The Vatican sought to up its green credentials this week by switching on its massive electricity generating solar panels on the Pope Paul VI Hall. The development is one of a series of intended environmental initiatives.
The Vatican says it aims to become the world's "first carbon neutral state", and is growing a 37-acre forest in Hungary to offset its annual carbon dioxide emissions. It has undertaken to use renewable energy for 20 per cent of its needs by 2020.
The panels on the 5,000 square metre roof of the huge Papal audience hall will produce 300 kilowatt hours of 'clean energy', supplying the energy needs of the hall itself and nearby buildings.
As more than 9,000 pilgrims gathered for Pope Benedict's weekly General Audience, 2,400 solar panels on the roof above began converting sunlight into electricity to light and heat the hall.
When the panels were switched on, said observers, the skies above Rome became clear and sunny after days of cloud and rain.
An inauguration ceremony was held in the Pontifical Academy of Sciences, attended by Cardinal Giovanni Lajolo, the Governor of Vatican City, Frank Asbeck, president of Solar World AG, the Germany company which donated the panels, and Carlo Rubbia, winner of the Nobel Prize for Physics.
A Vatican spokesperson said the solar panel project was one of several "concrete and tangible initiatives" to promote protection of the environment, and part of the "green culture characterised by ethical values" promoted by Pope Benedict.
Vatican officials say that the panels will save the equivalent of 80 tonnes of oil each year. They cannot be seen from the ground.
Environmental campaigners are welcoming the move. But they point out that there is much more scope for the Vatican to use its vast wealth on green and anti-poverty initiatives, given that the panels were provided free, and that more ambitious targets than 20 per cent renewability in 12 years are possible.