Patent Application
20130032135
1. Field of the Invention
The present invention is generally directed to apparatuses and methods for determining an orientation of an object and, more particularly, to apparatuses and methods for determining an orientation of a solar energy capture device using a sensor.
2. Background
For numerous reasons—including lowering the concentrations of greenhouse gases, strengthening the ozone layer, reducing global warming effects, and obtaining a sustainable source of energy—energy sources other than fossils fuels are becoming more popular. One common alternative energy source is solar energy.
There are two common systems for generating electricity from solar energy: a thermal system and a photovoltaic system. In a thermal system, a mirror assembly reflects sunlight onto a receiver. The receiver, in turn, may heat a fluid or gas. In some thermal systems, the receiver heats the fluid or gas to power a turbine to create electricity, for example, by turning a fluid into a gas. In other thermal systems, the receiver can simply heat the fluid or gas for process heat applications. In photovoltaic systems, a photovoltaic panel converts sunlight into electricity. In both systems, the orientation of the solar energy capture device—the mirror assembly in a thermal system or the photovoltaic panel in a photovoltaic system, for example—should continuously change as the position of the sun changes. For example, as the sun moves, the orientation of the mirror assembly needs to change to keep the reflected light focused on the receiver. In photovoltaic systems, the orientation of the photovoltaic panel should be changed to ensure that the panel is orthogonal to the direction of the sunlight to achieve peak efficiency.
One type of system for changing the orientation of solar energy capture devices is an azimuth-elevation system. In an azimuth-elevation system, the solar energy capture device can rotate about a vertical azimuth axis and an elevation axis that is perpendicular to the azimuth axis. However, rotation about the azimuth axis cannot be detected by many sensing devices due to azimuthal symmetry, as further described below.
Accordingly, there is a need for apparatuses for determining and changing the orientation of a solar energy capture device and for methods of determining and changing the orientation of the solar energy capture device.
In one embodiment, an apparatus for capturing solar energy includes a solar energy capture device having an orientation plane, and a sensor configured to determine a direction of gravity relative to a second plane. The solar energy capture device is configured to rotate about a pitch axis and a roll axis. The orientation of the second plane is fixed relative to the orientation plane. The orientation plane of the solar energy capture device is offset at an angle from the roll axis. The sensor can be an accelerometer.
In another embodiment, an apparatus for capturing solar energy includes a solar energy capture device having an of orientation plane, a frame for supporting the solar energy capture device, a joint connected to the solar energy capture device and the frame, and a sensor configured to determine the direction of gravity relative to a second plane. The joint is configured to allow rotation of the solar energy capture device about a roll axis and a pitch axis. The joint has a surface that has a fixed orientation relative to the solar energy capture device. The orientation plane of the solar energy capture device is offset from the orientation plane. The sensor is mounted to the surface of the joint that has the fixed orientation relative to the solar energy capture device. The sensor can be an accelerometer.
In one embodiment, a method for determining an orientation of a solar energy capture device having an orientation plane includes determining a direction of gravity relative to a second plane. The second plane has an orientation that is fixed relative to the orientation plane. The orientation plane is offset from the roll axis. The method also includes determining an orientation of the solar energy capture device based on the direction of gravity relative to the second plane.
The accompanying drawings, which are incorporated herein and form part of the specification, illustrate the present invention and, together with the description, further serve to explain the principles of the invention and to enable a person skilled in the relevant art(s) to make and use the invention.
The features and advantages of the present invention will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements.
In the detailed description that follows, references to “one embodiment,” “an embodiment,” “an example embodiment,” etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.
As shown in
Knowing that the direction of gravity G is vertical and that the Y axis of the orientation plane (the X-Y plane) of solar energy capture device 100 is aligned with roll axis RA, the pitch angle Θpitch—the angle between roll axis RA and the horizontal ground H—and the roll angle Θroll—the angle between pitch axis PA and the orientation plane—can be determined. Sensor 200 can resolve the direction of gravity relative to the X-Y plane to determine the angle between the roll axis RA and the direction of gravity G. The pitch angle Θpitch is equal to the angle between the roll axis RA and the direction of gravity G minus 90°.
To determine the roll angle Θroll, the cross product of the direction of gravity G and a unit vector along the Y axis is determined. The cross product is parallel to the horizontal ground H and orthogonal to roll axis RA because the Y axis is aligned with roll axis RA. The roll angle Θroll is equal to the angle between the Z axis and the cross product (of the direction of gravity and a unit vector along the Y axis) minus 90°.
One problem encountered, however, is that when solar energy capture device 100 is vertical, the direction of gravity G is aligned with the Y axis (and roll axis RA), so the cross product is zero, and the roll angle Θroll cannot be determined because azimuthal symmetry occurs—the direction of gravity relative to the orientation plane (the X-Y plane) never changes regardless of the roll angle Θroll. Further, accuracy is greatly reduced as solar energy capture device 100 (and its orientation plane) approaches the vertical orientation.
