CA2473042A1

CA2473042A1 - Solar energy control

Info

Publication number: CA2473042A1
Application number: CA002473042A
Authority: CA
Inventors: Maurice Tuchelt
Original assignee: SHEC Labs Solar Hydrogen Energy Corp
Current assignee: Individual
Priority date: 2004-07-06
Filing date: 2004-07-06
Publication date: 2006-01-06
Also published as: RU2380624C2; AU2005259731A1; EP1781997A1; CA2572299A1; CN101014810A; JP2008505301A; JP4908407B2; BRPI0513399A; AP2007003886A0; RU2007103233A; IL180535A0; AP2097A; US20080060636A1; MX2007000113A; WO2006002545A1

Description

,SOLAR ENERGY CONTROL
This invention is in the field of solar energy systems and in particular controlling the energy received by a solar receptor such as a boiler, oven, or the tike.
BACKGROUND
Considerable development is taking place in an attempt to efficiently and effectively harness solar energy. One typical system involves a curved mirror shaped to gather and focus solar rays into a cone-shaped focused solar beam. A solar receptor is placed near the apex of the cone and considerable heat can be generated irr the receptor to perform a desired function that requires heat energy. The curved mirrors are typically made up of an array of smaller flat mirror segments arranged on a curved frame to achieve the focusing effect, and can be quite large, depending on the energy requirement of the receptor.
Such solar systems are generally placed in arid locations where the sun is reliably available so that the heat generated by the solar beam will be at least substantially consistent. The solar receptors can include boilers, thermal reactors, Stirling engines, and the like. A problem with such systems is controlling the amount of heat energy received by the solar receptor. For example a Stirling engine has no control that ~rresponds to a throttle whereby the energy supplied to the engine corresponds to the load.
When powering a Stirling engine with solar energy from a mirror array, the solar energy supplied to the engine is substantially constant, and so the load must be maintained at a sufficient level to use all the solar energy supplied by the mirror array. ff the load drops, the engine very quickly overheats and is damaged. Similar overheating and damage can occur with other solar receptors as well.
To provide a level of control, the flat mirror segments on the mirror array can be mounted such that they can be moved by an actuator. Controllers activate the actuators and pivot the mirrors to produce the focused cone-shaped solar beam. The amount of energy received by the receptor can thus be varied. Thus when overheating is detected the mirror segments are moved out of focus to reduce the amount of energy received, such as when the load on a Stirling engine drops. Such systems also allow a receptor to be heated slowly by gradually bringing the flat mirror segments into focus until the maximum or desired energy is received. The movable mirror segments, actuators, and controls are complex and so these systems are very costly to build and maintain.
It is also known to prevent damage from overheating by moving a plate into position to block the solar beam, or a portion thereof. Such plates are made from refractory materials in order to withstand the intense heat of the solar beam, and are quite fragile and subject to damage from the elements.
SUMMARY OF THE INVENTION
zo It is an object of the present invention to provide a solar energy control apparatus that overcomes problems in the prior art. 1t is a further object of the present invention to provide such a control apparatus that prevents a portion of a focused solar beam from contacting a solar receptor.
It is a further object of the present invention to provide such a control apparatus that comprises a shutter movable from an open position, where the complete solar beam hits the solar receptor, to at least a partially closed position wherein a portion of the solar beam is blocked and prevented from hitting the solar receptor. It is a further object of the present invention to provide such an apparatus comprising one or more shutter plates, each having a cooling conduit defined in an interior thereof, and a source of cooling fluid connected to flow through the cooling conduit to remove heat from the shutter plate.
The present invention provides a shutter assembly adapted to be positioned between a curved mirror that is operative to focus solar rays into a focused solar beam, and a solar receptor that is oriented to receive the focused solar beam. The solar receptor will 1Q typically be a reaction chamber, Stirling engine, or the like and the curved mirror will be provided by an array of mirror segments.
In one embodiment, the shutter assembly comprises a plurality of shutter plates pivotally mounted to a shutter frame, and a shutter control operative to move the shutter plates i5 from an open position, where the complete solar beam hits the solar receptor, to a plurality of partially closed positions wherein varying portions of the solar beam are blocked and prevented from hitting the solar receptor, and then to a closed position where the solar beam is completely blocked. Each shutter plate includes an internal cooling conduit and a source of cooling fluid is connected to each cooling conduit such that 20 cooling fluid circulates through the cooling conduits to remove heat from the shutter plates.
In a send embodiment the shutter assembly comprises an annular shutter plate defining a central aperture. Again the annular shutter plate includes one or more internal cooling 25 conduits and a source of cooling fluid is connected to the cooling conduits such that cooling fluid circulates through the cooling conduits to remove heat from the annular shutter plate. The annular shutter plate is mounted transversely to the solar beam. When the annular shutter plate is located close to the solar receptor, the complete solar beam can pass through the central aperture and hit the solar receptor. As the annular shutter plate is moved away from the solar receptor toward the curved mirror the outer portion of the cone-shaped solar beam hits the annular shutter plate and is thus prevented from hitting the solar receptor. Due to the conical shape of the beam, the annular shutter plate can be wide enough that when located a considerable distance from the solar receptor, the great majority of the solar beam is blocked, with only a small portion passing through the central aperture to hit the solar receptor. In this embodiment a linear shutter control controls the distance between the annular shutter plate and the solar receptor.
The cooling fluid could conveniently and effectively be a mixture of water and glycol such as is used in engine cooling systems. Such a mixture pumped in large volumes has the ability to remove a large amount of heat from the shutter plates, and is safe and convenient to handle. It is contemplated that other Quids, both liquid and gaseous, could be used as cooling fluids as well.
It is also contemplated that the shutter plates could be insulated or reflective on a rear surface thereof facing the solar receptor. Then during periods of cloud or at night, the shutter plates could be closed and heat would be retained in the solar receptor rather than ZO radiating out through the opening in the shutter assembly.
DESCRIPTION OF THE DRAWINGS:
While the invention is claimed in the concluding portions hereof, preferred embodiments are provided in the accompanying detailed description which may be best understood in conjunction with the accompanying diagrams where like parts in each of the several diagrams are labeled with like numbers, and where:

