Solar Collection Apparatus and Methods Using Accelerometers and Magnetic Sensors
A mirror or other reflecting surface is used for collecting and reflecting incident solar radiation. The mirror is supported for independent motion about a pair of axes. An accelerometer generates signals representative of an amount and direction of motion of the mirror about each of the axes. Motors or other drive mechanisms independently drive the mirror about each of the axes. A tracking device provides information about the current position of the Sun. A control is connected to the accelerometer, the motors and the tracking device for maintaining a predetermined optimum orientation of the mirror as the Sun moves across the sky. Position sensors that sense the position of the mirror relative to the earth's magnetic field may also be employed.
This application claims benefit under 35 USC Sections 119(e) and 120 to the filing date of U.S. Provisional Application Ser. No. 60/807,456 filed by Mark S. Olsson on Jul. 14, 2006.
FIELD OF THE INVENTIONThe present invention relates to systems and methods for utilizing the energy of the Sun, and more particularly, to systems and methods for tracking the Sun to re-direct and concentrate incident solar radiation for lighting, heating and photovoltaic applications.
BACKGROUND OF THE INVENTIONIncreased usage of renewable energy sources such as solar radiation is important in reducing dependence upon foreign sources of oil and decreasing green house gases. Devices have been developed in the past that track the motion of the Sun to re-direct and concentrate incident solar radiation.
There are many variations of the foregoing devices, but to date, none has been widely adopted due to the complexity, reliability, accuracy and/or expense of the tracking mechanisms.
SUMMARY OF THE INVENTIONIn accordance with the present invention a solar tracking apparatus has a mirror or other reflecting surface for collecting and reflecting incident solar radiation. The mirror is supported for independent motion about a pair of axes. An accelerometer generates signals representative of an amount and direction of motion of the mirror about each of the axes. Motors or other drive mechanisms independently drive the mirror about each of the axes. A tracking device provides information about the current position of the Sun. A control is connected to the accelerometer, the motors and the tracking device for maintaining a predetermined optimum orientation of the mirror as the Sun moves across the sky.
According to another aspect of the present invention, one or more magnetic field sensors are used to sense rotation around an approximately vertical axis and one or more accelerometers are used to sense tilt around an approximately horizontal axis to provide signals indicative of heliostat mirror position in a coordinate system to a control system. The control system allows for precise positioning of a heliostat mirror and the directing of solar energy in a desired direction.
According to another aspect of the present invention, three orthogonal magnetic field sensors are used to sense rotation around an approximately vertical axis and three orthogonal accelerometers are used to sense tilt around an approximately horizontal axis to provide signals indicative of heliostat mirror position in a coordinate system to a control system. The control system allows for precise positioning of a heliostat mirror and the directing solar energy in a desired direction.
The entire disclosure of U.S. Provisional Application Ser. No. 60/807,456 of Mark S. Olsson, filed Jul. 14, 2006, is hereby incorporated by reference.
The mirror 70 (
The accelerometer 74 (
While it is possible over certain rotational limits, with appropriate calibration and alignment to use single axis sensors, it is desirable to use three axis sensors for both magnetic field and gravity. It is anticipated with ongoing reductions in the cost of sensors and greater sensor integration. For example, an Aichi Steel Corporation, Electro-Magnetic Products, AMI601 sensor would be suitable for this application. See http://www.aichi-mi.com/3products/ami%20cataloyue%20e.pdf.
The pivot mechanisms 72 are configured and arranged so that throughout the useful range of tracking tilts, the accelerometer 74 is not rotated in an unknown fashion about a vertical axis. If the accelerometer is rotated about a vertical axis, the pointing direction of the mirror 70 becomes ambiguous or indeterminate.
It will be understood that a wide variation of modifications of the embodiment illustrated in
A lower tension wire 420 (
Each of the counter-weight drive assemblies 426 and 428 (
The lower and upper counter-weight drive assemblies 426 and 428 are capable of reciprocal vertical motion within the bore of the support post 418. A control circuit (not illustrated) receives input from a MEMS accelerometer as previously described and causes the micro-motors of the lower and upper counter-weight drive assemblies 426 and 428 to move the mirror 402 into the optimum position for reflecting solar radiation onto a target (not illustrated in
Referring now to
For maximum durability, the sensor and control package might be mounted behind an uncoated transparent section of glass mirror. Optical sensors to determine the position of the sun can be integrated into the sensor and control package. The same suite of optical sensors can further be used to determine the relative position of the solar energy target. Various means of building optical sensors to sense light direction are known in the art. Optionally, photovoltaic cells can be integrated into the sensor and control package or optionally mounted in an adjacent fashion (1010). Batteries or capacitors can be used to store the energy from the photovoltaic cells to provide power to operate both motorized rotation axis. Alternately wired power (not shown) can be used. A wireless link (1016) or a wired link (not shown) can be used to remotely control each mirror and exchange data between each mirror's control system and a centralized control facility. If a wireless link is employed, a mesh networking topology is preferably used to allow data and control signals to be communicated across a heliostat array of large area extent. A large heliostat array might be usefully employed to produce hydrogen fuel by photo catalytic means.
Control signals from the mirror control system to each motorized rotation axis might be by wireless means. For lowest possible cost and long terms reliability it is desirable to reduce the number of cables, wires, and connectors as possible. Power to run the axis rotation motors might be provided by a hardwired means while control might be provided by wireless means. Rotation motors might each have their own small photovoltaic panel and energy storage means.
While several preferred embodiments of the present invention have been described, and some variations thereof, further modifications will occur to those skilled in the art. For example, any of the embodiments described herein can utilize accelerometers alone, or accelerometers and magnetic sensors. Therefore the protection afforded the subject in invention should only be limited in accordance with the following claims.
