Wind Capability

I have been skeptical of the claims that covering South Dakota with wind turbines could provide electricity for the entire country. But it checks out by adapting the analysis of MacKay (p.265).

MacKay envisions a square array of windmills spaced 5d apart (d = blade length), and finds that they provide power of 2.2 W/m^2, independent of d (large d = wider spacing and the effects cancel out).

A hexagonal array can be more densely packed (area ratio = 16.2/25). Also I took the typical wind speed in SD as 8 m/s (MacKay use 6 m/s). As a result, MacKay's power of 2.2 W/m^2 becomes 8 W/m^2. Since the area of SD is 2*10^11 m^2, the total wind power becomes 1600 GW. Assuming a wind-turbine capacity factor of about 1/3, the electrical energy becomes 4.2*10^12 kWH (4,200 TWh), which is about annual US usage.

Elliot (MacKay, p,234) comes up with the same number when estimating the practical potential of wind power. He says that we could carve a California-size chunk out of the wind states without too much disruption.