Patent Application
20130048752
The present disclosure relates generally to solar energy systems, and, more particularly, to systems and methods for constructing and/or arranging heliostats within a solar field. The disclosure also relates to systems and methods for maintaining and/or operating the heliostats of the solar field.
Embodiments of the present disclosure relate generally to systems, methods, and devices for maintaining and/or operating a solar field of a solar power system. A maintenance vehicle can be navigated through the solar field and/or heliostats operated in a specific manner to effect maintenance (such as cleaning, repair, or replacement) of certain heliostats. Control of the maintenance vehicle and/or operation of the heliostats can be such that the likelihood of damage to an indigenous animal, such as a desert tortoise, and/or its habitat is reduced and/or minimized. Thus, the co-existence of the solar field with threatened and/or endangered species or animals covered by a conservation plan can be facilitated. The maintenance vehicle can move through the solar field on permanent or conditional pathways within the solar field. Heliostats may be controlled to allow the maintenance vehicle to proceed along these conditional pathways.
Heliostats in one section of the solar field, e.g., close to the solar tower, can be arranged in a more ordered and high density pattern while heliostats in another section of the solar field, e.g., far from the solar tower, can be arranged in a more disordered pattern. Access to the heliostats in either the ordered or disordered pattern sections can thus be made available by controlling certain heliostats to open conditional pathways in the solar field for a maintenance vehicle. The density and arrangement of heliostats in various sections of the field can be optimized to improve and/or maximize solar energy production and/or revenue generation. The density/arrangement of the heliostats may be chosen without regard to symmetry with respect to cardinal directions.
In embodiments, a maintenance vehicle for cleaning heliostats in a solar field can include a main body, a translation system, and one or more cleaning modules. The translation system can be constructed to move the main body through the solar field. Each cleaning module can include at least one cleaning tool. In addition, each cleaning module can be configured to position each cleaning toll proximal to a corresponding mirror surface of one of the heliostats for cleaning.
In embodiments, a method of cleaning heliostats in a solar field with a maintenance vehicle can include determining no-drive zones within a solar field based on at least one of predicted animal movement, detected animal movement, predicted animal location, detected animal location, predicted animal habitat location, and detected animal habitat location. The method can also include moving the maintenance vehicle from a first location to a second location in the solar field while avoiding the determined no-drive zones.
In embodiments, a method of maintaining or operating heliostats deployed in a solar field can include electronically detecting or predicting presence or movement of a non-domestic animal within the solar field and effecting at least one solar field operation according to the detected or predicted animal presence or movement. The at least one solar field operation can include cleaning heliostats in the solar field in an order and/or at a rate according to the detected or predicted presence or movement, aiming the heliostats according to the detected or predicted animal movements, and operating a solar field vehicle within the solar field according to the detected or predicted presence or movement.
In embodiments, a method of maintaining or operating heliostats deployed in a solar field can include electronically monitoring the movements of a non-domestic animal over a period of time to determine at least one temporal movement pattern for the non-domestic animal, determining at least one current time parameter selected from the group including a current time of day and a current season of the year, predicting at least one of current location of the non-domestic animal and a confidence level of a prediction of a current location of the non-domestic animal, and effecting at least one solar field operation in accordance with the prediction. The at least one temporal movement pattern can include a daily movement pattern time of day describing trends of movement of the non-domestic animal within the solar field as a function of time of day, and a seasonal movement pattern time of day describing animal movement trends as a function of time of year. The at least one solar field operation can include cleaning heliostats in the solar field in an order and/or at a rate according to the detected or predicted presence or movement, aiming the heliostats according to the detected or predicted animal movements, and operating a solar field vehicle within the solar field according to the detected or predicted presence or movement.
In embodiments, a solar system can include a plurality of heliostats configured to re-direct insolation toward a target deployed in a solar field and a robotic heliostat cleaner configured to clean mirrors of the heliostats at different locations in the solar field. The robotic heliostat cleaner can include control circuitry that causes the robotic heliostat cleaner to travel in a manner that is contingent upon detected or predicted movements of a non-domestic animal within the solar field.
In embodiments, a method of maintaining or operating heliostats deployed in a solar field can include receiving location data indicating locations of animal within a heliostat field, and directing movement of a robotic maintenance vehicle responsively to the location data. The maintenance vehicle may be configured to perform maintenance operations on heliostats of the solar field.
In embodiments, a cleaning system for heliostats can include a wheeled maneuverable truck, a controller, a pivoting support, and a cleaning effecter apparatus. The controller can be configured to control the truck for maneuvering throughout a field of heliostats responsively to control commands. The pivoting support can carry a longitudinal member with an axis extensible horizontally and configured to hold the cleaning effecter apparatus at various positions remote from the truck. The cleaning effecter apparatus can be configured to reach downwardly to clean horizontally-oriented and upwardly-facing surfaces of multiple heliostats.
In embodiments, an apparatus and/or a system may be configured to perform any of the methods disclosed herein.
In embodiments, a system, device, or method can include a vehicle or truck, or use thereof. The vehicle or truck can carry a mechanical deflector configured to move animals away from the wheels of the vehicle or truck, or, for method claims, employs the deflector to deflect animals away from the wheels of the vehicle or truck.
Objects and advantages of embodiments of the present disclosure will become apparent from the following description when considered in conjunction with the accompanying drawings.
Embodiments will hereinafter be described with reference to the accompanying drawings, which have not necessarily been drawn to scale. Where applicable, some features may not be illustrated to assist in the illustration and description of underlying features. Throughout the figures, like reference numerals denote like elements.
Embodiments of the present disclosure relate generally to systems, methods, and devices for maintaining and/or operating a solar field of a solar power system. In particular, the disclosure relates to power plant magnitude systems rather than pilot systems. For example, the peak flux power level of aggregate flux to the tower and/or the target(s) is at least 5 megawatts, at least 10 megawatts, at least 20 megawatts, at least 50 megawatts, at least 100 megawatts, at least 250 megawatts, or at last 500 megawatts.
A maintenance vehicle can be navigated through the solar field and/or heliostats operated in a specific manner to effect cleaning of the heliostats. Control of the maintenance vehicle and/or operation of the heliostats can be such that the likelihood of damage to an indigenous animal, such as a desert tortoise, and/or its habitat is reduced and/or minimized. Thus, the co-existence of the solar field with threatened and/or endangered species or animals covered by a conservation plan can be facilitated. Although discussed in connection with the desert tortoise, the embodiments can be used to be responsive to the growth of vegetation which may move or die and reappear in different locations.
The maintenance vehicle can move through the solar field on permanent pathways within the solar field. Additionally or alternatively, at least some of the heliostats can be arranged and controlled in such a manner that the maintenance vehicle can pass through the solar field along conditional pathways, i.e., pathways via which a particular maintenance vehicle would normally not be able to pass when the heliostats are oriented to aim at a receiver in a solar tower.
The arrangement and control of the heliostats to allow access to heliostats by a maintenance vehicle moving through the solar field can enable different heliostat patterns as compared with conventional arrangements. In particular, heliostats in one section of the solar field, e.g., close to the solar tower, can be arranged in a more ordered and high density pattern while heliostats in another section of the solar field, e.g., far from the solar tower, can be arranged in a more disordered pattern. Access to the heliostats in either the ordered or disordered pattern sections can thus be made available by controlling certain heliostats to open conditional pathways in the solar field for a maintenance vehicle. The density and arrangement of heliostats in various sections of the field can be optimized to improve and/or maximize solar energy production and/or revenue generation. The density/arrangement of the heliostats may be chosen without regard to symmetry with respect to cardinal directions.
