The present invention relates generally to sun-tracking systems for photovoltaic panels. More particularly, the sun-tracking systems adjust the orientation of the photovoltaic panels with respect to the incoming sunlight to increase the photovoltaic panels' solar irradiation, therefore increasing the amount of electrical energy produced by the photovoltaic panels.
Due to the concerns over global warming and the limited amount of fossil fuels, alternative methods of energy production are desired. One such alternative source of energy is the solar energy produced by photovoltaic solar panels, which utilize the photoelectric effect to convert the energy of sun's radiation into electricity. The performance of such photovoltaic panels is determined by two factors: their efficiency in converting the sunlight into energy and their orientation relative to the incident angle of the sunlight.
Significant research has been done toward increasing the conversion efficiency of the photovoltaic panels, which is presently about 6% to 17%. Regarding the photovoltaic panels' orientation, it is known that a perpendicular orientation of the panels to the incident angle of sunlight maximizes the solar irradiation of the panels, thus maximizing the total amount of solar energy converted to electrical energy. The incident angle of sunlight varies in the east-west direction as a function of the time of day and the north-south direction as a function of the time of year. Accordingly, sun-tracking devices that attempt to keep the photovoltaic panel position perpendicular to the direction of the sunlight at different times of day and year are often mechanically complex, expensive to manufacture, and prone to malfunctioning.
A variety of techniques for adjusting the position of the photovoltaic panels exist in the field. Some systems for changing the angle of the photovoltaic panels have the panels arranged in a 2-D matrix of columns and rows. These systems can adjust the panel angle about two axes. The photovoltaic panels are pivoted by a mechanism that has multiple drive bars and pivoting points. Furthermore, all the panels in a given column are mounted above a tilt axis which rotates both the panels and the associated pivoting mechanisms, thus adding complexity to an already intricate panel pivoting mechanism.
Some other systems for changing the angle of the photovoltaic panels have a solar tracking system that changes the solar panel angle in the north-south direction only. The east-west axis may only be adjusted manually at the installation time. Thus, these systems lack the ability to automatically adjust the east-west orientation of the photovoltaic panels to follow the direction of the sunlight during the day.
Some systems that can adjust the position of the photovoltaic panels in two directions are of the alt-azimuth type. With these systems, the entire 2-D matrix of photovoltaic panels is mounted on a large rotating table that rotates in a plane parallel to the ground. Additional rotation is provided per individual panel or per panel group. With these systems the mechanism for rotating the table tends to be mechanically complex, subjected to high mechanical loads, and expensive.
Some other systems are roof mountable and can rotate the photovoltaic panels around two axes. The photovoltaic panels are rotated in the first direction through a centrally mounted motor and a suitable mechanical linkage. However, the rotation in the second direction is provided by hinging one side of the system frame to the surface (usually the roof), coupled with the elevation of the other side by a motorized rack and pinion. Thus, the range of the angles achievable in the second direction is limited.
Therefore, a need remains for systems that can adjust the angle of the photovoltaic panels in two directions, while being capable of withstanding high mechanical loads and providing a wide range of rotation angles.
The present invention relates to systems for adjusting the position of the photovoltaic panels such that they can be perpendicular to the incident sunlight. The orientation of the photovoltaic panels can be controlled about two axes to provide for separate pivot and tilt movements. The photovoltaic panels can be pivotably mounted along the longitudinal axis of tiltable frames. The substantially parallel photovoltaic panels in a frame can be simultaneously pivoted by a pivoting drive mechanism attached to the frame. Multiple tiltable frames can be arranged parallel to each other, thus creating a 2-D matrix of photovoltaic panels. The tiltable frames can be supported by an elevated structure permitting the unobstructed rotation of both the frames and the panels inside the frames. The frames can be tilted by a per-frame mechanism or a mechanism that is common to multiple frames. A controller can synchronize the tilt and pivot, such that the combined rotation of the photovoltaic panels results in the photovoltaic panels of the entire array being substantially perpendicular to the incident solar radiation. The system can track the position of the sun using solar intensity sensors or a table of sun positions to continuously maintain the perpendicularity of the photovoltaic panels with respect to the incident sunlight.
In one embodiment, an apparatus for controlling the orientation of photovoltaic panels has a plurality of photovoltaic panels having panel faces for producing an electrical current when exposed to sunlight. The photovoltaic panels are arranged parallel to one another and pivotably mounted along a longitudinal axis. A frame is extended about the longitudinal axis and dimensioned for holding the photovoltaic panels parallel to one another. The frame has first orientation means configured to adjust a pivot angle of the photovoltaic panels of the frame, and second orientation means configured to adjust a tilt angle of the frame, thus adjusting the tilt angle of the photovoltaic panels mounted along a longitudinal axis of a frame.
In one aspect, the apparatus further has one or more frames arranged to have substantially parallel longitudinal axes. The first orientation means are configured to set the frames to substantially the same tilt angle, thus setting the photovoltaic panels in the frames to substantially the same tilt angle. The apparatus also has girders to hold the frames in a common structure, and the support configured for attaching the apparatus with a base surface.
In another aspect, the apparatus has the first orientation means to adjust the pivot angle of the photovoltaic panels in all the frames to substantially the same value.
