Cloud Tracking

• US 20110060475A1
• Filed: 08/05/2010
• Published: 03/10/2011
• Est. Priority Date: 08/05/2009
• Status: Active Grant

• Current Assignee: First Solar Incorporated
• Original Assignee: First Solar Incorporated
• Inventors: Collins, Kevin, Baldwin, Robert R.
• Granted Patent: US 9,184,311 B2
• Time in Patent Office: Days
• US Class Current: 700/295
• CPC Class Codes: G01W 1/10 Devices for predicting weather conditions computers per se G06; display devices G09
• CPC Class Codes: G01W 1/12 Sunshine duration recorders measuring intensity of sunshine G01J
• CPC Class Codes: H01L 31/02021 for solar cells electrical connection means, e.g. junction boxes, specially adapted for structural association with photovoltaic modules H02S40/34
• CPC Class Codes: H02S 10/00 PV power plants; Combinations of PV energy systems with other systems for the generation of electric power
• CPC Class Codes: H02S 50/00 Monitoring or testing of PV systems, e.g. load balancing or fault identification
• CPC Class Codes: Y02E 10/50 Photovoltaic [PV] energy

Abstract

A cloud tracking system for photovoltaic power plant is disclosed. The cloud tracking system for photovoltaic power plant can include plurality of cloud shadow sensors positioned on the perimeter of the photovoltaic power plant.

Claims

1. A cloud tracking system for a photovoltaic power plant comprising:

plurality of cloud shadow sensors positioned on the perimeter of the photovoltaic power plant at a distance that permits early detection of moving clouds; and

a data collecting and process module configured to collect data from the sensors.

2. The cloud tracking system of claim 1, wherein the cloud shadow sensors comprise telemetry to send signals indicating intermittent irradiance changes caused by the incoming clouds.

3. The cloud tracking system of claim 1, wherein the cloud shadow sensors are ground based and arranged in at least two concentric rings called the outer detection perimeter and the inner detection perimeter respectively.

4. The cloud tracking system of claim 3, wherein the distance of the outer and inner detection perimeters from the photovoltaic power plant is designed to assure time for photovoltaic plant control response, detection of cloud trajectory, and grid interoperability.

5. The cloud tracking system of claim 3, wherein the distance of the outer detection perimeter from the photovoltaic power plant is a definable distance further than the inner detection perimeter.

6. The cloud tracking system of claim 5, wherein the further distance of the outer detection perimeter from the photovoltaic power plant is designed to facilitate calculation of cloud speed and trajectory.

7. The cloud tracking system of claim 6, further comprising at least a third detection perimeter designed to cooperate with the outer detection perimeter and the inner detection perimeter to provide additional data for the calculation of cloud trajectory.

8. The cloud tracking system of claim 3, wherein the spacing between ground sensors on the perimeters and the spacing between the outer detection perimeter and the inner detection perimeter are designed to assure determination of the speed and trajectory of the incoming clouds.

9. The cloud tracking system of claim 3, wherein the sensors on the inner detection perimeter are spaced closer than the sensors on the outer detection perimeter to better detect stray clouds not picked up at the outer detection perimeter.

10. The cloud tracking system of claim 3, wherein the distance of the detection perimeters from the photovoltaic power plant and the arrangement of ground sensors are designed to assure determination of the anticipatory action needed to mitigate the effects of intermittent cloud shadows on the photovoltaic power plant.

11. The cloud tracking system of claim 3 further comprising a power plant control system, wherein the control system can initiate ramp down of the photovoltaic plant output power by control of inverters when clouds are detected at the outer detection perimeter, wherein cloud detection can be confirmed and trajectory and speed determined at the inner detection perimeter by comparison to detection position and time elapsed at the outer detection perimeter, wherein the plant control system can initiate the start of the ramp down process based on the speed detected at the inner detection perimeter and the plant control system can initiate power ramp up when cloud shadows have cleared the photovoltaic plant array field and no other oncoming clouds are detected.

12. The cloud tracking system of claim 11, wherein the cloud shadow sensors are positioned in substantially the same plane of the photovoltaic plant array so that the magnitude of solar irradiance deviation can be detected and used by the control system to calculate the amount of power control needed.

13. The cloud tracking system of claim 11, wherein the timing of power ramp down and ramp up can be based on a pre-set ramp rate, wherein the initiation of the power ramp down can be delayed based on the measured cloud speed between the outer and inner detection perimeters.

14. The cloud tracking system of claim 11, wherein the power plant control module comprises an adaptive control algorithm for regulating the rate of change of output power so that the plant output power averaged over a rolling period of time is used to adjust the normal power level of the plant to reduce plant output variability.

15. The cloud tracking system of claim 1, wherein the data collecting and process module comprises a data storage device to generate a seasonal cloud shadowing profile.

16. The cloud tracking system of claim 1, wherein the photovoltaic power plant comprises a plurality of photovoltaic modules and wherein one of the cloud shadow sensors comprise a photodiode having photovoltaic properties sufficient to distinguish the cloud shadow sensors from the photovoltaic modules.

17. A method of tracking a cloud for photovoltaic power plant comprising:

positioning a plurality of cloud shadow sensors on the perimeter of the photovoltaic power plant at a distance that permits early detection of moving clouds; and

connecting a data collecting and process module to read and process signal from the sensors.

18. The method of claim 17, wherein the cloud shadow sensors comprise telemetry to send signals indicating intermittent irradiance changes caused by the incoming clouds.

19. The method of claim 17 further comprising arranging the cloud shadow sensors in two concentric rings called outer detection perimeter and inner detection perimeter.

20. The method of claim 19, further comprising the step of arranging a plurality of cloud shadow sensors in a third concentric ring comprising a third detection perimeter designed to cooperate with the outer detection perimeter and the inner detection perimeter to provide additional data for calculation of cloud trajectory.

21. The method of claim 17 further comprising

initiating ramp down of the photovoltaic plant output power by control of inverters when clouds are detected at the outer detection perimeter;

determining the trajectory and speed at the inner detection perimeter by comparison to detection position and time elapsed at the outer detection perimeter; and

initiating ramp up of the photovoltaic plant output power by control of inverters when cloud shadows have cleared the photovoltaic plant array field and no other oncoming clouds are detected.

22. The method of claim 21, wherein ramp down of the plant occurs within 5 minutes of detecting clouds at the outer detection perimeter.

23. The method of claim 21, wherein ramp up of the plant occurs within 5 minutes of clouds clearing the photovoltaic array.

24. The method of claim 21, wherein ramp down of the plant is delayed based on the speed of a cloud calculated at the inner detection perimeter.

25. The method of claim 21, wherein the cloud shadow sensors have the same photovoltaic characteristics of the photovoltaic power plant array and are positioned in substantially the same plane of the photovoltaic plant array so that the magnitude of solar irradiance deviation can be detected and used to calculate the amount power control needed.

26. The method of claim 21, wherein the timing of power ramp down and ramp up is based on a pre-set ramp rate.

27. The method of claim 26, wherein the power ramp down can be delayed based on a cloud speed measured between the outer detection perimeter and the inner detection perimeters.

28. The method of claim 21 further comprising

adjusting the power level of the plant to reduce plant output variability by using the plant output power averaged over a rolling period of time.