels may be used to power actuating motors and controls systems of this solar collection system.

Rotation

[0078] With the swing arm assemblies and the TCHs 300 locked together rotationally by the couplings 401, electric motors (not shown) may rotate the components in unison in order to track the elevation of the sun throughout the collection period, most often only on the scale of a degree or so at a time.

[0079] The rotation of the CPM alone about the pivot 435 (Fig 13.4) is for the purposes of setting the CPM up for collection, storing, or maintenance. It is most easily done by devices such as screw jacks (not illustrated) on the SAA 400 themselves and/or on the base support assembly 500 at one or more locations along the system. Locking mechanisms on the CPM pivot (not illustrated) fix the position of the CPM relative to the swing arm 421 at one of several precise angles, depending on whether the CPM is being set up for collecting, servicing, or storage.

[0080] A control system may be operatively connected to different sensors and actuators to implement a tracking system, or any adjustable aspect of the system, for purposes of efficiency and/or safety. Electric motor actuators may rotate the SCUs in accordance with the measured or predicted elevation of the sun above the horizon. The TCH rotates in unison to maintain the focus line correctly positioned.

[0081] As well, the flow of heat transfer fluid through the TCH may be controlled in response to the amount of solar energy available. If cloudy conditions, or early or late day conditions reduce the amount of solar energy available, the flow rate of thermal energy may be reduced and/or thermal fluid recycling increased, to achieve a desired temperature. Or in mid-day, cloudless conditions, the flow rate may be increased to maximize heat production.

[0082] The control system is preferably a conventional computing device having a processor, memory and implementing computer algorithms configured to implement the control steps described herein. The control system may be completely or partially automated.

Lens Cap 340

[0083] The TCH lenses 331 form continuous lines coincident with or adjacent to the focal line of solar insolation the CPM reflects at the circumference of the target conduit heater 300. The system may include a lens cap 340, which may be a rotatable covering for the lenses, to physically protect them when they are not in use, to reduce repeated thermal shocking of the lenses and lens cradles during solar collection when intermittent cloud cover occurs, to attenuate heat loss by radiation and conduction from the element pipe 301 and entry chamber 307 through the lenses to the environment, and/or reduce the time needed to bring the heater back up to full operating temperature each time solar collection restarts.

[0084] The lens cap 340 is shown in its open position in Figs 15.2 and 15.4, closed in 15.1, 15.3 and 15.5. It may comprise an insulation layer 343, an outer metallic support and protection layer 344, a cap shaft 345, and a means of attachment of the lens cap to the cap shaft, such as with straps 348. At each coupling 401 and swing arm assembly 400, the cap shaft 345 is secured inside a coupling shaft 346 which is supported by bearings mounted in the swing arm assembly 400. An actuator (not shown) may move the lens cap assembly from one or both ends of a TCH 300.

[0085] Operation of the lens cap assembly may be automated in connection with a control system comprising sensors or clocks which detect or predict the amount of sunlight reaching the system.

Turnabout 600

[0086] As described above, air passes through the return air sleeve surrounding the element pipe and then is directed into the central passage of the element pipe where it is heated. At one end of the TCH, a turnabout 600 receives the air from the return air sleeve of the last coupling 401 in row of SCUs 100 (Fig 16.4). The turnabout 600 comprises deflectors 604, 606, end plate 605, and cone 607, which funnel air into the central passage of the element pipe for heating.

Definitions and Interpretation

[0087] The corresponding structures, materials, acts, and equivalents of all means or steps plus function elements in the claims appended to this specification are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed.

[0088] References in the specification to "one embodiment", "an embodiment", etc., indicate that the embodiment described may include a particular aspect, feature, structure, or characteristic, but not every embodiment necessarily includes that aspect, feature, structure, or characteristic. Moreover, such phrases may, but do not necessarily, refer to the same embodiment referred to in other portions of the specification. Further, when a particular aspect, feature, structure, or characteristic is described in connection with an embodiment, it is within the knowledge of one skilled in the art to combine, affect or connect such aspect, feature, structure, or characteristic with other embodiments, whether or not such connection or combination is explicitly described. In other words, any element or feature may be combined with any other element or feature in different embodiments, unless there is an obvious or inherent incompatibility between the two, or it is specifically excluded.

