Kitekraft Startup

[PierreB]

@dougselsam

Looks like they are using off-the-shelf plastic large-scale model airplane propellers, like both Pierre and I did with our early experiments. Great for flying, not so great for producing power.

I obtained about 67% Betz limit by car with a tiny propeller that rotated by the trailing edge, in an unorthodox way (it turned slowly, generating low power, when it faced the wind). In fact this propeller was so tiny (23 cm diameter) that it was almost flat. So perhaps, in a multiple rotor system, it is a not too bad temporary solution for flygen AWES.

Now concerning Kitekraft, one thing bothers me. Below are quotes from the respective Youtube videos:

(power production mode; during this flight wind was too low to actually produce power)

Wind speed: 1…3m/s from east. (This is below the cut-in wind speed and thus too little for net-positive power generation. A product-version kite would remain on ground and wait for stronger wind.)
Peak positive power: 4.2 kW (at kite in 800V DC tether).

Wind speed: 1…4m/s from west. (This is below the cut-in wind speed and thus too little for net-positive power generation. A product-version kite would remain on ground and wait for stronger wind.)

The wind always seems to be too low. Is it so difficult to test with 5 or 6 m/s wind speed in order to know the real average net-positive power?

This reminds me a bit of the Makani technical videos. In one of them we can see that even with a wind speed of 10 m/s, the average power still seems negative:

20190418 CW-06 - Sixth All Modes Flight of Makani M600 [Full Flight]