Wind power is often touted as one of the “wedges” that will help us de-carbonize the global economy over the course of this century. However, a new study published in the journal Environmental Research Letters by Professors Amanda Adams and David Keith is a cautionary tale about the long-term prospects for wind power deployment in the face of potential physical constraints of the resource. The study assessed how reduction in wind speed associated with wind turbine scales reduces the capacity factor (CF), defined as “the ratio of actual power given the prevailing winds to the amount that would be produced if the turbines operated continuously as their maximum rated output.” Among the key take-aways from the study:
- Each wind turbine creates a “wind shadow” in which the air is slowed down by drag on the turbine’s blades. While discrete wind farms are able to compensate for this phenomenon by spacing them sufficiently to reduce the impact of wind shadows, this becomes more problematic and wind farms grow larger and start to interact. At this point regional wind patterns become more relevant;
- “Extraction of energy by wind turbine arrays is limited by the physics of atmospheric energy transport.” This suggests that maximum energy extraction from turbine arrays of very large wind power installations (larger than 100 square kilometers) is approximately 1 Wm-2 This suggest that recent estimates of wind power capacity of 56-148 TW may be high overestimated by a factor of as much as four;
- Wind power installations that could generate huge amounts of power, such as 100 TW, would also have profound effects on global wind patterns that could potentially be larger than the impacts of a doubling of carbon dioxide;
- The research here suggests a need for additional studies of realistic economic and social constraints of wind power siting, as well as potential climatic impacts of wind power extraction, to assess the resource’s ultimate potential.