Power Potential based on wind speeds and prop diameter.

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  • NASA Jerry ran us through these graphs and explained power potential as being exponential to wind speed and diameter, so higher winds and larger blades quickly make a lot more power. A rule of thumb is that as wind speed doubles, power goes up by a factor of 8 (exponential 3). Actually it is 2.7 and you can ask a 'wind expert' if it is the speed of the wind cubed or to the two point seven and a real expert knows the difference.

    But 3 works well enough. So 20 knots of wind has 8 times the power of 10 knots of wind and 40 knots of wind has 64 times the power of 10 knots of wind. One word: wow!

  • Next, armed with this, change the blade diameter and wind speed to calculate approximately how many watts you can obtain.

  • As you can see, there is a good jump in power from the common small 4 foot blades to 6 foot and 7 foot diameter blades.

  • Bear in mind; while in theory you can obtain about 33 percent more power from a perfect airfoil, folks who have flown wind generators know perfect blades are exposed to dust, dirt, birds, bearing wear, wind gusts, cable losses, corrosion, battery life, inverter losses and a variety of environmental effects that can quickly degrade performance.

  • While some pilots will polish and measure their wings to within 1000th of an inch, most wind gen folks put it up and forget about it so these figures are rather conservative and assume a blade that is in use and has degraded a bit over time, rather than some perfect blade that is remeasured and polished, repaired and refinished every single day.

Prop Diameter:
(in feet)		 For a wasteful family of 5, you need to make about 180 watts an hour every hour of the day, 365 days a year.. Your 'padding' for windless days will either be batteries (mildly expensive) or solar PV (exceptionally expensive). Our goal at this site is to teach you to pay for these expensive items with the utility savings you enjoy from wind power so the impact on your wallet of obtaining alternative energy is minimal.

Look up your local wind data and use that average wind speed and various prop sizes to calculate what type of system you want. Simply change the prop diameter and wind speed to see the approximate wattage and amperage you can expect for a 12 volt system from any reasonable airfoil. If you see a claim of more power from a smaller blade diameter, it probably isn't accurate.

If you are running a 24 volt DC system, divide the amps by 2. If you are running a 48 volt DC system, divide the amps by 4.

1KW=1000 watts
1 HP=746 watts
Wind Speed:
(miles per hour)
Output Wattage
Potential
Approximate Amps
at 12 volts
  • See how much more power there is at 50-60 mph? Almost all manufacturers and home-built systems furl or go into safety mode (depower) at 20-30 mph. These figures assume your generator is capable of producing that much power. Try our oversized 2kw-3kw gens with 7, 10 and 12 foot blades. or consider a 12kw system that can capture that all that raw storm power safely and easily without burning up your generators.

  • Also note that while you might get some power out of 3-5 knots of wind (yes, our blades may start turning at that low end), there isn't much power down there so we generally carve an airfoil that starts making power when winds are actually present to do the the job at hand (above 5 knots) and don't stall (stay quiet) until winds are much higher than most blades on the market.

  • Also note, that while a 7 foot diameter blade might be on a 2200 watt generator, the gen won't make that much power unless it is blasting 35 knots or better. NASA Jerry says 'Match the blade to the gen to the wind conditions for best performance." If you have light or medium winds, go with a 12 or 10 foot instead. This is one reason we often run a 4 or 5 foot diameter blade on large 2kw gens during winter storms that can blast 70 knots or better. Tthe maniacs here at the shop here at WindGenZen don't furl. We get every ounce of power out of our rigs and test them to their limits. You should furl (depower in storms) and we'll show you how to use our harshly field tested gens in the wild and wooly conditions in your neck of the woods and build a tough system that is bullet proof.

    The purpose of putting a larger gen on a smaller blade in head-on conditions like that is to prevent undersized gens from burning up in stronger winds. Most if not all manufacturers depower their units around 20-30 mph because their expensive gens are actually undersized for the task at hand. NASA Jerry, a sailor likes to capture the fantastic power from 20-40 knots and so our airfoil profiles are designed to take high wind abuse with our airfoil's high speed stall profile characteristics.

  • And in summer when winds are often light, a large blade on a small gen is fine, cheap to put together and will squeeze out as much power as you'll get from a larger gen. Matching the gen to the blade to the wind conditions is the trick for getting max output and the lowest cost per amp