Here is a particularly interesting article from the German press today, on the use of heliostats for both personal and public use. Villages in hilly and mountainous areas tend to be particularly depressing during the winter. Because villages in these areas are naturally located near the base where transport is easier and rivers tend to be, they also tend to be located in the darkest parts while higher up where nobody lives there is still a good amount of sunlight. The solution? Building a mirror to reflect the sunlight below. The mirror needs to be large, and its heading also needs to be controlled in order to continually reflect the sunlight onto the house or village below.
The article has two images:
this shows the size of a personal heliostat compared to a person, while
this shows the result - an otherwise dark and cold room in a house receiving full sunlight even in the winter.
The most striking example given in the article though is the Italian village of Viganella, which
made headlines in 2006 after spending 100,000 euros to install a mirror to reflect sunlight onto the village below. Before doing so the village spent a full 83 days each year without any sunlight at all, due to the mountain next to the village over which the Sun never rose during the darkest period of the year:
Before the installation of the mirror the poor village was like Siberia in the winter, according to residents.
According to
an Austrian company referenced in the Zeit article that makes about fifteen heliostats a year, a personal heliostat like the one in the first two pictures (a mirror of 2.5 metres or 8 feet on a mast about twice that height with a computer tracking system that keeps it focused on one area) costs about 10,000 euros.
The company that makes these heliostats is a fairly well-established company (80 years) that makes most of its money from different yet related ventures (air conditioning, ventilation, fireproofing, etc.) and says that heliostat technology has not yet reached the level of mass production, which is part of why it is still so expensive. The position of the Sun still has to be directly fed into the device instead of recognizing the Sun's position automatically. The pictures also don't show any protection against potential vandalism besides being located on a mast 4 metres up.
The next example given in the article is a heliostat in a hotel in the village of
Ischgl in Austria, which is 1377 metres above sea level and looks like this:
A businessman named Gunther Aloys there has installed a mirror on top of
one of the luxury hotels, which apparently looks kind of silly in the summer but when winter comes around and the clock strikes three, the entire village is plunged into shadow except for
the ice bar there, where everybody gathers to enjoy the only spot in the village that still has sunlight. You can see a picture of the hotel
here with the mirror. Total cost for that mirror is somewhere around 100,000 to 150,000 euros.
One town that did not end up acquiring the funding for a heliostat was
the Austrian town of Rattenburg. One of the darkest parts of the country in the winter, it made headlines a few years back with its plans to build a mirror to bring more sunlight in during the coldest months. Unfortunately the expected cost (four million euros) was just too much for a village of just 434 people, and plans have been shelved for now. The opportunity to build another major project of this type would have been a good opportunity to refine the technology a bit more, so its cancellation was particularly regrettable for companies that hope to eventually perfect and mass-market heliostats.
A few years after the installation of the mirror in Viganella the village still has all the regular problems one would expect with a village of its size (young people leaving for opportunities in the city, essential utilities still missing) and though the odd tourist comes in every once in a while to view the mirror, tourism has not exactly boomed. But the mirror does continue to work, and the 83 long days of shadow during the winter are now a thing of the past. This video shows the installation and the first usage of the mirror back in 2006 - skip ahead to about 5:15 to see the reaction to the mirror after it is set up and begins reflecting sunlight below.
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