Workers install solar panels on the Paul VI auditorium's roof
Pope Benedict XVI has become the first pontiff to harness solar power to provide energy for the Vatican.
Roof tiles on the Paul VI auditorium - used in poor weather for the Pope's weekly audience with pilgrims - are being replaced by 2,700 solar panels.
The photovoltaic cells will convert sunlight into electricity, generating enough power to light, heat or cool the 6,000 seat hall, engineers say.
Conserving global resources has been a priority for the German-born Pope.
Since he was elected in 2005, Benedict XVI has criticised "the unbalanced use of energy" in the world.
He has also said environmental damage was making "the lives of poor people on earth especially unbearable".
Working beneath a brilliantly clear Roman sky on Monday, a group of engineers in yellow T-shirts positioned the dark cells on the auditorium's roof.
The solar panels are replacing deteriorating cement roof tiles
Andre Koekenhoff, one of the workers, said the initiative was an attempt to make the Vatican "a little bit greener".
"With this plant, if it is working, in about two weeks we avoid 200 tonnes of carbon dioxide, and this is the equivalent to 70 tonnes of oil," he told the Associated Press news agency.
When the hall is not in use, the surplus energy produced will reportedly be fed into the Vatican's power network.
The Paul VI auditorium was designed by architect Pier Luigi Nervi and built in 1969, but the cement panels on its roof were deteriorating and it was decided last year to replace them with solar panels.
The panels, reportedly worth $1.5m, were donated as a gift to the German-born Pope by a Bonn-based company, Solar World, AP reported.
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