Energy from the cells, which will illuminate, heat or cool the building, will feed into a network that powers the Vatican, Cuscianna said.
A feasibility study for the planned conversion, published recently in the Vatican newspaper L'Osservatore Romano , found it made economic sense. It quoted from Benedict's speeches defending the environment and noted his predecessor, John Paul II, also championed the safeguarding of natural resources.
Last summer, Benedict called on Christians to unite to take "care of creation without squandering its resources and sharing them in a convivial manner."
The hall was built in 1969, designed by architect Pier Luigi Nervi .
Cuscianna said Nervi used concrete panels on the auditorium's 6,000-square-yard flattened vaulted roof in part to help keep pilgrims cool.
The new roof panels will appear similiar to the concrete panels they are replacing, minimizing the aesthetic impact, Cuscianna said. Weathering has deteriorated the condition of the concrete panels, which needed replacement, so Cuscianna thought it was the right time to make the move to solar in Mediterranean Italy, which enjoys many sunny days.
The Vatican is considering the installation of photovoltaic cells on roofs of other Holy See buildings, although centuries-old landmarks like St. Peter's Basilica won't be touched.
