Solar field layout and systems and methods for arranging, maintaining, and operating heliostats therein

Abstract

At least some of the heliostats can be arranged and operated in such a manner that the maintenance vehicle can pass through the solar field along conditional pathways. The arrangement and control of the heliostats to allow access to heliostats by a maintenance vehicle can enable different heliostat patterns as compared with conventional arrangements. In particular, heliostats in one section of the solar field, which may be less geometrically efficient, can be arranged at a higher density as compared to heliostat in another section of the solar field. In addition, the locations of heliostats in various sections of the field can be optimized based on ground coverage as viewed from a vantage point in the solar tower and/or revenue generation without constraining the locations to particular line or arc patterns.

1 . A method of designing and operating a solar thermal heliostat field, comprising:
 without constraining heliostat position to lines or arcs, optimizing positions for the heliostats in significant portions of the solar field responsively to a predicted ground obscuration by the heliostats as viewed from a location at or near a top of a solar tower in the solar field;   constructing a solar thermal heliostat field according to the optimized positions;   selecting a drive zone between a first location and a second location in the constructed solar field, at least a portion of the selected drive zone being bordered by some of the heliostats such that, when the bordering heliostats have a first orientation, a width of said portion defined by the bordering heliostats on opposite sides of the drive zone is insufficient to allow the maintenance vehicle to pass through said portion;   reorienting mirrors of the bordering heliostats from the first orientation to a second orientation such that the width of said portion defined by the bordering heliostats on opposite sides of the drive zone is sufficient to allow the maintenance vehicle to pass through said portion;   moving the maintenance vehicle from the first location to the second location along said drive zone; and   at said second location, maintaining one or more of the heliostats in the constructed solar field using the maintenance vehicle.   
     
     
         2 . The method of  claim 1 , wherein said maintaining includes cleaning one or more of the heliostats by reaching over at least one of the bordering heliostats. 
     
     
         3 . The method of  claim 1 , wherein the solar thermal heliostat field is constructed in the northern hemisphere; said optimizing is such that heliostat density in a first portion of the constructed field south of the solar tower is greater than that in a second portion of the constructed field north of the solar tower; a northern face of a receiver in the tower, at which heliostats in the second portion direct insolation, and a southern face of the receiver in the tower, at which heliostats in the first portion direct insolation, have substantially the same face area; and the first portion is a mirror image of the second portion with respect to an east-west line passing through a base of the solar tower. 
     
     
         4 . The method of  claim 1 , wherein said optimizing is such that heliostat density in a first portion of the constructed field west of the solar tower is greater than that in a second portion of the constructed field east of the solar tower; an eastern face of a receiver in the tower, at which heliostats in the second portion direct insolation, and a western face of the receiver in the tower, at which heliostats in the first portion direct insolation, have substantially the same face area; and the first portion is a mirror image of the second portion with respect to a north-south line passing through a base of the solar tower. 
     
     
         5 - 9 . (canceled) 
     
     
         10 . A method of making a solar field for a solar thermal power system having a tower-mounted receiver and a field over which at least 5000 heliostats are to be arrayed about the tower to concentrate solar energy onto the receiver, comprising:
 defining at least one portion of the field over which the heliostats are to be located;   the at least one portion having a first dimension along a radius extending from the tower location that is at least 0.5 times the height of the tower and a second dimension orthogonal to the first dimension that is at least the first dimension; and   without constraining to any geometric patterns positions of the heliostats within bounds of the at least one portion except to maintain the positions in the bounds of the at least one portion, optimizing the number and arrangement of the heliostats in the at least one portion by maximizing an average over time for ground obscuring efficiency of the heliostats with respect to a vantage point within 30 percent of the tower height from a position of the receiver, the efficiency being the area of ground obscured by mirrors of the heliostats divided by the aggregate area of the mirrors of the heliostats in the at least one portion.   
     
     
         11 . The method of  claim 10 , wherein the optimizing employs an optimization algorithm which includes one or a combination of global or local search stochastic/probabilistic tools, metaheuristic algorithm, genetic algorithm, simulated annealing algorithm, hill-climbing algorithm, genetic algorithm, dynamic programming, and/or an ant colony algorithm. 
     
     
         12 . The method of  claim 10 , wherein the at least a portion is the entire field. 
     
     
         13 . The method of  claim 10 , wherein the at least a portion is an extent of the field ranging from a distance of at least 5 times the tower height to a distance of less than 25 times the tower height. 
     
     
         14 . The method of  claim 10 , wherein the tower height is a range of tower heights and the optimizing includes determining an optimum precise tower height. 
     
     
         15 . The method of  claim 10 , wherein the without restricting to any geometric patterns means without restricting the heliostat positions so that they fall on a line or arc within a specific distance of a line or arc or within a range of positions within a predefined distance of a line or arc whose length is at least ten times an average spacing of the heliostats adjacent to or lying on the line or arc. 
     
     
         16 . (canceled) 
     
     
         17 . The method of  claim 11 , further comprising, selecting one or more times of day and/or times of year, wherein the optimization algorithm maximizes the amount of ground obscuration during the selected one or more times. 
     
     
         18 . The method of  claim 11 , wherein the optimization algorithm maximizes time-averaged ground obscuration as viewed from a point of view within a distance from a receiver on the tower that is not greater than 25 percent of a distance of the receiver from the ground. 
     
     
         19 . The method of  claim 10 , further comprising, installing heliostats in the at least one portion according to the optimized number and arrangement. 
     
     
         20 - 21 . (canceled) 
     
     
         22 . The method of  claim 10 , wherein said optimizing includes selecting a plurality of concentric drive zones centered on the solar tower, and using an annealing algorithm to determine the optimized number and arrangement of heliostats in the at least one portion, which is between adjacent ones of the drives zones, without any constraint to particular line or arc layouts. 
     
     
         23 . (canceled) 
     
     
         24 . The method of  claim 11 , wherein the optimization algorithm is weighted to maximize ground coverage during afternoon hours in the summer. 
     
     
         25 - 28 . (canceled) 
     
     
         29 . A system comprising:
 a solar tower; and   a plurality of heliostats deployed in a solar field and configured to redirect insolation to a target at or near the top of the solar tower in the solar field, a significant region of the solar field whose total heliostat deployment is at least 100 heliostats such that there are heliostats throughout most of the significant region of the solar field,   wherein a heliostat deployment pattern in the significant region is such that no parallel lines or arcs can be drawn through a series of twenty or more heliostats along which line or arc the heliostats are spaced apart not more than three times the average nearest-neighbor distance of the heliostats along the line or arc.   
     
     
         30 . The system of  claim 29 , wherein the significant region is the entire solar field beyond a radial distance from the tower at least 2.5 times the height of a solar receiver on the tower. 
     
     
         31 . The system of  claim 29 , wherein heliostats adjacent the tower lie along lines or arcs. 
     
     
         32 - 66 . (canceled) 
     
     
         67 . The method of  claim 19 , further comprising, re-orienting mirrors of heliostats in the at least one portion from a position reflecting sunlight onto the receiver so as to allow a maintenance vehicle to pass along a drive zone through said at least one portion.