Patent Application
20160047877
This invention relates generally to optical tracking and tracking systems and methods for ensuring on-sun orientation of a solar surface, and more precisely to systems deploying differential refractometers to determine and track on-sun orientation.
Energy derived directly from solar radiation promises to address a number of challenges that humanity is facing. Still, a number of obstacles are preventing more widespread adoption of solar systems. One of these challenges relates to efficient tracking of the sun as it traverses its daily trajectory in the sky.
Solar tracking is needed to obtain maximum insolation of a solar surface or to maintain an intended angle of incidence of solar radiation onto the solar surface. The exact sun tracking tolerances depend on whether the solar surface is a reflecting surface used for sunlight concentration purposes or a photovoltaic surface (PV) that converts sunlight into electrical energy.
There are many ways of tracking sunlight taught in the prior art. U.S. Pat. No. 4,154,219 to Gupta teaches a prismatic solar reflector, wherein a prismatic plate is mounted with its flat face exposed to the sun on a reflector panel for use in a solar energy collection system. The plate includes a plurality of triangular prisms with parallel longitudinal axes shaped to provide total internal reflection of incident light rays. Each prism has a cross section forming a right-angled isosceles triangle with the two equal-length, rear faces of the prism oriented at 45 degrees relative to the front face of the plate. The base of each prism forms or is parallel to a front plate surface which receives incident solar light rays. The rays are transmitted through the plate cross section without refraction in the plane of the cross section to be reflected from the two rear faces and back out the front face toward a solar receiver. The prism material has an index of refraction equal to or greater than the square root of two so that there is total internal reflection from the prism faces. The prismatic plate is mounted on a movable heliostat panel controlled by a tracking system to reflect to a solar receiver. The panel has a fixed axis directed toward a central receiver and a moving axis orthogonal to the fixed axis. The prismatic plate is mounted on the panel with the longitudinal axes of the prisms perpendicular to the moving axis. Tracking is accomplished by adjusting the panel orientation so that the plane of incidence of the incident solar rays is parallel to the longitudinal axes of the prisms and also so that the reflected solar rays intercept the receiver.
U.S. Pat. No. 4,910,395 to Frankel teaches an optical tracking sensor including a three-sides prismatic light splitter, wherein a three-sided transparent pyramid with a sharp vertex is used. The pyramid is used to split the incident beam into three parts, which are transmitted to respective photodetectors. The signals from the photodetectors are used for tracking. This invention makes several important improvements to an optical tracking system. The amount of energy incident on each photodetector is increased by 33% over a known four-detector system. The sensor inherently possesses a point vertex formed by three inclined surfaces, regardless of manufacturing tolerances. This directly contributes to increased sensor accuracy in comparison to known four-sided splitters. By reducing the number of sensors to three, the system's mechanical and electronic size and complexity is reduced.
U.S. Pat. No. 5,144,498 to Vincent teaches a variable wavelength light filter and sensor system, wherein a light filter apparatus is taught. The apparatus receives a light beam having wavelengths in a selected band and disperses the light into a plurality of rays, with each ray having a different wavelength for which the intensity peaks. The peak wavelength varies approximately continuously with displacement of spatial position in a chosen direction along the filter's light-receiving plane.
U.S. Pat. No. 7,235,765 to Clugston teaches a solar sensor including a reflective element to transform the angular response. The sensor utilizes a blocking element and curved reflective element between the sun and a photo-sensitive electronic device to provide high signal levels and the ability to shape the angular response of the overall sensor. A particular angular response can be achieved by combining the attenuating effects of the blocking element with the increased response of the curved reflector. These two elements may be combined into one physical structure, or may be separate. Further, the present invention contemplates the use of multiple blocking elements and multiple reflectors.
A shortcoming of prior art teachings is that they do not provide a low-cost, high-precision optical tracking system to track sunlight. While refractive devices and differential refractometers have been used for many applications, there has not been a cost-efficient and accurate solar tracking system effectively utilizing differential refraction and dispersion of light. The prior art teachings while appropriate for some applications, do not provide approaches that are compatible with low-cost, precision-oriented solar tracking systems that are updated on a periodic basis with minimal resources in order to maximize power output generated from their associated solar panel or the entire solar farm.
