About 3x as Much Wind Power Available at 80m than at 50m hub heights

A new National Renewable Energy Laboratory (NREL) study, taller wind turbines can produce more power.

This is no surprise to anyone. Trees and other objects on the ground slow the wind, and as you get higher, you enter the region of smooth laminar flow where more energy is available. Laminar flow starts at about 50m.

A wind turbine with a hub height of 50m will have half its swept area above 50m. A wind turbine with 50m blades and a hub height of 80m. See my drawing:

What is interesting is that we may need to revise all our assumptions about how much wind is available for electric power. In Colorado, NREL found 3x as much wind potential at 80m than a previous Colorado study using the 50m hub height assumption. After all, not only is there more swept in the laminar flow, but there are more areas where tall wind turbines would have the 30% minimum capacity factor NREL assumes is enough to make them economic.

Here’s a graph showing the increase in capacity factors going from 80m to 100m hub height.

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2 Comments

  1. It isn’t exactly news to anyone that better wind conditions exist at 80m rather than 50m (and 100m rather than 80m, more or less etc.).

    Whether or not the wind at various distances above the ground should be considered part of the potential resource depends on a host of economic factors. You might ask why developers ever build wind turbines on anything other than the tallest possible towers. Since the character of the wind was known, this new estimate is not exactly news unless they are making claims about the improved economics of capturing higher winds.

    (Now that I’ve spouted off, I guess I’d better go look at the study to see what they actually are saying.)

    • Tom said

      I agree, not exactly news… the news is that there is about 3x as much, as opposed to 2x or 10x.

      I believe, that the “tallest possible tower” has gotten taller over time, leading to changing economics and increasing hub heights… and requiring the new studies.

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