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Tree wind turbines

John LaurensonMarch 27, 2015

Tapping into the small, turbulent currents of air that blow around cities, a new French invention called the wind tree could bring wind power to urban areas.

Cité des Télécoms Business Park in Frankreich
Image: NewWind

Jerome Michaud-Lariviere was sitting in a garden on a seemingly windless day when he first came up with his novel idea. For all the stillness around him, he noticed the leaves on the trees moving. "There is energy there," he told himself. "Why not try to harvest it?"

The result is the wind tree. To date, Michaud-Lariviere's company, aptly named NewWind, has built two prototypes using the principle of biomimetics – the imitation of nature to solve problems.

In NewWind's small Paris office, where engineers are hunched over computer screens, aerodynamic studies manager Julia Revuz shows me a 70 centimeter-high green cone she calls an "aero-leaf".

Jérôme Michaud-Larivière
Image: NewWind

It is a vertical-axis Savonius wind turbine, invented by Finland's Sigurd Johannes Savonius in 1922, and is therefore what she describes as "proven technology."

There are 72 aero-leaves on the 12 meter-high, Italian-designed wind tree, the trunks and branches of which are shaped from a silver-colored metal. The size of these mini-turbines and the fact that they turn on their own axis gives them two major advantages over conventional wind turbines: they are silent and have rapid reaction times.

"When the wind speed varies, the wind turbine will be able to respond," Revuz told DW.

Urban wind power

France already has over 2,000 wind farms, and is planning to build another 8,000, both in the countryside and offshore. But some cities are interested in the wind tree as way of bringing wind power into towns.

Anne Ged is the director of the Paris Climate Agency. The agency is aiming to double the share of renewable energy in the French capital's energy mix, bringing it to 25 percent by 2020.

"It really is a good-looking project," Ged stressed, adding that the wind tree could be a sort of shop window for renewables. "If we are talking about renewable energy, we also need nice things in public spaces, because we need to raise public awareness of renewable energy."

NewWind estimates the cost of the wind tree at around $27,400 (25,000 euros). Each one would produce enough electricity to power fifteen streetlights, an electric car recharge station or a small family home - excluding heating.

Cité des Télécoms Business Park in Frankreich
Image: NewWind

The bigger picture

The company says the wind tree will produce electricity at 35 dollar cents/kWh which it describes as 'competitive'. But even if it works out at higher-than-market-price, Anne Ged says the price would still be worth paying for cities like Paris, or London and Berlin, which have also both expressed interest.

"When we talk about innovation, there's no point talking about short-term returns," she said. "But this innovation might lead to other ideas, which might contribute to other technology or processes that then lead to a more efficient business model."

But economics are not the driver for everyone. Alexandre Gady is president of the Society for the Protection of Landscapes and Aesthetics in France, an association that opposes what it describes as the disfiguring nature of wind farms.

Gady describes himself as a wind farm "non-believer". He says wind energy has flourished because people see it as a clean alternative to current sources of power. But that, he insists, is only a half-truth, because the intermittent nature of wind power means there will always be a need for fossil or nuclear fuel as a backup.

Small trees, small mercies

That said, he sees the innovative tree-like structure as an improvement on all other wind turbines. "Its scale is much smaller and much more seductive," he said. "It is pocket-sized compared to normal wind turbines which now measure 150 meters to the tip of the blade."

He also appreciates the artistic component of the tree, which he says implies an attempt to make something that actually fits into the landscape.

The wind tree could have an important role to play in increasing acceptance of wind power in France, which Gady says is dealing with more legal suits to move or dismantle wind farms than anywhere else in the world.

A wind tree prototype will be permanently installed in Paris before the United Nations Climate Change conference to be hosted there in December. The hope is that it will plant the idea of the wind tree around the world.