Heliostat calibration

Abstract

Embodiments relate to solar energy systems and methods of operating the same. In some embodiments, the solar energy system comprising: a plurality of heliostats configured to reflect sunlight to a target mounted on a tower, each heliostat including a respective heliostat controller, the target, the target being selecting from the group consisting of an energy conversion target and/or a secondary reflector; and a macro-array of light-intensity sensors characterized by a maximum sensor-sensor distance and mounted on the tower such that when any heliostat of the plurality of heliostats reflects a beam of light onto the macro-array of light-intensity sensors, the maximum dimension of the reflected beam's projection on the macro-array is at most twice the maximum sensor-sensor distance, wherein each heliostat controller is operative to control its respective heliostat so that the light beam reflected by the heliostat traverses the macro-array of light-intensity sensors.

1 . A solar energy system comprising:
 a. a plurality of heliostats configured to reflect sunlight to a target mounted on a tower, each heliostat including a respective heliostat controller, the target, the target being selecting from the group consisting of an energy conversion target and/or a secondary reflector; and   b. a macro-array of light-intensity sensors characterized by a maximum sensor-sensor distance and mounted on the tower such that when any heliostat of the plurality of heliostats reflects a beam of light onto the macro-array of light-intensity sensors, the maximum dimension of the reflected beam's projection on the macro-array is at most twice the maximum sensor-sensor distance,   wherein each heliostat controller is operative to control its respective heliostat so that the light beam reflected by the heliostat traverses the macro-array of light-intensity sensors.   
     
     
         2 . The system of  claim 1  wherein the macro-array of light-intensity sensors is substantially co-planar. 
     
     
         3 . The system of  claim 1 , where the macro-array of light-intensity sensors is a two dimensional macro-array. 
     
     
         4 . The system of  claim 1 , where the light-intensity sensors are configured to acquire time-series light intensity data while the reflected beam's projection traverses across the macro-array of light sensors. 
     
     
         5 . The system of  claim 1  wherein the heliostat controller is operative to:
 i) before the traversing of the projection of the reflection beam, direct the heliostat to the target mounted on the tower according to an initial set of aiming parameters; and   ii) after the traversing of the projection of the reflection beam, re-direct the heliostat to the target mounted on the tower according to a modified set of aiming parameters that is modified in accordance with light intensity data generated by light intensity sensors of the macro-array.   
     
     
         6 . The system of  claim 5  wherein the heliostat controller is operative to effect the re-directing according to the modified set of aiming parameters after the beam traversing. 
     
     
         7 . The system of  claim 5  wherein the heliostat controller is operative to effect the re-directing according to the modified set of aiming parameters immediately after the beam traversing. 
     
     
         8 . The system of  claim 4  wherein the heliostat controller is operative to effect the re-directing according to the modified set of aiming parameters immediately only after a time delay. 
     
     
         9 . The system of  claim 8  wherein during the period of the time delay, the controller is operative to re-direct the heliostat to the target according to the initial set of aiming parameters. 
     
     
         10 . The system of  claim 6  wherein the modified set of aiming parameters is modified in accordance with at least one of:
 i) distances between light-intensity sensors of the macro-array of light-intensity sensors; and   ii) a beam traversal speed of the traversing reflected heliostat beam.   
     
     
         11 . The system of  claim 1  further comprising:
 c. a heliostat-field controller operative to:
 i) select, from the plurality of heliostats, a sub-plurality of heliostats that is to be simultaneously directed to the target; and 
 ii) direct the selected sub-plurality of heliostats the target, 
   wherein the heliostat field controller is operative to carry out the heliostat selection in accordance with respective light intensity measurements of macro-array taken when each heliostat's reflected beam respectively traverses the macro-array.   
     
     
         12 . The system of  claim 11  wherein the heliostat-field controller is operative to effect the selection in accordance with at least one of:
 i) distances between light-intensity sensors of the macro-array of light-intensity sensors; and   ii) a beam traversal speed of the traversing reflected heliostat beam.   
     
     
         13 . The system of  claim 1  wherein the system further comprises:
 c) electronic circuitry configured to measure at least one beam projection parameter of the heliostat beam according to the light intensity measurements acquired by light-intensity sensors while the heliostat beam traverses the macro-array of light-intensity sensors.   
     
     
         14 . The system of  claim 13  wherein the electronic circuitry is configured to effect the measuring in accordance with at least one of:
 i) distances between light-intensity sensors of the macro-array of light-intensity sensors; and   ii) a beam traversal speed of the traversing reflected heliostat beam.   
     