With two-axis kinematics, azimuthal symmetry occurs whenever one axis is vertical. Accordingly, azimuthal symmetry is always present with azimuth-elevation kinematics about the azimuth axis because the azimuth axis is vertically fixed. Similarly, degeneracy occurs when the combination of rotations about the two axes produces rotation about the vertical.
In one embodiment as shown in
The orientation of solar energy capture device 100 can be described relative to the direction of a vector normal to a plane (“orientation plane”) fixed relative to solar energy capture device 100. For example, in one embodiment, if solar energy capture device 100 is parabolic, the orientation of device 100 can be described by the direction of a vector normal to a plane that is tangent to the vertex of object 100. In another embodiment in which object 100 is substantially planar, for example, the orientation of object 100 can be described by the direction of a vector normal to the plane in which device 100 lies.
In an embodiment in which solar energy capture device 100 is substantially planar and the orientation plane is defined as the plane within which device 100 lies, it may be desirable to change the orientation of solar energy capture device 100 such that the normal vector of the orientation plane of solar energy capture device 100 bisects the angle between the incident light and a receiver in a solar thermal system. In another embodiment, it may be desirable to change the orientation of solar energy capture device 100 such that the normal vector of the orientation plane of solar energy capture device 100 is aligned with the angle of incident light from the sun in a photovoltaic system.
Apparatus 10 further includes sensor 200. Sensor 200 can resolve the direction of gravity relative to a plane (“sensor plane”). Sensor 200 and the sensor plane have an orientation that is fixed relative to the orientation of solar energy capture device 100. Sensor 200 can be mounted on apparatus 10 at any suitable location that is fixed relative to solar energy capture device 100, for example, directly to solar energy capture device 100, a surface of a joint that has a fixed orientation relative to solar energy capture device 100, or any other location that is fixed relative to solar energy capture device 100. Accordingly, as solar energy capture device 100 rotates about the roll axis and the pitch axis, sensor 200 and its sensor plane rotates about the roll axis and the pitch axis.
Sensor 200 can be any device capable of resolving the direction of gravity relative to a plane, for example, an accelerometer that can measure acceleration along two or more axes, or an inclinometer that can measure angles of an object with respect to gravity along two or more axes. In one embodiment, sensor 200 is a 3-axis accelerometer—an accelerometer capable of measuring acceleration along three axes, for example, the X, axis, the Ys axis, and the Zs axis as shown in FIGS. 4-7—and thus capable of resolving the direction of gravity relative to three planes—the Xs-Ys plane, the Xs-Zs plane, and the Ys-Zs plane. Sensor 200 can be any suitable accelerometer type, for example, capacitive, piezoelectric, piezoresistive, Hall effect, magnetoresistive, or any other suitable type. In one embodiment, sensor 200 can be an ADXL327 3-Axis, capacitive accelerometer produced by Analog Devices, Inc. In another embodiment, sensor 200 is a 2-axis accelerometer. In yet another embodiment, sensor 200 can be a two-axis inclinometer. In other embodiments, sensor 200 can be any suitable inclinometer type that uses, for example, gyroscopes, partially-liquid-filled cavities, pendulums, or other mechanisms.
In one embodiment, the sensor plane is aligned with an exterior surface of the sensor package. For example, the sensor plane may be parallel to the exterior surface of the sensor package. In another embodiment, the sensor plane is offset from the exterior surface of the sensor package.
In one embodiment in which sensor 200 is a 3-axis accelerometer, one axis of the sensor 200 that defines the sensor plane is parallel to the plane of solar energy capture device 100 having a normal vector with a desired alignment direction.
Control unit 300 includes a processor and memory. Control unit 300 is operatively connected to sensor 200 such that control unit 300 can determine the orientation of solar energy capture device 100 based on one or more output signals of sensor 200. Control unit 300 is also operatively connected to actuators(s) 400. Control unit 300 is adapted to generate and manipulate one or more control signals that cause actuator(s) 400 to change the orientation of solar energy capture device 100. In one embodiment, control unit 300 can be integrated with sensor 200, in another embodiment, control unit 300 can be a separate device from sensor 200.
Apparatus 10 can also include at least one actuator 400 coupled to solar energy capture device 100. Actuator(s) 400 can be adapted to change the orientation of solar energy capture device 100. Actuator(s) 400 can selectively apply a force to solar energy capture device 100 to change its orientation. In one embodiment, actuator(s) 400 can be linear actuators having a drive component, for example, a motor or hydraulic pump and cylinder, and a variable length member that can selectively change its length. Linear actuators can include, for example, a cable actuation mechanism including a motor and a cable, a hydraulic piston, a scissor-jack, a linear screw drive, or any other suitable linear actuator having a variable length member. In such embodiments, changing the length of the variable length member rotates solar energy capture device 100 about the pitch axis and the roll axis. In another embodiment, actuator(s) 400 can be motors directly coupled to members that rotate about the roll axis and the pitch axis.
