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Solar modules deployed in France in 1992 still provide 75.9% of original output power
(www.pv-magazine.com)
This is a most excellent place for technology news and articles.
Fortunately and unfortunately, there have been so many changes and breakthroughs on solar power over the last 50 years that this doesn't really tell us much about current technology.
What's not included in the article is how much additional power might be produced by replacing them with newer systems.