On Jan 5, 2009, at 2:11 PM, Jed Rothwell wrote:
Some useful energy info here. See:
http://www.pickensplan.com/theplan/
The windspeed map looks newer than the ones I have from EIA. Seems
to be from Stanford U. but I have not tracked down the original yet.
- Jed
Looks like it came from here:
http://www.3tiergroup.com/
http://firstlook.3tiergroup.com/
(The above takes a while to fully load.)
The above mapping facility has the advantage of compensating for
windmill height, which is why it probably varies from the DOE maps.
http://en.wikipedia.org/wiki/Wind_power states
“The wind blows faster at higher altitudes because of the reduced
influence of drag of the surface (sea or land) and the reduced
viscosity of the air. The variation in velocity with altitude, called
wind shear, is most dramatic near the surface. Typically, the
variation follows the 1/7th power law, which predicts that wind speed
rises proportionally to the seventh root of altitude. Doubling the
altitude of a turbine, then, increases the expected wind speeds by
10% and the expected power by 34%.”
The power from wind is proportional to the cube of the velocity, so
the power increases with the 3/7 power of altitude. At 15,000 ft the
power is only 60 percent more than at 5000 ft. The majority of that
altitude benefit can be obtained by building wind walls on high
rugged mountain tops, which concentrate wind over their ridges.
A non-economic wind power class 2 location at an altitude of 50 m has
average wind speed of 5.6 m/s and power density of 200 W/m^2.
Applying the 1/7th power law, a 1 km tower in that location would
experience an average wind speed of (1000m/50m)^(1/7) *(5.6 m/s) =
1.53*(5.6 m/s) = 8.54m/s. This turns a useless wind class 2
location, into a wind class 6 location, with 600 W/m^2 wind power
density.
I have often thought it may be economic to build "wind walls", huge
3D geometric structures, possibly mixed geodesic, capable of running
very large windmills mounted to the steel beam structure. Such a
structure should be much more economical to build than a single high
tower for each turbine.
Alaska often has sustained high winds, hurricane force, at high
elevations. Windmills built along mountain ridges could produce vast
amounts of energy. One problem is avoiding shutdown during peak
energy production periods. This can be accomplished by providing an
additional set of small diameter high wind speed turbines that do not
have to be feathered.
Best regards,
Horace Heffner
http://www.mtaonline.net/~hheffner/
