Geologist/Environmental Scientist Compiles Data on High-Altitude Wind as Renewable Energy Source

Date: 06-24-2009

Kathleen McPartland
Public Affairs
Cristina Archer
Geological and Environmental Sciences

Cristina Archer, faculty in the Department of Geological and Environmental Sciences at California State University, Chico, has collaborated with Ken Caldeira of the Carnegie Institution’s Department of Global Ecology to compile the first-ever global survey of wind energy at high altitudes.

Archer is a world expert in wind power and has done considerable research on mapping the wind resource near the ground. Also a meteorologist, Archer is interested in large-scale flows in the atmosphere. She is the author of a paper on jet streams and how they are slowly shifting toward the earth’s poles. Archer said, “Linking wind power and jet streams was a natural evolution in my research. Ken Caldeira, who was my former supervisor at the Department of Global Ecology, had looked at high-altitude winds in the past and was interested in moving forward with this idea, so we agreed to collaborate on the research.”

The two researchers used 28 years of public data from the National Center for Environmental Prediction and the Department of Energy to assess the potential for wind power. They transformed the data in such a way that they could extract information regarding wind power density at each level in the atmosphere.

In an article on Archer’s research in the online journal ScienceDaily on June 16, 2009, jet streams were described as “meandering belts of fast winds at altitudes between 20,000 and 50,000 feet that shift seasonally, but otherwise are persistent features in the atmosphere.” Jet streams have great potential for energy production because they are large (usually a few hundred miles wide and almost three miles thick), persistent and can reach speeds between 57 and 300 miles per hour.

The highest wind power densities are over Japan and eastern China, the eastern coast of the United States, southern Australia and northeastern Africa, reported lead author Archer in the ScienceDaily article. “The median values in these areas are greater than 10 kilowatts per square meter,” she wrote. “This is unthinkable near the ground, where even the best locations have usually less than one kilowatt per square meter.”

“For cities that are affected by polar jet streams, such as Tokyo, Seoul and New York, the high-altitude resource is phenomenal,” said Archer. “New York, which has the highest average high-altitude wind power density of any U.S. city, has an average wind power density of up to 16 kilowatts per square meter.”

Even at the high altitudes, there are times when the winds do not blow. About 5 percent of the time wind may not reach speeds sufficient for generating power, even in the best locations. “This means that you either need back-up power, massive amounts of energy storage or a continental or even global scale electricity grid to assure power availability,” said Caldiera. “So, while high-altitude wind may ultimately prove to be a major energy source, it requires substantial infrastructure.”

“There are actually a variety of companies developing technologies for retrieving winds at various altitudes, from a few hundreds of meters all the way up to the jet streams at 30,000 feet,” said Archer. Technologies include carousels of kites, flying electric generators and membrane wings with tiny turbines.

Archer received her MS in civil and environmental engineering in 1995 from the Politecnico di Milano in Milan, Italy, and a second MS in meteorology from San Jose State University in 1998. She then started her PhD in civil and environmental engineering at Stanford University, where her thesis work focused on the Santa Cruz Eddy, a vortex that forms over the Monterey Bay, as well as on wind power resource assessment for the United States and the world.

After completing her PhD in 2004, Archer worked for a couple of years at the Bay Area Air Quality Management District in San Francisco, a state agency that manages air pollution issues from stationary sources in the Bay Area. She then joined the Department of Global Ecology of the Carnegie Institution for Science at Stanford in 2007, where she worked on global climate change effects on the jet streams and on high-altitude wind power. She came to CSU, Chico in the fall of 2009 as an assistant professor, while keeping an appointment at Stanford University as a consulting assistant professor with the Department of Civil and Environmental Engineering. Her research focuses on renewable energy, especially wind power; numerical modeling of both atmospheric phenomena and air pollution; and global climate change.