Throughout the present disclosure, various examples are described for maintaining or operating the solar field in a manner that facilitates co-existence with the one or more animals. For example, the solar field can located in the Mojave Desert in the southwestern United States, and the animal can be the desert tortoise (i.e., Gopherus agassizii). While certain examples presented herein may relate to the particular case of the desert tortoise, the teachings of the present disclosure are applicable to facilitating the co-existence between the solar field and animals other than desert tortoises according to one or more contemplated embodiments.
One or more of the following features can be used to facilitate the co-existence between a solar field and an animal, such as the desert tortoise: (i) measures are taken to minimize or eliminate the likelihood of damage to an animal or its habitat by a maintenance vehicle used for heliostat cleaning or maintenance even if one or more of these measures reduce the efficiency of the solar power system; (ii) the maintenance vehicles are operated in a manner so even in the ‘worst case’ an overwhelming majority of the field (e.g., at least 95% or 99% or 99.5% of the field) is designated as a “no-drive” zone where motor vehicles are not permitted to operate and/or physically constrained from operating; (iii) the solar field includes a plurality of heliostats (for example, at least hundreds or thousands of heliostats) deployed such that the mirrors of the heliostats are supported by a relatively thin pole and are situated high enough to allow free passage of most desert animals underneath; (iv) the area of ground disturbed when installing the thin-pole-mounted heliostats is minimal, thereby minimizing the impact upon wildlife in the region; and (v) the mirrors of the heliostats are large enough to provide shade relief to animals during the daytime.
Referring now to
In an embodiment, a secondary reflector can receive the reflected insolation 10 from the heliostats 12. The secondary reflector can then reflect the insolation downward to a receiver located at or nearer to ground level. In embodiments, two or more solar towers 18 can be provided in a single solar field 16 or in respective solar fields 16. Each tower 18 can be associated with a respective solar system receiver, for example, a solar system steam receiver. In an embodiment, at any given time, a given heliostat may be directed to a solar receiver of any one of the towers.
In an embodiment, more than one solar receiver 20 can be mounted in tower 18. The aim of the heliostat may be adjusted to move the centroid of a reflected beam 10 projected at the tower 18 from one of the solar receivers in the tower 18 to another of the solar receivers in the same tower. Solar receivers 20 can include any combination of steam generators, steam superheaters, steam reheaters, photovoltaic panels, molten salt receivers, air receivers, helium receivers, particle receivers, or any other receiver configured to convert solar energy to electricity or heat.
Towards this end and referring to
The maintenance vehicle 30 can proceed along a drive path between heliostats 12A, 12B, which are sufficiently spaced apart to allow the vehicle 30 to pass. For example, the maintenance vehicle 30 can have a maximum width D30 that is less than a distance between the heliostats 12A, 12B. The heliostats 12A, 12B may be sufficiently spaced apart that even when angled or aiming at the receiver, the distance D12AB between the outermost parts of the heliostats 12A, 12B is still greater than the width D30 of the vehicle 30 to allow the vehicle 30 to pass. Alternatively, the heliostats 12A, 12B may be arranged closer together such that outermost parts of the heliostats interfere with the vehicle 30. In order to thus let the vehicle 30 pass, the mirrors of the heliostats 12A, 12B can be controlled to move to a horizontal position, such that a distance Dmax between the horizontal mirrors is greater than the width D30 of the vehicle.
While heliostats 12A, 12B adjacent to the drive path of the vehicle 30 may be directly accessible to the vehicle 30, others of the heliostats 12C-12E away from the path may be isolated or buried with respect to the drive path. The maintenance vehicle 30 can include an arm 34 that can reach over heliostats to access these buried heliostats 12C-12E. The arm 34 can be a robotic arm with a generally vertically extending portion 36A, a generally horizontally portion 36B, and a generally vertically extending portion 36C terminating in a cleaning effecter 38. One or more portions of the arm 34 can be telescopic to enable changes in length that can reach over the heliostats adjacent to the path, e.g., heliostats 12A, 12B, to access buried heliostats, e.g., heliostats 12C-12E. Of course other arrangements for the arm 34 that allow access to the buried heliostats are also possible according to one or more contemplated embodiments. For example, vehicle 30 can be provided with a crane for reaching over heliostats adjacent to a drive path of the vehicle (see
Examples of a maintenance vehicle 30 include but are not limited to cleaning vehicles, e.g., for facilitating mirror washing, as well as other types of heliostat maintenance vehicles, e.g., for repairing and/or replacing heliostat mirrors. The maintenance vehicle 30 can have a length, width, and height, each of which is at least 0.5 m, at least 1 m, at least 1.5 m, at least 2 m, at least 3 m, or at least 10 m. A ratio between different dimensions of the maintenance vehicle 30 (i.e., ratio between one of length, width, and height, and another of length, width, and height) can be at least 0.25, at least 0.5, at least 0.75, at least 1, at least 1.25, at least 1.5, at least 2, or at least 4. Alternatively or additionally, the ratio between different dimensions of the maintenance vehicle 30 can be at most 0.025, at most 0.5, at most 0.75, at most 1.0, at most 1.25, at most 1.5, at most 2.0, at most 4.0, at most 6.0, at most 8.0, or at most 10.0. The maintenance vehicle may have any type of vehicular shape, including, but not limited to, rectangular prismatic or substantially cylindrical.
Maintenance vehicle 30 may be a relatively large vehicle, such as a flatbed truck or similar vehicle (see
For a maintenance vehicle designed to clean the surface of the mirror 13 of the heliostats, the cleaning end 38A of the arm 34 can include, for example, a contact cleaning element 37, as shown in
One or more cameras 38F may be attached to the cleaning effecter 38 and/or one or more cameras 30F may be attached to the vehicle 30 to acquire images of heliostats. The images may be acquired from multiple angles while the vehicle is stationary or moving (using the multiple positions of the vehicle during movement to acquire multiple views). A controller may acquire the images and process to calculate a position and orientation of heliostats to be cleaned. The images may also be processed to determine if heliostats need to be cleaned. The heliostat position and orientation may then be confirmed to lie within predetermined ranges to allow cleaning and/or may be accurately and precisely calculated to control the orientation and positioning of the cleaning effecter 30.
As used herein, a heliostat is considered a buried relative to a particular maintenance vehicle if there is no path for any set of heliostat mirror orientations by which the vehicle may come into direct contact with the heliostat without first coming into contact with or colliding with another heliostat of the solar field. In other words, for a buried heliostat, every path from an initial location of the vehicle (or a location outside of the solar field) to the buried heliostat would require a collision with one or more other heliostats other than the buried heliostat.
The terms buried heliostat or conditionally-accessible heliostat refers to the ability of a particular vehicle to come into contact with the heliostat in view of the geometric properties of the vehicle and the geometric properties and layout of the heliostats of the solar field. When the heliostat is considered buried, contact between the vehicle and the buried heliostat is prevented by other heliostats for all possible heliostat mirror orientations/configuration for the set of all heliostats in the solar field. As will be discussed below, when the heliostat is conditionally accessible, this refers to the prevention of contact under certain conditions (i.e., mirror orientations/configurations) only.
