Wind farms can slow down the winds in their wake for tens of kilometres, potentially reducing the electricity production capacity of other wind farms downwind considerably, reports a paper published online this week in Nature Energy. Adequate laws may not exist to discourage such inefficient siting of the wind farms.

Turbines are known to reduce the speed of the air in their downwind wake. Due to the difficulties in measuring these changes in wind speeds, most studies into this effect turn to computer models to determine how much the wind speed is diminished at a given distance downwind from a turbine. It is similarly challenging to measure the exact effect of the wake on downwind electricity production - and it is even harder to quantity this between wind farms with multiple turbines.

Julie Lundquist and colleagues use a unique record of the change in electricity production of a wind farm in West Texas when another farm was built upwind. Bringing together data on the energy production at the downwind farm, they estimate that the downwind farm may have lost as much as US$2 million annually in lost electricity production. They then use computer models to verify their findings. Reviewing relevant US laws and regulations thoroughly, the authors find that no adequate legal framework exists to deter this inefficient siting of wind farms. This study shows that although wind is often seen as one of the most benign electricity sources, wiser selection of locations for wind farms would avoid circumstances where neighbours unintentionally end up extracting from each other’s resource.