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Green Futures

Green Futures

This article originally appeared in Green Futures magazine. Green Futures is the leading international magazine on environmental solutions and sustainable futures, published by Forum for…

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Bladeless Turbine: The Future of Wind Energy?

The Saphonian turbine is more efficient, quieter and safer for birds, its makers claim. Could it represent the future of wind energy?

Innovation always pushes boundaries, but what about pushing the laws of physics? Tunisian start-up Saphon Energy claims it can do exactly that with the Saphonian, a bladeless turbine that harvests more energy from the wind than previously thought possible.

The makers claim that the turbine exceeds Betz’ Law, which caps the amount of kinetic energy that a turbine can harvest at 59.3% of the wind’s total energy.

“The basic idea is that you can’t take all the energy out, because the air would stop moving”, says Ken Caldeira, a climate scientist at the Carnegie Institution for Science.

The Saphonian replaces the blades and rotor with a concave disk. The wind pushes on it in a “back-and-forth 3D knot motion”, explains Hassine Labaied, Saphon’s CEO. The kinetic energy of the wind is first converted to mechanical energy via pistons (connected to the disk), then to hydraulic energy, and then to electricity. Labaied claims to have “very promising results”, showing the turbine is 2.3 times more efficient than a bladed turbine – a level of efficiency that would put it above Betz’ limit.

Related Article: Rural Alaska Shows us the Way for Wind Energy Installations

But not everyone is convinced. Caldeira described the claim as “wacky”. The company plans to address such skepticisms in a detailed demonstration that will be published later in the year.

Whether or not the questions over the turbine’s efficiency are resolved, other advantages it offers are undisputed. It’s quieter than standard turbines, and doesn’t pose a threat to birds.

But its cutting edge will likely be its lower cost. Saphon expects total investment costs to be 30-45% below that of current turbines, since the most expensive parts – the blades and the gearbox – have been replaced with less expensive plastics, fabrics and a hydraulic motor.

That’s an advantage that even Caldeira would be willing to embrace. “The efficiency of extraction is not the issue right now”, he says: “It’s really if you can do it cheaper.”

By. John Eischeid


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  • Ken Caldeira on November 26 2012 said:
    "The makers claim that the turbine exceeds Betz’ Law, which caps the amount of kinetic energy that a turbine can harvest at 59.3% of the wind’s total energy."

    I am a climate scientist and not in a position to offer an informed engineering assessment of any class of turbine technology. It is possible that the Saphonian turbine is a marvelous piece of creative engineering.

    Nevertheless, the laws of physics prevail.

    Perhaps someone in Saphon is misapplying "Betz limit",for example, by referring to blade [or sail etc] area instead of swept area.

    If the Betz Limit is wrong then at least one equation on this page is wrong: http://www.wind-power-program.com/betz.htm

    Which equation is wrong?

    If Betz was wrong, why isn't the Wikipedia page updated?

    http://en.wikipedia.org/wiki/Betz'_law

    Physics will win out over rhetoric.

    Ken Caldeira 25 Nov 2012

    http://dge.stanford.edu/labs/caldeiralab/

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