When a vehicle is referred to as coming into contact with a particular heliostat above, this refers to the ability of the vehicle body to directly contact the heliostat at a position along the drive path of the vehicle and not by using an elongated arm 34 to reach the heliostat. Thus, when a vehicle 30 is designated as being able to contact a particular heliostat, it refers to a location on the body of the vehicle and/or on a wheel (or track or tread or tread for tracked/treaded drive vehicle) and/or any location on the vehicle within 4 m or 3 m or 2 m or 1 m of the vehicle's center of mass, which may physically contact or touch the particular heliostat.
Certain heliostats may block direct access to the buried heliostat by the maintenance vehicle 30 because the heliostats have been deployed relatively closely to each other in a relatively dense fashion, the mirrors of the heliostats are sufficiently large enough so as to block passage between adjacent heliostats, and/or the heliostats have been deployed in a particular geometric fashion (e.g., staggered) that may limit maneuverability of the maintenance vehicle among the heliostats (e.g., due to the vehicle's turning radius or the vehicle's length).
In embodiments, the heliostats 12 in a solar field 16 or in a particular portion of a solar field 16 may be arranged such that the space between adjacent heliostats is insufficient for a maintenance vehicle to pass between. The maintenance vehicle may thus only be able to traverse the solar field 16 or portions thereof via well-defined drive zones or lanes. Referring now to
The drive zone may be defined relative to one or more dimensions of maintenance vehicle 30 in that one may constitute a drive zone for a relatively smaller vehicle may not constitute a drive zone for a relatively larger vehicle. In the solar field 16, at least a majority or most (e.g., at least 80% or 90% or 95% or 99% or more) of the solar field 16 can be considered part of a “no-drive” zone. A maintenance vehicle 30 is unable to access or move through the “no-drive” zone, thereby providing cover and/or sanctuary to animals within the solar field. Thus, the possibility of damage to an animal by movement of in the solar field is greatly reduced and/or minimized.
Moreover, the arrangement of heliostats can allow for movement of animals through the solar field 16, even in the “no-drive” zones where heliostat density may be significant. Referring now to
The area underneath heliostat 12 is defined by the mirror 13 being in a substantially horizontal orientation, thereby defining a first horizontal clearance L1 and a second horizontal clearance L2, each having a width (not shown), in which an animal may roam free unobstructed by the heliostat 12 and/or a maintenance vehicle 30. A support structure 15, such as a pylon, holds the mirror 13 at a specific orientation. The support structure 15 provides an obstruction at ground level having a length L3 and a width (not shown) which an animal would not have access too. However, the length L3 is substantially smaller than the lengths L1 and L2, thereby allowing at least a majority or most of the region underneath a heliostat 12 to be accessible to an animal, such as the desert tortoise. It is noted that desert animals, including but not limited to desert tortoises, tend to be shorter than the vertical clearance H1 provided by the heliostats.
Control of maintenance operations and/or actual operation of the solar power system, including the heliostats in the solar field and/or electricity generation, may be based on a number of factors including, but not limited to, a cleaning schedule, animal information, and optimizing energy production. For example, referring to
Regarding animal information 62, the control system 60 may take into account one or more different factors, including, but not limited to, observed animal location, predicted animal location, observed animal movement, predicted animal movement, observed animal habitat location, and/or predicted animal habitat location. For example, an animal in the solar field 16 may be tagged with a radio transmitter or other tagging mechanisms such that the location of the transmitter or tag sufficiently describes the location of the animal. In another example, radar, sonar, ultrasound, infrared imagers, and/or visual light imagers may be used to monitor the location and/or movement of the animal. In another example, data regarding an animal location or movement may be used to predict location of the animal at a later period of time, to predict movement of the animal at a later period of time, or to predict a location and shape of an occupancy zone of an animal or an animal's habitat (see the discussion associated with
One or more image-processing techniques or combination of image-processing techniques can be used to determine and/or predict animal location, movement, and/or habitat. For example, it is possible to acquire either a static image and/or a series of images (e.g., video) using one or more cameras at one or more locations in the solar field 16 and/or on any maintenance vehicle 30 and/or a imaging vehicle (i.e., smaller and/or more mobile with a maintenance vehicle) and/or at any other location capable of imaging a portion of the solar field 16. One non-limiting example of such an image-processing technique relates to the motion-detection routines that are commonly employed by digital cameras. In yet another example, a database of images of one or more ‘target species’ is maintained, and it is possible to attempt to match a candidate image from the solar field, which may or may not include an animal, with one or more image of animals in the database of images of the target species, e.g., endangered or threatened species. Such a database may be included, for example, in memory 64.
Alternatively, acoustic systems such as acoustic imaging, or passive audio detection and pattern recognition may be used to locate and identify animal movement and location information and events. For example, locations can be determined by acquiring audio from multiply positioned microphones and triangulating to determine position and velocity. Further prediction information may be generated based on models of animal behavior and current position and trajectory as well as historic position and trajectory information. In all embodiments where optical methods and apparatus are described, it will be understood that these may be replaced by such acoustical methods and apparatus where practical to provide the identified ultimate functions. In addition satellite or aerial imagery (visual or non-visual spectrum including radar, infrared, ultraviolet imaging data) may be used to predict movement of animals or other vulnerable areas of concern and provided as input as described above to systems for route planning.
In embodiments, an image and/or any other physical reading of a region of the solar field 16 may be classified as either (i) indicative of a presence of the non-domestic animal and/or (ii) not indicative of the presence of the non-domestic animal. This classification may depend on the physical readings from the field and/or one or more thresholds for deciding when the data indicates the presence of an animal in the solar field. The values of these thresholds may depend upon the costs associated with a “false positive” (i.e., determining that there is an animal present when in fact no animal is present) and with a “false negative” (i.e., determining that there is no animal present when in fact there is an animal present). These thresholds may be determined on a per-species basis, where more consideration, such as lower threshold values which may lead to more false positives, is given to endangered or threatened species. Information provided to control system 60 regarding animal information 62 may include input from a human operator or expert, such as a naturalist. For example, images of portions of the solar field may be provided to a human operator for further classification, i.e., determining if an animal is actually an endangered species necessitating a lower threshold value.
The location of an animal habitat may be detected in a number of ways. In one example, naturalists may manually walk within solar field 16 and identify the locations of the animal habitat 74, including habitats that may be located underground and subject to disruption by a maintenance vehicle. In another example, images may be manually and/or automatically acquired and manually and/or automatically analyzed. In yet another example, the movements of an animal are tracked over time, and a location of the animal's domicile/habitat is determined based on the results of the tracking (see, for example, the discussion associated with
In addition to a database of animal images, memory can include images of various portions of the solar field 16 or of different scenarios for use by control system 60 in determining maintenance or control outputs 68. Additionally or alternatively, the cleaning history of heliostats and/or drive zones utilized can also be stored in the memory. As will be described in further detail below, certain heliostats may be left uncleaned or certain drive zones may be impassable due to the presence of an animal or its habitat. Memory 64 may store this information for access by control system 60. For example, control system 60 may use this information in prioritizing heliostats for cleaning, re-aiming or compensating for dirty heliostats, and/or selecting drive zones or alternative drive zones for cleaning heliostats.
