Linearity Testing of Photovoltaic Cells (Poster)
International PV standards require that the short-circuit current or response of the reference device be linear with total irradiance. Accredited calibration laboratories can not assume that their reference device is linear unless another accredited laboratory has performed the measurement. The NREL PV performance laboratory is ISO 17025 accredited for primary reference cell, secondary reference cell and secondary module calibrations. Limited labor resources necessitated the development of a technique to determine linearity without taking significant labor or technical skill. The two-lamp method is insensitive to the spectrum of the light or spatial nonuniformity changing as the irradiance is varied. It does assume that the temperature does not change with irradiance and that the light-source spectrum resembles the solar spectrum. This requirement is only because nonlinear mechanisms in the photo-current are wavelength dependent. A laser for example may show the same device as linear or very nonlinear with irradiance depending on the wavelength. The two-lamp method assumes that the lamp intensities when individually irradiating the sample are the same as when both lamps irradiate the sample. The presence of room light only limits the lowest irradiance that can be evaluated. Unlike other methods, the two-lamp method does not allow the current to be corrected for nonlinear effects. The most appealing aspect of the two-lamp method when compared with other methods for a high-volume calibration laboratory is that it is fast and does not require operator intervention to change the irradiances and is difficult for the operator to make mistakes that would affect the outcome.
- Research Organization:
- National Renewable Energy Lab. (NREL), Golden, CO (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC36-99-GO10337
- OSTI ID:
- 893065
- Report Number(s):
- NREL/PO-520-39860; TRN: US200623%%775
- Resource Relation:
- Conference: Prepared for the 2006 IEEE 4th World Conference on Photovoltaic Energy Conversion (WCPEC-4), 7-12 May 2006, Waikoloa, Hawaii
- Country of Publication:
- United States
- Language:
- English
Similar Records
Linearity Testing of Photovoltaic Cells: Preprint
Photovoltaic Calibrations at the National Renewable Energy Laboratory and Uncertainty Analysis Following the ISO 17025 Guidelines