The present invention relates to a radiation reflection device used to focus radiation from a moving source onto a stationary receiver.
The primary application of such an invention relates to reflecting the radiation from the sun onto a stationary target. In such an application, wherein the device is used to orient a reflective surface to reflect light onto a target, the device may be termed a “heliostat”. In another sunlight reflecting application, wherein the device is implemented in an array used to orient a plurality of reflective surfaces to reflect light onto a target, the device may be termed a “ganged heliostat”. Light concentration achieved by heliostats or ganged heliostats has several uses which include thermal energy conversion, photovoltaic energy conversion, and daylighting.
In other applications, the device may be used to reflect any other type of electromagnetic radiation such as radio signals, sound waves, moonlight, etc.
A prior art exists in heliostat devices. Various heliostats of the prior art require complex computer control of encoder type servo or stepper motors such as the device disclosed in U.S. Pat. No. 4,440,150 (Kaehler). Various heliostats of the prior art require a half-angle gearing system such as the devices disclosed in U.S. Pat. No. 5,027,047 (Logan et al.) and U.S. Pat. No. 4,586,488 (Noto). Various heliostats of the prior art require an external sensor feedback system and complicated drive arrangement such as the device disclosed in U.S. Pat. No. 6,899,096 (Nakamura). The present invention, when employed in a heliostat, does not require a complicated external computer control, encoder type motors, or a half-angle gear system.
A prior art exists in ganged heliostats such as devices disclosed in U.S. Pat. No. 4,110,010 (Hilton), U.S. Pat. No. 4,056,313 (Arbogast) and U.S. Pat. No. 3,466,119 (Francia). These devices include a high number of parts and a high complexity of parts. Also, various ganged heliostats of the prior art (e.g. U.S. Pat. No. 4,110,010) require daily adjustment to compensate for the declination of the sun. Such a requirement increases operating cost of the device and the likelihood of focusing errors. The present invention, when employed in a ganged heliostat, does not require continual adjustment to compensate for solar declination and is simpler in construction than ganged heliostats of the prior art.
The present invention relates to a radiation reflection device which can be used to orient a mirror to reflect radiation from a moving radiation source to a stationary receiver. The device can be used either singly, or implemented in a ganged array.
The device includes a reflective surface, or mirror and a mirror frame which is attached to the mirror. The device orients the mirror to a position bisecting the incidence vector (i.e.—a vector through the mirror centre and the source of radiation) and the reflection vector (i.e.—a vector through the mirror centre and the stationary receiver), thus achieving the reflection of light from source to target (imaging).
The device includes a linkage that is aligned perpendicular to the incidence vector. This linkage is referred to as the incidence linkage. The device includes a linkage that is aligned perpendicular to the reflection vector. This linkage is referred to as the reflection linkage.
The incidence linkages and reflection linkages are interconnected in a parallelogram pattern. Vertices of the parallelogram pattern define a parallelogram bisecting line that bisects the angle between the incidence and reflection linkages. The device includes traversing bolts that pass through the vertices of the parallelogram bisecting line. The traversing bolts also pass through slots of the mirror frame and indirectly locate the mirror to a position necessary for imaging.
The advantages of the present invention will be more apparent from the following detailed description in reference to the accompanying drawings.
Six embodiments of the invention will be described: embodiment ‘1’, embodiment ‘2’, embodiment ‘3’, embodiment ‘4’, embodiment ‘5’, and embodiment ‘6’. The embodiments ‘1’, ‘2’, ‘4’, ‘5’, and ‘6’ are heliostats and embodiment ‘3’ is a ganged heliostat. Each embodiment will be described with respect to a solar reflecting (concentrating) application.
The heliostat of embodiment ‘1’ will now be described with reference to
Tilt motor 1102, which is fixed to the carriage at tilt motor plate 1605, is fixed to linkage 1400 at its centre of rotation. Pan motor 1101 is fixed to coupling 1602, which is fixed to main shaft 1001. Pan motor 1101 and tilt motor 1102 are controlled to continually adjust incidence linkage 1400 such that it remains perpendicular to the incidence vector. Reflection linkage 1300 is fixed to the carriage posts 1603 such that it is perpendicular to the main shaft 1001. Since main shaft 1001 is collinear with the receiver, linkage 1300 is always perpendicular to the reflection vector.
Each of the linkages includes three holes; one at the centre and one at either end. The distance between the centre hole and either end-hole is the same for each linkage. Linkage 1401 is connected to linkage 1400 at one end and linkage 1402 at the other end. The joints between linkages 1400 and 1401 and between linkages 1401 and 1402 are rotatable. Similarly, linkage 1301 is connected to linkage 1300 at one end and linkage 1302 at the other end. The joints between linkages 1300 and 1301 and between linkages 1301 and 1302 are rotatable. Traversing bolt 1501 passes through the centre hole of linkages 1301 and 1401 and through the mirror frame guides 1201 and mirror frame guides 1202. Traversing bolt 1502 passes through the centre hole of linkages 1302 and 1402 and through mirror frame guides 1201 and mirror frame guides 1202. A bolt at the centre of linkage 1300 passes through a sleeve fixed to the centre of guides 1201. A bolt at the centre of linkage 1400 passes through a sleeve fixed to the centre of guides 1202.