Additionally or alternatively, the control system 60 can receive information 66 regarding the solar field in order to determine a maintenance and/or operating output 68. For example, the solar field information 66 can include, but is not limited to, the location of heliostats 12 within the solar field 16, a desired operation of heliostats 12 (e.g., sun tracking information), maintenance vehicle size, maintenance vehicle location (e.g., position along a path), location of permanent drive zones for a particular maintenance vehicle (e.g., drive zones 40 or 42 in
The control system 60 may use the animal information 62, memory module 64, and/or solar field information module 66 to determine maintenance and/or operating criteria for the solar field 16. Output 68 from control 60 may be directed to one or more components of the solar field 16, such as the individual heliostats 12, maintenance vehicle 30, and/or any other component or system of the solar power system. For example, output 68 may include instructions or control algorithms for cleaning heliostats in the solar field. The control system 60 may determine a cleaning order of heliostats or select a particular pathway along designated maintenance vehicle drive zones, for example, to avoid an animal or habitat in a maintenance vehicle drive zone. Heliostat cleaning history may be used to determine priority for certain heliostats that haven't been cleaned in a predetermined period of time.
Additionally or alternatively, operation of the heliostats may be controlled by the control system 60 (or another control system based on the output from control system 60) to account for maintenance or lack thereof. For example, dirty heliostats may reflect insolation at the receiver 20 with less efficiency. Other heliostats may be re-aimed to compensate for the reduced reflected flux caused by the dirty heliostat. Optimization may be performed by the control system 60 to re-aim one or more of the heliostats, whether clean or dirty, so as to maintain a temperature uniformity of the receiver 20. Dirty heliostats may be re-directed at less temperature critical regions of the receiver or a different receiver, such as an evaporator section. The control system 60 can also control certain heliostats 12 to compensate for other heliostats currently undergoing maintenance. For example, when a portion of the solar field is being cleaned, heliostats in a second portion of the solar field may be re-aimed at the receiver 20 to compensate for the loss of flux due the heliostats being cleaned.
Control system 60 can also control the heliostats to reposition for cleaning For example, the mirrors 13 of the heliostats 12 may be re-oriented to a substantially horizontal position to allow for cleaning by the maintenance vehicle 30. Re-orientation of the mirrors 13 of the individual heliostats 12 may also occur to allow for a conditional drive zone for use by a particular maintenance vehicle. For example, the mirrors 13 of heliostats 12 substantially adjacent to a conditional drive zone may be re-oriented to a substantially vertical position to allow the maintenance vehicle 30 to pass by. Additionally or alternatively, the heliostats may be controlled so as to avoid any potential disruption to an animal located in the solar field. For example, if an animal in the solar field has a height sufficient to contact the heliostat mirror 13 for certain mirror orientations, the control system 60 may control the heliostats around the animal to avoid those mirror orientations.
Control system 60 may also control the operation of the maintenance vehicle 30 within the field. For example, the speed of maintenance vehicle 30 within the field may be limited in accordance with a threshold or confidence level that an animal is present, even if the animal is determined not to be currently in the maintenance vehicle drive zone. If it is estimated that there is only a small likelihood of a presence of an animal, the maintenance vehicle 30 may be allowed to operate in a particular region of the solar field subject to one or more constraints. Such constraints can include but are not limited to speed constraints, the use of water or cleaning solution to clean the heliostats, maximum flow rates of water or cleaning solution in cleaning the heliostats, noise constraints, and/or other operating parameters of the maintenance vehicle.
Referring now to
Alternatively or additionally, the maintenance vehicle 30 can wait in the drive zone 40 until the animal leaves the drive zone before proceeding along the designed pathway. Whether to wait or pursue an alternative pathway in view of the blockage by an animal may be determined based on a time the animal is estimated to be in the drive zone. This estimation may be made according to species identification (e.g., tortoises would be estimated to spend more time in the drive zone than faster moving animals), time of the year, and/or historical recorded speed in the solar field for the particular animals. In the event that the estimated amount of time is less than a predetermined threshold, then the maintenance vehicle may pause along the pathway until the animal no longer blocks the pathway. Otherwise, the maintenance vehicle may proceed along an alternative pathway to avoid the blockage.
In another example, control system 60 may be controlled to avoid cleaning certain heliostats responsively to a calculated predicted probability the animal will be in the pathway for an extended period of time or if operation of the solar tower system requires the flux from the heliostats. Cleaning of the heliostats may thus be delayed for a period of time, such as hours, days, weeks, or other period of time. Identification of dirty heliostats and time between cleanings may be stored in, for example, memory 64 and cleaning scheduled (for example, prioritized) responsively to this stored data. Because the mirror surface of an uncleaned heliostat may be dirty, the heliostat may be less effective at directing insolation at the tower 18 thereby reducing the system efficiency; however, the coexistence of threatened or endangered animal species within the solar field may outweigh this reduction in system efficiency.
Referring now to
Alternatively or additionally, daily or annual movement patterns of animal 72 may be analyzed to predict a location/movement of an animal 72 or to determine a location of the habitat 74. For example, the movement of an animal (or a set of animals) can be monitored over a predetermined period of time, such as several days, a week, a month, or even several months. Based on this data, it can be predicted where an animal or group of animals are generally located as a function of time of day or time of year. The maintenance vehicle may thus be prohibited from entering the predicted locations at those times. For example, a tortoise may spend more time in a first region early in the day (or during a particular time of year) and more time in a second region closer to night (or during another time of year). The maintenance vehicle may thus be prohibited from operating, or at least allowed to operate with certain constraints, in the first region early in the day and in the second region closer to night.
In embodiments, conditionally accessible pathways or conditional drive zones 90 may exist within the field 16 of heliostats 12 for a particular maintenance vehicle 30. Conditional drive zones 90, as used herein, refers to a particular pathway through the solar field 16 that is only accessible to a particular maintenance vehicle 30 when the mirrors 13 of heliostats 12 adjacent to the drive zone are in a particular orientation. For example, referring to
A heliostat, as used herein, can include either a single mirror (see
In order for the maintenance vehicle 30 to pass along conditional pathway 90, it is not necessary that the mirror be arranged in a substantially vertical position 13V. Rather, the heliostats 12 and maintenance vehicle 30 may be designed and arranged to allow the mirrors 13 to be at an angle different from vertical. For example, the width WT at the top of the maintenance vehicle 30 and the width WB at the bottom of the maintenance vehicle 30 may be designed to allow the maintenance vehicle 30 to pass along pathway 90 even when the mirrors 13 are oriented different from vertical 13V, as shown in
In contrast, heliostats 12 in other parts of the field 16 may be spaced closely together such that even when the mirrors 13 are arranged in a substantially vertical orientation 13V, the distance WHB between adjacent heliostat support structures 15 is less than the width WB of the maintenance vehicle. Thus, there may be insufficient distance between the heliostats to allow the maintenance vehicle 30 to pass through regardless of mirror orientation. It is appreciated that this due to the combination of the size of the maintenance vehicle 30, size of the heliostats 12, structure of the heliostats 12, arrangement of the heliostats 12, and/or separation distance between heliostats 12. Such heliostats may be referred to as buried heliostats since they are not directly accessible by the maintenance vehicle 30.