[0089] It is further noted that the claims may be drafted to exclude any optional element. As such, this statement is intended to serve as antecedent basis for the use of exclusive terminology, such as "solely," "only," and the like, in connection with the recitation of claim elements or use of a "negative" limitation. The terms “preferably,” “preferred,” “prefer,” “optionally,” “may,” and similar terms are used to indicate that an item, condition or step being referred to is an optional (not required) feature of the invention.

[0090] The singular forms "a," "an," and "the" include the plural reference unless the context clearly dictates otherwise. The term "and/or" means any one of the items, any combination of the items, or all of the items with which this term is associated.

[0091] As will be understood by one skilled in the art, for any and all purposes, particularly in terms of providing a written description, all ranges recited herein also encompass any and all possible sub-ranges and combinations of sub-ranges thereof, as well as the individual values making up the range, particularly integer values. A recited range (e.g., weight percents or carbon groups) includes each specific value, integer, decimal, or identity within the range. Any listed range can be easily recognized as sufficiently describing and enabling the same range being broken down into at least equal halves, thirds, quarters, fifths, or tenths. As a non-limiting example, each range discussed herein can be readily broken down into a lower third, middle third and upper third, etc.

[0092] As will also be understood by one skilled in the art, all ranges described herein, and all language such as "between", "up to", "at least", "greater than", "less than", "more than", "or more", and the like, include the number(s) recited and such terms refer to ranges that can be subsequently broken down into sub-ranges as discussed above.

Claims

WHAT IS CLAIMED IS:

1. A solar energy collection system comprising:

(a) a solar collection unit comprising an elongate, hemi-parabolic reflector having a focus line;

2. The system of claim 1 wherein the heat transfer fluid is a gas, such as nitrogen or air.

3. The system of claim 1 or 2, wherein the reflector comprises a plurality of rectangular mirrors arrayed in vertical columns and horizontal rows, each mirror has a curved cross- section occupying a unique position of a parabolic segment such that collectively the cross- sections of a vertical row of the mirrors complete a trace of the parabolic segment.

4. The system of claim 3 wherein each of the plurality of mirrors is mounted independently to a support structure, configured to allow each mirror to thermally expand and contract without restraint.

5. The system of claim 4 wherein the support structure comprises cable adjusters for adjusting the position of the focus line.

6. The system of any one of claims 3 to 5, wherein each mirror is mounted to the support structure and adjustably positioned to have its focus line align with the focus line of other mirrors, on the target conduit heater.

7. The system of any one of claims 1 to 6, wherein the target conduit heater defines a central internal passage through which the heat transfer fluid passes and a longitudinal entry chamber which is coincident with the focus line of the solar collector unit, through which solar radiation may pass through into the central internal passage.

8. The system of claim 7 further comprising a lens assembly associated with the entry chamber, comprising a plurality of lenses for modulating the direction and concentration of the solar radiation passing into the entry chamber and central internal passage.

9. The system of claim 8 further comprising a removeable lens cap for covering the lens assembly, preferably an insulating lens cap.

10. The system of claim 9 wherein the lens cap is moved between an open position and a closed position by an actuator operatively connected to a light sensor.

11. The system of claim 7 or 8, wherein the target conduit heater comprises at least one insulating layer and/or a reflective layer to reduce conductive and/or radiant heat loss from the central passage.

12. The system of any one of claims 7 to 11, further comprising a central heat element positioned within the central passage, which heat element is heated by incoming solar radiation and which heats the heat transfer fluid within the central passage.

13. The system of claim 12 wherein the central heat element comprises a central rod-like structure with attached fins to increase heat transfer surface area.

14. The system of any one of claims 7 to 13, wherein the target conduit heater defines a countercurrent flow passage in an outer concentric passage, and a turnaround for directing the heat transfer fluid from the outer concentric passage into the central passage.

15. The system of any one of claims 7 to 14 further comprising air mixers within the central passage.

16. The system of any one of claims 1 to 15, wherein the solar collection unit is aligned from east to west, and further comprising a subsystem for tracking the elevation of the sun and adjusting the position of the solar collection unit accordingly.