a windspeed question for the guru's

[bob g]

after many years of waiting and planning it looks like my move back to kansas will become a reality later next year

my property is in the east central part of the state, in a decent wind area (cat3-4), the winds in summer are predominately
from the south and in the winter from the north as could be expected.

my property is on the north face of the largest hill/ridge in the area, and the centerline of the ridge runs east/west or perpendicular
to the prevailing winds.  winds from the south have no obstructions clear to the horizon (perhaps 25 or more miles) and from the
north there is a little treeline down low on the hill, but probably the treetops are over 100ft lower than the top of the ridge.

i am aware how wind accelerates up a hill gaining speed, and have witnessed this phenomena on this specific hill, where if the wind is blowing
anywhere around there it is blowing like hell up there.

the average windspeed in the area is between 9.7 and 12 mph depending on the source you want to use, so i figure 10mph to be safe as
the average annual windspeed, and i figure the hill effect probably gets me closer to 18-20 mph average annual speed up on the ridge.

i plan on a tilt up tower of likely no more than 25-30 ft

my thinking is, if i were to go higher i would likely move above the gains in windspeed from the hill effect, and as i hate heights i am not sure
there would be any more to gain by going higher anyway.

the question is how high before you start to lose the hill effect?

and lastly about how much power can one expect from a 10 ft machine running in 18-20 mph windspeeds?

 i don't need a lot of power 500 watts average at around 15 mph would thrill me to death.

also 30 mph winds are not out of the question in that part of kansas, also there are times that 40-50mph winds are pretty steady for
several days in spring and fall.  i would assume that the hill effect would make for some real interesting speeds up on that ridge.

i will be installing a couple kwatts of solar panels, and really do not need to worry about low windspeed cutin, however i would like to target
for the 15-20mph speeds of the ridge, so maybe if i only need 500watts i can use a smaller rotor than a 10ft?

any suggestions?

thoughts and comments are welcome

thanks
bob g

[jlt]

 A 10 f turbine is a standard design.I is better to dump excess power than not have enough 

[wpowokal]

Bob I personally would not go too high unless there are obstructions that necessitate you placing your turbine above these, having said that ground does cause some turbulence but your suggested height is probably reasonable. If time ever allows me to place a turbine at my current location I will place it at around the heights you suggest, then I can compare it with those units half way up the hill.

I would caution about overestimating turbine output unless you have exceptional winds and I agree with jlt.

allan

[SparWeb]

It sounds hokey, but why not go out some breezy day and fly a kite!

Gives you a direct feel for the wind direction and speed.  Tie some streamers to the line as you feed it out, they will either flap straight out or wave madly if there's lots of turbulence.  If you can't keep the kite straight out and it wanders crazily, then the turbulence around the hill will defeat the advantage in wind speed.

Maybe you can find a "sweet spot" with that technique, too.  I've not done it myself, but others have, so maybe some searching will turn up a story or two.

[Ungrounded Lightning Rod]

How steep is the hill/ridge?

There has been some discussion lately about problems with furling using the offset-rotor, tilted-tail-hinge design if the wind has a significant upward component to it - as it may if the hill is steep and especially if you're near the top of it.

[B529]

bob g,

I'm on top of a west facing ridge, open to the west, west prevailing wind. I definitely experience the gain from being on top of the ridge. I couldn't even begin to guess the gain from being on the ridge, would take lots of anemometers to accurately make that claim. From my experience from installing turbines and collecting wind/output data, I would not take into consideration ridge gain when predicting output. Predicting wind/output is tricky business, aim low, especially on a short tower. With all due respect I believe your predictions are very generous, once again especially on a short tower. As far as getting too high to loose the effect, I seriously doubt you could install a tower high enough to loose the effect of ridge gain.