As shown in the left side of
Referring now to
In contrast, maintenance vehicle 30B is shorter in length than maintenance vehicle 30B, but has the same width. Although maintenance vehicle 30B was prevented from moving through the field of heliostats 12 by section 110, maintenance vehicle 30B is allowed to move along a conditional pathway 112 due to its reduced size. It is also noted that heliostats 12 adjacent to the conditional pathway 112 can be controlled and re-oriented to accommodate the turning and movement of the maintenance vehicle 30B as it proceeds along pathway 112.
Finally, maintenance vehicle 30C is shorter in length than either maintenance vehicle 30C, but has the same maximum width and a rounded front shape. Although maintenance vehicle 30B may necessitate re-orientation of the heliostats adjacent to its pathway 112 as it passes through the field, maintenance vehicle 30C is sufficiently small that it can turn and move along pathway 114 with the mirrors 13 of the heliostats 12 maintained in a consistent position. Accordingly, the concept of a buried heliostat and/or buried location (versus conditionally accessible heliostat or conditionally accessible location) is based on the vehicle as well as the arrangement of heliostats, in particular vehicle dimensions or turning radius.
Maintenance vehicle 30 may proceed along one or more conditional drive zones 90 and/or one or more permanent drive zones 40, 42 in order to clean and/or maintain the mirror 13 of one or more heliostats 12 in the field, including heliostats adjacent to a drive zone and/or isolated from the drive zone (i.e., buried). Such a cleaning can be a contact cleaning, as illustrated in and discussed with respect to
In embodiments, islands of buried heliostats in the solar field 16 may be bordered by permanent drive zones and/or conditionally accessible drive zones 90. For example, as shown in
The same “just-in-time” concept can also be applied to mirrors 13 to be cleaned. In other words, buried heliostats 12 would continue to focus insolation onto the receiver until cleaning of the particular heliostat 12 is imminent. Additional control of the heliostats may take into account obstruction of the heliostat line of sight during cleaning. For example, cleaning of one or more heliostats using arm 36B may block reflected insolation from one or more heliostats, which may have already been cleaned or are waiting to be cleaning, from reaching the designated aiming point on the target in tower 18. Accordingly, the heliostats may be temporarily re-aimed to avoid obstruction caused by the arm 36B.
It is also noted that the location of pathway 90 need not be a set pathway or a regular pathway (i.e., a concentric circle pathway as illustrated in
Heliostats 12 remote from the pathway 90 are not directly accessible by the vehicles 30; instead, intervening heliostats prevent direct access. To reach these buried heliostats 12, one or more arms 36B attached to the maintenance vehicles 30 may reach over the intervening heliostats 12. The arms 36B can include one or more cleaning ends 36C to clean multiple heliostats simultaneously. The cleaning ends 36C can include a brush or a short-range squirt or spray device, which may operate over a distance between the device and the mirror surface of less than 2 m. The maintenance vehicles 30 can continue along the circumferential conditional pathways 90, leaving behind a section 130 of substantially clean heliostats in their wake, as shown in
The maintenance vehicle 150 may include one or more cranes 152 with a boom 156 that can reach out into the field of heliostats away from the conditional pathway 90. A roller-type cleaning device 154 or any other type of cleaning device may be supported by the boom 156 for providing direct contact with the mirror 13 (see
In embodiments, the heliostat density and/or arrangement may not be consistent throughout the solar field 16. Rather, heliostat density may vary depending upon location in the solar field 16. For example, the heliostat density, as measured by heliostats per unit angle, may increase toward the outer edge (i.e., away from the tower 18) as compared to the inner portion of the field 16. The heliostat density may increase by a factor of 1.2, 1.5, 2, 3, or 5 between an inner portion of the field 16 and an outer portion of the field 16.
The heliostat density for a region/section of the solar field is the number of distinct heliostats within the region (or sub-region) of land divided by the area of the region/section of land. The region/section of land may be any shape including but not limited to rectangular, wedge-shaped, annular-shaped, triangular, or any other shape. It is appreciated that in a single solar field some regions may have some sub-regions with a greater heliostat density and other sub-regions with a lesser heliostat density. For example, it may be advantageous to deploy heliostats at a greater heliostat density closer to a given tower, and with a lesser heliostat density farther from the tower(s).
Although not an explicit requirement, any of the embodiments described herein may refer to “single-tower” systems where heliostats 12 associated with a tower 18 and/or configured to re-direct insolation to a tower 18 or portion thereof substantially only re-directs insolation to a single tower 18, even if more than one tower 18 is located at a given solar power system site. This feature may apply to any heliostat and/or set of heliostats (for example, north-field heliostats and/or south field heliostats and/or west field heliostats and/or east-field heliostats). In some embodiments, no insolation is re-directed to other towers 18 from the heliostats associated with the single tower 18.
Over a period of time (for example, at least one week, at least 1 month, at least 3 months, at least 6 months, at least 9 months, at least 1 year, at least 2 years, or at least 3 years), a heliostat 12 or group of heliostats that re-directs insolation to a solar tower 18 may, in fact, be configured such that less than 30%, less than 20%, less than 10%, less than 5%, less than 3%, or less than 1% of all of the insolation re-directed by the heliostat 12, by each heliostat 12 of the group, or by the group as a whole is directed to other towers 18 other than the designated solar tower 18.
The term geometrically efficient refers to a ratio between a size of a lone heliostat seen from a tower and/or the amount of insolation reflected by a lone heliostat at a particular time of day/year and the physical size of the heliostat. Thus, when looking down from the top of the tower upon a solar field, southern heliostats may appear smaller than equivalently-sized and equivalently-located northern heliostats due to cosine effects. The term lone heliostat efficiency parameter of a heliostat deployed in a location refers to the size of the heliostat as it would appear viewed from the target at or near the top of the tower for the case where there are no other heliostats in the field. The term lone heliostat efficiency parameter may be used interchangeably with geometrical efficiency of a heliostat.
A distance between the tower and the heliostat relates to a distance between a centroid of the tower at ground level and a location of the heliostat. A location of a heliostat is defined as the ground-level downward projection of the heliostat centroid. A distance between two heliostats is the Cartesian distance between their respective locations. The size of a heliostat or the area of heliostat is the area of all mirrors of its mirror array. Some heliostats can include a single mirror 13, as shown in, for example,
The total mirror size or the aggregate mirror size for heliostats deployed in a region/section of land is the total/aggregate size of all of the heliostats (i.e. the aggregate area of all mirrors where each heliostat bears a mirror assembly having one or more mirrors) within the region/section/sub-section of land. The various heliostats in this land may include any number of mirrors in the mirror assemblies.
It is also possible to compute the total mirror density or the aggregate mirror density for heliostats deployed in the region/section of land as the ratio between the total mirror size or the aggregate mirror size and the area of the land region or sub-region. Measurement units for heliostat density are number of heliostats per unit of area, e.g., heliostats per m2. On the other hand, mirror density is typically dimensionless, e.g., as mirror area per unit of land area.
Cardinal directions refer to due north, due east, due south and due west (in any order). A time that is referred to as late afternoon may begin any time after 1 PM, after 2 PM, or after 3 PM local solar time, while it may end at sunset, 15 minutes before sunset, 30 minutes before sunset, 60 minutes before sunset, 90 minutes before sunset, or even 2 hours before sunset.
