11 Blade Rotor

I have a Windmax H12 low wind generator with a 5 blade rotor (69inches) rated at 1kw @ 28 mph. The 28mph wind is a rarity here usually 10-20mph is normal. The Missouri Wind and Solar folks sell a 11 blade rotor (62 inches). They claim will turn up the rpm at less wind speed. What has been your experience? The Windmax is a nice machine. It sits on a 65 ft. tower, hooked to 2 stowaway batteries for 24 v. input. I have a Outback GTFX 2524 Grid-tied Inverter and am tied only to the grid . So far it makes an average of 1 KW a day IF WE ARE REAL LUCKY. Return on investment? NEVER Help Thanks Doug Gassett


  • BB.BB. Super Moderators, Administrators Posts: 33,085 admin
    Re: 11 Blade Rotor

    I don't have any information--Have you tried the www.otherpower.com forum at Otherpower Discussion Board?

    Since power is based on the square of the swept area:
    • 62^2 / 69^2 = 0.81
    So, just from an area point of view, the smaller blades will have access to ~20% less wind power--I am not sure if you could make up the losses with lower RPM increased efficiency...

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • russruss Solar Expert Posts: 593 ✭✭
    Re: 11 Blade Rotor

    Pure smoke - the cross sectional area of the rotors is what counts.

    More area equals more power. Forget the fancy sales talk about more blades or shrouds - that is all so much BS and nothing more.

    If you have an annual average wind speed of 20 mph that would be among the more windy places in the country. Most places don't even average 10 mph.

    Paul Gipe at www.wind-works.org is another good source of information.
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: 11 Blade Rotor

    if you want to slide the curve to lower wind speeds to reap the same power you need to lengthen the 5 blades that you have, but this may cause the safety measures on the turbine to be exceeded and not be able to handle the extra power available when wind speeds hit the higher marks even if briefly hit. also it may be necessary to modify the tail to move the extra large propellers into the wind. ask the advice of the company as to your options.
  • russruss Solar Expert Posts: 593 ✭✭
    Re: 11 Blade Rotor

    Look at the power curve for the unit in question. Below wind speeds of 5 m/s there is very little power in the wind to begin with. The claims of starting a t 3 mph wind speed are just a bad joke.

    Very few locations have an annual average wind speed of 5 m/s either.
  • keyturbocarskeyturbocars Solar Expert Posts: 375 ✭✭
    Re: 11 Blade Rotor

    Just curious Doug, how long have you had your Windmax wind turbine? Any problems (other than lower power output than desired)? Where are you located in the US (curious what the wind maps say for your area).
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