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lab:zephyr:rotors [2016/07/16 20:02] – [Rotors] chrono | lab:zephyr:rotors [2016/07/25 13:46] – [Power Estimation] chrono | ||
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====== Rotors ====== | ====== Rotors ====== | ||
- | Compared to drag-only type rotors (Savonius), | + | Compared to drag-only type rotors (Savonius), lift-only type rotors (Darrieus) |
A drag-only type rotor can develop more torque, even at early stages in low wind conditions, but that would require a very specific and resource-intensive generator to accommodate for the very low rotational speed. A typical low end for a direct driven axial flux permanent magnet alternator with many poles is about 100 revolutions per minute. Everything under 100 rpm means huge additional resource investments into rare earth magnets and loads of copper (windings). | A drag-only type rotor can develop more torque, even at early stages in low wind conditions, but that would require a very specific and resource-intensive generator to accommodate for the very low rotational speed. A typical low end for a direct driven axial flux permanent magnet alternator with many poles is about 100 revolutions per minute. Everything under 100 rpm means huge additional resource investments into rare earth magnets and loads of copper (windings). | ||
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^ <x 12> | ^ <x 12> | ||
^ <x 12> | ^ <x 12> | ||
- | ^ <x 12> | + | ^ <x 12> |
**Example: eXperimental Turbine Lenz-Rotor with 0.96 m² surface @ 4 m/s** | **Example: eXperimental Turbine Lenz-Rotor with 0.96 m² surface @ 4 m/s** | ||
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| Decent VAWT | 0.30 | | | Decent VAWT | 0.30 | | ||
| Good VAWT | 0.35 | | | Good VAWT | 0.35 | | ||
- | | Superb | + | | Good HAWT | 0.40 | |
- | | Superb | + | | Big Grid MW+ HAWT | 0.45 | |
=== Torque === | === Torque === | ||
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<x 20> | <x 20> | ||
- | Re = {{V ∗ D ∗ \rho}/{\u}} | + | Re = {{V ∗ D ∗ \rho}/{\nu}} |
</x> | </x> | ||
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^ <x 12> | ^ <x 12> | ||
^ <x 12> | ^ <x 12> | ||
- | ^ <x 12> | + | ^ <x 12> |
- | ^ <x 12>\u</x> | m²/s | Kinematic viscosity of Air (1.57e-5 at 25 °C) | | + | ^ <x 12>\nu</x> | m²/s | Kinematic viscosity of Air (nu) ~1.57e-5 at 25 °C | |
**Example: Helical Gorlov-Rotor with 35 cm radius @ 4 m/s** | **Example: Helical Gorlov-Rotor with 35 cm radius @ 4 m/s** |