Closed loop tracking system using signal beam
The invention is a system and method for heliostat mirror control. Here, each heliostat mirror generates a low intensity “signal beam”, directed at an angle off from the heliostat mirror's high intensity and sensor blinding “main beam” of reflected solar energy. The low intensity signal beams may be created by reflecting a small portion of the incident solar light at an angle from the main beam, by reflected artificial light, or from lasers shinning onto mirrors from known locations. The signal beams are detected by optical sensors mounted way from the main heliostat receiver focus, and can be used in a closed loop control system to efficiently ensure that individual heliostat mirrors in a heliostat array accurately track sunlight and direct the sunlight to a central receiver. Because heliostat mirrors need not be taken “off sun” for positioning, the system allows heliostat arrays to be run at high efficiency.
1. A closed-loop tracking system comprising:
a plurality of heliostats, wherein each of the plurality of heliostats comprises a mirror configured to generate a main beam and an optical element configured to generate a signal beam at an angular offset from said main beam, wherein each signal beam is spread over a range of angles;
a receiver configured to concurrently receive the main beam from each one of the plurality of heliostat mirrors; and
a signal beam target to concurrently receive the signal beam from each one of the plurality of optical elements, wherein the signal beams from the plurality of optical elements are concurrently transmitted to and received by the signal beam target.
2. The closed-loop tracking system in claim 1 , wherein each of the signal beams varies in color over the range of angles.
3. The closed-loop tracking system of claim 2 , further comprising an array of optical sensors configured to read said signal beams concurrently received at said signal beam target.
4. The closed-loop tracking system of claim 3 , wherein said array of optical sensors are coupled to said signal beam target.
5. The closed-loop tracking system of claim 4 , further comprising a computer configured to receive sensor data from said array of optical sensors and to control an orientation of said mirrors.
6. The closed-loop tracking system of claim 5 , wherein said computer is configured to determine if said mirrors are at an optimal position by using solar angle data as determined either by a solar angle sensor or by at least time and date.
7. The closed-loop tracking system of claim 5 , wherein said computer is configured to determine if said mirrors are at an optimal position by using data that includes relative spatial locations of said mirrors, said receiver, and said array of optical sensors.
8. The closed-loop tracking system of claim 2 , wherein each of said plurality of optical elements comprises an artificial light source configured to produce said signal beam by illuminating a corresponding mirror, causing said mirror to emit said signal beam at the angular offset from said main beam.
9. The closed-loop tracking system of claim 2 , wherein each of said plurality of optical elements comprises an artificial collimated light source coupled to a corresponding mirror, said artificial collimated light source configured to produce said signal beam at the angular offset from said main beam.
10. The closed-loop tracking system of claim 2 , wherein each one of said signal beams has unique characteristics identifying it to the corresponding one of said plurality of mirrors.
11. The closed-loop tracking system of claim 2 , wherein each one of said signal beams has unique identification information encoded therein to identify it to the corresponding one of said plurality of heliostat mirrors.
12. The closed-loop tracking system of claim 3 , wherein said array of optical sensors comprises one or more digital cameras located away from said signal beam target and directed toward said signal beam target.
13. The closed-loop tracking system of claim 5 , further comprising one or more actuators coupled to each one of said plurality of mirrors, wherein each of said one or more actuators is configured to be capable of orienting said one of said plurality of mirrors to a desired angular position.
14. A closed-loop tracking system comprising:
a plurality of heliostat mirrors;
a plurality of signal mirrors, wherein each one of said plurality of signal mirrors is coupled to a corresponding one of said plurality of heliostat mirrors;
a receiver configured to receive a main beam of sunlight reflected from each one of said plurality of heliostat mirrors; and
a signal beam target to receive a signal beam from each one of said plurality of signal mirrors, wherein said signal beam is directed at an angle other than that of said main beam, wherein each signal beam is spread over a range of wavelengths, wherein the signal beams from the plurality of signal mirrors are concurrently transmitted to and received by the signal beam target.