Heliostat Assignment in a Multi-Tower Field

Abstract

Methods, systems, and apparatus, including computer programs encoded on one or more computer storage devices, for collecting solar energy using heliostats arranged about a collection of solar energy receivers. For each heliostat, estimated efficiencies of the heliostat in directing solar rays to two or more receivers at various times of day are determined. Each heliostat is assigned to direct solar rays to two or more different receivers at two or more different times of day, wherein each heliostat directs solar rays to one receiver at a time and the assigning is based on the determined estimated efficiencies for the heliostat at the various of times of day. In some implementations, the receivers are repositionable.

1 . A method for operating a multi-tower heliostat field, comprising:
 for each heliostat of a plurality of heliostats that are arranged about a plurality of receiver towers, determining a plurality of estimated efficiencies of the heliostat in directing solar rays to two or more receiver towers at a plurality of times of day, wherein each receiver tower has a receiver mounted to the tower that is configured to receive solar rays reflected from heliostats included in the plurality of heliostats;   assigning each heliostat to direct solar rays to two or more different receiver towers at two or more different times of day, wherein each heliostat directs solar rays to one receiver tower at a time and the assigning is based on the determined estimated efficiencies for the heliostat at the plurality of times of day.   
     
     
         2 . The method of  claim 1 , wherein:
 determining a plurality of estimated efficiencies of each heliostat further comprises determining a plurality of estimated efficiencies of the heliostat in directing solar rays to the two or more receiver towers at a plurality of times of day on a plurality of days of a year; and   assigning each heliostat to direct solar rays to two or more different receiver towers is further based on the determined estimated efficiencies at the plurality of times of day on the plurality of days of the year.   
     
     
         3 . The method of  claim 1 , wherein assigning each heliostat to direct solar rays to two or more different receiver towers comprising assigning each heliostat to direct solar rays to two or more different receiver towers that are each positioned south of the heliostat for a heliostat field in the northern hemisphere and that are each positioned north of the heliostat for a heliostat field in the southern hemisphere. 
     
     
         4 . The method of  claim 1 , further comprising:
 for each heliostat, controlling positioning of one or more reflective surfaces included on the heliostat based on a position of the Sun and which receiver tower the heliostat is assigned to direct solar rays toward.   
     
     
         5 . The method of  claim 1 , wherein each receiver is configured to receive solar rays at a receiver face, the method further comprising:
 selectively moving one or more receivers mounted to one or more receiver towers to adjust positions of the one or more receiver faces.   
     
     
         6 . The method of  claim 5 , wherein the positions of the one or more receiver faces are adjusted in accordance with positions of heliostats assigned to direct solar rays to the one or more receivers corresponding to the receiver faces. 
     
     
         7 . The method of  claim 5 , wherein the positions of the one or more receiver faces are adjusted based on an azimuth direction of the Sun. 
     
     
         8 . The method of  claim 5 , wherein moving one or more receivers comprises rotating the one or more receivers about a vertical axis to adjust the positions of the one or more receiver faces. 
     
     
         9 . The method of  claim 5 , wherein moving one or more receivers comprises rotating the one or more receivers about a horizontal axis to adjust the positions of the one or more receiver faces. 
     
     
         10 . The method of  claim 5 , wherein moving one or more receivers comprises moving the receiver towers that correspond to the one or more receivers to adjust the positions of the one or more receiver faces. 
     
     
         11 . The method of  claim 1 , wherein assigning each heliostat to direct solar rays to two or more different receiver towers at two or more different times of day further comprises:
 for a particular heliostat, determining whether a benefit of reassigning the particular heliostat from a first receiver tower to a second receiver tower outweighs a cost of the reassigning, wherein the assigning is based at least in part on the determination.   
     
     
         12 . The method of  claim 1 , wherein assigning each heliostat to direct solar rays to two or more different receiver towers at two or more different times of day further comprises:
 for a particular heliostat, determining flux distributions over surfaces of a first receiver and a second receiver when the heliostat is assigned to direct solar rays to first and second receiver towers that correspond to the first and second receivers, wherein the assigning is based at least in part on the determination of flux distribution.   
     
