Techniques for monitoring solar array performance and applications thereof

Abstract

An automated method to monitor performance of a terrestrial solar cell array tracking the sun. The solar cell system includes drive means that adjust a position of the array along different respective axes with respect to the sun using the drive means. The techniques include predicting the position of the sun during a time period, and sampling an output parameter of the array indicative of performance. The sampled data may be used to identify a fault in the solar cell array, for example a misalignment or a failure of one or more solar cells, in which case a notification of that fault may be generated for the operator or a control signal may be output for correcting the fault. Alternatively, an output signal may be sent to an external system associated with the solar cell system. Various alignment testing routines for checking the solar tracking are described. These routines may involve moving a solar cell array to a reference position at the start of, or during, an alignment routine in order to improve accuracy of position measurement during the routine.

What is claimed is: 
     
         1 . An automated method of monitoring a photovoltaic solar cell array of a terrestrial solar cell system that tracks the sun, the system comprising two drive means each of which is operable to adjust a position of a plurality of solar cells about a respective different axis, the method comprising:
 (a) predicting a position of the sun during the course of the day using a sun position predictor and determining respective actuations for the drive means corresponding to the solar cell array being substantially aligned with the sun during the course of the day; and   (b) sampling an output parameter of said plurality of solar cells to monitor the performance of the solar cell array.   
     
     
         2 . The method of  claim 1 , further comprising:
 moving, using one of the two drive means, the plurality of solar cells from a first position to a second position a first predetermined amount to one side of the first position, and sampling the output parameter at the second position;   moving, using said one of the two drive means, the plurality of solar cells to a third position a second predetermined amount to the other side of the first position, and sampling the output parameter at the third position; and   determining a fourth position using the sampled output parameters at the second and third positions, the fourth position corresponding to a prediction of the position at which the output parameter has a maximum value.   
     
     
         3 . The method of  claim 2 , wherein the first predetermined amount is equal to the second predetermined amount, and wherein said determination of the fourth position comprises calculating a weighted average of the second and third positions using weighting factors corresponding to the sampled output parameters at the second and third positions. 
     
     
         4 . The method of  claim 2 , wherein said moving from the first position to the second position comprises moving the plurality of solar cells to a reference position, and then moving the plurality of solar cells from the reference position to the second position. 
     
     
         5 . The method of  claim 1 , further comprising:
 moving, using one of the two drive means, the plurality of solar cells from a first position to a second position to one side of the first position, said second position corresponding to a first predetermined decrease in the output parameter;   moving, using said one of the two drive means, the plurality of solar cells to a third position to the other side of the first position, said third position also corresponding to a second predetermined decrease in the output parameter; and   determining a fourth position using the second and third positions, the fourth position corresponding to a prediction of the position at which the output parameter has a maximum value.   
     
     
         6 . The method of  claim 5 , wherein the first predetermined decrease is equal to the second predetermined decrease, and wherein the fourth position is midway between the second and third positions. 
     
     
         7 . The method of  claim 6 , wherein said moving from the first position to the second position comprises moving the plurality of solar cells to a reference position, and then moving the plurality of solar cells from the reference position to the second position. 
     
     
         8 . An automated method of monitoring a terrestrial solar cell system having a solar cell array that tracks the sun, the system comprising two drive means each of which is operable to adjust the position of a plurality of solar cells about a respective different axis, the method comprising:
 (a) predicting a position of the sun during the course of the day using a sun position predictor and determining respective actuations for the drive means corresponding to said plurality of solar cells being substantially aligned with the sun during the course of the day;   (b) in response to a trigger event, sampling an output parameter associated with the performance of the solar cell array and storing the sampled output parameter in a data memory, wherein said sampling occurs for a plurality of trigger events resulting in storage of a plurality of sampled output parameters; and   (c) analyzing said stored sampled output parameters and generating an output signal in response to the analysis.   
     
     
         9 . The method of  claim 8 , wherein in response to the analysis indicating a fault condition, the output signal is a notification of the fault condition. 
     
     
         10 . The method of  claim 8 , wherein in response to the analysis indicating a misalignment, the output signal is a control signal operable to reduce the misalignment. 
     
     
         11 . The method of  claim 8 , wherein the output signal comprises a notification to a human operator of the solar cell system. 
     
     
         12 . The method of  claim 11 , where the notification identifies an error condition for the solar cell system. 
     
     
         13 . The method of  claim 8 , wherein the output signal comprises a control signal for a system external to the solar cell system. 
     
     
         14 . An apparatus for tracking the sun comprising:
 a photovoltaic solar cell array of a terrestrial solar cell system;   two drive means each of which is operable to adjust a position of a plurality of solar cells along respective different axes; and   a controller operable to predict a position of the sun during the course of the day and to determine respective actuations for the two drive means corresponding to said plurality of solar cells being substantially aligned with the sun during the course of the day,   wherein the controller is operable to sample an output parameter for said plurality of solar cells, to analyze a plurality of sampled values for the output parameter, and to generate an output in response to the analysis.   
     
     
         15 . The apparatus of  claim 14 , wherein the controller is operable to control the two drive means so that said output parameter is sampled at different positions of the plurality of solar cells to determine if there is an alignment fault with the plurality of solar cells. 
     
     
         16 . The apparatus of  claim 15 , wherein the controller is arranged to move to a desired position via a reference position. 
     
     
         17 . The apparatus of  claim 14 , wherein the controller is operable to output a notification to an operator if said analysis identifies a fault with said plurality of solar cells. 
     
     
         18 . The apparatus of  claim 14 , wherein the controller is operable to output a control signal to a remote system in response to said analysis of the plurality of sample values. 
     
     
         19 . The apparatus according to  claim 14 , wherein the solar cells are concentrating solar cells. 
     
     
         20 . The apparatus of  claim 14 , wherein the solar cell array comprises a plurality of groups of solar cell modules, and wherein the apparatus further comprises:
 an elongated frame including at least one longitudinal support configured to mount the groups of solar cell modules in a longitudinally-extending and spaced-apart arrangement; and   a plurality of vertical supports positioned along the longitudinal support.