For a background in basic optics, the reader is directed to Geometrical and Visual Optics, Second Edition, by Steven Schwartz.
In view of the shortcomings of the prior art, it is an object of the present invention to provide low-cost, high-precision solar tracking apparatus and methods that support periodic updates of on-sun orientation with minimal cost of maintenance and operation, without requiring complex computational algorithms of computer or machine vision.
The objects and advantages of the invention are secured by an optical differential solar tracking system that uses an optical dispersion assembly having two prisms attached to it in a mirror-symmetric fashion. A mirror-symmetric geometry of the prisms signifies that while one set of corresponding rectangular faces of the prisms face each other, another set of corresponding rectangular faces of the prisms face outward of the optical dispersion assembly towards the sun, and the third set of corresponding rectangular faces of the prisms face inward into the optical dispersion assembly or away from the sun. The inward faces of the prisms are each directed at two optical attachments that gather light rays of constituent colors produced by the prisms as a result of dispersion of solar light incident on the respective sunward faces of the prisms, and consequently select light rays of a single color from the constituent color light rays produced by the prisms. Preferably the, optical attachments further collimate the light rays of a single color selected by them for downstream transmission.
The distal ends of the optical attachments are further connected to two optical links for carrying the single color collimated light rays selected by the optical attachment. In the preferred embodiment, each optical attachment comprises an optical tap for collecting the dispersed light produced by the respective prism, and an optical tube or waveguide that further selects light rays of a single color from the light gathered by the respective optical tap. In alternative embodiments, the optical attachment can be selected as one or a combination of the following optical devices: an optical slit, a pinhole, optical filter, spatial filter, one or more fiber optic tube, or one or more optical waveguide. Other types of optical devices for collecting and carrying light rays of a single color from the light dispersed by the prisms are possible, without deviating from the principles of the invention.
The distal ends of the optical links are connected to two respective photosensors, or two respective sets of photosensors, which convert the light rays carried by the optical links into corresponding electrical signal. The voltage, current or electrical power associated with the electrical signals produced by the photosensors varies according to the frequency or color or wavelength of light rays received by the photosensors and in turn carried by the respective optical links.
The outputs from the two photosensors, or the two sets of photosensors as taught above, are fed to the two inputs of a differential amplifier circuit that produces a gain which varies according to the difference in the strengths of the electric signals at its two inputs. The strength of the electric signals can be measured as electric voltage, electric current or a combination of both (electrical power). Because of the mirror-symmetric arrangement of the prisms in the optical dispersion assembly, as the position of the sun with respect to the system changes, the angle of incidence θ of solar light increases on one prism and decreases on the other, thereby producing a shift in the colors of the constituent light rays produced by the two prisms. This shift in the constituent light rays produced by the two prisms is different for the two prisms because of the difference in the angles of incidence of the solar light on the corresponding sunward faces of the two prisms.
Specifically, the color of the light produced by one prism red-shifts, while the color of the light produced by the other prism blue-shifts, as the position of the sun with respect to the system changes. Since the value of the gain produced by the differential amplifier circuit depends on the values of its two inputs, which in turn depends on the frequencies or colors or wavelengths of the single color light rays selected and carried by respective optical attachements and further carried by respective optical links, this apparatus can be used to track a given orientation of the system with respect to the sun.
Once the above system is rigidly attached to a solar surface or a solar panel or a group of solar surfaces or solar panels, and is calibrated to an on-sun orientation, representing a position of the solar surface or surfaces directly facing the sun so as to maximize the energy produced by the solar surface or surfaces, the system can track the movement of the sun by automatically adjusting its orientation so as to follow or track the gain produced by the differential amplifier in the position when the system was calibrated to its on-sun orientation.
In a preferred embodiment, the entire arrangement can be duplicated so as to produce two such gains, each controlling one axis of orientation of the solar surface, such as its altitude and azimuth orientations, or its horizontal and vertical orientations. In this manner, the system taught by the present invention operates as a dual-axis optical differential solar tracking system. Preferably, the prisms are acrylic in composition, and are equilateral, with a nominal angle (θ) of 60°. Preferably, the output of the differential amplifier is further connected to a processing unit that produces electrical signals according to the value of the gain, for controlling the orientation of the solar surface or surfaces.
