It does seem to have a distinctive odor about it.
The distribution of investors is also a bit interesting.

On 5/29/2014 11:38 AM, RussellMc wrote:
> This portable personal Wind Turbine is a good idea - but would need to ve=
ry
> handsomely break the laws of Physics to achieve its claims.
> Probably makes in the range 5% - 15% of claimed output.
> Longevity suspect.
> Funded to $72k of 50k target so far :-(.
> What are Kickstarter thinking???
>
>
> https://www.kickstarter.com/projects/skajaquoda/trinity-the-portable-wind=
-turbine-power-station
>
> And their videois terrible
>
>            https://www.youtube.com/watch?v=3DVaDqM0R97Uw
>
>
> Their graph (towards bottom of kickstarter page) shows power out of 13.5W
> at 16 mph
> 16 mph =3D~ 7 m/s
>
> Derivable rule of thumb:
>
>          At 100% efficiency a WT makes 600 W/m^2 at 10 m/s wind speed
>
> Swept area here =3D 0.3m x 0.1m =3D 0.03m^2
> So 100%  efficiency for 0.03 m^2 gives 18W at 10 m/s
> Power changes as V^3 so power at 7 m/s compared to 10 m/s =3D (7/10)^3 ~=
=3D 34%
> So output at 100% efficiency at 7 m/s =3D 0.34 * 18 ~+ 6.2 Watt.
>
> Betz limit =3D- theoretical max for unducted WT =3D~ 59% so theoretical m=
ax =3D~
> 3.6W.
>
> Best WT get 40%+
> Very good mainly drag with some lift get ~=3D30%
> Drag only 20% more likely.
>
> Their "airfoil design is very suspect.
> 20% would be lucky BUT assume 30%.
>
> 6.2 x 30% =3D~~ 2 Watt.
> Not the 13+W claimed.
>
> As they claim that this is a tested and finished design they are being mo=
re
> than (or less than ) economical with the truth.
>
> In a 15 m/s "breeze" ~=3D 33 mph =3D "quite fast" it may make design watt=
age
> claimed at half that speed.
> 15 m/s is not usually experienced.
> Diameter is about 0.1m so circ =3D~ Pi/10
>
> At 15 m/s at TSR (tip to wind speed) =3D 1
> RPS =3D 15/(Pi/10) ~=3D 47 RPS
> RPM =3D 60 x RPS =3D~ 3000 RPM.
> Operating TSR with any sort of efficiency (and the airfoils would need li=
ft
> - which they appear not to have) is liable to be >=3D 2:1
> =3D 6000 RPM or 50 RPS
> Looking at the construction, I'd want to be standing 100m or so away of
> that at 6000 RPM - a thrown airfoil dart could go 'quite a way'.
>
> Verdict: Not a chance.
>
>
>
>            Russell

--=20
John Ferrell W8CCW

"Go confidently in the direction of your dreams.
  Live the life you have imagined."
=96 Henry David Thoreau


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