As onshore and offshore wind energy farms have proliferated globally in recent years, new research led by 兔子先生传媒文化作品 highlights a previously underexplored consequence: a wake effect from upwind wind farms that can reduce the energy production of their downwind neighbors.
The study, undertaken in collaboration with the听听and the听, combines legal and economic analysis with atmospheric modeling to demonstrate that wake effects鈥攚hich occur when groups of turbines reduce wind speed for up to several miles behind them鈥攁re measurable and predictable, yet remain largely unaccounted for in current U.S. property law.
The research in the journal听Nature Energy.
鈥淭he findings highlight the need for coordinated development and awareness of the big picture in order to maximize wind energy generation nationwide,鈥� said Julie Lundquist, lead author of the study and an associate professor in 兔子先生传媒文化作品鈥檚听Department of Atmospheric and Oceanic Sciences (ATOC).
Wind energy developers seek out sites with reliable wind resources as well as convenient access to electrical transmission lines, leading to dense turbine deployment in choice areas with little coordination between competitors. Nearly 90 percent of U.S. wind farms are located within 25 miles of another wind farm鈥攁nd often much closer.
Yet much like a homeowner whose once-unimpeded views are blocked by new construction, the study shows that existing wind farms stand to lose valuable energy production if they suddenly find themselves downwind of a new neighbor and its wind- and energy-reducing wake.
Using publicly-available data on monthly energy generation and dominant wind direction, the researchers modeled the wake effect on a pair of West Texas wind farms, using a third as a control. They found that wind speed reductions due to the establishment of the upwind farm reduced generation at the now-downwind farm by 5 percent from 2011-2015, an estimated revenue loss of around $3.7 million.
鈥淛ust as upstream water users can knowingly or unknowingly impose additional costs downstream, the same effect is in play here,鈥� said Daniel Kaffine, a co-author of the study and a professor in 兔子先生传媒文化作品鈥檚听Department of Economics. 鈥淲e had a general sense of this interaction before and wanted to explore it further using a mix of social science and atmospheric data.鈥�
Kaffine and Lundquist, both fellows in the听Renewable and Sustainable Energy Institute (RASEI), noted that Texas made for a good case study because of its current and future stake in wind energy development, as well as historical parallels concerning usage rights for the state鈥檚 oil and gas resources.听
Over a century ago, oil and gas law recognized the 鈥渞ule of capture,鈥� which allows a landowner to capture a neighbor鈥檚 oil resources by sucking them from an adjacent well.听听This resulted in poor well-field recoveries and waste, so states intervened to regulate production through well-spacing, pooling and other coordination measures.听Similarly, states have developed water law regimes that protect rights for prior users. But current U.S. property law contains no such provisions for wind energy.听
鈥淚t took oil and gas and water law decades to create these legal regimes,鈥漵aid K.K. DuVivier, a co-author of the study and a professor at DU鈥檚 Sturm College of Law. 鈥淚t appears that wind energy has not yet reached a similar stage of maturity. I hope this research will help raise awareness about the extent of the waking problem and educate those seeking a legal remedy.鈥�
Turbine wakes have been observed to extend up to 25 miles, potentially spanning multiple state and county jurisdictions and complicating matters even further.
鈥淚n the immediate future, some business incentives might change,鈥� Kaffine said. 鈥淓nergy firms might put more emphasis on securing leases upwind to ensure they have enough of a buffer.鈥�
But while legal guidance may lag behind, Lundquist emphasized that the team鈥檚 sophisticated atmospheric science simulations show the wake effect is a highly predictable atmospheric phenomenon that can be modeled and planned for in light of the new data.听
鈥淚t鈥檚 encouraging that the wake effects seen in the economic analysis are captured by the atmospheric simulations,鈥� said Jessica Tomaszewski, a graduate student in ATOC who co-authored the new study.
鈥淭he strongest wakes occur at night, when the atmosphere is stable and wind speeds and directions meet specific criteria,鈥� said Lundquist. 鈥淥ut of the month of wakes simulated, only 28 hours, or less than 4 percent of the time, had wakes in excess of 20 percent of the downwind farm鈥檚 capacity, suggesting this episodic issue can be predicted and managed.鈥�
鈥淥wners and grid managers can use this information to get ahead of the issue. New research at NREL in manipulating wakes might be helpful,鈥� said Tomaszewski. 鈥淯ltimately, however, better coordination will be necessary to maximize the public benefits of wind energy.鈥�
Taking the wake effect into account will be especially crucial for the large number of offshore wind farms currently in development off the U.S. east coast, Lundquist added.
鈥淥ffshore wind farms are important, but they are expensive to build and mistakes will be equally expensive,鈥� she said.
鈥淭his project explores the links among economic, legal, and social issues and the geophysical processes in wind energy production,鈥� said Tom Baerwald, program director for the National Science Foundation鈥檚 Dynamics of Coupled Natural and Human Systems program, which funded the research. 鈥淭hese findings advance our understanding of these interactions, and provide guidance for successful development of renewal energy for the future.鈥�
The researchers hope to expand their efforts to measure wind farm wake effects by incorporating aircraft measurements as well as capturing data on a more frequent timescale from other sites around the country.
The National Science Foundation (NSF) provided additional funding via a Graduate Research Fellowship. NREL and the U.S. Department of Energy鈥檚 Wind Energy Technologies Office provided additional funding.
