I have just bought a turbine and have set it up, trouble is when I put a voltage meter on the output and found that in a 25kph wind it was producing 130 volts! As my system is based on 24 volts I am concerned that this will damage my batteries..Am I right?
Thanks
Colin

Personally, I would not try to build a DIY wind turbine to produce 40kWh per day! A production quality 5kW wind turbine, mounted at a site with average wind speeds of 5.4 m/s (my location) would produce around 33kWh per day. And the blades would each be over 10 feet long – over 20 ft sweep diameter.

If you want to look at production wind turbines, your first step is to determine the AVERAGE wind speed at your site. There are wind maps that contain this information – some maps show the average wind speeds at different heights. Your closest airport may have some average wind speeds for your area as well – even TV station weather departments.

Once you know your average wind speed, you can look at the production charts for various wind turbines to find out how much power they produce at that wind speed. A wind turbine may be rated at 5kW or 10kW, but it only produces that power at very high wind speeds. I’ve found that most wind turbines produce power at 1/10th to 1/5th of their rated power level, at 5.4 m/s which is the average wind speed for my location.

And don’t forget to price in a professional tower that is at least 30 feet higher that the tallest item in a 500 foot radius from your tower. You can expect to pay as much for the tower as you pay for the wind turbine.

Cuz I still don’t get how this all works. With all the different terminology – watts, KW,KW-hr, volts, amps, etc, “ratings”, “averages”, etc., etc, etc, ..

I just want to know, if you want to produce enough electricity to power an average home, approx. 40KW-hr per day, what Generator will do the job, how many RPMs does the shaft have to rotate, and how much “force” is required to rotate the shaft at that RPM speed?

All at a “continuous” operation of shaft and Generator?

Also, I just watched a video on how a wind turbine works………they have the Generator up top, by the blades, in the “box”.

Why are their 2 different shafts and why are their gears? It said “low speed shaft” and “high speed shaft”?

Is it “boosting” the electricity produced thru the use of gears?

I have some very specific, yet general, questions.

1) What would be the most “efficient” Electric producing Generator, to produce enough electricity to power the average home. Say approx. 40 KW-hr per Day!! i.e. requring the least amount of energy, wind, RPM of shaft, “force” upon shaft to rotate it.

2) What would be the required RPM of the Shaft of said Generator to produce the required electricity for an average home?
I just saw one video which showed a HAWT. That at 89.6 RPM it produced 101.4 Watts, at 268.9 RPM it produced 2,738.3 Watts (30.0 mph of wind). Clearly there is NOT a linear relationship between RPM and Watts produced.

3) What is the “resistance (mechanical)” or “friction” in the shaft? Or more specifically, what would be the “force” required to rotate the shaft at the required RPM to produce the required electricity, i.e. approx. 40KW-hr?
In other words, is the shaft of a generator “stiff” and difficult to rotate, requiring alot of “force”. Or is it “looser” requiring little “force”.
This would seem to be important to me. Because if you have a Generator which “can” produce alot of electricity, but even in a 60 mph wind the shaft won’t rotate because it is so “tight”. If you see my point?

To relate this to your discussion and information on wind turbines, this would be equivalent to how much “force” is required by the wind, upon the blades, to turn the shaft at whatever RPM to produce the desired electricity.
Maybe you use the term “torque” upon the shaft to rotate it, whereas I am using the term “force”.

Thank you.

Thanks for the reply. It will surely help me.

The formula for maximum power available, helps people understand that you can’t just keep putting a bigger and bigger motor on the blades and expect more power – there is a maximum that’s available, given the size of the sweep area (blades) and how strong the wind is blowing at the moment (velocity). It also points out that WIND SPEED has a huge impact on power output as the power available is CUBED by the wind speed.

Also, as a DIY wind turbine, you’ll likely find that your output is half of the maximum. Do it yourself wind turbines are not as efficient as large commercial units.

Regarding your generator, you need to know what the output is at around 400-500 RPM, and then you can use W=VxI to estimate the output in a strong wind.

if i’m not wrong, wouldnt i be more sure of the power output of my homemade windmill if i use W = V x I?
using the voltage and amperes from my windmill?

For my generator, what i know is that it puts out about 18 V with a quick twist of the rotor axle.

Can i use this voltage reading for calculating the windmill power?

Thank you…

Unfortunately there is no single simple formula for a VAWT. As the shapes for a VAWT can differ, (Darrieus,Savonius,Giromill – lift or drag) the formulas can become very complex.

In this study of a Darrieus VAWT, the study broke the blade into 50 separate segments, as each segment has a different angle of attack on the wind. ( http://www.reuk.co.uk/VAWT-Vertical-Axis-Wind-Turbine.htm ) .

As you’re make a VAWT as a hobby, why not simply post the power output you get, to share with others.

Bruce.

I understand why a HAWT is more effecient than a VAWT. I was wondering if there was a different formula for VAWTs. Something like replacing “diameter x height” with “sweep area”. It seems that the formula above is based on wind facing area and using this replacement would work for VAWTs if there isn’t another one. To get too much farther you’d have to start calculating wind directional changes. And how would you measure the power comming off if its high torque and low speed?

A VAWT is never as efficient as a HAWT as half the time the blades are turning INTO the wind. There are designs that block the wind on the returning side, or cause the blades to go limp, but these designs just add complexity.

Here’s a link to one VAWT I built:

http://greenterrafirma.com/diy-vawt.html

The beast turns great without the motor, but my gearing was to great – add the gearing and you need a wind storm to make it go around. If you want to try this design, I’d recommend using fins that are twice as long, and adding another bicycle rim to the middle.

Let me know how your system works out… love to see pics.

Bruce.

I’m working on a novel design for a VAWT. Do you have a similar formula for a the power you can get from a VAWT so I can compare my result with the standard?
Also how (if at all) would the formula change if the VAWT was slow, with high torque?