Optical soiling measurement device for photovoltaic arrays

• US 10,312,859 B2
• Filed: 01/22/2018
• Issued: 06/04/2019
• Est. Priority Date: 05/12/2017
• Status: Active Grant

• Current Assignee: Atonometrics, Inc.
• Original Assignee: Atonometrics, Inc.
• Inventors: Gostein, Michael, Stueve, William
• Primary Examiner(s): Pham, Hoa Q
• Application Number:
  US15/877,207
• Publication Number:
  US 20180331653A1
• Time in Patent Office: 498 Days
• Field of Search: 3562391, 356445, 3562392, 3562398, 3562372, 2503391
• CPC Class Codes: G01N 15/0612 Optical scan of the deposits G01N15/0625 takes precedence
• CPC Class Codes: G01N 2015/0046 in gas, e.g. smoke
• CPC Class Codes: G01N 2021/157 Monitoring by optical means
• CPC Class Codes: G01N 2021/4735 Solid samples, e.g. paper, glass
• CPC Class Codes: G01N 21/47 Scattering, i.e. diffuse reflection G01N21/25, G01N21/41 take precedence G01N21/55 takes precedence
• CPC Class Codes: G01N 21/552 Attenuated total reflection
• CPC Class Codes: G01N 21/94 Investigating contamination, e.g. dust G01N21/85 takes precedence
• CPC Class Codes: G01N 21/9501 Semiconductor wafers manufacturing processes per se of semiconductor devices implementing a measuring step H01L22/10
• CPC Class Codes: G01N 2201/061 Sources
• CPC Class Codes: H01L 31/042 PV modules or arrays of single PV cells supporting structures for PV modules H02S20/00
• CPC Class Codes: H02S 40/10 Cleaning arrangements
• CPC Class Codes: H02S 40/30 Electrical components
• CPC Class Codes: H02S 50/00 Monitoring or testing of PV systems, e.g. load balancing or fault identification
• CPC Class Codes: H02S 50/15 using optical means, e.g. using electroluminescence
• CPC Class Codes: Y02E 10/50 Photovoltaic [PV] energy

Abstract

A device comprising a transparent window, a photoemitter, a photodetector, and a measurement unit, wherein said photoemitter is configured to illuminate soiling particles accumulating on a surface of said transparent window, said photodetector is configured to generate a signal based on detection of light that passes through said transparent window and reflects and/or scatters from said soiling particles, and said measurement unit determines a soiling level of said transparent window based upon a measurement of said signal.

Claims

1. A device comprising

a soiling sensor, an irradiance sensor, and at least one measurement unit;

wherein said irradiance sensor is configured to measure sunlight; and

wherein said device is configured to allow soiling particles to accumulate similarly on said soiling sensor and on said irradiance sensor; and

wherein said soiling sensor

comprises a transparent window, a photoemitter, and a photodetector, and

wherein said photoemitter is configured to emit light that illuminates soiling particles accumulating on a surface of said transparent window, and

said photodetector is configured to generate a signal based at least upon detection of a portion of said light that passes through said transparent window and reflects and/or scatters from said soiling particles; and

said at least one measurement unit determines a soiling level of said transparent window, wherein said soiling level corresponds to a fractional reduction in transmission of sunlight by said soiling particles, based at least upon a measurement of said signal of said soiling sensor; and

wherein said at least one measurement unit is configured to calibrate said soiling sensor based at least upon comparing readings from said irradiance sensor and said soiling sensor before and after cleaning.

2. The device of claim 1, wherein said light emitted by said photoemitter is incident upon said transparent window at an angle less than the angle of total reflection.

3. The device of claim 1, wherein said photoemitter is configured to emit said light at a wavelength that is not dominant within sunlight and wherein said photodetector is configured to substantially reject light at wavelengths other than said wavelength.

4. The device of claim 1, wherein said photoemitter is configured to operate in a pulsed or modulated mode, and said signal from said photodetector is detected synchronously with said pulse or said modulation.

5. The device of claim 1, further comprising a reference photodetector which is configured to receive a portion of said light from said photoemitter and to produce a signal therefrom, and wherein said soiling level is determined by comparison of said signals from said photodetector and said reference photodetector.

6. The device of claim 1, wherein said device is configured to correct readings of said irradiance sensor by said determinations of said soiling level to account for soiling particles obscuring said irradiance sensor.

7. The device of claim 1, wherein said photoemitter and/or said photodetector are configured to be incident upon an edge face of said transparent window.

8. A method comprising

allowing soiling particles to accumulate similarly on a surface of a transparent window and on an irradiance sensor configured to measure transmitted sunlight,

illuminating said surface of said transparent window by emission of light from a photoemitter,

measuring by a photodetector a portion of said light that scatters or reflects from said soiling particles on said transparent window,

determining a soiling level of said transparent window, wherein said soiling level corresponds to a fractional reduction in light transmission, from a signal from said photodetector, and

calibrating said soiling level at least by comparing said signal with measurements of said irradiance sensor before and after cleaning of said transparent window and/or said irradiance sensor.

9. The method of claim 8, wherein said light is incident upon said transparent window at an angle less than the angle of total reflection.

10. The method of claim 8, further comprising directing a portion of said light from said photoemitter to a reference photodetector, and determining said soiling level by comparing signals from said photodetector and said reference photodetector.

11. The method of claim 8, further comprising operating said photoemitter in a pulsed or modulated mode and detecting signals from said photodetector synchronously with said pulse or said modulation.