The on-sun orientation of a solar surface with the optical dispersion assembly rigidly attached to it as described above, will correspond to the solar surface directly facing the sun and producing maximum electrical energy. Preferably, during such on-sun orientation, the single color light rays selected and carried by the optical attachments, and subsequently carried by the respective optical links, will be approximately in the middle of the visible color spectrum. Preferably, the optical links carrying the light rays from the optical attachments to the photosensors are fiber optic tubes.
In an advantageous embodiment of the invention, the orientation of the solar surface or multiple solar surfaces is controlled by a mobile robot that docks to a docking station connected to the solar surface or surfaces. Such a docking station could be provided for every solar surface or for multiple solar surfaces. In this way, a single mobile robot can control the orientations of many solar surfaces by visiting those solar surfaces and docking with the respective docking stations. In this embodiment, the optical dispersion assembly is rigidly attached to the solar surface with the optical links carrying light signals from the optical links to the mobile robot through the docking station, while the mobile robot contains the photosensors and the differential amplifier circuit and any processing unit or other electrical circuitry required to produce electrical signals based on the gain of the differential amplifier, for controlling the orientation of the solar surface or surfaces.
There are optical and electrical couplings on the docking station such that, when the mobile robot is in its docked position, the optical connection required to carry the light rays carried by the optical links to the photosensors onboard the mobile robot is completed. Further, when the mobile robot is in its docked position, the electrical connection required to carry the electrical signals produced by the differential amplifier circuit or any processing unit or other electrical circuitry onboard the mobile robot, to the drive assembly or assemblies of the solar surface or surfaces, in order to control its or their orientation, is also completed. This way, the same mobile robot can control the orientation of multiple solar surfaces by docking to respective docking stations, receiving the optical signals or light rays produced by the prisms, and in turn transmitting corresponding electrical signals to the drive assemblies of the solar surfaces. In an advantageous embodiment of the invention, the system and its components explained above are duplicated, such that the mobile robot as taught above can control two independent axes of orientation of the solar surface or surfaces. In this manner, the system taught by the present invention operates as a dual-axis optical differential solar tracking system.
Preferably, the docking station has a hood that reduces or prevents the ambient light that might otherwise affect the optical couplings on the docking station once the mobile robot is in its docked position. Such a hood can allow scattering of ambient light around the optical coupling without impacting the optical coupling. In another preferred embodiment of the invention, the electrical connection required to form between the differential amplifier circuit or any processing unit or other electrical circuitry on the mobile robot and the drive assembly or assemblies of the solar surface or surfaces for controlling its or their orientation, is a wireless connection.
Preferably the photosensors receiving the light rays produced by the prisms and carried by the optical links are RGB (Red, Green, Blue) sensors with a spectral range of 640 nm-470 nm. Each photosensor produces an electrical output whose voltage, current or a combination of both, varies according to the frequency (or corresponding wavelength or color) of the light rays received at the input of that photosensor. The differential amplifier circuit receiving the outputs of the photosensors produces an electrical signal at its output whose voltage, current or a combination of both, vary according to the difference in the values of its two inputs.
The methods claimed by the present invention further teach the steps required to operate the differential prismatic solar tracking system of the current invention. In an advantageous embodiment of the invention, a calibration step is performed prior to placing the system in production and subsequently on an as-needed basis, in order to maintain proper operation of the system.
In the calibration step, an alternate method is used to first determine the on-sun orientation of the solar surface or surfaces, representing a position of the solar surface or surfaces that maximizes the energy produced by the solar surface or surfaces. With the apparatus taught above by the present invention rigidly attached to a solar surface, such an alternate method can comprise determining the GPS (Global Positioning System) or Longitude and Latitude coordinates of the location of the solar system, and adjusting the orientation of the solar system to its on-sun orientation according to known altitude and azimuth, or, horizontal and vertical, angles of the sun at that location. Such orientation data values for the sun, for any geographical coordinates of the earth, for specific dates and times, is readily available as will be known to an average person skilled in the art. In another embodiment, such an alternate method may simply comprise a visual step of observing the position of the sun at the location of the solar surface and adjusting its orientation to an on-sun orientation.
