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Optical signal aiming for heliostats

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Optical signal aiming for heliostats


Methods and systems for managing heliostat aiming toward a target are described. Solar rays incident on a reflective surface of a heliostat mirror are reflected toward the target. One or more optical signalers are arranged at positions about the target. An optical signal received from one of the one or more optical signalers is detected. An error in an orientation of the reflective surface is determined based on the optical signal.

Google Inc. - Browse recent Google patents - Mountain View, CA, US
Inventor: Ross Koningstein
USPTO Applicaton #: #20120279485 - Class: 126573 (USPTO) - 11/08/12 - Class 126 
Stoves And Furnaces > Solar Heat Collector >With Control Means Energized In Response To Actuator Stimulated By Condition Sensor >Including Sun Position Tracking Sensor

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The Patent Description & Claims data below is from USPTO Patent Application 20120279485, Optical signal aiming for heliostats.

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TECHNICAL FIELD

This specification relates to aiming heliostats toward solar energy receivers.

BACKGROUND

Heliostats can be used to collect radiation from the Sun. Specifically, a heliostat can include one or more mirrors to direct solar rays toward a receiver mounted on a receiver tower. Some types of heliostats are capable of moving their mirror or mirrors as the Sun moves across the sky, both throughout the day and over the course of the year, in order to more efficiently direct solar rays to the receiver. Solar rays that are directed to the receiver can then be used to generate solar power. A field of heliostats can be placed surrounding one or more receivers to increase the quantity of radiation collected and optimize the amount of solar power that is generated.

The solar energy can be converted to electricity by the receiver or a generator that is coupled to the receiver. Typically, a working fluid that circulates within a receiver is heated by solar energy incident on the receiver. The heated working fluid can then be used to power a turbine and generator to produce electricity.

SUMMARY

In general, in one aspect, a method for managing heliostat aiming toward a target is described. Solar rays incident on a reflective surface of a heliostat mirror are reflected toward the target. One or more optical signalers are arranged at positions about the target. An optical signal received from one of the one or more optical signalers is detected. An error in an orientation of the reflective surface is determined based on the optical signal.

These and other embodiments can each optionally include one or more of the following features. The orientation of the reflective surface can be adjusted in response to determining the error. Adjusting the orientation can include adjusting at least one of the azimuth or elevation of the reflective surface or adjusting the orientation can include adjusting the orientation along an axis other than along an azimuthal or elevational axis of the reflective surface. The one or more optical signalers can be multiple optical signalers and determining an error in an orientation can include determining which optical signaler of the multiple optical signalers transmitted the optical signal.

The one or more optical signalers can include multiple retroreflectors positioned about the target. The optical signal can be received from a particular one of the retroreflectors. In some implementations, determining the error in the orientation includes determining a frequency of a change in light that forms the optical signal and, based on the frequency, determining that the optical signal was received from the particular one of the multiple retroreflectors. In some implementations, determining the error in the orientation includes determining a color of light that forms the optical signal and, based on the color, determining that the optical signal was received from the particular one of the multiple retroreflectors. In some implementations, determining the error in the orientation includes determining a polarization of light forming the optical signal and, based on the polarization, determining that the optical signal was received from the particular one of the multiple retroreflectors. In some implementations, determining the error in the orientation includes determining a phasing of light forming the optical signal and, based on the phasing, determining that the optical signal was received from the particular one of the multiple retroreflectors. Based on determining that the optical signal was received from the particular retroreflector, the error in orientation can be determined.

Determining an error in an orientation of the reflective surface based on the optical signal can include determining that the optical signal exceeds a threshold signal strength. Two optical signals can be received from two optical signalers. Determining an error in an orientation of the reflective surface based on the two optical signals can include determining that a difference in signal strength between the two optical signals exceeds a threshold difference.

The target can be a receiver configured to receive solar rays. The target can be a location that is a distance away from a receiver that is configured to receive solar rays, such that solar rays from the heliostat mirror are not reflected to the receiver.

