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Wind turbines helping crops

January 6, 2011  By Fruit & Vegetable

windturbine02January 4, 2011 — Wind
turbines in farm fields may be doing more than churning out electricity.

January 4, 2011 — Wind
turbines in farm fields may be doing more than churning out electricity.

The giant turbine blades
that generate renewable energy might also help crops stay cooler and dryer,
help them fend off fungal infestations and improve their ability to extract
growth-enhancing carbon dioxide from the air and soil.


Speaking at the recent
annual meeting of the American Geophysical Union, a researcher at the U.S.
Department of Energy’s
Ames Laboratory and his co-researcher from the
University of Colorado announced the preliminary findings of a months-long
research program aimed at studying how wind turbines on farmlands interact with
surrounding crops.

“We’ve finished the first
phase of our research, and we’re confident that wind turbines do produce
measureable effects on the microclimate near crops,” said Ames Laboratory
associate and agricultural meteorology expert Gene Takle.

According to Takle, who is
also a professor of agricultural meteorology and director of the Climate
Science Program
at Iowa State University, the slow-moving turbine blades that
are becoming a familiar sight, channel air downwards, in effect bathing the
crops below via the increased airflow they create.

His colleague in the
research is Julie Lundquist, assistant professor, Department of Atmospheric and
Oceanic Sciences
, at the University of Colorado at Boulder, joint appointee at
the U.S. Department of Energy’s National Renewable Energy Laboratory, and
Fellow of the Renewable and Sustainable Energy Institute. Lundquist’s team uses
a specialized laser known as a lidar to measure winds and turbulence from near
the Earth’s surface to well above the top tip of a turbine blade.

“Our laser instrument
could detect a beautiful plume of increased turbulence that persisted even a
quarter-mile downwind of a turbine,” Lundquist said.

Both Takle and Lundquist
stressed that their early findings have yet to definitively establish whether
or not wind turbines are in fact beneficial to the health and yield potential
of crops planted nearby. However, their finding that the turbines increase
airflow over surrounding crops, suggests this is a realistic possibility.

“The turbulence resulting
from wind turbines may speed up natural exchange processes between crop plants
and the lower atmosphere,” Takle said.

For instance, crops warm
up when the sun shines on them, and some of that heat is given off to the
atmosphere. Extra air turbulence likely speeds up this heat exchange, so crops
stay slightly cooler during hot days. On cold nights, turbulence stirs the
lower atmosphere and keeps nighttime temperatures around the crops warmer.

“In this case, we
anticipate turbines’ effects are good in the spring and fall because they would
keep the crop a little warmer and help prevent a frost,” said Takle. “Wind
turbines could possibly ward off early fall frosts and extend the growing

Other benefits of wind
turbines could result from their effects on crop moisture levels. Extra
turbulence may help dry the dew that settles on plants beginning in late
afternoon, minimizing the amount of time fungi and toxins can grow on plant

Another potential benefit
to crops is that increased airflows could enable plants to more readily extract
atmospheric carbon dioxide, a needed “fuel” for crops. The extra turbulence
might also pump extra carbon dioxide from the soil. Both results could
facilitate the crops ability to perform photosynthesis.

Takle’s wind turbine
predictions are based on years of research on so-called agricultural shelter
belts, which are the rows of trees in a field, designed to slow high-speed
natural winds.

“In a simplistic sense, a
wind turbine is nothing more than a tall tree with a well-pruned stem. For a
starting point for this research, we adapted a computational fluid model that
we use to understand trees,” said Takle. “But we plan to develop a new model
specific to wind turbines as we gather more data.”

The team’s initial
measurements consisted of visual observations of wind turbulence upwind and
downwind of the turbines. The team also used wind-measuring instruments called
anemometers to determine the intensity of the turbulence. The bulk of the
wind-turbulence measurements and the crop-moisture, temperature and carbon
dioxide measurements took place in the spring of 2010.

“We anticipate the impact
of wind turbines to be subtle. But in certain years and under certain
circumstances the effects could be significant,” said Takle. “When you think
about a summer with a string of 105-degree days, extra wind turbulence from
wind turbines might be helpful. If turbines can bring the temperature down
below 100 degrees that could be a big help for crops.”

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