Once the on-sun orientation is established using an alternate method in the calibration step, the corresponding gain, or gains in the case of a dual-axis solar tracking system as taught above, are measured and established by the system. These values can be recorded in the processing unit as taught above. Subsequently after the calibration step has been performed, as the position of the sun changes and the value of the gain changes, or the values of the gains in case of a dual-axis system change, the processing unit or other circuitry in the system can automatically adjust the electrical signals sent to the drive assembly or assemblies of the solar surface, so as to maintain or match or track the gain value or values as established in the calibration step, and hence regain the on-sun orientation of the solar surface. Such a system is called a negative feedback loop system, as will be apparent to an average person skilled in the art. In another embodiment of the invention, the matching of the gain as taught above is performed within predetermined bounds so as to accommodate engineering imperfections of the system.
In an advantageous embodiment of the invention, the calibrated gain or gains as taught above, for multiple solar surfaces are recorded by the onboard processing unit or electrical circuitry of a mobile robot which travels to these multiple solar surfaces, docks to the respective docking stations provided with these multiple solar surfaces, and performs the calibration step as taught above. Subsequently after the calibration step, as the position of the sun with respect to these solar surfaces changes, and their orientation is no longer the on-sun orientation with respect to the position of the sun, the mobile robot travels to these multiple solar surfaces on a periodic basis, docks to the respective docking stations, receives the optical signals or light rays from the prisms on the optical dispersion assembly or prism assemblies in a dual-axis solar tracking system as taught above, and transmits the corresponding electrical signals through the docking station to the drive assembly or drive assemblies of the solar surfaces so as to track or match the value of the gain or gains established in the calibration step as taught above, and restores their on-sun orientation. In this manner, the same mobile robot travels to multiple solar surfaces and restores the on-sun orientation of those solar surfaces, thus economizing on the resources required to operate and maintain an array or a farm of solar surfaces or panels.
An alternate embodiment of the invention utilizes diffraction gratings instead of prisms to decompose incident solar light into its constituent colors. In this embodiment, the rest of the apparatus taught above is engineered such that single color light rays are selected from the output of the diffraction gratings and fed into the optical links and subsequently to the rest of the components of the system as per above teachings. Such an embodiment has the promise to further reduce the overall cost of the system.
Clearly, the apparatus and methods of the invention find many advantageous embodiments. The details of the invention, including its preferred embodiments, are presented in the below detailed description with reference to the appended drawing figures.
The figures and the following description relate to preferred embodiments of the present invention by way of illustration only. It should be noted that from the following discussion, alternative embodiments of the structures and methods disclosed herein will be readily recognized as viable alternatives that may be employed without departing from the principles of the claimed invention.
Reference will now be made in detail to several embodiments of the present invention(s), examples of which are illustrated in the accompanying figures. It is noted that wherever practicable similar or like reference numbers may be used in the figures and may indicate similar or like functionality. The figures depict embodiments of the present invention for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the invention described herein.
The present invention will be best understood by first reviewing the three dimensional perspective view of a solar tracking system 100 illustrated in
Optical dispersion assembly 102 may comprise a cylindrical or a rectangular tube, or another suitable structure that would allow light to only enter from one end, onto sunward faces 104B, 106B of prisms 104, 106. In the preferred embodiment of the current invention, dispersive prisms 104, 106 are composed of acrylic glass and are equilateral prisms, having a nominal angle (θ) of 60°. Thus each base of the prism will form an equilateral triangle as represented in
Turning our attention to
Light changes speed as it moves from one medium to another (for example, from air into the glass of the prism). This speed change causes the light to be refracted and to enter the new medium at a different angle as governed by Huygens principle which provides a basis for understanding of wave propagation of light. The degree of bending of the light depends on the angle that the incident beam of light makes with the surface, and on the ratio between the refractive indices of the two media as governed by Snell's law, which explains refraction of light.
