"Free" green energy: NY Times reports that in one of India's biggest solar installations, each of the 36,000 panels are wiped down every five days by people with long-handled dust mops

In Solar Power, India Begins Living Up to Its Own Ambitions - NYTimes.com

Every five days or so, in a marriage of low and high tech, field hands with long-handled dust mops wipe down each of the 36,000 solar panels at a 63-acre installation operated by Azure Power.