The function of linkages 1301, 1302, 1401, 1402 is similar to the function of linkages 1303, 1304, 1403, 1404. The function of traversing bolts 1501, 1502 is similar to the function of traversing bolts 1503, 1504.
It should be noted that the centre of mass of the rotating parts of the device coincides with the central axis of the shaft of pan motor 1101 and the central axis of the shaft of tilt motor 1102. Therefore, the torque requirement of the motors is minimized.
The heliostat of embodiment ‘2’ is shown in
Embodiment ‘2’ includes a sensor feedback system used to control pan motor 2101 (analogous to pan motor 1101 of embodiment ‘1’) and tilt motor 2102 (analogous to pan motor 1102 of embodiment ‘1’). Pan sensors 2804 and 2805 are fixed to the carriage posts 2603. Tilt sensors 2802 and 2803 are fixed to the incidence linkage 2400. The sensors are of the photovoltaic type or photoresistor type. The sensors send signals to an electronic control system used to control pan motor 2101 and tilt motor 2102.
Pan motor 2101 rotates the heliostat carriage until the sunlight incident on pan sensors 2804 and 2805 is equal (i.e.—the sensor pair is balanced). Tilt motor 2102 rotates linkage 2400 until the sunlight incident on tilt sensors 2802 and 2803 is equal (i.e. the sensor pair is balanced). When each sensor pair is balanced, linkage 2400 has achieved a position wherein it is perpendicular to the incidence vector. Once this is achieved, the mechanism of the heliostat causes the reflective surface to be oriented for imaging as described above. A sensor feedback system of this type allows non-encoder type motors (e.g.—DC gear motors) to be employed as pan motor 2101 and tilt motor 2102.
It should be noted that initial setup of the heliostat is easily achieved. During setup, the main shaft 2001 is aimed at the receiver. No further calibration is necessary. The device does not require any type of periodic adjustment.
The ganged heliostat of embodiment ‘3’ will now be described with reference to
Incidence linkage 3300 (analogous to reflection linkage 1300 of embodiment ‘1’) is mounted on, and rotates about, main shaft 3001 which is adjusted by the incidence aiming means. Therefore, the incidence aiming means indirectly aligns linkage 3300 to a position perpendicular to the incidence vector. When linkages 3300 and 3400 are aligned to positions perpendicular to the incidence and reflection vectors respectively, the mechanism comprising the linkages, guides, and mirror frame achieves a mirror position necessary for imaging.
It should be noted that the centre of mass of the rotating parts of the device lies midway between the split ends of wire 3701. Therefore, the tension requirement of 3701 is minimized.
Optionally, an additional wire 3706 (not shown in the Figures) may be employed in the ganged heliostat element. Wire 3706 would include a plain end and a split end (similar to wire 3701). If employed, the wire 3706 would be connected at its plain end to the receiver, and at its split end to holes 3704 and 3705. When put in tension, wire 3706, together with tensioned wire 3701, adjust and position the reflection linkage.
The novel reflection aiming means achieved by wire 3706 may also be combined with the half-angle gearing method used in heliostats of the prior art as shown in the device of
A reflection linkage that is positioned using the wire type reflection aiming means is connected to a gear G1. Gear G1 turns gear G2 which turns gear G4 which turns gear G6 which turns gear G8. Gear G1 also turns gear G3 which turns gear G5 which turns gear G7 which turns gear G8. The gear ratio between gear G1 and gear G8 is 2:1.
The heliostat of embodiment ‘4’ will now be described with reference to
Tilt motor 4102 is mounted to tilt motor plate 4605. The shaft of tilt motor 4605 is fixed directly to the mirror frame guides 4202. Incidence linkage 4303 is connected at one end to reflection linkage 4606 and fixed to sensor plate 4801 at its other end. Incidence linkage 4403 is connected at one end to reflection linkage 4605 and fixed to sensor plate 4801 at its other end. The joints between linkages 4303 and 4606 and between linkages 4403 and 4605 are rotatable. Traversing bolt 4503 passes through linkages 4303 and 4403 and through mirror frame guides 4201 and 4202.
Sensors 4802, 4803, 4804, and 4805 are located on sensor plate 4801. Pan motor 4101 rotates the heliostat carriage until the sunlight incident on pan sensors 4804 and 4805 is balanced. Tilt motor 4102 rotates the guides 4201 and 4202 until the sunlight incident on tilt sensors 4802 and 4803 is balanced. When each sensor pair is balanced, sensor plate 4801 has achieved a position wherein it is perpendicular to the incidence vector. When sensor plate 4801 is aligned perpendicular to the incidence vector, incidence linkages 4303 and 4403 are perpendicular to the incidence vector.
Reflection linkages 4605 and 4606 are fixed to the carriage posts 4603 such that linkages 4605 and 4606 are perpendicular to the main shaft 4001. Since main shaft 4001 is collinear with the receiver, reflection linkages 4605 and 4606 are always perpendicular to the reflection vector.
When incidence linkages 4303 and 4403 and reflection linkages 4605 and 4606 are aligned to positions perpendicular to the incidence and reflection vectors respectively, the mechanism comprising the linkages, traversing bolts, guides, and mirror frame achieves a mirror position necessary for imaging.
The heliostat of embodiment ‘5’ will now be described with reference to
The heliostat of embodiment ‘6’ will now be described with reference to