The refractive index of many materials, such as glass, varies with the wavelength or color of the light, a phenomenon known as dispersion. This causes light of different colors to be refracted differently and to leave the prism at different angles, creating an effect similar to a rainbow. This can be used to separate a beam of white light into its constituent spectrum of colors. This is fundamentally the basis of the decomposition of light by a dispersive prism into its constituent colors. While the preferred embodiment uses prisms to disperse light into its constituent colors, an alternate embodiment may utilize diffraction gratings to decompose light into its constituent colors, without departing from the principles of the invention. In such an embodiment as claimed by the invention, instead of prism 104, 106 two diffraction gratings will be affixed to optical dispersion assembly 102 in a mirror symmetric fashion. Light dispersed from these grating will be collected by optical attachments 105, 107 which may further collimate these light rays and select light rays of a single color to feed to optical links 120, 122 as taught above.
Referring to
In the preferred embodiment shown in
While the following teachings will be provided in the context of the preferred embodiment that uses a combination of optical taps 108, 110 and optical tubes 112, 114 for optical attachments 105, 107 respectively, in alternative embodiments, as will be obvious for persons skilled in the art, optical attachments 105, 107 can comprise a variety of different optical components for the purpose of gathering dispersed light produced by prisms 104, 106, selecting light rays of a single color therefrom, and then optionally collimating those light rays. For example, optical attachments 105, 107 can comprise any one or more of the optical components selected from an optical slit, a pinhole, optical filter, spatial filter, one or more optical tubes or optical waveguides. Other types of optical components can be used for optical attachments 105, 107 within the scope of the current invention.
According to the main embodiment, the distal ends of optical tubes or waveguides 112 and 114 are connected to two optical links 120 and 122 as represented in
According to the invention electrical signals 130, 132 are then provided as inputs to a differential amplifier circuit 128 that produces an electrical gain at its output 134 based on the difference of its inputs 130 and 132. The output of differential amplifier circuit 128 is generally proportional to the difference in the levels of electrical signals 130, 132, as measured by the corresponding voltage, current or a combination of both (electrical power). Thus electrical output 134 is generally proportional to the difference in the frequencies of single color light rays carried by optical links 120 and 122, carried by optical tubes 110 and 114, and in turn selected by optical taps 108 and 112 from the constituent light rays produced by prisms 104 and 106 as a result of dispersion of solar light 108.
It will be apparent to persons with average skill in the art that electrical gain at output 134 of differential amplifier 128 can be measured as an increase or decrease of electrical voltage, current or electrical power (combination of voltage and current). Similarly, the output of each photosensor 124, 126 can be an electrical signal as measured by electrical voltage, current or electrical power, and is based on the frequency (υ), wavelength (λ) or color of single color light rays carried by each optical link 120, 122 to is respective input.
According to the invention, angles of incidence θ1,θ2 will be identical when the apparatus is in its on-sun orientation, thereby directly facing the sun. However as the sun moves from the on-sun orientation, there will be an opposing change in the two angles of incidences θ1 and θ2. In other words, as the position of the sun with respect to the system changes, angle of incidence θ1 will increase while angle of incidence θ2 will decrease. Conversely, angle of incidence θ1 may decrease while angle of incidence θ2 may increase. Consequently, according to the invention, the colors of the constituent light rays produced by prisms 104, 106 as a result of dispersion of light 108 will shift in opposing directions of the visible color spectrum. Specifically, the colors of constituent light rays produced by one prism will blue-shift while the colors of constituent light rays produced by the other prism will red-shift.
Indeed this opposing shift in color will be experienced by single color light rays 116, 118 selected by respective optical tubes 112, 114. Specifically, the color of the single color light rays 116 carried by optical tube 112 will blue-shift while the color of the single color light rays 118 carried by optical tube 114 will red-shift as the position of the sun with respect to the system changes. Alternatively, the color of the single color light rays 116 carried by optical tube 112 may red-shift while the color of the single color light rays 118 carried by optical tube 114 may blue-shift as the position of the sun with respect to the system changes.
