Hello,
They have installed some wind turbines next to my house. the monsters have a 80m tall mast and 70m diameter blades!
http://www.enercon.de/en-en/61.htm
however, what surprised me the most is that they claim that they deliver a max power of 2.3MW with a 45kph wind...
I was trying to calculate how much energy you could get form such a wind and could not come up with anything remotely close to that 2.3MW figure...
here is what I assumed:
- The energy is obtained from the wind kinetic energy
- the wind speed will drop by 1/2 (releasing 3/4 of it's kinetic energy to the mill).
- mass of air acting on mill = blade surface (estimated at 5% of the blade disk=3.14*(70/2)²*0.05=192m²) * 45000/3600 (speed in m/s) * 1.225 (air density) ~= 3Tonnes / second!
- kinetic energy of 3 tonnes at 45 kph = 1/2*3000*(45000/3600)² = 234_KJ
so, even if the darn thing was able to drop the wind to 0_Kph, it seems that it would be short a factor 10 on what the manufacturer pretends...
increasing the blade surface assumption would help, but since I do know that the blade cover less than 50% of the disk area, I do not think that this will cut it either..
any idea where I have things wrong?
cyrille