System and method for aligning heliostats of a solar power tower

1. A heliostat alignment system for a solar power tower with a focal area and an off-focal area location substantially close to the focal area of the solar power tower, comprising:

a plurality of heliostats that each include a reflective mirror and include a sun tracking mechanism that moves and aligns the reflective mirror to reflect sunlight towards the focal area of the solar power tower;

a communication device that—upon the misalignment of a heliostat—provides a communication link between the off-focal area location and the misaligned heliostat, the communication device includes a sensor located at each of the heliostats and arranged such that—upon the misalignment of a heliostat—the sensor of the misaligned heliostat receives a signal from the off-focal area location through the communication link; and

a processor that interprets the communication link between the off-focal area location and the misaligned heliostat to identify the misaligned heliostat from the plurality of heliostats; wherein the processor determines and communicates a correction for the identified misaligned heliostat.

2. The heliostat alignment system of claim 1 , further comprising a retro-reflectance device mounted to the solar power tower at the off-focal area location and arranged to reflect light from a misaligned heliostat back to the misaligned heliostat.

3. A heliostat alignment system for a solar power tower with a focal area and an off-focal area location substantially close to the focal area of the solar power tower, comprising:

a plurality of heliostats that each include a reflective mirror and include a sun tracking mechanism that moves and aligns the reflective mirror to reflect sunlight towards the focal area of the solar power tower, each heliostat including a transmitter that transmits a signal;

a communication device that—upon the misalignment of a heliostat—provides a communication link between the off-focal area location and the misaligned heliostat, wherein the communication device includes a sensor located at the off-focal area location that facilitates the communication link with the misaligned heliostat; and

a processor that interprets the communication link between the off-focal area location and the misaligned heliostat to identify the misaligned heliostat from the plurality of heliostats; wherein the processor determines and communicates a correction for the identified misaligned heliostat;

wherein—upon the misalignment of a heliostat—the misaligned heliostat transmits a signal to the sensor through the communication link.

4. The heliostat alignment system of Claim 3 , wherein the sensor located at the off-focal area location is mounted to the solar power tower.

5. The heliostat alignment system of Claim 3 , wherein each transmitter is the reflective mirror of the heliostat and the signal includes the reflected sunlight from the reflective mirror of the heliostat, wherein each heliostat includes a reflection modification element that modifies the reflection of sunlight towards the solar power tower, and wherein the sensor detects the modified reflection of sunlight.

6. The heliostat alignment system of Claim 5 , wherein the sensor is a photodiode.

7. The heliostat alignment system of Claim 5 , wherein the sensor is an infrared sensor.

8. The heliostat alignment system of Claim 5 , wherein the reflection modification element of each heliostat includes a cover that blocks the reflection of sunlight towards the solar power tower.

9. The heliostat alignment system of Claim 5 , wherein the reflection modification element of each heliostat is the sun tracking mechanism of the heliostat and wherein the sun tracking mechanism moves the reflective mirror to direct reflected sunlight substantially away from the solar power tower.

10. The heliostat alignment system of Claim 5 , wherein the reflection modification element of each heliostat includes a light filter that modifies the light reflected towards the solar power tower from the reflective mirror of the heliostat.

11. The heliostat alignment system of claim 10 , wherein the light filter absorbs a frequency of the electromagnetic spectrum that is detectable by the sensor.

12. The heliostat alignment system of claim 10 , wherein the light filter is electrically actuated.

13. The heliostat alignment system of claim 10 , wherein the light filter is a coating on the reflective mirror.

14. The heliostat alignment system of Claim 5 , wherein the reflection modification element of each heliostat includes a vibration element that dithers the reflective mirror of the heliostat and modifies the light reflected towards the solar power tower from the reflective mirror of the heliostat.

15. The heliostat alignment system of claim 14 , wherein the vibration element dithers the reflective mirror at a frequency in the audio frequency range.

