wind speed versus blade size

[jbear]

I am trying to get a wind genny ready to assemble.

We have very un-common wind wind speds here in the UP of MI.

During the off wind season our winds may only hit 8-10 mph, when wind seaon occurs it is not a problem to run 25-35 mph 24/7 and have sustained wind speeds of 65 mph or greater for days.

Now the big question:

Which blade size will be the most logical size to work with?

Keep in mind that we are off grid with no grid connection possible, are running on a small bank of 16, 225 ahr. bat's with a 2500 watt inverter, 12v system set up do to the limits of the inverter.  Jbear

[scottsAI]

Hello jbear,

Answer will depend on your goals and cost.

System requirements for the wind speeds are quite different.

8. -25 mph follow standard plans.
   
25. -65 mph need something new. Furling system at these speeds not a good idea. Actually what would you need a furling system for? Tornadoes?
    
    

Both are doable, one feller here did 150 mph wind speeds, propeller from large plane!

Two step variable pitch blades may be one way to go.

Or

Two wind turbines or two sets of blades, change them seasonally.

What are your thoughts?

Have fun,

Scott.

[jbear]

Scott

Thanks for the reply. Obviously cost is always a factor, at least where I come from.

We catch the winds from Lake Supior and at times they can be very intimidating for a wind genny situation.

After all the looking around and studying I figure the best bet is with wind for us. We have plenty of sun but a longer wind season.

Would you be inclined to think the regular "by the book" plans will hold up into the 30-40 mpr area?

My other problem is that I can not always be around to lock out one leg in the event we have extra force winds so what would be the simplest solution to that one?

Jim

[jbear]

Scott

I also forgot to ask, wich of the sizes may have a better chance for servival and still give a reasonable output at lower winds? Jim

[scottsAI]

Hello jbear,

Which is more important power when the wind is 10mph or 30mph?

Common with RE is to have two sources of power (not backup)

70% wind, 40-50% solar, that way when one does not work the other probably does.

If the wind gen must handle high winds without intervention, then I would design it for the high winds. Not a standard design.

But the first question above looks like it will be the deciding factor?

Food for thought.

7. ' dia wind turbine with TSR = 2, 36% eff.
   
10. mph = 70watts at 80RPM.
    
25. mph = 1100watts at 200RPM
    
50. MPH = 8800watts at 600RPM
    
65. mph = 19300watts at 780RPM
    
    

Power is cubic, one heck of a generator!!!

Air Plane wood blades go much higher RPM, not a problem.

Nice 25 HP induction motor to get the 20kw this could generate.

If the blades are not fully loaded then the RPMs go up, as much as 2x (no load).

You see the design requirements are much different between the low speed and high speed systems.

No furling in the high speed, you just take anything the wind blows!

The low speed designs handling the high speeds? I would worry about doing that. I read about the failures in the high wind speeds. Some successes, how lucky do you feel?

Larger blades gets more power in the lower wind speeds, but the power of the wind becomes too much to handle.

A more complicated design with variable pitch could be your solution. Larger blades. Change the TSR for the wind speed, drop to TSR = 1 at the higher speeds to protect the blades (constant RPM is best choice). This would be my choice. Not my choice for the first wind gen design.

Have fun,

Scott.

[thefinis]

One solution would be to build two turbines one for low winds and one for the high wind season. Your high wind turbine would take a smaller more durable blade set while the large low wind turbine would need to have a good furling  system with a manual furling system to shut it down in high wind times.

If I had to choose one I would go for the high wind system that is where the best power is and probably when you need the most power.

Finis

[jbear]

Scott

Sorry for the delay in responding, PC problems.

My biggest problem first off is the lack of $$$$$$ so I must build as much as I can from scratch. I am not familiar with a lot of the terms used on this site as I am totally new to this whole program. I am-or was a builder/mason by trade, very much uneducated in this type of electricity. However, I can wire a house and make code. can wire a car etc. and get it to work just fine so ??

I have decided to build the 10 foot axial flux genny with the 8 foot plans for the genny itself. I have everything except the mags and wire just laying around.

Got to get the mags and wire!

Can I set this thing up so as to self regulate it's own output to the batterys?

a charge controller? Currently we are running (permanently) in the off grid situation. Running a Trace inverter, 2500, charging 16-225 amhr. batt's at present with no forseeable up-grade do to cost, system is 12 volt converted to 120 AC.

just what do I need to get this thing up and runing besides building it?

Need lots of help as you can see. Jim

[jbear]

Finis

I think I will follow your advice as I have been leaning in that direction. 2 units instead of one.

I do have a couple of other question's of things that I do not understand.

If the genny's are producing AC power why would a person want to convert it through a rectifier to DC? would it not be simpler to run the AC power right into the inverter to charge the battries?

As a first time project that I really need, would you recommend building the Flux plan 8ft. unit with 10ft. blades or skip it all together and build something larger?

I simple can not play around with gas units any longer, am sort of straped for cash as I am permantly disabled as of a couple of years ago. can still get out and do this that and the other, just takes time.

if you go back one or two posting's you will see what I am working with for storage of power. At present we chage every other day, when the temps come up it will go hback to every 3rd. day.  Thanks, Jim