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Highlight Seminar Series: Cristina Archer, University of Delaware

Highlight Seminar Series: Cristina Archer, University of Delaware

Date: September 21, 2017

Time: 12:30 p.m. - 1:30 p.m.

Location: Maeder Hall

Professor Cristina Archer, of the University of Delaware, will speak on “Wind energy, atmospheric turbulence, and hurricanes: How to save lives and money with wind turbine wakes” as part of the 2017/2018 Highlight Seminar Series at the Andlinger Center for Energy and the Environment at Princeton University.

The 2017/2018 Highlight Seminars Series will be held on Thursdays from 12:30 p.m. – 1:30 p.m. in Maeder Hall at the Andlinger Center. Lunch will be served at 12:00 noon in the auditorium lobby of Maeder Hall.

Wind is already the cheapest renewable energy source and in certain cases electricity from wind is even cheaper than that from coal, natural gas, and nuclear power plants. This advantage is due in part to the fact that wind farms have been installed in the best locations, characterized by high and relatively steady winds. As the best spots eventually run out, wind farms will be installed inevitably at locations with lower and less reliable winds. How can wind power remain competitive in these less ideal conditions? Future improvements in wind turbine design and engineering are expected to improve wind turbine performance by a few percents. The most promising improvement, however, is expected to arise from smarter wind farm layouts that take into account the effects of wind turbine wakes. Understanding wind turbine wakes is therefore important to ensure future wind energy growth and competitiveness.

Results from sophisticated wake modeling simulations, called Large-Eddy Simulations, have already shown that smart array layouts can improve the performance of a wind farm by 13-33%. These smart layouts include increasing spacing between turbines along and/or across the prevailing wind direction and staggering, rather than aligning, consecutive rows of turbines.

In addition to improving wind farm performance, understanding wind turbine wakes can also bring unexpected benefits in the case of offshore wind farms. Large arrays of offshore wind turbines have been shown to provide protection from wind damage and from storm surge in coastal communities during hurricanes. This benefit, again, comes from the wind turbine wakes. Because wind turbines extract kinetic energy from the atmosphere, they lower wind speeds in their wakes. During hurricanes, these wakes can extend several kilometers downwind of a wind farm. Because winds are reduced in these wakes, wind stress on the ocean surface, which is proportional to the square of wind speed, is reduced too in the wakes. Storm surge, which is the sea level rise accompanying high-wind events and which is proportional to wind stress, is therefore dramatically reduced too. In addition, the lower winds also reduce ocean waves and surface friction, which feed into the hurricane core, weakening the hurricane. Results for hurricanes Katrina, Isaac, and Sandy show that tens to hundreds of thousands of offshore wind turbines can not only power the nation, but also reduce winds by 25-41 m/s and storm surges by 6-79%.

In conclusion, understanding wind turbine wakes is crucial to improve wind farm performance, keep wind energy economically competitive, and add protection from high-wind events in coastal communities. Wind turbine wakes can save you money and potentially save your life too!

Cristina L. Archer is an associate professor in the College of Earth, Ocean, and Environment at the University of Delaware, where she has a joint appointment between the Physical Ocean Science and Engineering program and the Department of Geography.  She received her Ph.D. in Civil and Environmental Engineering from Stanford University in 2004. She held a post-doctoral position there in 2004-2005 and then worked as an atmospheric modeler in the air quality district of San Francisco in 2005-2007. Dr. Archer joined the Carnegie Institution for Science in 2007 as a research associate. She was an assistant professor in the Department of Geological and Environmental Sciences of the California State University Chico during 2008-2011. She joined the University of Delaware in 2011. Dr. Archer’s research interests include wind power, meteorology, air quality, climate change, and numerical modeling.