Methods and systems for operating solar tower systems

Abstract

A solar energy system can be controlled and operated responsively to detected and/or predicted changes in insolation conditions. By placing an imaging aperture of an imaging device as part of an external surface of a solar receiver, an orientation of each heliostat in a heliostat field can be determined. The imaging device can be used to image at least a portion of the heliostat field based on light passing through the imaging aperture, which is proximate to, adjacent to, or at least partially within the capture area of the solar receiver so as to acquire at least one image indicating a change in a distribution of insolation levels falling on the portion of the field. Characteristics of heliostats within the portion of the field can be calculated based on the at least one image. Aiming directions of one or more can be changed based on the calculated characteristics.

1 . A method of controlling a solar energy system, the system having a tower-based first receiver and a field of heliostats controlled to direct insolation toward a capture area of the first receiver, a subset of the heliostats being controlled to direct insolation at respective aiming points within the capture area, the method comprising:
 using at least one camera, imaging said field from light passing through an imaging aperture, which is proximate to, adjacent to, or at least partially within the capture area of the first receiver, to acquire at least one image indicating a change in a distribution of insolation levels falling on said field;   using an image processor, responsively to said at least one image, calculating characteristics of heliostats within the field of heliostats; and   responsively to said characteristics, changing aiming direction of one or more heliostats in said field.   
     
     
         2 . The method of  claim 1 , wherein the calculating includes identifying shaded heliostats and unshaded heliostats. 
     
     
         3 . The method of  claim 1 , wherein the calculating includes determining a magnitude of change in insolation levels falling on each heliostat in said at least one image. 
     
     
         4 . The method of  claim 1 , wherein the calculating is effective to determine variations in insolation levels falling on heliostats as a result of at least one of dirt, breakage of heliostats, shading by structures, shading by clouds, and shading by flora or fauna. 
     
     
         5 . The method of  claim 1 , wherein the changing the aiming direction results in a change in a flux distribution across the capture area of the first receiver. 
     
     
         6 . The method of  claim 1 , wherein the changing the aiming direction includes calculating a characteristic of a change in a flux distribution responsively to said characteristics of heliostats. 
     
     
         7 . The method of  claim 1 , wherein the calculating characteristics of heliostats includes calculating characteristics of shaded heliostats within the field of heliostats. 
     
     
         8 . The method of  claim 1 , wherein the imaging aperture is located at least partially within the capture area of the first receiver. 
     
     
         9 . The method of  claim 1 , wherein the imaging aperture is completely within the capture area of the first receiver. 
     
     
         10 . The method of  claim 1 , further comprising cooling the at least one camera using a heat exchanger connected thereto so as to transfer heat to a heat transfer fluid. 
     
     
         11 . The method of  claim 1 , wherein the at least one camera has a heat exchanger and a pump or fan configured to move a heat transfer fluid across a heat transfer surface of the heat exchanger, the heat exchanger being configured to cool the camera thereby. 
     
     
         12 . The method of  claim 1 , further comprising actively cooling the at least one camera including conveying a heat transfer fluid across a heat transfer surface conducting heat from the camera. 
     
     
         13 . The method of  claim 1 , wherein the changing the aiming direction includes calculating another characteristic and a consequence of maintaining a respective aiming direction of at least one heliostat. 
     
     
         14 . The method of  claim 1 , wherein the aiming direction changed by said changing intercepts said capture area. 
     
     
         15 . The method of  claim 1 , wherein the aiming direction of the at least one heliostat changed by said changing intercepts a capture area of a second receiver. 
     
     
         16 . The method of  claim 1 , wherein the changing includes aiming at least one of the one or more heliostats from respective multiple aiming points so they no longer intercept the first receiver. 
     
     
         17 . The method of  claim 1 , further comprising, responsively to said characteristics, calculating a total energy flux on an external surface of the first receiver. 
     
     
         18 . The method of  claim 17 , wherein the changing aiming direction includes, responsively to at least a result of said calculating the total energy flux, directing heliostats to reflect the solar radiation onto aiming points on the external surface of the first receiver based at least in part on the calculated total energy flux. 
     
     
         19 . The method of  claim 18 , wherein the calculating the total energy flux and directing are repeated continuously during operation of the solar energy system. 
     
     
         20 - 22 . (canceled) 
     
     
         23 . A method of controlling a solar energy system, the method comprising:
 reflecting sunlight from each of a plurality of heliostats to an energy conversion target mounted on a tower; and   controlling each heliostat of the plurality of heliostats so that a light beam reflected by each heliostat traverses imaging device array positioned within an area defined by the energy conversion target.   
     
     
         24 . The method of  claim 23 , further comprising, acquiring multiple images of each of the plurality of heliostats using the imaging device array. 
     
     
         25 . The method of  claim 24 , further comprising, estimating at least one geometric parameter of each of the plurality of heliostats based at least in part on the acquired images. 
     
     
         26 . The method of  claim 25 , further comprising, orienting each of the plurality of heliostats to reflect sunlight to the energy conversion target, based at least in part on the at least one geometric parameter. 
     
     
         27 . The method of  claim 25 , wherein the estimating is further based on the nominal geometric parameter of each of the plurality of heliostats. 
     
     
         28 . The method of  claim 25 , further comprising, determining the solar flux distribution of each heliostat on an external face of the energy conversion target based at least in part on light intensity of the light beam reflected by each of the plurality of heliostats as seen in the acquired images. 
     
     
         29 . The method of  claim 28 , further comprising, determining a shape of the reflected light beam based at least in part on the determined solar flux distribution of each of the plurality of heliostats. 
     
     
         30 . The method of  claim 28 , further comprising, directing at least one heliostat of the plurality of heliostats to reflect incoming solar radiation onto aiming points on the external surface of the energy conversion target based at least in part on the determining the solar flux distribution. 
     
     
         31 . A method of controlling a solar energy system, the system having a receiver mounted on a tower and a field of heliostats arranged to direct insolation toward a capture aperture of the receiver, the method comprising:
 generating at least one image from light received through an imaging aperture from insolation reflected from a region coinciding with locations of at least a subset of the heliostats within the field of heliostats,   the at least one image indicating a change in a distribution of insolation levels falling on the at least a subset of the heliostats,   the imaging aperture being located adjacent to or fully or partially within the capture aperture,   the generating including imaging a scene, containing the at least a subset of heliostats,   the change in a distribution of insolation levels resulting in a change in a flux distribution across the capture aperture;   using at least one programmable controller that is connected to control positions of the at least a subset of the heliostats within said field of heliostats, calculating characteristics of heliostats within the field of heliostats responsively to said at least one image; and   using said at least one programmable controller, responsively to at least a result of said calculating, changing aiming directions of one or more heliostats to effect a target flux distribution responsively to data stored in the at least one programmable controller.   
     
     
         32 . The method of  claim 31 , wherein the changing the aiming directions includes calculating a characteristic of the change in a flux distribution and is additionally responsive to a result of said calculating. 
     
     
         33 . The method of  claim 31 , wherein the calculating includes identifying shaded heliostats and unshaded heliostats. 
     
     
         34 . The method of  claim 31 , wherein the calculating is effective to determine variations in insolation levels falling on heliostats as a result of at least one of dirt, breakage of heliostats, shading by structures, shading by clouds, and shading by flora or fauna. 
     
     
         35 . The method of  claim 31 , further comprising actively cooling the camera using a thermoelectric cooling system.