     
         13 . A method for operating a multi-tower heliostat field, comprising:
 for each receiver tower of a plurality of receiver towers about which are arranged a plurality of heliostats, assigning a set of heliostats to direct solar rays to the receiver tower, wherein each receiver tower has a receiver mounted to the tower that is configured to receive solar rays reflected from heliostats included in the plurality of heliostats; and   for each receiver tower, based on a level of solar energy absorbed by the receiver mounted to the tower, reassigning which heliostats from the plurality of heliostats are included in the set of heliostats that are assigned to direct solar rays to the receiver tower.   
     
     
         14 . The method of  claim 13 , further comprising:
 for each receiver tower, monitoring the level of solar energy absorbed by the receiver mounted to the tower during daylight hours.   
     
     
         15 . The method of  claim 14 , wherein when the monitored level of solar energy drops below a first predetermined threshold value for one or more of the receiver towers, closing in a subset of the receiver towers and reassigning the heliostats included in the sets of heliostats assigned to direct solar rays to the closed-in subset of receiver towers to different receiver towers included in the plurality of receiver towers. 
     
     
         16 . The method of  claim 15 , wherein when the monitored level of solar energy rises above a second predetermined threshold value for one or more of the receiver towers, re-activating one or more of the closed-in receiver towers and reassigning at least some of the heliostats to direct solar rays to the reactivated one or more receiver towers. 
     
     
         17 . The method of  claim 13 , further comprising:
 for each heliostat, controlling positioning of one or more reflective surfaces included on the heliostat based on a position of the Sun and which receiver tower the heliostat is assigned to direct solar rays toward.   
     
     
         18 . The method of  claim 13 , wherein each receiver is configured to receive solar rays at a receiver face, the method further comprising:
 selectively moving one or more receivers mounted to one or more receiver towers to adjust positions of the one or more receiver faces.   
     
     
         19 . The method of  claim 18 , wherein the positions of the one or more receiver faces are adjusted in accordance with positions of heliostats assigned to direct solar rays to the one or more receivers corresponding to the receiver faces. 
     
     
         20 . The method of  claim 18 , wherein the positions of the one or more receiver faces are adjusted based on an azimuth direction of the Sun. 
     
     
         21 . The method of  claim 18 , wherein moving one or more receivers comprises rotating the one or more receivers about a vertical axis to adjust the positions of the one or more receiver faces. 
     
     
         22 . The method of  claim 18 , wherein moving one or more receivers comprises rotating the one or more receivers about a horizontal axis to adjust the positions of the one or more receiver faces. 
     
     
         23 . The method of  claim 18 , wherein moving one or more receivers comprises moving the receiver towers that correspond to the one or more receivers to adjust the positions of the one or more receiver faces. 
     
     
         24 . The method of  claim 13 , wherein reassigning which heliostats from the plurality of heliostats are included in the set of heliostats that are assigned to direct solar rays to the receiver tower, further comprises:
 determining whether a benefit of reassigning the heliostats from a first receiver tower to a second receiver tower outweighs a cost of the reassigning, wherein the reassigning is based at least in part on the determination.   
     
     
         25 . The method of  claim 13 , wherein reassigning which heliostats from the plurality of heliostats are included in the set of heliostats that are assigned to direct solar rays to the receiver tower, further comprises:
 determining flux distributions over surfaces of a first receiver and a second receiver the heliostats are assigned to direct solar rays to first and second receiver towers that correspond to the first and second receivers, wherein the reassigning is based at least in part on the determination of flux distribution.   
     
     
         26 . A method for operating a multi-tower heliostat field, comprising:
 for each receiver tower of a plurality of receiver towers about which are arranged a plurality of heliostats, assigning a set of heliostats to direct solar rays to the receiver tower, wherein each receiver tower has a receiver mounted to the tower that is configured to receive solar rays reflected from heliostats included in the plurality of heliostats; and   based on estimated levels of solar ray intensity at different times of the day, closing in a subset of the receiver towers during one or more time periods a day and reassigning the heliostats included in the sets of heliostats assigned to the closed-in subset of receiver towers to different receiver towers included in the plurality of receiver towers during those time periods.   
     