Claims
1. A solar tracking apparatus, comprising:
- means for collecting and reflecting incident solar radiation;
- means for supporting the solar radiation collecting and reflecting means for independent motion about a pair of axes;
- accelerometer means for generating signals representative of an amount and direction of motion of the solar radiation collecting and reflecting means about each of the axes;
- motor means for independently driving the solar radiation collecting and reflecting means about each of the axes;
- tracking means for providing information about the current position of the Sun; and
- control means connected to the accelerometer means, the motor means and the tracking means for maintaining a predetermined optimum orientation of the solar radiation collecting and reflecting means as the Sun moves across the sky.
2. The solar tracking apparatus of claim 1 wherein the solar radiation collecting and reflecting means is configured for concentrating incident solar radiation.
3. The solar tracking apparatus of claim 1 wherein the accelerometer means is mounted on the solar radiation collecting and reflecting means.
4. The solar tracking apparatus of claim 1 wherein the support means includes a pair of pivot mechanisms.
5. The solar tracking apparatus of claim 1 wherein the accelerometer means includes a MEMS accelerometer device.
6. The solar tracking apparatus of claim 1 wherein the motor means includes first and second electric motors and first and second drive linkages for coupling the electric motors, respectively, to the support means.
7. The solar tracking apparatus of claim 1 wherein the solar radiation collecting and reflecting means is supported so that both axes are substantially in the same horizontal plane when the solar radiation collecting and reflecting means is in a horizontal orientation.
8. The solar tracking apparatus of claim 7 wherein the solar radiation collecting and reflecting means is a mirror with a configuration selected from the group consisting of planar, parabolic and parabolic trough.
9. The solar tracking apparatus of claim 1 and further comprising means for sensing a reference position of the solar radiation collecting and reflecting means relative to the earth's magnetic field vector and for generating signals representative of the reference position and supplying them to the control means.
10. The solar tracking apparatus of claim 9 wherein the accelerometer means and the reference position sensing means are provided by three-axis sensors.
11. A heliostat mirror pointing system employing both accelerometer and magnetic sensors to determine mirror position relative to the earth's gravitational vector and the earth's magnetic field vector.
12. The heliostat mirror pointing system of claim 11 wherein one axis of rotation is approximately vertical.
13. The heliostat mirror pointing system of claim 11 wherein one axis of rotation is approximately horizontal.
14. The heliostat mirrorpointing system of claim 11 wherein the magnetic sensor is used to sense rotation around said vertical axis.
15. The heliostat mirror pointing system of claim 11 wherein the accelerometer sensor is used to sense rotation around said horizontal axis.
16. The heliostat mirrorpointing system employing 3-axis magnetic sensors to determine mirror position relative to the earth's magnetic field vector.
17. The heliostat mirror pointing system of claim 16 wherein one axis of rotation is approximately vertical.
18. The heliostat mirror pointing system of claim 16 wherein one axis of rotation is approximately horizontal.
19. The heliostat mirror pointing system of claim 16 wherein the magnetic sensor is used to sense rotation around horizontal and vertical axis.
20. A heliostat mirror control system employing both accelerometer and magnetic sensors to determine mirror position relative to the earth's gravitational vector and the earth's magnetic field vector.
21. The heliostat mirror control system of claim 20 wherein said control system is a member of a mesh network.
22. The heliostat mirror control system of claim 20 wherein said control system uses a wireless control means.
23. The heliostat mirror control system of claim 20 wherein photovoltaic devices are used to provide power to said control system.
24. The heliostat mirror control system of claim 20 wherein photovoltaic devices are used to store energy in one or more capacitors to provide power for said control system.
25. The heliostat mirror control system of claim 20 wherein photovoltaic devices are used to store energy in one or more rechargeable batteries to provide power for said control system.
26. A solar tracking apparatus, comprising:
- a reflective surface for collecting and reflecting incident solar radiation;
- a pivot mechanism that supports the reflective surface for independent motion about a pair of axes;
- an accelerometer that generates signals representative of an amount and direction of motion of the reflective surface about each of the axes;
- at least one motor coupled to independently drive the reflective surface about each of the axes;
- a data source that provides information about the current position of the Sun; and
- a control circuit connected to the accelerometer, the motor and the data source for maintaining a predetermined optimum orientation of the reflecting surface as the Sun moves across the sky.
27. The solar tracking apparatus of claim 26 wherein the reflective surface is configured for concentrating incident solar radiation.
28. The solar tracking apparatus of claim 26 wherein the accelerometer is mounted on the reflective surface.
29. The solar tracking apparatus of claim 26 wherein the reflective surface is supported by a pair of pivot mechanisms.
30. The solar tracking apparatus of claim 26 wherein the accelerometer is a MEMS accelerometer device.
31. The solar tracking apparatus of claim 29 wherein the apparatus includes first and second electric motors and first and second drive linkages for coupling the electric motors to corresponding ones of the pair of pivot mechanisms.
32. The solar tracking apparatus of claim 26 wherein the reflective surface is supported so that both axes are substantially in the same horizontal plane when the reflective surface is in a horizontal orientation.
33. The solar tracking apparatus of claim 26 wherein the reflective surface is a mirror with a configuration selected from the group consisting of planar, parabolic and parabolic trough.
34. The solar tracking apparatus of claim 26 and further comprising means for sensing a reference position of the solar radiation collecting and reflecting means relative to the earth's magnetic field vector and for generating signals representative of the reference position and supplying them to the control circuit.
35. The solar tracking apparatus of claim 34 wherein the accelerometer and the reference position sensing means are provided by three-axis sensors.
Type: Application
Filed: Jun 14, 2007
Publication Date: Jan 17, 2008
Inventor: Mark S. Olsson (La Jolla, CA)
Application Number: 11/763,267