Fig. 1 is a schematic side view of a shutter assembly of the invention set up between a curved mirror and a solar receptor in the open position with all of the solar beam being received by the solar reoeptar;
Fig. 2 is a schematic side view of an embodiment of the shutter assembly of Fig. 1 with pivoting shutter plates showing the shutter assembly in a partially closed position with only a portion of the solar beam being received by the solar receptor;
Fig. 3 is a schematic side view of an alternate embodiment of the shutter assembly of Fig. 1 with an annular shutter plate showing the shutter assembly in a partially closed position with only a portion of the solar beam being received by the solar receptor;
Fig. 4 is a perspective rear view of a shutter assembly comprising pivoting shutter plates such as could be used in the embodiment of Fig. 2 showing the shutter plates in the open position;
Fig. 5 is a perspective front view of the shutter assembly of Fig. 4 showing the shutter plates in the open position;
Fig. 6 is a perspective rear view of the shutter assembly of Fig. 4 showing the shutter plates in partially closed position;

Fig. 7 is a perspective front view of the shutter assembly of Fig. 4 showing the shutter plates in an almost fully closed position, and also showing a shield plate to protect the shutter mechanism;
Fig. 8 is a schematic perspective rear view showing the internal cooling conduit in one of the shutter plates;
Fig. 9 is a front view of sn alternate annular shutter plate such as would be used in the shutter assembly of Fig. 3;
Fig. 10 is a schematic illustration of the operation of the shutter assembly of Fig.
lo.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS:
Fig. 1 schematically illustrates a shutter assembly 2 of the invention set up between a curved mirror 4 and a solar receptor 6 such as are known in the prior art. The curved mirror 4 focuses solar rays into a cone-shaped solar beam 8, and the solar receptor 6 is positioned substantially at the apex of the cone to receive the solar beam 8.
The heat generated by the solar beam 8 in the solar receptor 6 is used in various ways as are well known in the art.
In Fig. 1, the shutter assembly 2 is shown in the open position where all of the solar beam passes through the shutter assembly and is received by the solar receptor 6.
Fig. 2 schematically illustrates the operation of an embodiment of the shutter assembly 2 that uses movable shutter plates to block the solar beam 8 and prevent varying portions thereof from hitting the solar receptor 6. Fig. 2 illustrates the shutter assembly 2 in a partially closed position with only a portion of the solar beam 8 being received by the solar tsceptor 6.
Such a shutter assembly 2 is illustrated in Figs. 4 - 8. The shutter platxs 10 are pivotally mounted on a shutter frame 12 and define a central aperture 14. The shutter plates 10 are also pivotally connected via links 20 to a shutter ring 16 that rotates with respect to the shutter frame 12 in response to rotation of a drive motor 18. Thus the shutter plates 6 can pivot from the open position of Figs. 4 and 5, through the partially closed position of Fig.
6, and through the more fully closed position of Fig. 7 to a completely closed position.
It can thus be seen that as the shutter plates 6 move from the open position to the closed position, varying portions of the solar beam 8 will be blocked and prevented from hitting the solar receptor 6. The heat energy received by the solar receptor 6, and thus the temperature thereof, can be thus be finely controlled by activating the drive motor 18 to open or close the shutter plates 10. As can be seen, unlike a camera shutter, the shutter plates 10 do not overlap. The solar beam 8 can pass between the edges of the shutter plates 10, as well as through the center of the central aperture 14. Fig. 8 illustrates the front of the shutter assembly 2 that faces the curved mirror 4 with a shield plate 21 installed to protect the shutter mechanism.