     
         27 . The method of  claim 26 , wherein closing in a subset of the receiver towers and reassigning the heliostats is further based on estimated levels of solar ray intensity at different times of the day and at different times of the year. 
     
     
         28 . The method of  claim 26 , further comprising:
 for each heliostat, controlling positioning of one or more reflective surfaces included on the heliostat based on a position of the Sun and which receiver tower the heliostat is assigned to direct solar rays toward.   
     
     
         29 . The method of  claim 26 , wherein each receiver is configured to receive solar rays at a receiver face, the method further comprising
 selectively moving one or more receivers mounted to one or more receiver towers to adjust positions of the one or more receiver faces.   
     
     
         30 . The method of  claim 29 , wherein the positions of the one or more receiver faces are adjusted in accordance with positions of heliostats assigned to direct solar rays to the one or more receivers corresponding to the receiver faces. 
     
     
         31 . The method of  claim 29 , wherein the positions of the one or more receiver faces are adjusted based on an azimuth direction of the Sun. 
     
     
         32 . The method of  claim 29 , wherein moving one or more receivers comprises rotating the one or more receivers about a vertical axis to adjust the positions of the one or more receiver faces. 
     
     
         33 . The method of  claim 29 , wherein moving one or more receivers comprises rotating the one or more receivers about a horizontal axis to adjust the positions of the one or more receiver faces. 
     
     
         34 . The method of  claim 29 , wherein moving one or more receivers comprises moving the receiver towers that correspond to the one or more receivers to adjust the positions of the one or more receiver faces. 
     
     
         35 . A heliostat field system comprising:
 a plurality of heliostats;   a plurality of receiver towers, wherein each receiver tower has a receiver mounted to the tower that is configured to receive solar rays reflected from a set of heliostats included in the plurality of heliostat, wherein the set of heliostats are assigned to direct solar rays to the receiver tower; and   an assignment control system configured to assign each heliostat to direct solar rays to two or more different receiver towers at two or more different times of day, wherein each heliostat directs solar rays to one receiver tower at a time and the assigning is based on estimated efficiencies of the heliostat in directing solar rays to the two or more receiver towers determined for a plurality of times of day.   
     
     
         36 . The heliostat field system of  claim 35 , further comprising:
 a heliostat tracking control system configured to control, for each of the plurality of heliostats, positioning of one or more reflective surfaces included on each heliostat based on a position of the Sun and which receiver tower the heliostat is assigned to direct solar rays toward.   
     
     
         37 . The system of  claim 35 , wherein the assignment control system is further configured to assign the plurality of heliostats to direct solar rays to a subset of the receiver towers, such that the remaining receiver towers are closed-in, based on estimated levels of solar ray intensity at different times of the day. 
     
     
         38 . The system of  claim 35 , wherein the assignment control system is further configured to assign the plurality of heliostats to direct solar rays to the plurality of receiver towers, such that the closed-in receiver towers are reactivated, based on the estimated levels of solar ray intensity at different times of the day. 
     
     
         39 . The system of  claim 35 , further comprising:
 a solar energy level monitoring system configured to monitor, for each of at least some of the receiver towers, a level of solar energy absorbed by the receiver mounted on the receiver tower;   wherein the assignment control system is further configured to assign each heliostat to direct solar rays to two or more different receiver towers based on the monitored levels of solar energy.   
     
     
         40 . The system of  claim 39 , wherein the assignment control system is further configured to assign the plurality of heliostats to direct solar rays to a subset of the receiver towers, such that the remaining receiver towers are closed-in, when at least some of the monitored levels of solar energy are below a predetermined first threshold value. 
     
