Patent Application
20120186626
The present invention relates to the art of solar energy collection and, more particularly, to a drive system for a solar collector.
Solar power systems fall generally into two categories: fixed position flat panel systems, and tracking solar collection systems. Fixed position flat panel systems employ one or more stationary panels that are arranged in an area having an unobstructed view of the sun. As the earth rotates, the sun's rays move over the stationary panel(s) with varying degrees of intensity depending upon geographic location, the time of day and the time of the year. In contrast, tracking solar collection systems collect, and focus the sun's rays onto one or more solar collectors. Tracking solar collectors employ a tracking system that follows the sun's path in order to enhance energy collection. Simply put, fixed position flat panels represent a passive solar collection system, while tracking solar collector systems represent a more active energy collection system.
Tracking systems for solar collectors take on a variety of forms, from complex computer and satellite (GPS) tracking to the use of photodiodes. GPS tracking relies on determining a particular location on the ground, and correlating that location to the location of the sun at a given, known, time of day. More conventional systems utilize an auxiliary alignment sensor that employs photodiodes. The photodiodes rely on differential sensing parameters to track the sun. That is, one or more photodiode cells are exposed to the sun's rays. The sun's rays impinge upon the photodiodes and a controller determines how much, for example, voltage is produced by each photodiode cell. The controller then orients the plurality of photodiode cells until voltage from each cell is substantially similar. At this point, an offset is calculated and the solar collector is oriented to a desired orientation. The offset represents a distance between a solar collector and the photodiodes. The need to calculate an offset increases tracking complexity and reduces collection efficiency.
The tracking system shifts the solar collector using a drive system. In some cases, the drive system includes a complex arrangement of gears and drive shafts. In other arrangements, a powered mechanical strut is positioned to shift the solar collector into a desired alignment. Powered mechanical struts are limited by mechanical clearance angles. The mechanical clearance angles constrain the drive system to shifting the solar collector axis along a path that is less than 180°. Powered mechanical strut systems are also limited by highly non-linear translation. That is, both rotation and torque responses of the linear translation of the powered mechanical strut to creating a rotation of the solar collector are highly non-linear.
According to one exemplary embodiment, a solar energy collection system includes a reference member that establishes a mechanical reference point, a support member rotatably mounted relative to the reference member, and a drive system operatively coupled between the reference member and the support member. The drive system includes a linear actuator having a fixed portion operatively connected to the reference member and a strut portion that is selectivity extendable relative to the fixed portion. The strut portion includes an end section. A first connector member is operatively connected between the reference member and the end section of the strut portion, and a second connector member is operatively connected between the support member and the end section of the strut portion. Selective extension and retraction of the strut portion relative to the fixed portion selectively shifts the support member along a desired path.
According to another exemplary embodiment, a method of positioning a solar collector mounted to a support member includes shifting a strut portion relative to a fixed portion of a linear actuator. The fixed portion is coupled to a reference member that establishes a mechanical reference point. The method further includes pivoting a first connector member positioned between a first end section of the strut portion and the reference member, and pivoting a second connector member positioned between the first end section of the strut portion and the support member. The method also includes rotating the support member moveably mounted to the reference member from a first position to a second position.
Additional features and advantages are realized through the techniques of the present invention. Other embodiments and aspects of the invention are described in detail herein and are considered a part of the claimed invention. For a better understanding of the invention with the advantages and the features, refer to the description and to the drawings.
The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The forgoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
With reference now to
In accordance with an exemplary embodiment, drive system 40 includes a linear actuator 46 having a fixed portion 54. Fixed portion 54 includes a first end portion 56 that is pivotally mounted to reference member 4. First end portion 56 extends to a second end portion 57 through a hollow interior 59 that houses a drive component 62. Drive component 62 is operatively connected to a controller 68. Controller 68 selectively activates drive component 62 to position support member 16. In order to refine positioning of support member 16, controller 68 includes a position sensor 66. Position sensor 66 provides feedback and/or feedforward control to aid in providing a high degree of precision for positioning support member 16. Position sensor 66 can take a variety of forms including servos, gravitometers, magnetometers, optical sensors, Hall effect sensors, resistance sensors, and/or other forms of position sensing elements. In accordance with one aspect of the exemplary embodiment, drive component 62 comprises an electric motor. In accordance with another aspect of the exemplary embodiment, drive component 62 comprises a pneumatic piston. In accordance with yet another aspect of the exemplary embodiment, drive component 62 comprises a hydraulic piston. In accordance with still another aspect of the exemplary embodiment, drive component 62 comprises a piezo-electric inchworm. At this point it should be clear that the particular type of drive component 62 can vary. Drive component 62 is configured to shift a strut portion 70 relative to fixed portion 54
Strut portion 70 includes a first end section 72 that extends to a second end section 73 that is arranged within hollow interior 59. Strut portion 70 is configured to shift within hollow interior 59 relative to fixed portion 54. Strut portion 70 also includes a pivot joint 80 arranged at first end section 72. Drive system 40 is also shown to include a first connector member 84 and a second connector member 85. First and second connector members 84 and 85 can be formed from a variety of materials including various metals such as titanium, aluminum, magnesium, steel, copper and/or alloys thereof, or composites including various plastics and/or carbon fiber arrangements. In accordance with one aspect of the exemplary embodiment, first and second connector members 84 and 85 are formed from a lightweight material that may be readily dynamically stabilized yet also provides a desired stiffness. First connector member 84 includes a first end 89 that extends to a second end 90. First end 89 of first connector member 84 is pivotally connected to reference member 4 through a pivot joint member 92. Second end 90 of first connector member 84 is pivotally connected to pivot joint 80 provided on strut portion 70. Similarly, second connector member 85 includes a first end 97 that extends to a second end 98. First end 97 of second connector member 85 is pivotally connected to support member 16 through a pivot joint component 100. Second end 98 of second connector member 85 is pivotally connected to pivot joint 80 provided on strut portion 70. At this point it should be understood that while shown as ball joints, pivot joint 80, pivot joint member 92, and pivot joint component 100 can take on a variety of forms including universal joints, and simple hinge joints.
With this arrangement, when strut potion 70 is fully extended, a force is applied to first and second connector members 84 and 85 that results in a translation of support member 16 to a first position such as shown in
Continued retraction of strut portion 70 applies force to first and second connector members 84 and 84 that results in continues rotation of support member 16 to a third position such as illustrated in
At this point it should be understood that the exemplary embodiments provide a system for shifting solar collectors in one axis into alignment with solar rays. Of course, it should be understood, that the exemplary embodiments can be configured to shift solar collectors in multiple axes into alignment with solar rays. The drive system of the exemplary embodiments employs a linear actuator that is configured to shift a support member through an arc that is greater than 180° with enhanced linearity, high mechanical precision and mechanical stiffness and low cost. In addition, it should be understood that by varying the length of the connector members an/or the various connection points between the connector members and the reference member and support member, a range of translatable rotation may be established that approaches 360°. It should be further understood that the above described arrangement provides a light weight structure that can be readily dynamically stabilized yet provides the desired stiffness that leads to high precision placement. Finally it should be understood that the first through fifth positions described above are exemplary.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, element components, and/or groups thereof.
The description of the present invention has been presented for purposes of illustration and description, but 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. The embodiment was 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
While the preferred embodiment to the invention had been described, it will be understood that those skilled in the art, both now and in the future, may make various improvements and enhancements which fall within the scope of the claims which follow. These claims should be construed to maintain the proper protection for the invention first described.
