Method and apparatus for forecasting shadowing for a photovoltaic system
First Claim
1. A method for preventing an impending decrease in electric power supplied by a photovoltaic (PV) system connected to a power grid and by a connectable additional supplier of electric energy associated with the PV system below a limit value due to forthcoming shadowing caused by cloud formation or cloud movement, or both, comprising the steps of:
- analyzing the cloud formation or the cloud movement in a predetermined region between the PV system and a part of the firmament visible from the PV system,determining with a computing device, based on results of the analysis, a need for enacting a measure for maintaining a minimum of supplied power into the power grid,measuring the predetermined region with a camera,acquiring with the camera at predetermined time intervals images of the region, wherein the images are composed of a plurality of pixels,marking in the images a computed position of the sun,comparing sequential images with one another, andanalyzing a change in the luminous intensity of the pixels with respect to the computed position of the sun and a location of the camera.
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Abstract
In a method for forecasting shadowing of a photovoltaic (PV) system due to cloud formation or movement, part of the firmament is imaged with fisheye optics onto the input optics of a digital camera. Pixel groups associated with luminous intensity ranges are formed. The spatial arrangement of the groups is analyzed to forecast shadowing of a photovoltaic system. A line extending from the PV system to the sun is formed and is continuously tracked. A reference line located inside a region around the line is formed. Passage of clouds across a reference line is analyzed. The result of the analysis is used to increase the electric power from the PV system to a minimum value through supply of additional backup energy or to reduce the electric power consumption by disconnecting users to ensure that key users do not experience a drop in supplied power below a minimum value.
55 Citations
16 Claims
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1. A method for preventing an impending decrease in electric power supplied by a photovoltaic (PV) system connected to a power grid and by a connectable additional supplier of electric energy associated with the PV system below a limit value due to forthcoming shadowing caused by cloud formation or cloud movement, or both, comprising the steps of:
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analyzing the cloud formation or the cloud movement in a predetermined region between the PV system and a part of the firmament visible from the PV system, determining with a computing device, based on results of the analysis, a need for enacting a measure for maintaining a minimum of supplied power into the power grid, measuring the predetermined region with a camera, acquiring with the camera at predetermined time intervals images of the region, wherein the images are composed of a plurality of pixels, marking in the images a computed position of the sun, comparing sequential images with one another, and analyzing a change in the luminous intensity of the pixels with respect to the computed position of the sun and a location of the camera. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A device for preventing an impending decrease in electric power supplied by a photovoltaic (PV) system connected to a power grid and by a connectable additional supplier of electric energy associated with the PV system below a limit value due to forthcoming shadowing caused by cloud formation or cloud movement, or both, comprising:
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a digital camera having an image sensor composed of pixels, fisheye optics imaging a visible part of the firmament at least partially onto a predetermined region of the image sensor, a memory device storing images of the region recorded at predetermined time intervals, a storage device storing parameters representing a solar trajectory, and a computing device configured to receive as an input a position of the sun at the predetermined time intervals together with at least two stored images, to compare the at least two images with each other, and to analyze a change in luminous intensity of the pixels in the at least two images with respect to the position of the sun. - View Dependent Claims (16)
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Specification