Publication: Analysis of measured photovoltaic ...

DOI:10.1016/j.solener.2014.10.017

A study was conducted to determine and compare the measured energy production of photovoltaic (PV) modules for three climatically diverse locations: Cocoa, Florida; Eugene, Oregon; and Golden, Colorado. The PV modules were 2010 vintage and included single-crystalline silicon (x-Si), multi-crystalline silicon (m-Si), cadmium telluride (CdTe), copper indium gallium selenide (CIGS), amorphous silicon (a-Si) tandem and triple-junction, amorphous silicon/crystalline silicon or heterojunction with intrinsic thin-layer (HIT), and amorphous silicon/microcrystalline silicon (a-Si/μx-Si). Annual performance metrics for reference yield, final PV yield, performance ratio, and the losses associated with angle-of-incidence (AOI), PV module temperature, and low light or irradiance level were determined.

Results showed considerable variation in energy production because of both the site-to-site differences in reference yield and the PV module characteristics; for example, the best-performing PV modules in Cocoa had final PV yield values nearly 60% greater than the lowest performing PV module in Eugene. In Cocoa, the final PV yield of the a-Si/μx-Si PV module was greater, after considering measurement uncertainty, than other PV modules in Cocoa, except for the CdTe PV module. In Eugene, more PV modules performed more similarly to each other. The final PV yield values for the a-Si/μx-Si and CdTe PV modules were not measurably greater than the final PV yield values for the HIT and a-Si PV modules. In Golden, the final PV yield values of the PV modules varied the least, within measurement uncertainty, except for one PV module.

Losses from AOI effects were from 2½% to 3%; losses from PV module temperature were from 2.3% to 10.8%; and low-light-level effects ranged from a loss of 7.4% for a CIGS PV module deployed in Eugene to a gain of 0.3% for a CdTe PV module deployed in Cocoa. Spectral effects also appeared to be present, with increased performance of the CdTe modules and a-Si PV module in Cocoa and decreased performance in Golden.