In some embodiments, apparatus 10 may include two, three, or more than three actuators 400. In some embodiments, actuator(s) 400 can include one, two, three, or more than three linear actuators. Linear actuator(s) 400 coupled to solar energy capture device 100 may comprise the same type or different types of actuators. For example, in some embodiments, first and second linear actuators 400 may both comprise a cable-actuated mechanism. In other embodiments, for example, a first linear actuator 400 may comprise a cable actuator and a second linear actuator 400 may comprise a hydraulic piston actuator.
Apparatus 10 may be used as an individual unit for determining and changing the orientation of a single solar energy capture device 100 or as a series of units in an array for determining and changing the orientation of a plurality of solar energy capture devices 100. For example, in one embodiment, a plurality of apparatuses 10 each having a solar energy capture device 100 may be arranged in a solar field. In one embodiment such as a thermal system, the plurality of apparatuses 10 may be arranged to concentrate the reflected sunlight onto a receiver that powers a heat engine which, in turn, drives a rotary generator, for example, a turbine. In one embodiment, apparatuses 10 in an array can be arranged in one or more linear or arcuate rows.
In one embodiment, the orientation plane of solar energy capture device 100 having a normal vector with a desired alignment direction is offset at an angle from roll axis RA. When offset at an angle, the orientation plane can intersect the roll axis RA. For example, the top edge of a substantially planar solar energy capture device 100 can be further away from roll axis RA than the bottom edge of solar energy capture device 100. Accordingly, when roll axis RA is vertical, the normal vector of the orientation plane of solar energy capture device 100 is pointing below the horizon. Further, when solar energy capture device 100 is orientated in a vertical position, roll axis RA is not aligned with the direction of gravity. Thus, rotation about roll axis RA can be determined because azimuthal symmetry does not exist at this orientation. In one embodiment, azimuthal symmetry will not occur at any operable orientation of solar energy capture device 100. In another embodiment, azimuthal symmetry will not occur until solar energy capture device 100 is rotated about the pitch axis to an orientation beyond the vertical orientation such that the normal vector is pointing below the horizon.
In one embodiment, the angle of offset between the orientation plane of solar energy capture device 100 having a normal vector with a desired alignment direction and roll axis RA is between about 5° and about 25°. In another embodiment, the offset angle is between about 10° and about 20°. In another embodiment, the offset angle is about 15°. In other embodiments, the offset angle can be less than about 5° or more than about 25°. In some embodiments, offset angle can be any angle that places the azimuthally symmetric orientation (with roll axis RA being vertical) beyond the useful range of solar energy capture device 100.
In some embodiments, the offset angle can be 0°. For example, the offset angle between the orientation plane of solar energy capture device 100 and roll axis RA can be 0° when the vertical orientation of the orientation plane of solar energy capture device 100 is well beyond the operable range of apparatus 10, for example, an operable range that does not require roll axis RA to approach its vertical orientation.
Joint 600 rotatably couples solar energy capture device 100 to frame 500 such that solar energy capture device 100 can rotate relative to frame 500. In one embodiment, joint 600 defines pitch axis PA and roll axis RA. For example, as shown in
In one embodiment as shown in
Upper yoke 604 can be coupled to attachment plate 308. Attachment plate 608 is securely coupled to back surface 102 of solar energy capture device 100 using any suitable adhesive or any suitable fasteners. In one embodiment, solar energy capture device is coupled to joint 600 such that an orientation plane of solar energy capture device 100 is offset from roll axis RA.
In one embodiment, as shown, for example, in
In another embodiment, sensor 200 may be coupled to attachment plate 608 of joint 600, which is coupled to solar energy capture device 100. Accordingly, the sensor plane of sensor 200 rotates about pitch axis PA and roll axis RA as solar energy capture device 100 rotates about these same axes. The orientation plane of substantially planar solar energy capture device 100 having a normal vector with a desired orientation can be offset at an angle from roll axis RA. Accordingly, when solar energy capture device 100 is oriented such that it is substantially vertical, roll axis RA is not substantially vertical and, thus, not parallel to the direction of gravity, preventing azimuthal symmetry at this vertical orientation of solar energy capture device 100.
With reference to
Apparatus 10 may further include a control unit 300 (not shown in
As shown in
As shown in
Because bracing 610 angles solar energy capture device 100 relative to attachment plate 608, the orientation plane (the Xd-Yd plane as illustrated) of solar energy capture device 100 is offset from roll axis RA. Consequently, when solar energy capture device 100 is substantially vertical, the roll axis RA is not substantially vertical. Thus, the direction of gravity will not be parallel to roll axis RA, and azimuthal symmetry does not occur at this orientation.