Since the value of gain at output 134 produced by differential amplifier 128 depends on the values of its inputs 130, 132, which in turn depends on the frequencies or colors or wavelengths of the single color light rays at the inputs of optical sensors 124, 126, carried by respective optical links 120, 122 and previously carried by respective optical tubes 112, 114, this apparatus can be used to track a given orientation of the system with respect to the sun.
The explanation of how this is accomplished is given henceforth. As the position of the sun with respect the apparatus changes, the value of gain at output 134 will change as a result of shift in the color of light rays 116, 118 carried by optical tubes 112, 114 as taught above. If gain at output 134 is partially fed back to differential amplifier circuit 128 in a negative feedback fashion (not shown), and if the gain is used to control the orientation of a solar panel or solar panels, the apparatus will follow the movement of the sun such that a given value of the gain corresponding to a given orientation of the solar panel or solar panels, is maintained by the negative feedback loop (not shown) of differential amplifier circuit 128. It will be apparent to those with average skill in basic electronics the implementation of such a negative feedback amplifier circuit that tracks a net zero gain, or a fixed value gain, by feeding part of the gain back to the input of the amplifier. Therefore, the negative feedback electronic circuitry of differential amplifier 128 is not explicitly shown in
A desirable orientation of a solar surface or a panel, or a group of solar surfaces or panels, is the on-sun orientation, which represents a position of the solar surface or surfaces directly facing the sun. The on-sun orientation is desirable because it allows the solar panels to generate maximum electrical power and hence allow a solar farm of such solar panels to yield maximum output, as will be apparent to those with skilled in the art. According to the invention, the apparatus taught above can be used to track or follow the on-sun orientation of solar panels.
This is accomplished by performing an initial calibration step as taught by the methods of the invention. Let us refer to
The invention claims several methods of determining such on-sun orientation using alternate means. A preferred embodiment comprises determining GPS (Global Positioning System) or Longitude and Latitude coordinates of the location of the solar surface or surfaces, and adjusting the orientation of the system to its on-sun orientation according to known altitude and azimuth, or, horizontal and vertical, angles of the sun at that location. Such orientation data values for the sun, for any geographical coordinates of the earth, for specific dates and times, is readily available as will be known to an average person skilled in the art. In another preferred embodiment, such an alternate method comprises a visual step of observing the position of the sun at the location of the solar surface and adjusting its orientation so as to directly face the sun and hence acquire its on-sun orientation.
In this on-sun position, single color light rays 116, 118 will be selected by optical tubes 112, 114 from the constituent light spectrum produced by prisms 104, 106 as a result of dispersion of solar light 108, as taught above. In an advantageous embodiment, in the calibration step whereby the system is in its on-sun orientation, light rays 116, 118 will fall approximately in the middle of the visible spectrum of light colors produced by prisms 104, 106 and hence will be approximately green in color.
As represented in
It will be apparent to those with average skill in the art, that due to engineering differences between photosensors 124 and 126 the difference in electrical signals 130 and 132 may not be exactly zero or close to zero. Similarly, due to the internal bias of amplifier 128, gain at its output 134 may not be zero or close to zero. Indeed, it is conceivable to calibrate the system intentionally in a position that does not represent its on-sun orientation. In such a scenario the calibrated gain may be substantially different from zero. Hence the system as taught above may be used to track an arbitrary orientation of the apparatus with respect to the sun without departing from the principles of the invention.
As shown in
In the preferred embodiment depicted in
It will be apparent to those skilled in the art, processing unit 136 may comprise any number of intervening electrical circuitry or mechanical components between gain at output 134 of differential amplifier 128 and drive assembly 140 of solar surface 150 without departing from the principles of the invention.
A dual-axis solar tracking system is often desirable because it provides better control of the orientation of the solar surface or panel, or group of solar surfaces or panels, to stay closely positioned to their on-sun orientation, thereby maximizing the power output of the individual surfaces and consequently of the entire solar array or solar farm. A highly advantageous embodiment of the invention provides for such a dual-axis solar tracking system, by duplicating the entire apparatus taught above, so as to control two independent axes of control, or axes of orientation, of the solar surface or surfaces.
