How is a giant mirror bringing light to a valley-floor settlement in the Italian Alps?
Villagers in the Italian Alps are enjoying bright winters for the first time in their lives.
Thanks to a giant mirror, they are no longer deprived of sunlight for three months a year. From high on the valley side above the village of Viganella, a 40 m2 mirror now reflects sunlight down into the main square. It is computer-operated and can change direction to constantly follow the sun’s path. In the future, it could play a vital role in helping tourism and businesses while preventing more people from migrating away.
Why was the mirror needed?
How was the mirror built?
What will be the impact of the mirror?
Viganella lies in complete shadow for some months of the year. It is situated at the bottom of the narrow Antrona valley, north of Turin and close to the Swiss border. The village’s problem is that the surrounding valley sides are too steep to always allow sunlight to strike the main Piazza – the village square which locals call “il cuore di Viganella” (the heart of Viganella). On 11 November, the sun disappears and does not reappear until 2 February. No direct light reaches Viganella for the 83 days in-between.
“It's like Siberia,” one of the village's residents told the BBC (07 November 2005). With only around 200 mostly elderly inhabitants now living in Viganella, it seems that local climate has been having an adverse effect on population numbers. Many younger people have migrated away, judging by census data showing that the village has almost halved in size since the 1960s.
However, the sun has only ever been just out of reach during the winter months. Its rays naturally strike the south-facing slopes of the valley just a few hundred metres above the site of the village – tantalisingly close! This led some villagers to start wondering if they could perhaps bring the light a little nearer...
Aspect is the angle from which the sun shines. In Europe, south facing slopes are warmer than north facing slopes. In the southern hemisphere, the aspects are reversed. In a typical V-shaped river valley or U-shaped glacial trough, north-facing slopes receive less annual insolation (solar energy) This poses many difficulties for settlement and economic activity. With a shorter thermal growing season, agriculture can be limited or impossible and population densities are correspondingly low on north-facing slopes of some major Alpine valleys. In other high altitude areas such as the Scottish Highlands, snow can be seen to remain on north facing slopes at high altitude until much later in the year compared with south facing slopes.
A steep valley shape can sometimes bring advantages to the south-facing slope, as the sun’s rays arrive at an almost perpendicular angle, maximising insolation received per unit area. However, settlements built on the valley floor – perhaps for transport reasons, or attracted by other site factors such as flat land or river water - can be left almost entirely in shade. The steep angle of the valley sides means that shadow is cast onto the valley floor for almost the entire day, even in summer. Only when the sun is moving directly overhead can any direct light reach settlements at the bottom of very narrow valleys.
Some geographers use the term ubac to describe a north-facing slope. South-facing slopes are called adret slopes.
According to The Times (12 November 2006), the story began when Major Pierfranco Midali commissioned a sundial for the village church. He told Giacomo Bonzani, the local architect who made the sundial, “not to bother with November 11 to February 2.” Instead, he joked that they should “leave it unfinished so people would understand there is no light then.”
This inspired Bonzani to start conducting experiments in his back garden to help solve Viganella’s light problem. He devised the prototype for a giant motorised mirror about eight metres wide that could track the movement of the sun, always reflecting light back into the village’s main square. He told the BBC “In theory, it could be snowing in the village, but so long as the sun is out further up the valley, Viganella's Piazza can have snow and sunshine at the same time.”
“I was a bit sceptical at first,” admitted Franco, owner of one of the Piazza’s bars, when interviewed by the Sunday Times (12 November 2006). “But now I’m all for it. It’s freezing here (in Winter) and we have to keep the light on all the time.”
The project was completed in various stages:
The cost of £67,000 was met by a private bank, the village council and regional authorities, all of whom were impressed by the plan.
A full-size model was then built, consisting of a 40 m2 sheet of steel weighing more than a ton and guaranteed to stand up to the strongest winds. Computer-controlled motors enable it to follow the sun.
It was flown by helicopter to a designated spot half a mile away on the mountainside of the Colma peak and placed among pine trees at a height of 1,200 metres.
From there, it now reflects the suns’ rays down onto the village Piazza, lighting up an area of 300 square metres for at least six hours a day.
Tourism may improve, not least because visitors will be curious to see the mirror in action.
Local ecosystems will change as different plant and insect species will colonise gardens now that growing conditions have been ameliorated (improved).
The rate of migration away from the village could fall now that the push factor of lack-of-light has been removed. Since 1961, population has fallen from 367 to only 185 in February 2005. Many of those that remain are elderly and dependent. Perhaps the village will even receive some new in-migrants now that sunlight hours have increased.
This story links together several strands of physical and human geography. These are: (1) glacial landforms (understanding the processes that have produced such a steep valley), (2) climate (understanding the role that aspect plays in shaping local climate), (3) settlement (the role that physical site factors play) and (4) decision-making (environmental management). As such, it could be a very useful case study for students to learn. A good sketch map is essential and one is available to view on the BBC site.
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