As shown in
Solar energy capture device 100 can have a plane, for example, defined by axis Yd and axis Xd, having a normal vector with a desired alignment direction. Accordingly, when solar energy capture device 100 is substantially vertical and axis Zd is substantially horizontal, roll axis RA is not vertical and thus not aligned with the direction of gravity, preventing azimuthal symmetry about roll axis RA.
At step 1100, the direction of gravity relative to an orientation plane of solar energy capture device 100 can be determined. For example, the direction of gravity relative to the orientation plane (e.g., the Xd-Yd plane as shown in
At step 1200, the current orientation of solar energy capture device 100 is determined. For example, the pitch angle and the roll angle of solar energy capture device 100 can be determined by using the direction of gravity relative to the orientation plane determined at step 1100 and a known offset angle ΘRA between the orientation plane and the roll axis RA. In one embodiment, the direction of the vector normal to the orientation plane can be determined using the determined pitch and roll angles. The determined direction of the normal vector can be used to characterize the current orientation of solar energy capture device 100.
At step 1300, the orientation of solar energy capture device 100 is changed based on the determined current orientation of solar energy capture device 100. In one embodiment, the orientation of solar energy capture device 100 is changed by collectively actuating the first and second actuators to rotate the solar energy capture device 100 about the pitch axis and by differentially actuating the first and second actuators to rotate the solar energy capture device about the roll axis.
In one embodiment at step 1300, the orientation of solar energy capture device 100 is changed to a desired orientation. In some embodiments, the desired orientation is based on the current position of the sun, which can be determined by known orbital patterns determined by date. As will be appreciated, the current position of the sun may be determined by one or more data elements including, but not limited to, date, time, and geographic location (e.g., latitude and longitude coordinates). In another embodiment, the position of the sun is determined by using a sensor. Using the current position of the sun, a desired orientation of the solar energy capture device 100 can be determined. For example, if solar energy capture device 100 is a mirror assembly for a thermal system, the desired orientation can be one that positions the mirror assembly so that the reflected light is focused on a receiver. If solar energy capture device 100 is a photovoltaic panel, the desired orientation can be, for example, an orientation that positions the photovoltaic panel to be perpendicular to the incident light from the sun.
In other embodiments, the orientation of solar energy capture device 100 is changed to a desired orientation based on weather conditions. Sensor 200 can determine the current orientation of solar energy capture device 100 during orientation changes based on the weather conditions. For example, a substantially planar solar energy capture device 100 can be positioned at a vertical hail-safe orientation to minimize damage to solar energy capture device 100 during a hail storm. Solar energy capture device 100 can be positioned at a wind-safe orientation that minimizes the wind resistance of solar energy capture device 100 during periods of strong winds. For example, a substantially planar solar energy capture device 100 can be moved to a vertical orientation in which the plane of solar energy capture device 100 is substantially parallel to the direction of the wind. In one embodiment, weather conditions are detected using meteorological measuring devices. In other embodiments, weather conditions are predicted using computerized meteorological models, and the timing of the orientation changes is based on the meteorological predictions.
In yet another embodiment, the orientation of solar energy capture device 100 is changed to a desired orientation for maintenance operations during which sensor 200 determines the current orientation of solar energy capture device 100. For example, solar energy capture device 100 can be positioned at an orientation that creates user access to the front surface of solar energy capture device 100 for washing or for repair, or solar energy capture device 100 can be positioned at an orientation for stowing.
In one embodiment, control unit 300 performs steps 1000-1200 and controls step 1300. Sensor 200 can provide real time direction of gravity information to control unit 300, allowing for real time determination of solar energy capture device 100 orientation and for desired orientation changes.
In some embodiments, the method is repeated after a predetermined time interval, for example, every thirty minutes, every hour, every other hour, or any other suitable time interval. In some embodiments, the orientation of solar energy capture device 100 is continuously updated in real-time.
The present invention has been described above with the aid of functional building blocks illustrating the implementation of specified functions and relationships thereof. The boundaries of these functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternate boundaries can be defined so long as the specified functions and relationships thereof are appropriately performed.
The foregoing description of the specific embodiments will so fully reveal the general nature of the invention that others can, by applying knowledge within the skill of the art, readily modify and/or adapt for various applications such specific embodiments, without undue experimentation, without departing from the general concept of the present invention. For example, although the figures illustrate the device 100 as a solar energy capture device, apparatus 10 can be adapted to determine and change the orientation of other objects such as communication antennas, weapon platforms, and directed-energy appliances, for example. Therefore, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein.
It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the present specification is to be interpreted by the skilled artisan in light of the teachings and guidance. The breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.