In yet another aspect, the apparatus has the second orientation means to adjust the tilt angle of all the frames to substantially the same value.
In another aspect, the apparatus further has a controller configured to coordinate the first orientation means and the second orientation means such that the resulting orientation of the panel faces is substantially perpendicular to the direction of sunlight.
In another aspect, the apparatus has a measurement device configured to measure the direction of the sunlight and to provide the measured direction to the controller.
In another aspect, the apparatus has an energy metering device configured to measure the energy produced by the photovoltaic panels.
In another embodiment, an apparatus for controlling the orientation of photovoltaic panels has a frame extending about a longitudinal axis and dimensioned for holding the photovoltaic panels parallel to one another. The frame further has a plurality of panel holders configured to pivotably hold the photovoltaic panels, and first orientation means configured to adjust a pivot angle of the photovoltaic panels of the frame. Second orientation means are configured to adjust a tilt angle of the frame, thus adjusting the tilt angle of the photovoltaic panels held by the holders along the longitudinal axis of a frame.
For a further understanding of the nature and advantages of the invention, reference should be made to the following description taken in conjunction with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the embodiments of the present invention.
a is a partial perspective view illustrating a chain and sprocket tilting mechanism for the tilting of frames.
b is a partial perspective view illustrating a gear mechanism for the tilting of the frames.
a and 7b show side views of two positions of the photovoltaic panels driven by a linear actuator mechanism.
The present invention relates to the systems for adjusting the position of the photovoltaic panels such that they can be perpendicular to the incident sunlight. The orientation of the photovoltaic panels can be controlled about two axes to provide for separate pivot and tilt movements. The photovoltaic panels can be pivotably mounted along the longitudinal axis of tiltable frames. The substantially parallel photovoltaic panels in a frame can be simultaneously pivoted by a pivoting drive mechanism attached to the frame. Multiple tiltable frames can be arranged parallel to each other, thus creating a 2-D matrix of photovoltaic panels. The tiltable frames can be supported by an elevated structure permitting the unobstructed rotation of both the frames and the panels inside the frames. The frames can be tilted by a per-frame mechanism or a mechanism that is common to multiple frames. A controller can synchronize the tilt and pivot, such that the combined rotation of the photovoltaic panels results in the photovoltaic panels of the entire array being substantially perpendicular to the incident solar radiation. The system can track the position of the sun using solar intensity sensors or a table of sun positions to continuously maintain the perpendicularity of the photovoltaic panels with respect to the incident sunlight. The details of the exemplary embodiments of the present invention are explained with reference to
Still referring to
Panel orientation apparatus 300 can also have conductor wires 210 for transferring the electrical current generated by the photovoltaic panels off the apparatus to the electrical grid. The power delivered to the electrical grid can be metered by metering device 220, which may measure either the total energy generated by the photovoltaic panels or the energy generated by a group of the photovoltaic panels or a single photovoltaic panel or a fraction of photovoltaic panel. Irradiation sensor 240 detects the direction of the sunlight and can be connected to controller 230, which can calculate the required control parameters for the frame drive and panel drive. The required parameters include the final position of the shafts of the frame and panel drives. Controller 230 can send control signals to the frame drive and panel drive through control wires 250. The electrical energy produced by the photovoltaic panels can also be used to power controller 230 and metering device 220, but they can also be powered externally. The adjustment of the frame tilt angle is shown with reference to
a shows an embodiment of a tilt angle adjusting mechanism that can simultaneously change the tilt angle for all the frames in the panel orientation apparatus 300. Frames 50 are mounted on girder 40 using frame shafts 71. Frame sprocket 100 can be fixedly connected to each frame shaft 71 for the tilting of frame 50. The tilt angle of frames 50 can be changed by frame drive 70, which provides torque to frame sprockets 100 through frame drive chain 90 that connects all frame sprockets 100 to frame drive 70.
b shows another embodiment of the tilt angle adjusting mechanism that uses a single frame drive 70 to change the tilt angle. With this embodiment, frames 50 have frame gears 130 fixedly attached to frame shafts 71. Frame gears 130 engage with drive gears 120, which are fixedly attached to driveshaft 110. Frame drive 70 rotates driveshaft 110 and drive gears 120 attached thereto, which, in turn, rotate frame gears 130, thus adjusting the tilt angle of the frames. The amount of tilt is based on the control signal received from the controller. Other mechanisms for the adjustment of frames' tilt angles are possible, like, for instance, rack and pinion, belt and pulley, worm drive, and hydraulic or pneumatic cylinders, or a combination of different mechanisms. A dedicated frame drive 70 per each frame 50 or a group of frames is also possible.
a and 7b show another embodiment of a mechanism for adjusting the panel pivot angle. Here, one end of raiser arm 155 is fixedly connected with panel shaft 170, while the opposite end of the raiser arm is pivotably connected with linear bar 166. As linear bar 166 moves (left and right as shown on
As will be understood by those skilled in the art, the present invention may be embodied in other specific forms without departing from the essential characteristics thereof. For example, the frame drive and the panel drive may receive electrical energy directly from the photovoltaic panels. Furthermore, the frames may host different numbers of photovoltaic panels having differing sizes. Many other embodiments are possible without deviating from the spirit and scope of the invention. These other embodiments are intended to be included within the scope of the present invention, which is set forth in the following claims.