In 2001, LABSOLAR, together with the National Renewable Energy Laboratory (NREL) and the Arizona State University (ASU), designed a 4-year experiment to assess the performance of a-Si devices operating in different climatic conditions. Three identical sets of commercially available a-Si PV modules from five different manufacturers were simultaneously deployed outdoors in

three sites with distinct climates (Site A — NREL: Golden, Colorado-USA, climate: dry continental, with cold winters and warm summers, Site B — ASU PV Testing Laboratory: Mesa, Arizona-USA, climate: dry desert, with cool winters and hot summers and Site C — LABSOLAR: Florianopolis — Brazil, climate: moist maritime, with warm winters and hot summers) in a round robin exposure experiment.

The experiment aims to determine the light-induced degradation and stabilisation characteristics of a-Si regarding specific history of exposure, and to monitor and compare degradation rates in different climates. Figure 10 presents results from the first year of measurements, showing, for four different a-Si PV module manufacturers, that modules deployed at the site with the highest minimum operating temperature experienced the highest stabilised output level. Each PV module set is deployed outdoors at one site for 12 months, is shipped back to NREL for measurements under a SPIRE 240A simulator at STC, is then sent to the next (second) site in the second year; and to the remaining site (third) in the third year, before being sent back to the original site were it was first deployed outdoors for a final deployment period. Every permutation of sites includes STC measurements at NREL. More detailed results have been presented elsewhere [6].