     
         15 . The system of  claim 1  wherein the system further comprises:
 c) electronic circuitry configured to measure at least one of:
 i) a shape of the heliostat beam; 
 ii) a flux intensity map of the heliostat beam; 
 iii) an offset of the heliostat beam; and 
 iv) an indication of beam area. 
   according to the light intensity measurements acquired by light-intensity sensors while the heliostat beam traverses the macro-array of light-intensity sensors.   
     
     
         16 . The system of  claim 15  wherein the electronic circuitry is configured to effect the measuring in accordance with at least one of:
 i) distances between light-intensity sensors of the macro-array of light-intensity sensors; and   ii) a beam traversal speed of the traversing reflected heliostat beam.   
     
     
         17 . The system of  claim 1  wherein: the heliostat controllers collectively are configured so that multiple overlapping heliostat reflection beams including first and second heliostat reflection beams simultaneously traverse the macro-array to simultaneously illuminate one or more of the light-intensity sensors. 
     
     
         18 . The system of  claim 17  wherein:
 i) the light-intensity sensors of the macro-array are image sensors; and   ii) the system further comprises:
 c) electronic circuitry operative to:
 A) determine, from the images generated by the image sensors, relative light intensity contributions of the overlapping first and second heliostat beams when the first and second beams overlap and traverse the macro-array; and 
 B) in accordance with the relative light intensity contributions, determine at least one of:
 I) a shape of the first and/or second heliostat beam; 
 II) a flux intensity map of the first and/or second heliostat beam; 
 III) an offset of the first and/or second heliostat beam; and 
 IV) an indication of beam area. 
 
 
   
     
     
         19 . The system of  claim 17  wherein the heliostat controllers collectively are configured so that the first and second heliostat beams overlap at some times and are disjoint at other times while the first and second beams traverse the macro-array. 
     
     
         20 . The system of  claim 19  wherein:
 i) the light-intensity sensors of the macro-array are image sensors; and   ii) the system further comprises:
 c) electronic circuitry operative to determine when the first and second beams are disjoint, and in accordance with the disjoint time period(s), determine at least one of:
 I) a shape of the first and/or second heliostat beam; 
 II) a flux intensity map of the first and/or second heliostat beam; 
 Ill) an offset of the first and/or second heliostat beam; and 
 IV) an indication of beam area. 
 
   
     
     
         21 . The system of  claim 1  wherein each of the light sensors of the macro-array are image sensors. 
     
     
         22 . The system of  claim 21  wherein the image sensors are selected from the group consisting of a CCD microarray and a CMOS microarray. 
     
     
         23 . The system of  claim 1  wherein each of the light sensors of the macro-array are photo-detectors incapable of detecting an image. 
     
     
         24 . The system of  claim 23  wherein each of the light sensors are photo-voltaic cells. 
     
     
         25 . The system of  claim 1  wherein each of the light-intensity sensors is mounted to the tower. 
     
     
         26 . The system of  claim 1  wherein the energy conversion target is selected from the group consisting of solar boiler target and a molten salt solar receiver. 
     
     
         27 . The system of  claim 26  wherein the solar boiler target is selected from the group consisting of a solar evaporator, a solar re-heater and a solar superheater. 
     
     
         28 . The system of  claim 1  wherein the energy conversion target includes one or more photovoltaic and/or photo-electrovoltaic cells. 
     
     
         29 . The system of  claim 1  wherein a height of the tower is at least 25 meters. 
     
     
         30 . The system of  claim 1  wherein a height of the tower is at least 100 meters. 
     
     
         31 . The system of  claim 1  further comprising:
 c. a projector configured to project artificial light onto the heliostat such that the traversing reflected beam that traverses the macro-array includes the artificial light generated by the projector.   
     
     
         32 . The system of  claim 31  wherein the projector is mounted on the tower. 
     
     
         33 . A method of operating a solar energy system, the method comprising:
 a. respectively reflecting sunlight from each of a plurality of heliostats to a target mounted on a tower, the target being selecting from the group consisting of an energy conversion target and/or a secondary reflector; and   b. respectively controlling each heliostat of the plurality so that the light beam reflected by the heliostat traverses the macro-array of light-intensity sensors characterized by a maximum sensor-sensor distance and mounted on the tower such that when any heliostat of the plurality of heliostats reflects a beam of light onto the macro-array of light-intensity sensors, the maximum dimension of the reflected beam's projection on the macro-array is at most twice the maximum sensor-sensor distance.