Giga wind turbine

[JumbleDuck]

I did see some old KickStarter ads. for a 5V USB charger looking remarkably similar. I wonder if they might have been trying to start under a different name. Still calling it a GIGA though and it is dated mid-2019.

GIGA | A Portable Wind Turbine for USB Charging

I'm pretty sure I have done this before, but in case not. 1A@5V USB charging is 5W. A small turbine like that is most unlikely to be more than 10% efficient, so that means 50W going through it. It's ~30cm diameter, so that's 700W per square metre needed in the approaching flow. That takes 10.5 m/s, which is spang in the middle of F5. However, they show it mounded on the ground, where wind speed will, thanks to obstacles and the boundary layer, be much less. At a conservative estimate, half as much, so that mean 21 m/s, on the F8/F9 boundary for much charging

Yeah. Right. About as likely as those silly toys someone persuaded the O2 to buy.

 

[Mistroma]

I'm pretty sure I have done this before, but in case not. 1A@5V USB charging is 5W. A small turbine like that is most unlikely to be more than 10% efficient, so that means 50W going through it. It's ~30cm diameter, so that's 700W per square metre needed in the approaching flow. That takes 10.5 m/s, which is spang in the middle of F5. However, they show it mounded on the ground, where wind speed will, thanks to obstacles and the boundary layer, be much less. At a conservative estimate, half as much, so that mean 21 m/s, on the F8/F9 boundary for much charging

Yeah. Right. About as likely as those silly toys someone persuaded the O2 to buy.

Yes, sounds about right. I think I remembered a figure of about 1/8th the output of a Rutland 913 from a previous very generous estimate simply based on swept area. It's been more than 10 years since I did calculations for the Rutland but vaguely remember efficiency estimates in region of 17% - 24% when trying to predict likely real world output. I think that was when I was trying to persuade myself it had been a good idea to buy a Rutland 913.

I suspect you are correct with 10% for this design. People often say that these are sensible in Scotland due to the low insolation levels. However, it doesn't take much effort to show that's not correct. Tiny wind-gens are a niche market these days (up a mountain in the middle of the night). Possibly very popular with winter campers near the village of Rjukan in Norway (average daily hours sunlight from September to March is zero).