In general, in another aspect, a system is described. The system includes a receiver assembly that includes a receiver tower, a receiver mounted on the receiver tower, an aperture included in the receiver and one or more signalers positioned at one or more distances from the aperture. The receiver tower is a support structure configured to support the receiver. The aperture is configured to receive solar rays reflected from multiple heliostats. The one or more signalers are configured to receive solar rays reflected from at least one of the heliostats and, in response, to transmit an optical signal toward the one heliostat.

These and other embodiments can each optionally include one or more of the following features. The one or more signalers can be one or more retroreflectors mounted at one or more positions proximate to a circumference of the aperture. The one or more signalers can be multiple signalers and each signaler can be configured to transmit an optical signal that is different than an optical signal transmitted by each of the other signalers. Each signaler can be a retroreflector that is configured to transmit an optical signal that has a different frequency of change in signal than optical signals transmitted by the other signalers. Each signaler can be a retroreflector that is configured to transmit an optical signal that has a different color than optical signals transmitted by the other signalers. Each signaler can be a retroreflector that is configured to transmit an optical signal that has a different polarization than optical signals transmitted by the other signalers. Each signaler can be a retroreflector that is configured to transmit an optical signal that has a different phasing than optical signals transmitted by the other signalers.

The system can further include multiple heliostats. Each heliostat can include a reflective surface that is configured to reflect solar rays incident on the surface toward the receiver. Each heliostat can further include a sensor that is configured to receive optical signals from the one or more signalers. Each heliostat can include an actuator configured to adjust an orientation of the reflective surface and a controller. The controller is configured to determine errors in orientation of the reflective surface based on the optical signals received by the sensor and is further configured to provide signals to the actuator to adjust the orientation of the reflective surface in response to the determined errors.

The one or more signalers can be multiple signalers, and each signaler can be configured to transmit an optical signal that is different than an optical signal transmitted by the other signalers. The controller can be further configured to determine which particular signaler from the multiple signalers transmitted a particular optical signal based on the difference in optical signals transmitted by the multiple signalers. The controller can be further configured to determine that the received optical signals exceed a threshold signal strength. The controller can be further configured to determine whether a difference between signal strengths of two optical signals received from two optical signalers exceeds a threshold difference and determine an error in orientation based on the determination.

Particular embodiments of the subject matter described in this specification can be implemented so as to realize one or more of the following advantages. The amount of time a heliostat is reflecting sunlight off-target, that is, not toward a desired location at a receiver, can be minimized, thereby increasing the solar energy received by the receiver. An error detection system to detect that the heliostat is off-target can be formed using relatively inexpensive components. The optical signalers at the receiver, which in some implementations are retroreflectors, can be relatively inexpensive although durable and reliable devices that can endure the hot temperatures experienced at the receiver. For example, an optical signaler can be a retroreflector made with quartz, which can easily withstand high temperatures.

The details of one or more embodiments of the subject matter described in this specification are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a solar energy system including a receiver in a field of heliostats.

FIGS. 2A and 2B show schematic representations of the front surface of the receiver shown in FIG. 1.

FIG. 3 is a schematic representation of frequency and phase modulated optical signals and an error detection algorithm

FIG. 4 is a schematic representation of phased optical signals.

FIG. 5 shows a block diagram representing an example system that includes a receiver and a heliostat.

FIG. 6 is a flowchart showing an example process for maintaining a heliostat on-target.



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Previous Patent Application:
Fuel oil supply system from a remote source including recirculated heating of fuel oil and supplemented supply pressure
Next Patent Application:
Heliostat for collecting sunlight and method of controlling the same
Industry Class:
Stoves and furnaces
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stats Patent Info
Application #
US 20120279485 A1
Publish Date
11/08/2012
Document #
13100216
File Date
05/03/2011
USPTO Class
126573
Other USPTO Classes
126714, 126572
International Class
/
Drawings
7



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