Solar energy collection utilizing heliostats

Abstract

Heliostats are utilized to direct solar energy to a target configured for collecting the solar energy. The heliostats include mirrors that are adjustable so as to track the position of the sun relative to the target as the position changes over time. The heliostats are configured for self-alignment without the need for external control or surveying.

1 . A method for collecting solar energy, the method comprising:
 positioning a minor of a heliostat such that the minor receives solar energy along a direction of incidence and directs solar energy to a target along a direction of reflection; and   maintaining the mirror in alignment with the target by:   operating an image capturing device of the heliostat to capture an image of the sun and an image of the target;   determining a centroid of the image of the sun and a centroid of the target;   averaging the centroids to obtain an averaged centroid, wherein the averaged centroid is located at a distance from a reference pixel on the image capturing device; and   adjusting the minor to an aligned position at which the distance between the averaged centroid and the reference pixel is about zero.   
     
     
         2 . The method of  claim 1 , comprising repeating the steps of operating, determining, averaging, and adjusting one or more times. 
     
     
         3 . The method of  claim 1 , comprising operating a controller in signal communication with the image capturing device to receive signals corresponding to the captured images, determine the centroids, and average the centroids. 
     
     
         4 . The method of  claim 3 , comprising operating the controller to adjust the minor by sending a control signal to an adjustment device of the heliostat. 
     
     
         5 . The method of  claim 4 , wherein the adjustment device comprises a motor configured to move the mirror along or about an axis. 
     
     
         6 . The method of  claim 3 , wherein the controller is located at the heliostat. 
     
     
         7 . The method of  claim 1 , wherein the image capturing device is mounted on the minor. 
     
     
         8 . The method of  claim 1 , wherein the solar energy is transmitted through a fisheye lens enclosing the minor and the image capturing device. 
     
     
         9 . The method of  claim 1 , wherein the target is a solar thermal collector tower. 
     
     
         10 . The method of  claim 1 , comprising initializing operation of the heliostat by positioning a light source between the image capturing device and the target along the direction of reflection, and directing light from the light source to the image capturing device. 
     
     
         11 . The method of  claim 10 , comprising:
 capturing an image of the light source;   determining a centroid of the image of the light source;   averaging the centroid of the image of the sun and the image of the light source to obtain an averaged centroid, wherein the averaged centroid is located at a distance from a reference pixel on the image capturing device; and   adjusting the minor to an aligned position at which the distance between the averaged centroid and the reference pixel is about zero.   
     
     
         12 . The method of  claim 1 , comprising sending a command to the heliostat by transmitting one or more light pulses to the image capturing device to produce a control signal, and operating a controller of the heliostat to read the control signal, wherein the command is encoded by the one or more light pulses. 
     
     
         13 . The method of  claim 12 , comprising operating the controller to move the mirror in response to the control signal. 
     
     
         14 . The method of  claim 12 , wherein transmitting comprises operating a light source between the image capturing device and the target. 
     
     
         15 . The method of  claim 12 , wherein transmitting is done during nighttime. 
     
     
         16 . The method of  claim 12 , comprising operating the controller to move the mirror to a test position in response to the control signal, wherein at the test position the mirror is aligned with a light source, and further comprising directing light from the light source to the minor, and determining whether the light is reflected in the mirror. 
     
     
         17 . The method of  claim 16 , wherein determining whether the light is reflected in the minor comprises operating a camera to capture an image of the mirror. 
     
     
         18 . A heliostat, comprising:
 a mirror movable along or about one or more axes;   an adjustment device configured for moving the minor;   an image capturing device positioned for capturing an image of the sun and an image of a target; and   a controller in signal communication with the image capturing device and with the adjustment device, the controller configured for:   receiving signals from the image capturing device corresponding to the image of the sun and the image of the target;   determining a centroid of the image of the sun and a centroid of the target;   averaging the centroids to obtain an averaged centroid, wherein the averaged centroid is located at a distance from a reference pixel on the image capturing device; and   controlling the adjustment device to adjust the mirror to a position in alignment with the target, at which position the distance between the averaged centroid and the reference pixel is about zero.   
     
     
         19 . The heliostat of  claim 18 , wherein the adjustment device comprises a motor configured to move the mirror along or about an axis. 
     
     
         20 . The heliostat of  claim 18 , wherein the image capturing device is mounted on the mirror. 
     
     
         21 . The heliostat of  claim 18 , comprising a fisheye lens on the image capturing device. 
     
     
         22 . The heliostat of  claim 18 , comprising a photovoltaic array and battery for providing electrical power to one or more power-consuming components of the heliostat. 
     
     
         23 . A solar energy collection system, comprising:
 a target configured for collecting solar energy; and   a plurality of heliostats according to  claim 18 , and arranged such that each heliostat is capable of being aligned with the target along a respective direction of reflection.   
     
     
         24 . The system of  claim 23 , wherein the target is a solar thermal collector tower. 
     
     
         25 . The system of  claim 23 , comprising a plurality of light sources, each light source movable between an operating position at which the light source is positioned in a line of sight of one or more of the image capturing devices of the heliostats and a non-operating position at which the light source is outside of the line of sight of the image capturing devices. 
     
     
         26 . The system of  claim 25 , wherein the light sources are mounted to the target. 
     
     
         27 . The system of  claim 23 , comprising a plurality of cameras, each camera positioned to capture an image of one or more of the mirrors of the heliostats. 
     
     
         28 . The system of  claim 27 , wherein the cameras are mounted to the target.