Wind Maps for California [RE-wrenches]

[matthew tritt]

Bob-O,

True enough. For a real laugh, take a look at the wind data accumulating
sensors at most airports. They are generally mounted on a building with
about 6 or 8 feet of space between the roof, or wall, and the sensor.
10 meters from the ground yes, 10 meters from the effective ground no. 10
meters is the nationally accepted sensor height for most ground-based
meteorological stations but, on the water, they are generally mounted much
closer to the surface on buoys. This is especially strange as, you will
notice from the maps, most of our wind resource in Cal. is right along the
coast.

Since the observed winds are often calculated at a point very close to the
surface, there is a very good chance that the actual, useable winds are
considerably greater than published. Using the "1/7th rule" to calculate
winds at greater heights gives a reasonably accurate picture of the power
available at those heights; I'm just too thick to make the formula work for
me most of the time.

Another curious thing is the way in which anemometers are often mounted on
poles. There is a 10 meter PG&E weather monitor tower near here (put there
to calculate which way the radioactivity will travel during an "Event" at
Diablo Canyon) with the cups mounted on the down-wind side of the tower. All
the data gathered for our prevailing Westerlies is, therefore, hopelessly
flawed because of down-wind turbulence (not to mention being located 15 feet
from a highway!).

In spite of greater efficiencies of very tall towers, many ridge-top sites
are not suitable for their use, because of installation problems and FAA
height restrictions. Don't totally discount the appropriateness of shorter
towers in certain applications. In some cases they are the only solution
available and may be a very good choice. (IMHO)

Matt
----- Original Message -----
From: "Bob-O Schultze, Electron Connection" <econnect at snowcrest.net>
To: <RE-wrenches at topica.com>
Sent: Wednesday, December 18, 2002 8:41 AM
Subject: Re: Wind Maps for California [RE-wrenches]


> Amigos,
> IMO, the whole program of taking wind data readings from a 10m tower
> and extrapolating it for higher (but not actually recorded) tower
> heights is hopelessly flawed.
> As David points out, there is still some turbulence at 10m even where
> the measurement site is ideally situated. In reality, the data sites
> are rarely so situated. I can show y'all pictures of all five of the
> wind data sites here in Siskiyou county. One, maybe two give
> semi-accurate data. the others are in the trees, right next to the
> freeway where turbulence from trucks affect them, on and on. If your
> 10m data is flawed, then any mathematical extrapolation from that
> data is bogus. Garbage in, garbage out.
> Bob-O
>
> >Yes, the wind increases with height above the ground. These are
> >estimates of the
> >windspeeds based on the assumed wind shear that is expected. I
> >consider 30m to be
> >the minimum height for good wind energy. Wind turbines mounted at
> >10m generally do
> >not work and if they do have very low energy production and much
> >shorter life due to
> >turbulence.
>
> --
> Bob-O Schultze, Electron Connection
> PO Box 203, Hornbrook, CA 96044
> 800.945.7587 or 530.475.3402
> fax 530-475-3401
> www.electronconnection.com
>
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