Coleman wonder turbine gives 3x the Betz limit!

Thanks to Doug Selsam for this helpful commentary on the Coleman 600W turbine that is only 2 feet in diameter and produces three times the notoriously obsolete “Betz limit“.

About hugh

I live off-grid in NW Scotland and have spent my life playing with wind turbines. I also love small hydros. Hands on renewable energy is my thing and I like to learn and to share my experiences.
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4 Responses to Coleman wonder turbine gives 3x the Betz limit!

  1. Roger Brown says:

    Hi Hugh –

    How can anything beat the Betz limit though? My understanding Betz is a idealized theoretical max based on blades with zero drag.

    • admin says:

      Sorry, Roger, I was being ironic. I quite often see products being touted on the internet with improbable performance claims and, like you, I respect the known laws of physics and treat such claims with mild hilarity.

  2. Gavin McPherson says:

    I think this is a rebranded version of the Sunforce 600W. The manuals are almost identical and Sunforce are listed for technical support.

    Coleman 600W manual

    Sunforce 600W manual

    The Sunforce 600W rotor diameter is 1.31m (giving a Cp of about 0.4) and the Coleman 600W rotor diameter is quoted as 0.65m (giving a magic Cp of about 1.5).

    It looks like Coleman somehow mistook the turbine radius for its diameter. The blades look about 2 foot long to me – see figures 11&12.

    A purchaser might not be disappointed by the turbine’s output, though they may be a little surprised by its size!


    • admin says:

      Thanks, Gavin, I think you have the answer. Although I am still skeptical even after the performance has been divided by four. Still it is physically possible now.

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