While the particular arrangement illustrated is simple and convenient, it is contemplated that other arrangements would also serve the purpose of moving the shutter plates 10 in and out of the solar beam 8 to block reception by the solar receptor 6, and such other arrangements are contemplated to fall within the scope of the invention.
Fig. 8 illustrates in one shutter plate 10 the internal cooling conduit 22 that is defined in the interior of each shutter plate 10. The shutter plates 10 are quite thick, and the cooling conduit 22 is provided quite simply in the illustrated embodiment by drilling a pair of holes 24 from the outer edge of the shutter plate 10 on an angle toward the inner end thereof. The holes 24 meet near the inner end and thus form the cooling conduit 22.
Hose barbs 2G are attached to the exposed ends of the holes 24 to facilitate connection of S the cooling conduit 22 to a cooling fluid source 28. A cooling fluid, such as a water-glycol mixture, air, or the like is circulated from the cooling fluid source 28 through the cooling conduit 22.
The holes 24 are sized such that they pass quite close to the surface of the shutter plate 10 to quickly draw heat away from the surface_ The shutter plates are made from material that conducts heat well and also withstands exposure to the elements. Aluminum provides a good material for the shutter plates 10, however other materials such as copper could also be used. The front surface of the shutter plates 10, facing the curved mirror 4, could also be polished to reflect the solar beam 8 such that less heat is absorbed that must be removed by the cooling fluid. The shutter assembly 2 could be oriented at an angle to the solar beam 8 as well, such that reflected solar rays do not reflect back on the shutter assembly 2 from the mirror.
Further, where the shutter assembly 2 is located closely adjacent to the solar receptor 6 as in Figs. 1 and 2, the shutter plates 10 could be insulated or reflective on a rear surface thereof facing the solar receptor 6. Then during periods of cloud or at night, the shutter plates 10 could be closed and heat would be retained in the solar receptor 6 rather than radiating out through the central aperture 14 and being lost.
Fig. 9 illustrates an alternate shutter assembly 102, suitable for use as illustrated in Figs. 3 and 10. The shutter assembly 102 comprises an annular shutter plate 110. A
plurality of internal cooling conduits 122 are defined in the annular shutter plate 110 in a similar manner to that described above and are connected to a cooling fluid source.
The annular shutter plate 110 is again made from heat conductive material to facilitate removal of heat by cooling fluid circulating thmugh the cooling conduits 122.
As illustrated in Fig. 10 when the annular shutter plate 110 is located in position A, close to the solar receptor 6, all of the solar beam 8 passes through the central aperture 114 and hits the solar receptor 6. The aimular shutter plate 110 is mounted on a track or the like such that same can be moved away from the solar receptor 6. As the annular shutter plate moves away from the solar receptor 6 the outer portions of the conical solar beam 8 10 are blocked by the annular shutter plate 110. In position -B; a smallportiorr~of-Ehe solar beam 8 is blocked, while at position C a very large portion of the solar beam 8 is blocked.
While the particular arrangements illustrated are simple and convenient, it is contemplated that other arrangements would also serve the purpose of moving the shutter plates 10 in and out of the solar beam 8 to block reception by the solar receptor 6, and such other arrangements are contemplated to fall within the scope of the invention.
Thus the foregoing is considered as illustrative only of the principles of the invention.
Further, since numerous changes and modifications will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all such suitable changes or modifications in structure or operation which may be resorted to are intended to fall within the scope of the claimed invention.