Solar trees - a printable technology for future energy grows at the Milan expo | Science| In-depth reporting on science and technology | DW | 05.06.2015
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Solar trees - a printable technology for future energy grows at the Milan expo

The German Pavilion at Expo Milano is a feast of new technology. Some of it (seemingly) low-tech, some of it hi-tech. Its solar trees are clearly hi-tech, and architect Lennart Wiechell tells DW all about them.

DW: The solar trees of the German Pavilion are impressive. They form part of the building and show, they provide shade, and they address the expo theme of "Feeding the Planet, Energy for Life" by presenting a novel approach to solar power. But what are they exactly - aside from a metal structure and meshing made up of unconventional solar panels?

Lennart Wiechell: It's amazing because these solar panels are printed. So you can use a special color and with that color you can print any shape of solar panel, in any form, and in many different colors.

These ones are blue, but you can have red or yellow and green as well. And the interesting thing is you can easily design different shapes, and this is a new freedom for architects and designers, and for every product you can create your own solar panel.

Lennart Wiechell, architecht of the German Pavilion

Lennart Wiechell, architect of the German Pavilion

How they work

So tell us a little more about the solar panels and how they are made...

It's a very lightweight construction. It's a net made of steel, very thin steel ropes, and the net forms hexagonal shapes, and in this net we fix the printed panels. As a system, it's very easy to mount and also to dismantle - if you want to use it somewhere else.

And how does it work when it picks up the sun, how does it transfer the energy?

Just like common photovoltaic panels, but with a key difference: These panels work from both sides - from the front and back - and also from different angles, so even from very, very steep angles, the sun can enter into the panels, and you can use it with diffused light, so not only direct light.

EXPO Milano - solar trees

A light, flexible netting that could potentially fit any structure

So you can position the panels - not only to the south - but to the west, east, and even to the north. And all this together creates even more energy than normal panels.

That's the thing, isn't it - we're accustomed to this vision of solar panels on roofs at a particular angle, facing a particular direction, whereas these seem to face any old direction.

Yes, and that's the new freedom I mentioned earlier. So designers can now find their own panels for each project - they're no longer forced to use the prefabricated dimensions as we see across the landscape, all these farms with huge panels on the roofs.

Expo Milano - printed solar cells

Glued between two window panes, the technology could be used on skyscrapers

With this technology you can find your own design strategies. On [the pavilion's] VIP terrace, we glued this new solar film between two window panes, and this shows we can easily integrate it in skyscrapers and other office buildings.

Competitive technology

Expo Milano - Grätzel solar cells

New solar technology is a competitive field - the Grätzel system can also be seen at Expo Milano

But this is not the only pavilion featuring new solar power technology. The Austrian pavilion also has something. Can you describe the difference between theirs and yours?

The Austrians are using the Grätzel system. It's another technology using the photosynthesis process. The disadvantage is that you can only integrate this chemical fluid between glass panels.

Watch video 03:20

The secret of the Grätzel Cell - Tomorrow Today (09.07.2012)

With our system you can print on different materials, you can use different shapes, and it's even less expensive. But it's good to present everything, and then the idea of the expo is to invite the people to see it and to take these ideas and use them in their design in offices or at home and develop new products.

The adaptability of these new technologies is, however, a very important point. Could you use your solar technology on clothing, for instance, or bags?

Yes, on clothing, or on smartphones - for instance, a new charger could be a small panel with a cable attached and while driving a car you could put it on your window [to charge your phone]. So, hopefully, people coming here will invent new products with this new technology.

Lennart Wiechell is an architect with Schmidhuber in Munich. He was one of the designers of the German Pavilion at Expo Milano 2015, as well as at the 2010 expo in Shanghai.

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