A location at or near a top of a solar tower may be at the top within a tolerance that is at most 25% of a height of the tower, at most 20% of a height of the tower, at most 15% of a height of the tower, at most 10% of a height of the tower, at most 15% of a height of the tower, or at most 5% or a height of the tower.
A non-dumping period of time relative to one or more target(s) 20 at or near the top of the tower is a period of time whereby the flux incident upon the target 20 is at most 95%, at most 90%, at most 85%, or at most 80% of a peak flux incident upon the target. This peak flux may be for a given day as a per-day peak flux, a given month as a per-month peak flux, or a given year as a per-year peak flux. Typically, the non-dumping period of time is not at night or in a no-insolation or extremely low insolation period of time. During the non-dumping period of time, the amount of flux may be at least 15%, at least 20%, at least 30%, at least 40%, at least 50%, or at least 60% of the peak flux incident upon the target at or near the top of the tower. For example, the non-dumping periods of time may occur early in the morning, late in the afternoon, and/or during the winter. However, this is not a limitation, and may depend on one or more physical parameters of the solar power system.
When referring to a square grid with respect to the disclosed embodiments, a square grid within a square can be aligned with the corners if the corners of the square are grid points. The distance between horizontally and vertically adjacent grid points is the grid parameter of the square grid. An x % square grid within an enclosing square has a grid parameter whose length is x % of the length of a side of the enclosing square. For example, a 1% square grid that is aligned with the corners of an enclosing square given by points {(x1,y1), (x1,y2), (x2,y1) and (x2,y2)} will have grid points at {(x1,y1), (x1+0.01*(x2−x1),y1, (x1+0.02*(x2−x1),y1) . . . (x1+0.99*(x2−x1),y1), (x2,y1), (x1,y1+0.01*(y2−y1)), (x1+0.01*(x2−x1),y1+0.01*(y2−y1)), etc.}.
The center for each of the locations closest to the tower, i.e., L1, L4, L7, L10, L13, L16, L19, and L22, can be at a distance from the tower 18 of, for example, approximately 350 m. The center for each of the locations farthest from the tower, i.e., L3, L6, L9, L12, L15, L18, L21, and L24, can be at a distance from the tower 18 of, for example, approximately 750 m. The center for each of the other locations, i.e., L2, L5, L8, L11, L14, L17, L20, and L23, can be at a distance from the tower 18 of, for example, approximately 550 m.
Table 2 below shows heliostat density values for the different locations identified in
To illustrate, locations L13 and L1 shows that the densities in the southern field 220S and the northern section 220N at the same distance are different. A south-north density ratio can be defined for locations similarly situated with respect to the tower 18 in the south section 220S and the north section 220N. In particular, for L13 and L1, a south-north density ratio is 2.32/2.09=1.11. Comparing the L14 value and the L2 value results in a south-north density ratio of 2/1.66=1.2. Comparing the L15 value and the L3 value results in a south-north density ratio of 1.62/1.25=1.3. Accordingly, with increasing distance from the tower 18, the south-north density ratio between similarly arranged locations (i.e., at equal distance from the tower 18) may increase.
The heliostat density in a southern portion of the solar field may exceed the heliostat density in the northern portion of the solar field. The embodiment described in
In the northern hemisphere, southern heliostats may tend to be weaker than their similarly situated northern counterparts due to cosine effects. In contrast, in the southern hemisphere, northern heliostats may tend to be weaker than their similarly situated southern counterparts due to cosine effects. It may be advantageous then to deploy heliostats at an increased density in regions with weaker heliostats (relative to the regions with stronger heliostats) in order to provide additional insolation-reflection capacity to compensate or at least partially compensate for the weakness. Additionally or alternatively, the weaker heliostats may include larger mirrors.
In addition, a west-east density ratio can also be defined. To illustrate, locations L7 and L19 shows that the densities in the western section 220W and the eastern section 220E at the same distance are different. A west-east density ratio can be defined for locations similarly situated with respect to the tower 18 in the western section 220W and the eastern section 220E. In particular, for L7 and L19, a south-north density ratio is 2.14/2.08=1.03. Comparing the L8 value and the L20 value results in a south-north density ratio of 1.88/1.75=1.05. Comparing the L9 value and the L21 value results in a south-north density ratio of 1.52/1.4=1.08. Accordingly, with increasing distance from the tower 18, the west-east density ratio between similarly arranged locations (i.e., at equal distance from the tower 18) may increase.
The heliostat density in the western portion 220W of the solar field may exceed the heliostat density in the eastern portion 220E of the solar field. Electrical tariffs for electricity in the afternoon period may be greater than electrical tariffs for electricity in the morning period. Accordingly, the placement of heliostats, for example, as described herein, may be optimized to maximize afternoon electricity production and/or afternoon insolation to the tower 18 in order to maximize the revenue or to maximize a revenue/field cost function. Such a revenue/field cost function may take into account the density or number of heliostats and/or aggregate size of mirrors or mirror density, for example, in some sort of ratio or other function that captures revenue per heliostat or mirror capital cost. This maximization of afternoon electricity production and/or maximization of afternoon insolation to the tower may come at the expense of morning electricity production and/or morning insolation to the tower because the total number of heliostats and/or total amount of mirror area that may be deployed in the solar field may be fixed and/or constrained.
When designing a solar field for preferential production of afternoon power with a limited number of heliostats (for example, due to budgetary or geographic constraints), a greater number of heliostats may be arranged in the western portions of the field than the eastern portions. Even though the heliostats in the western section of the field may be weaker in terms of the amount of tower-received insolation as compared to similarly situated heliostats in the eastern section of the field, the arrangement of heliostats may be to prefer these weaker western heliostats for the purpose of generating elevated levels of afternoon electricity.
To design a solar field, a cost function can be established that constrains the total number of heliostats and/or total mirror area that can be deployed in a north-south field that includes northern portions and southern portions. The solar field may be required to have elevated afternoon production of electricity and/or elevated aggregate reflection of insolation to a target associated with a solar energy tower even at the expense of the morning electricity production and/or morning insolation redirection from heliostats to a solar tower target. In response to the cost function, a heliostat layout can be designed that specifies a deployment where there are more heliostats arranged in the southern portion of the field as compared to the northern portion of the field. The deployment may be according to any scheme and/or feature including, but not limited to, any combination of the schemes and/or features disclosed herein. Alternatively or additionally, a cost function can be used to design a solar field where more heliostats are deployed in the western section of the field than in the eastern section and/or at a greater density in the western section than in the east eastern section.
The concept of north-south and east-west mirror images is illustrated in
As shown in
The following paragraphs apply to tower-heliostat systems based in the northern hemisphere, where the total number of heliostats (or the aggregate mirror size of all heliostats) south of the tower exceeds the total number of heliostats (or the aggregate mirror size of all heliostats) north of the tower. For systems based in the southern hemisphere, the total number of heliostats (or the aggregate mirror size of all heliostats) south of the tower would exceed the total number of heliostats (or the aggregate mirror size of all heliostats) north of the tower. The description below can thus be applied to the southern hemisphere embodiment by interchanging the recitations of northern and southern to account for this feature.