Referring to
Let us return our attention to the calibration step taught above as claimed by the methods of the invention. To summarize, in the calibration step gain produced by differential amplifier at its output 134 in response to the on-sun orientation of solar surface 150 is established. In the dual-axis solar tracking embodiment of the current invention, each differential amplifier 128 belonging to each of the duplicated apparatuses of the current invention will produce a gain in response to the on-sun orientation of solar surface 140, and each of these gains will be established in the calibration step. These established values of the gains may also be recorded in processing unit 136 as shown in
Now, let us understand the operation of the system after the calibration step.
Referring to
It will be understood by an average person skilled in the art, that based on the characteristics of the electrical, electronic and mechanical components of the system there may be a delay between the time of the movement of the sun to a new position away from the on-sun orientation of the system, to the restoration of the on-sun orientation of the system by its the drive assembly or assemblies. Such a delay will be anticipated in the operation of the system without departing from the principles of the invention.
If will be obvious to an average person of the art, that the calibration step taught above is not necessary for the successful operation of the system. With the gain, or gains in the case of a dual-axis solar tracking embodiment of the current invention, pre-recorded so as to achieve an on-sun orientation of the system, the system can be let to operate, whereby it will regain the on-sun orientation according to the pre-recorded gain or gains. The gain, or gains in case of the dual-axis solar tracking embodiment can be pre-recorded in the processing unit as taught above, or another suitable component of the system. Indeed it is possible to have the pre-recorded gain or gains, correspond to some arbitrary orientation of the system, or any random orientation, and allow the system to go into operation without departing from the principles of the invention. It is further possible to not have any gain or gains pre-recorded in the system, and to not perform the calibration step of above teachings, and still let the system go into operation, without departing from the principles of the invention.
In the preferred embodiment of the current invention, optical links 120 and 122, as depicted in
In a highly preferred embodiment of the invention, the orientation of solar surface or groups of solar surfaces is controlled by a mobile robot. This preferred embodiment is represented in
In this embodiment, as shown in
In an advantageous embodiment, docking station 162 has a hood 164 that reduces or prevents the ambient light that might adversely affect the optical couplings on the docking station once the mobile robot is in its docked position. Hood 164 can allow scattering of ambient light through gaps 166 between hood 164 and docking station 162 that may arise as a result of engineering imperfections of docking station 162 and hood 164 or because of regular wear and tear from the operation of the system, without adversely affecting the operation of the optical couplings.
Such a design as explained above is easily extended to the dual-axis solar tracking embodiment of the current invention. In such an embodiment, prism assemblies required to control both axes of orientation of solar surface or surfaces will be rigidly connected to the solar surface or surfaces, while photosensors, differential amplifier circuits, and any processing unit or units required to control the two axes of orientation of solar surface 150 or surfaces (not shown) will be onboard mobile robot 160. Similarly, docking station 162 will contain optical couplings required to complete the optical connections for carrying light rays from the optical tubes of the two respective prism assemblies, and electrical connections required to deliver electrical signals to dual-axis drive assembly 140 or assemblies (not shown) to control each axis of orientation of the solar surface or surfaces.
In an advantageous embodiment of the invention, the electrical connections required to deliver signals to drive assembly or assemblies of solar surface or surfaces comprise a wireless connection. Several wireless technologies may be suitable for this purpose as will be known to someone skilled in the art. Such a wireless connection can provide several benefits to the installation and operation of the system, including lowering the cost of manufacturing by obviating the need of corresponding electrical links on the mobile robot, solar panels and couplings on the docking station, and lowering the cost of maintenance of the system by reducing wear and tear on electrical wiring. Further, the invention provides the benefit of not requiring any additional or external power source for the operation of the optical differential solar tracking system taught by the invention. Solar energy produced by the solar surfaces will be sufficient to power the electronic and mechanical components of the system according to the above teachings.
In view of the above teaching, a person skilled in the art will recognize that the apparatus and method of invention can be embodied in many different ways in addition to those described without departing from the principles of the invention. Therefore, the scope of the invention should be judged in view of the appended claims and their legal equivalents.
