Computer-implemented system and method for correlating satellite imagery for use in photovoltaic fleet output estimation

摘要

The calculation of the variance of a correlation coefficient matrix for a photovoltaic fleet can be completed in linear space as a function of decreasing distance between pairs of photovoltaic plant locations. When obtaining irradiance data from a satellite imagery source, irradiance statistics must first be converted from irradiance statistics for an area into irradiance statistics for an average point within a pixel in the satellite imagery. The average point statistics are then averaged across all satellite pixels to determine the average across the whole photovoltaic fleet region. Where pairs of photovoltaic systems are located too far away from each other to be statistically correlated, the correlation coefficients in the matrix for that pair of photovoltaic systems are effectively zero. Consequently, the double summation portion of the calculation can be simplified to eliminate zero values based on distance between photovoltaic plant locations, substantially decreasing the size of the problem space.

主权项

1. A computer-implemented method for correlating satellite imagery through bounded area variance for use in photovoltaic fleet output estimation, comprising the steps of:
correlating a set of pixels in satellite imagery data of overhead sky clearness to a bounded area within a geographic region, each pixel representing collective irradiance over a plurality of points within the bounded area, each point suitable for operation of a photovoltaic system comprised in a photovoltaic fleet; converting the collective irradiances, as represented by the set of pixels correlated to the bounded area, into a set of point clearness indexes for the plurality of the points under each pixel, relative to clear sky irradiance; averaging the point clearness indexes in the set of point clearness indexes for all of the points within the bounded area into an area clearness index; determining a variance of the area clearness index as a bounded area variance by sequentially evaluating only the points within the bounded area that have not already been evaluated, the evaluating comprising the steps of:
choosing a point within the bounded area not yet evaluated;determining a zero correlation value for the chosen point;pairing the chosen point with each of the points remaining within the bounded area that have not already been evaluated;finding a correlation coefficient for each of the point pairings; andcalculating a covariance for each of the point pairings whose correlation coefficient exceeds the zero correlation value and adding those point pairings' covariances to the variance of the area clearness index; and for each of the points within the bounded area, determining a variance of the point clearness index for that point as a ratio of the variance of the area clearness index and the physical area relative to the point clearness index for that point, cloud speed over the geographic region, and a time interval relating to a time resolution of observation for the collective irradiance, wherein the steps are performed on a suitably-programmed computer.