I have two anemometers on my tower at 35' and 62'. The annual average at  62" is 2.9 mph faster than 35', that is a HUGE difference, roughly twice the output.  A 25'-30' tower is  waaaay too short, go higher!!!! Putting up a taller tower really doesn't take much more effort or expense in the whole scheme of things. My tower is the shortest tower I've installed at 76' rotor height, my next tower will be 120'.

Kevin

[electronbaby]

I am also in agreement that a taller tower would not be a bad idea. Yes there are some exceptions to this rule, however determining them is very hard to do without being at the site personally, being familiar with your specific micro wind regime, and taking some basic measurements just to be sure. It is a wise idea to fly a kite or balloon with streamers attached to the tether to get a good feel for your turbulence window, and even this window will change with changing wind direction, and intensity. Surrounding tree rows, and ridges play a big part in seriously changing the wind quality around your site. Please research "displacement height". By knowing your Alpha (somewhat) and distribution, there are some power calculators that can be used to get a better handle on how this will effect your power production.

on the other side of the coin, however technical you make it, it is just an educated guess at the end of the day. I always thought that part of the beauty of homebrew small wind was that equipment could be built and had for very little money. This by default allows you to not be too concerned with large investments and "payback" periods as you normally would be with large expensive commercially available equipment.

just my two cents.

[dlenox]

Bob,

Your property sounds like exactly what I have here on my place in WV.  I live on the top of the ridge with the prevailing wind blowing in from the West, up the ridge to me.

From my experience, the one thing that you have to be careful of is - the angle of the wind as it approaches your turbine, you want to be careful that it does not come from 'underneath' the turbine as this can have a dramatic effect on preventing your turbine from properly furling.  Placement of the tower is critical in this instance and you want to keep it away from the 'edge' of the ridge so that the wind can level off.

I have experienced this first hand with my 17' turbine and would be happy to share the gorey details of it - offline would probably be best - and you can either phone me or email me offline at dlenox at briery dot com.

Dan Lenox

[ruddycrazy]

The turbine beside my shed is 36 metres below the top of the hill and the hill is about a 30 degree incline, when a gale comes thru the genny will take off topping out my 20 amp guage then die back to around 5-10 amps. The previous turbines and towers I've built had all failed when a gale came thru and in but one case a blade was found over 200 metres away.  The little 2hp motor conversion has been going for a couple of years now with my original 3 metre blades set and after last weekends winds it still going near perfect. Although it was raining and windy I was in my shed most of the day using my lathe and milling machine and the wind genny kept the batteries topped up and at the end of a 8 hour working day they were still on 25 volts. With my farm to put a wind genny on the hill will mean well over 150 metres of wire run and the tower would need to be near tank proof to survive the constant high winds. So for me putting my wind gennies on a slope is about the only option.

Cheers Bryan

[bob g]

thanks guys:

i don't know why buy i missed the responses to this topic until today.

anyway

the hill/ridge is a flat top about 500-600 ft x 1200 ft
it lays basically east/west

winds from the south face no trees or any obstruction for at least 35 miles that i know of

i plan on place the mill about 300 ft back from the edge, or basically in the middle of the flat top

guessing the incline from the south to be about 15-20 degrees max
from the north about 20 degrees max

floating a balloon with streamers makes sense to me, as i can weight the streamers to get some indication of windspeed
at various elevations.

when the wind blows, it is significantly faster up on that plateau, as evidenced by the difficulty of just walking up there.
if there is a 50mph wind, its best not to go walking around up there.

because my need for wind power is fairly low, perhaps i will build something that is designed around power winds
and use electromechanical furling such as an actuator to take absolute control of furling, and not fly the thing when winds
are too low, or definitely not fly when the winds are high or gusting.

btw, there is no way  i will be deploying a tower over about 30 ft max, i refuse to climb a tower of any height, therefore
it must be a tiltup and must be short enough to tilt up/down using some hydraulic means rather than a gib pole and truck method
or some other complex method requiring the aid of others and a lot of luck.

thanks guys

bob g