(By Robert Lee Hotz, The Wall Street Journal) – Large wind farms slightly increase temperatures near the ground as the turbines’ rotor blades pull down warm air, according to researchers who analyzed nine years of satellite readings around four of the world’s biggest wind farms.
The study showed for the first time that wind farms of a certain scale, while producing clean, renewable energy, do have some long-term effect on the immediate environment.
Using sensors aboard a NASA satellite, researchers at the University at Albany-State University of New York, and the University of Illinois systematically tracked a cluster of wind farms in central Texas as the installations grew from a few dozen turbines in 2003 to more than 2,350 by 2011.
On average, the nighttime air around the wind farms became about 0.72 degree Celsius warmer over that time, compared with the surrounding area, the scientists reported Sunday in the peer-reviewed journal Nature Climate Change.
“The warming trend corresponds very well with the growth of the wind turbines,” said wind-energy expert Somnath Baidya Roy at the University of Illinois, who was part of the research group. “The warming is going to level off when you stop adding more turbines.”
Despite long-standing interest in the environmental impacts of such large-scale alternative-energy installations, this is the first time anyone has measured how wind turbines can alter local temperatures over the long term, the scientists said. So far, the scientists don’t know if these higher temperatures affect local rainfall or other weather patterns.
“We don’t know whether there is a change in weather due to the temperature change,” said atmospheric scientist Liming Zhou at the University at Albany, who led the study, which was funded by the National Science Foundation. “The temperature change is small.”
As wind farms become popular and much more widespread, however, they “might have noticeable impacts on local-to-regional weather and climate,” Mr. Zhou said. But more research is needed, he said.
The researchers didn’t identify the companies operating the wind farms in the region where they monitored temperature changes. To track the growing numbers of wind turbines in the area, the scientists used records kept by the Federal Aviation Administration of construction projects that might interfere with air safety.
Texas has more wind-turbine capacity than any other U.S. state, with many large commercial wind farms. Typically, these commercial wind turbines each sit atop a tower about 250 feet tall, capturing the wind with rotor blades that are about 100 feet long, Mr. Roy said.
Normally, the nighttime air is a layer cake of cool and warm air, caused as hot air rises and cold air sinks, with the coolest air closest to the ground. As the giant rotor blades churn the air, they draw the warmer nighttime air down to the surface.
“If you have a wind turbine spinning, there is a lot of turbulence in the wake just like a boat in the water,” said Mr. Roy. “The turbine pulls warm air from aloft and pulls it down and takes cooler air underneath and pushes it up. That creates a warming effect near the surface.”
Although the researchers detected some daytime warming because of the wind farms, the temperature changes were highest in the predawn hours, when the air normally is still and not so turbulent, the researchers said.
Copyright 2012 Dow Jones & Company, Inc. All Rights Reserved. Reprinted here for educational purposes only. Visit the website at wsj.com.
1. What conclusion did researchers who analyzed 9 years of satellite readings around four of the world’s largest wind farms make? Be specific.
2. By how many did the number of turbines on wind farms in central Texas increase between 2003 and 2011?
3. How do the researchers know the temperature increase was caused by the wind turbines?
4. What don’t researchers yet know about the increase in temperature?
5. How large are commercial wind turbines?
6. Read the information under “Background” below and watch the video under “Resources.”
a) Define subsidies. Did you know that wind energy was/is subsidized by the government, i.e. the taxpayer? Explain your answer.
b) We hear much in the news about the positives of using wind to generate electricity. As you learn more about the negatives associated with wind energy, does it cause you to change your support for or against the use of wind farms to generate electricity? Explain your answer.
7. If a study determined that energy-generating coal plants were causing an increase in temperature, do you think it would have been a bigger news story? Explain your answer.
U.S. Wind Subsidies
WIND: (from instituteforenergyresearch.org/energy-overview/wind)
Historically, harnessing the power of the wind as an energy source has freed man from manual labor for centuries. Windmills were first broadly used to mill grain by turning stones, and later as an efficient means of pumping water into storage for later use on demand. Today, wind power is turned into electricity by converting the rotation of turbine blades on windmills into electrical current.
Wind power is typically generated by large-scale wind farms which are located either on land or just off shore where they are connected to power grids that distribute their electricity to end users. Some small consumers of power also employ wind power where construction of transmission lines is expensive or prohibited.
Today, wind power provides almost 1 percent of all the energy consumed in the United States. Though wind power has increased substantially since 1970, it constitutes only a small fraction of U.S. electricity supply. In 2010, wind power accounted for 2.3 percent of all electricity generated in the U.S.
Wind power can be viable for companies in areas where prevailing conditions are favorable, especially if the government compels the production of renewable energy.
However, sufficient wind for economically generated power is not always available. For example, according to the Energy Information Administration, relatively few areas in the eastern half of the United States are rated as having “class six” winds – 15.7 mph at a height of 33 feet – or “superb” for wind power generation. Other areas of the country hold great promise for expanding wind power generation, but in many instances opposition has grown just as the industry has approached commercial viability.
Like solar power, wind power requires an extensive amount of land or, in the case of near-shore power generation, sea. For comparison purposes, and taking into account capacity (or load factors), the land area covered by a wind power station of the same energy output as a nuclear power station would be about 2,000 times as great.
Recent technological and efficiency gains have led to more sophisticated wind units, capable of producing over 3 megawatts each, and trading surface disturbance for the larger, higher and more visible newer units.
Though wind farms release no emissions into the air, they have their own set of environmental problems. Rotating wind turbines can injure or kill birds and bats. They also strike some individuals as aesthetically degrading to the landscapes and seascapes they occupy. Some complain of noise. Others have objected to the transmission lines necessary to transmit electricity from remote locations to the electricity consumers.
Wind power has seen substantial growth in recent years, aided by tax subsidies and state government mandates to purchase renewable energy through establishment of “renewable portfolio standards,” or RPS. Many utilities mandated by the government to sell a certain amount of their electricity from renewable sources have turned to wind power as one of the less expensive renewable power sources.
The Federal Government has extended the production tax credit for wind several times since it was first introduced as part of the Energy Policy Act of 1992. Most recently, the Emergency Economic Stabilization Act of 2008 extended the production tax credit through 2012. However, President Obama’s economic stimulus signed into law in February 2009 makes a 30 percent investment tax credit available to wind farms in lieu of the production credit, and the section 1603 grants allow wind farms to take that 30 percent as an immediate rebate of their investment cost instead of taking the 30 percent over time as a tax credit.
Visit the National Wind Watch Association website at: wind-watch.org/faq-electricity.php.
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