Wind Turbine Height and Increased Efficiency

Author: Velocity Suite GIS Analyst

In the January release of the EIA Electricity Monthly Update, one of the articles explored the correlation between the increased height of modern wind turbines and growth of wind turbine capacity. The article describes a 37% increase in average hub height (196 feet to 265 feet) between 2001 and 2014 – a time period that coincides with an average turbine capacity increase from 1 MW to 2 MW. The article attributes the increase to greater wind speeds at higher altitudes along with the ability to outfit larger blades on taller turbines.

By querying and analysing the appropriate data, the relationship between turbine height and increased efficiency can be explored through the Velocity Suite’s database. After isolating wind farms that utilize only one generating unit, a figure can be obtained by dividing the unit’s operating capacity by the total number of turbines within the wind farm’s geographic footprint – MW per obstacle. This value was applied to every obstacle within the wind farm’s boundary and then divided by the individual height above ground value for each turbine, creating a MW per foot value.

It is important to note that this method distributes the capacity of a generating unit evenly across all wind turbines within the footprint, creating a false equivalency between turbines. Furthermore, the analysis was limited to wind farms with boundaries verified through aerial imagery. Ultimately, approximately 200 wind farms with over 8,300 turbines were included in the analysis.

A Time Series Animation Map (below) was created using the data from this analysis within the Velocity Suite EV Map. The animation displays turbines as their construction was reported to the FAA (Federal Aviation Administration) between July of 2000 and December of 2015. The embedded legend allows for a quick reference to the height of a cluster of units while the size of the point demonstrates the efficiency – a large point represents a high MW/ft value.

The correlation coefficient between the height of a wind turbine and its MW/ft value was .464, suggesting that factors beyond the mere height of a turbine influence the effectiveness . The Time Series Animation Map not only allows the user to see the geographic distribution of the more efficient turbines; users also can see temporal distribution as more efficient turbines come online later in the animation.

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