     
         41 . The system of  claim 40 , wherein the assignment control system is further configured to assign the plurality of heliostats to direct solar rays to the plurality of receiver towers, such that the closed-in receiver towers are reactivated, when at least some of the monitored levels of solar energy are above a predetermined second threshold value. 
     
     
         42 . The heliostat field system of  claim 35 , wherein at least one or more of the receiver towers includes a receiver that is repositionable such that a face of the receiver that receives solar rays can be repositioned. 
     
     
         43 . The heliostat field system of  claim 42 , wherein the face of the receiver is repositionable in accordance with positions of the heliostats assigned to direct solar rays to the receiver. 
     
     
         44 . The heliostat field system of  claim 42 , wherein the face of the receiver is repositionable based on an azimuth direction of the Sun. 
     
     
         45 . The heliostat field system of  claim 42 , wherein the assignment control system is further configured to control repositioning of the face of the at least one receiver. 
     
     
         46 . The heliostat field system of  claim 42 , wherein the at least one receiver is configured to rotate about a vertical axis to adjust the position of the receiver face. 
     
     
         47 . The heliostat field system of  claim 42 , wherein the at least one receiver is configured to rotate about a horizontal axis to adjust the position of the receiver face. 
     
     
         48 . The heliostat field system of  claim 42 , wherein the receiver tower on which is mounted the at least one receiver is a receiver tower that is configured to move. 
     
     
         49 . The heliostat field system of  claim 35 , wherein the assignment control system is further configured to:
 for a particular heliostat, determine whether a benefit of reassigning the particular heliostat from a first receiver tower to a second receiver tower outweighs a cost of the reassigning, wherein the assigning is based at least in part on the determination.   
     
     
         50 . The heliostat field system of  claim 35 , wherein the assignment control system is further configured to:
 for a particular heliostat, determine flux distributions over surfaces of a first receiver and a second receiver when the heliostat is assigned to direct solar rays to first and second receiver towers that correspond to the first and second receivers, wherein the assigning is based at least in part on the determination of flux distribution.   
     
     
         51 . A method for operating a multi-tower heliostat field, comprising:
 for each receiver mounted to a receiver tower of a plurality of receiver towers about which a plurality of heliostats are arranged, assigning a set of multiple heliostats to direct solar rays to a receiver face of the receiver; and   adjusting a position of the receiver face at a plurality of times throughout the coarse of a day.   
     
     
         52 . The method of  claim 51 , wherein adjusting the position of the receiver face is based on an azimuth direction of the Sun at the plurality of times throughout the coarse of the day. 
     
     
         53 . The method of  claim 51 , wherein adjusting the position of the receiver face comprises rotating the receiver about a vertical axis. 
     
     
         54 . The method of  claim 51 , wherein adjusting the position of the receiver face comprises rotating the receiver about a horizontal axis. 
     
     
         55 . The method of  claim 51 , wherein adjusting the position of the receiver face comprises moving the receiver tower. 
     
     
         56 . The method of  claim 51 , further comprising:
 for each receiver, determining a plurality of estimated efficiencies of the receiver in receiving solar rays at the receiver face from the set of multiple heliostats at a plurality of times of day;   wherein adjusting the position of the receiver face is based on the estimated efficiencies for the receiver at the plurality of times of day.   
     
     
         57 . The method of  claim 51 , wherein adjusting the position of the receiver face is based on a level of solar energy absorbed by the receiver. 
     
     
         58 . The method of  claim 51 , wherein adjusting the position of the receiver face is based on estimated levels of solar ray intensity at different times of the day. 
     
     
         59 . The method of  claim 51 , further comprising:
 for each heliostat of the plurality of heliostats, determining a plurality of estimated efficiencies of the heliostat in directing solar rays to two or more receiver towers of the plurality of receiver towers at a plurality of times of day; and   wherein assigning a set of multiple heliostats to direct solar rays to a receiver face of the receiver comprises assigning a plurality of sets of multiple heliostats to direct solar rays to the receiver face at a plurality of times of the day based on the determined estimated efficiencies of the plurality of heliostats.