Global wind power capacity may be overestimated

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Global wind power resources may be grossly overstated, and previous estimates of peak production levels of 2 to 7 watts per square meter may need to be scaled back to something closer to .5 to 1 watt per square meter, according to the results of a new study by Amanda S Adams of University of North Carolina and David W Keith of Harvard University.

One of the biggest upsides to wind energy is that in some areas, it seems infinitely scalable. Need more power? Put up more turbines! Need even more power? Put up a whole wind farm full of turbines!

Previous estimates of global wind power capacity assumed that the entire surface area could be covered in turbines, with a power production potential of anywhere from 2 to 7 watts per square meter, which meant that all that was needed to make more power was more turbines and more land to put them all.

But the results of the new study titled, "Are global wind power resource estimates overstated?" suggest that there are other limitations to wind power production, such as the interactions between wind farms themselves.

"People have often thought there’s no upper bound for wind power - that it’s one of the most scalable power sources." - Harvard applied physicist David Keith

Wind turbines create their own "wind shadow" of slower air behind them, due to the drag from the blades of the turbine. When placing multiple turbines in a large installation, these wind shadows are taken into account, and each turbine is spaced far enough apart to minimize the effects on other nearby turbines.

But it's not just the turbines themselves that create areas of slower wind. Once wind farms get large enough, they also act to create wind shadows of their own, affecting local and regional wind patterns.

Taking into consideration the effects of large-scale wind farms on other nearby installations, the new research suggests that the generating capacity of large wind farms (consisting of more than 100 square kilometers) may peak somewhere between .5 and 1 watts per square meter.

"Most estimates have implicitly assumed that extraction of wind energy does not alter large-scale winds enough to significantly limit wind power production. Estimates that ignore the effect of wind turbine drag on local winds have assumed that wind power production of 2–4 W m2 can be sustained over large areas. New results from a mesoscale model suggest that wind power production is limited to about 1 W m2 at wind farm scales larger than about 100 km2. We find that the mesoscale model results are quantitatively consistent with results from global models that simulated the climate response to much larger wind power capacities. Wind resource estimates that ignore the effect of wind turbines in slowing large-scale winds may therefore substantially overestimate the wind power resource.

Developing our clean energy future depends on good policies, which rely on getting accurate data and making accurate projections. While there are other limitations to wind power, such as the local wind energy density, or the proximity of a generating station to the area of energy demand, this new estimate of wind power capacity might also limit or affect how wind power policies are shaped.

Tags: Energy | Renewable Energy | Wind Power

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