Referring to
As shown in
For each visited position of the center 304 of region 302 within the range 308, another comparison of total number of heliostats and/or total mirror size in the northern version of region 302 versus the total number of heliostats and/or total mirror size in the southern version of region 302. This can be carried out for the large or even infinite number of positions within range 308. Thus, it is possible to effect a number of comparisons. In some embodiments, a comparison may be performed each time the center 304 of region 302 is moved. Alternatively or additionally, the center 304 of region 302 can be restricted to movements equal to 5%, 1%, 0.1%, or 0.01% of a dimension of the range 308, i.e., the length of a side of the square defined by range 308.
Based upon this movement distance, it is possible to discuss a set (for example, a large set) of one-by-one comparison between the northern sub-region and its southern mirror counterpart according to the positions within range 308. For this set of comparisons, a majority of the comparisons in the set may exhibit one or more of the following features: (1) the number of heliostats in both the northern sub-region and the southern sub-region is at least 2, 3, 5, or 10 heliostats, or at most 12, 10, 7, 5, or 3 heliostats; (2) a ratio between the total number of heliostats in the southern region, e.g., region 287A, to the total number of heliostats in the northern region, e.g., region 283A, is at least 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.1, 1.12, 1.14, a 1.16, 1.17, 1.18, 1.19, or 1.2; (3) a ratio between the aggregate size of the total number of heliostats in the southern region, e.g., region 287A, to the aggregate size of the total number of heliostats in the northern region, e.g., region 283A, is at least 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.1, 1.12, 1.14, a 1.16, 1.17, 1.18, 1.19, or 1.2. For example, in the
A parameter α may be defined for a given location in the solar field. In particular, the parameter α may define a ratio between a distance between the given location and the tower, and a height of the central tower and/or of the target at or near the tower of the tower. Locations with a larger a may generally be further from the tower. For example, for a larger field (i.e., greater than 50,000 heliostats) and a tower height of between approximately 130 m and 140 m, when distance to the tower from a specific location is 550 m, then the a parameter may be between about 3.9 and about 4.25. In embodiments, a majority, a substantial majority, or even an entirety of the northern region 252 and the corresponding southern region 254 may have an alpha value that exceeds 2.5, 2.7, 3, 3.25, 3.5, 3.75, 4, 4.25, 4.5, 4.75, 5, 6, 7, 8, 9 or 10.
In embodiments, co-located multiple single-tower solar fields can be provided at a single geographic location, as shown in
A point-schematic diagram of a solar field is a to-scale diagram describing heliostat layout in the solar field whereby individual heliostats are represented by single dots, each respectively located at the respective heliostat location (see, for example,
A dominant observable layout pattern in some point-schematic diagrams of solar field is where most or all heliostats within in non-local regions of the solar field are an in arc layout pattern, which is typically very ordered. According to these layouts, within non-local regions having the arc layout heliostat deployment scheme, there is generally no visually discernable disorder observable within these non-local regions in their point-schematic diagrams. In other examples, the heliostat layout may be constrained so that heliostats are deployed at regular intervals on straight lines that traverse significant, non-local portions of the solar field. In both cases, the heliostats can be deployed in regular intervals on the lines or on the arcs/curves. Thus, deployment of heliostats at substantially regular intervals on lines or curves/arcs contributes to the lack of visually discernable disorder observable in the point-schematic diagram.
In order for the heliostat layout to be considered line- or arc-pattern dominant, it is generally clearly discernible to the naked eye viewing a point-schematic diagram that the heliostats are regularly deployed on an arc or curve, such as shown in
In embodiments, the efficiency of a solar tower system can be optimized by deploying some, most, or substantially all of the heliostats that are relatively far from the tower in a manner such that these far heliostats are arranged in a pattern generally considered disordered. For example, the far heliostats may be distributed in a manner not constrained to situations where a line pattern or an arc pattern that is consistent over non-local regions is the dominant layout pattern and/or not constrained to a highly ordered layout patterns lacking any significant visible degree of disorder. By relaxing such constraints, and by employing one or more optimization routines (i.e., where the routines may enjoy more degrees of freedom, over significant regions of the solar field but not necessarily an entirety of the field), improved efficiency may be realized over more ordered layout schemes.
Heliostats may be arranged in a manner that facilitates higher efficiency conversion of insolation into a useful form of energy such as steam, electricity, and biomass.
By removing the constraints requiring the larger-scale line or arc patterns, even though the field layout may be less aesthetically appealing, it is possible to obtain a more efficient heliostat layout. Efficiency may relate to the total intensity or amount of insolation directed to the receiver in a tower as a function of the capital investment cost. For example, efficiency may be measured as the total reflection capability divided by some measure of the total area of the mirrors of the heliostats. In addition, the relatively disordered field may be more difficult to maintain due to the lack of predefined pathways through the heliostat field. The use of conditional drive zones in these disordered regions may allow the use of the disordered pattern while allowing access to heliostats in these regions by a maintenance vehicle.
Without the requirement for an ordered pattern, the layout resulting from a large-scale optimization routine may exhibit one or more of the following features:
In embodiments, methods for computing a heliostat layout can include global optimization, metaheuristic, and/or other computational techniques. Such computation of the heliostat layout may be in a manner where the heliostat layout is substantially free from the constraints associated with ordered or arc/line-dominant patterns over a non-local region of the field. The resulting heliostat layout may be characterized by a relatively high heliostat field insolation-redirection efficiency parameter.
In Field 2, there may be a difference in the arrangement between heliostats proximal to the tower 18, for example, in central region 402, and heliostats distant from the tower 17, for example, in outer regions 400. A distant heliostat can be defined as a heliostat whereby a ratio between the tower-heliostat distance and the height of the tower is at least 2, 2.5, 3, 3.5, 4, 4.5, 5, 7.5, or at least 10. Within this central region 402, heliostats may be arranged in a more ordered, relatively dense arrangement, while heliostats in the outer regions 400 may be substantially disordered.
Multi-region schemes can be developed wherein for regions close to the tower 18, e.g., region 402, heliostats are deployed in some sort of regular grid pattern. This regular grid pattern, or other types of packing patterns, can improve and/or maximize heliostat packing even at the expense of using too many heliostats or too much aggregate mirror area to maximize a per-mirror area metric. In these close regions, the dominant heliostat layout pattern may be a very ordered grid pattern such as a triangular grid pattern or a hexagonal close packed pattern.
For regions further from the tower 18, e.g., regions 400, where the heliostats are distant from the tower 18, a much less ordered heliostat layout scheme or an irregular/disordered scheme may be used. When a layout pattern exhibits a significant amount of irregularity and/or disorder this means that the irregularity and/or disorder are clearly discernible upon viewing a point-schematic diagram of a solar field. However, this does not require a mostly-disordered or completely-disordered layout scheme. In embodiments, the disordered layout features may co-exist with one or more additional features discernible from the point-schematic diagram of a solar field.
In embodiments, by optimizing heliostat layout for ground coverage as viewed from a location at or near the top of the tower (or any other above ground location) and by not constraining heliostat layout to require deployment of heliostats on lines or regular arcs/curves (or by requiring heliostat layout on lines or arcs but not further constraining the layout so as to require layout of most heliostats at regular intervals on the lines or arcs), it is possible to achieve a relatively high level of mirror-induced ground obscuring for a given heliostat density and/or mirror density. This relatively high level of ground coverage by heliostats at one or more locations in the solar field may be useful for facilitating a more efficient conversion of solar radiation into useful energy.