16. The heliostat alignment system of claim 14 , wherein the vibration element is a speaker coil.

17. The heliostat alignment system of claim 14 , wherein the vibration element is a piezoelectric actuator.

18. The heliostat alignment system of claim 14 , wherein the vibration element dithers the reflective mirror and modifies the light reflected towards the solar power tower according to a signal characteristic selected from the group consisting of:

frequency and phase.

19. The heliostat alignment system of claim 14 , wherein the signal of the misaligned heliostat is common to the signals of at least a subset of the heliostats.

20. The heliostat alignment system of claim 19 , wherein the processor instructs a first heliostat of the subset of the heliostats with a common signal to pause transmission of the signal and a second heliostat of the subset of the heliostats with a common signal to pause transmission of the signal, and wherein the processor interprets a pause in the communication between the sensor and the misaligned heliostat to identify the misaligned heliostat.

21. The heliostat alignment system of claim 20 , wherein the processor performs a binary search function to identify the misaligned heliostat.

22. The heliostat alignment system of claim 14 , wherein the signal of the misaligned heliostat is unique to the misaligned heliostat, and wherein the processor interprets the unique signal detected at the sensor and identifies the misaligned heliostat.

23. The heliostat alignment system of claim 22 , wherein each of the transmitters transmits a signal that is unique in a signal characteristic selected from the group consisting of: frequency and phase.

24. The heliostat alignment system of claim 23 , wherein the processor performs a Fourier transform analysis to determine the unique frequency or phase of the signal detected by the sensor.

25. The heliostat alignment system of claim 22 , wherein each of the transmitters transmits a signal that is unique in pattern.

26. The heliostat alignment system of claim 22 , wherein each of the transmitters transmits a light filtered at a unique frequency.

27. A method for aligning heliostats that track the sun and reflect sunlight towards a focal area of a solar power tower, comprising the steps of:

providing a sensor at each of the heliostats;

establishing a communication link between an off-focal area location substantially close to the focal area of the solar power tower and a misaligned heliostat, including sending a signal from the off-focal area location to the sensor of the misaligned heliostat;

identifying the misaligned heliostat through the communication link;

detecting a correction for the identified misaligned heliostat; and

realigning the misaligned heliostat to reflect sunlight towards the focal area of the solar power tower.

28. The method of claim 27 , wherein the step of sending a signal from the off-focal area location to the sensor of the misaligned heliostat includes reflecting a signal from the misaligned heliostat to the off-focal area location to the sensor of the misaligned heliostat.

29. A method for aligning heliostats that track the sun and reflect sunlight towards a focal area of a solar power tower, comprising the steps of:

providing a sensor at the off-focal area location substantially close to the focal area of the solar power tower;

providing a transmitter at each of the heliostats;

establishing a communication link between the off-focal area location and a misaligned heliostat, including establishing a communication link between the sensor at the off-focal area location and the misaligned heliostat and transmitting a signal from the misaligned heliostat to the sensor;

identifying the misaligned heliostat through the communication link;

detecting a correction for the identified misaligned heliostat; and

realigning the misaligned heliostat to reflect sunlight towards the focal area of the solar power tower.

30. The method of Claim 29 , wherein the step of transmitting a signal from the misaligned heliostat to the sensor includes transmitting a signal common to at least a subset of the heliostats.

31. The method of Claim 29 , wherein the step of transmitting a signal from the misaligned heliostat to the sensor includes transmitting a signal unique to the misaligned heliostat.

32. The method of Claim 31 , wherein the step of identifying the misaligned heliostat includes performing a Fourier transform analysis to identify the unique signal of the misaligned heliostat.

33. The method of Claim 31 , wherein the step of transmitting a signal unique to the misaligned heliostat includes transmitting a signal unique in a signal characteristic selected from the group consisting of: frequency and phase.

34. The method of Claim 31 , wherein the step of transmitting a signal unique to the misaligned heliostat includes reflecting light to the sensor in a unique pattern.

35. The method of Claim 31 , wherein the step of transmitting a signal unique to the misaligned heliostat includes reflecting a light filtered at a unique frequency to the sensor.