Power (W) to Annual Power (KWH)

[fathernature]

Howdy again,

I'm the guy with the 30MPH winds. Anyway, I've decided to put together a business plan for a small commerical site of one 100 KW wind mill. I'm going to do wind testing with a 60 ft 5" diam PVC pipe with guyed wires. So I'm trying to figure out what kind of steady wind I get here.

I have been doing a lot of research and came across an equation that has been really quite helpful. It is P (w) = 0.5 X 1.225 (air density at sea level) X A (swept rotor area in M squared) X C (coefficient of performance) X Ng (generator efficiency) X Nb (gearbox efficiency) X V (veloctiy to the power of three).

So I've tested this equation with turbine power curves and it works, thankfully for me the beginner otherwise I'd be totally confused. So now I want to calculate the annual KWH output of my proposed 100KW rated turbine at my site to be tested so I can figure out if a profit can be made? Can anyone let me know how to convert my Watts into KWH's so I can apply the wholesale electric rate? It wouldn't hurt if the equation was explained a bit more too but as long as my math if on, I'm good to go testing.

Thanks

[Chagrin]

1000 watts supplied for one hour is one KWH. Nothing magical here.

..was that the question?

[richhagen]

If relationship of the energy in the wind is proportional to the cube of the wind speed.  What that would mean is that the average wind speed may not be the best measure, or at least not the only measure to consider if you are trying to calculate the annual energy output of your turbine.  If the wind was 12 mph 24/7/365 the average wind speed would be 12, however if the winds were calm for 12 hrs and 24 mph for the other 12 each day, the average wind speed would still be 12 mph however the total energy generated would be greater because the generator (if it didn't furl yet) would be producing about 8 times as much power half of the time (if it had the same efficiency at both wind speeds), and overall the output would be 4 times greater.  It seems to me that you need the average windspeed plus the standard deviation or some other measure to estimate the "gustiness" of the wind to accurately estimate the annual energy output of your turbine.  One of the many experts on this board probably already has a solution to that problem.

Just having fun,

RichHagen

 

[fathernature]

Thanks,

Who thought KW to KWH could be so simple.

About the second comment, thanks for that information, it will make my calculations much more accurate. I do have a 'Wind Speed Distribution Chart' in which I can read how many hours the turbine would experience each wind speeds and can therefore calculate the KWH for each wind speed over the year and add them up by using this chart and the turbines power curve.

Thanks!

[kenp]

Do you know what kind of equipment you would need for a 100Kw plant?  I'm guessing that our formulae for small wind setups won't quite work out. I live near a 50Kw mill that is regulated to spin at 60 rpm regardless of the windspeed. I believe it has brakes on the tips of the blades to keep the speed constant. You may have to leave the 30mph days out of the equation when figuring out your wind average. Then again, I could be 100% wrong.

Good luck with that project.

KenP

[Windswept Cypress]

I have posted a response that is too long for the comment section as a regular post.

Cypress

[elvin1949]

cypress

reply to your self

it will post

elvin

[Windswept Cypress]

Thanks, elvin.

See: Wind Resource Measurement on a Commercial Site, which is a

Topical post rather than a Comment post, is what I should have said.  I did not want to risk it being cut off, since it is long, and someone said comments limited size only.

Cypress

[gatu]

Depending on the area for which a turbine is designed, it will usually reach rated power between 12-15 meters per second (around 25-30 MPH)In a high wind area, the tubine will be designed for higher rated wind speed than in a low wind area. Most commercial turbines stop when wind speed exceeds 25 meters per second, so no problem with 30 mph winds.

You will have to relate the power curve of the turbine to the number of hours at each wind speed in order to determine estimated power output, as wind turbines are most efficient at extracting power when the blades tips move at the correct multiple of wind speed.

If you can, measure wind speeds at 10 meters, and at 20 meters, you can then (assuming your site is relatively flat) use the log law of wind sheer to determine how wind speed changes with height.

http://www.iesd.dmu.ac.uk/wind_energy/wetc132.html

This will tell you how rough your surface is, and allow you to estimate if there is any economic gain from raising the hub height (higher wind speed, but more expensive tower)

Also, consider if it is worth using a larger turbine, even if it means bringing in other investors, as $/kw would be lower, and generation a higher proportion of rated due to higher hub height.