The concept of ground coverage is discussed below with reference to
Other than heliostat density and/or mirror density, ground coverage for a specific area of the solar field in which heliostats are deployed may depend on a number of additional factors, including, but not limited to: (1) the time of the day and/or day of the year; (2) the geographical location of the solar field; (3) the actual heliostat layout of the portion of the solar field for which ground coverage is being analyzed (e.g., the geometry of the heliostats, such as the distance between heliostats, angles of vectors connecting heliostats, or any other aspect of heliostat layout); (4) the size, shape, or height of each heliostat; (5) the height of the tower (or the height of the viewing location whose height and position is made to coincide with the location of the solar target); and (6) the distance of the portion of the solar field (i.e. for which ground coverage is being determined or analyzed).
In embodiments, ground coverage can be analyzed at one or more locations in the solar field for one or more times of the day and/or one or more times of the year. For example, one or more heliostat layouts can be analyzed and assigned a score according to the ground coverage provided by the heliostat layout. For example, the viewing location can be a location of the solar target at or near the solar tower. The score may be assigned according to a selected time of the day or year, or according to some time-average or weighted time-average. Alternatively or additionally, the score may be computed by analyzing the ground coverage in multiple locations in the solar field. For a given number of heliostats and/or a given amount of mirror to be deployed in a given area of land, there may be number of potential heliostat layouts. When heliostats are not restricted to deployment on lines or regular arcs/curves, the number of potential heliostat layouts may indeed be quite large. Each of these potential heliostat layouts may be associated with a different ground coverage score.
Embodiments described herein can relate to techniques for generating a solar field design describing the locations of at least some of the heliostats in a central-tower solar thermal plant. A search of the space of heliostat configurations can be performed to analyze various ground coverage or other parameters derived from ground coverage. The search space, which corresponds to the space of possible heliostat layout schemes, may be quite large. Rather than attempting to employ a brute force technique, a global optimization algorithm can optimize the locations of at least 50, 100, 500, 1000, 5000, or more of the heliostats in the field.
An optimization tool may be employed to obtain an approximation of a global optimum for a given ground-coverage-derived function in the large search space of heliostat layouts or for certain portions of the heliostat field. Optimization tools can include, but are not limited to, global or local search stochastic/probabilistic tools, metaheuristic algorithms, genetic algorithms, simulated annealing algorithms, hill-climbing algorithms, genetic algorithms, dynamic programming, and/or ant colony algorithms. A ground-coverage-derived function can include a time-averaged total ground coverage throughout the field or a region of the field. This time-averaged ground coverage function may be a weighted function giving preference to greater ground coverage in the summer months and/or in the late afternoon hours at the expense of other times of the day and/or other days of the year.
In embodiments, a method for determining a solar field layout can include first selecting one or more portions of the solar field for heliostat placement. Locations can be determined for a group of heliostats, such as heliostats within a larger area of the solar field, such area constituting is at least 50%, 70%, 80%, or 90% of the solar field. Using one or more optimization techniques, a field layout scheme for the selected portions of the solar field can be generated. Subsequently, heliostats may be installed in the solar field according to the generated layout scheme.
The generation of the field layout scheme may be such that ground coverage or ground obscuring by heliostats as viewed from a location at or near the top of the tower can be optimized. Ground coverage/obscuring may be just one metric of the overall ability of heliostats in a region of the solar field to re-direct insolation to the top (or near the top) of the solar tower. Other metrics may also be used. Additionally or alternatively, for one or more non-local regions of the solar field, such as regions of the solar field that are relatively distant from the tower, when optimizing the layout scheme for the one or more portions of the solar field, significant amounts of clearly discernible disorder may be introduced into the layout scheme.
The presence of the mirror 13 of heliostat 12 will obscure the ground as viewed from viewing location 500. Due to different orientation of the heliostat at different times of the day, the size and/or location of an obscured region can change for a given heliostat 12. For example, due to the orientation of the mirror 13MO in the morning, an obscured region 502 is generated with respect to the viewing location 500, while the orientation of the mirror 13AF in the afternoon may result in a smaller obscured region 504. For any time of the day in the northern hemisphere, the size of a ground obscured region caused by a lone heliostat at a given distance due north of the tower may be greater than the size of the ground obscured region that would be caused by the same lone heliostat if deployed at the same distance due south of the tower. In the southern hemisphere, this situation would be reversed such that the southern heliostats may cause more ground obscuring per heliostat than corresponding northern heliostats.
By moving the heliostats farther apart, as shown in
The portion of a mirror 13 that is blocked and/or the size of the obscured region, e.g., 510, and/or the distance between obscured regions, e.g., size of gap 524, may be used in the optimization of heliostat field layout. By not constraining the heliostat layout to regular consistent patterns and by effecting a ground coverage per density range optimization procedure that includes ground coverage considerations, an efficient heliostat layout may be obtained.
By refraining from imposing an arc or line constraint upon a solar field layout, the amount of ground obscuring heliostats (i.e., either at a point in time or time-averaged over one or more time periods) may be optimized. In embodiments, this may relate to the case where heliostat locations are allowed to significantly deviate from any lines or arcs that may define regular or ordered patterns within the solar field. Additionally or alternatively, the deployment of heliostats may be restrained to, for example, concentric arcs; however, the heliostat placement along each arc can be substantially irregular to a significant degree.
Referring now to
The region of the irregular and/or disordered heliostat placement can be restricted to an outer portion of the field, such as regions 400 of the solar field shown in
In embodiments, the solar field of heliostats may provide any combination of any feature disclosed herein, including but not limited to any combination of the following feature (for ranges, any combination of upper and lower limits defines a possible range):
Referring to
In the various embodiments above or in the claims, the vehicle or truck may be equipped with a curved cow catcher type of device to harmlessly deflect animals away from the path of wheels. The blade may have a flexible edge to permit to hug the surface. Alternatively, a proximity detector (acoustic, infrared, or other) or imaging device (laser scanner, radar, camera, etc.) and a series of jets generators may be provided on such a cow catcher (or as an alternative) to push animals away from vehicle's path. Skirts may be provided on the sides to prevent animals from moving beneath the wheels.
Features of the disclosed embodiments may be combined, rearranged, omitted, etc., within the scope of the present disclosure to produce additional embodiments. Furthermore, certain features may sometimes be used to advantage without a corresponding use of other features.
It is, thus, apparent that there is provided, in accordance with the present disclosure, systems and methods for arranging, maintaining, or operating heliostats within a solar field. Many alternatives, modifications, and variations are enabled by the present disclosure. While specific embodiments have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles. Accordingly, Applicant intends to embrace all such alternatives, modifications, equivalents, and variations that are within the spirit and scope of the present invention.
The present application claims the benefit of U.S. Provisional Application No. 61/307,994, filed Feb. 25, 2010, U.S. Provisional Application No. 61/355,271, filed Jun. 16, 2010, U.S. Provisional Application No. 61/378,382, filed Aug. 30, 2010, and U.S. Provisional Application No. 61/380,237, filed Sep. 5, 2010, all of which are hereby incorporated by reference herein in their entirety.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US2011/026273 | 2/25/2011 | WO | 00 | 11/5/2012 |
| Number | Date | Country | |
|---|---|---|---|
| 61307994 | Feb 2010 | US | |
| 61355271 | Jun 2010 | US | |
| 61378382 | Aug 2010 | US | |
| 61380237 | Sep 2010 | US |
