4 Million Wind Turbines Could Support About Half of 2030 Energy Demand

Wind energy could provide up to half the world's power supply with little environmental impact, according to a new study by researchers at the University of Delaware and Stanford University.

The study debunks previous assessments that suggested wind wouldn't be a feasible way to power much of the world's grid due to environmental and power output concerns. According to the University of Delaware's Cristina Archer, about 4 million turbines could provide the world with 7.5 terawatts of energy annually, about half of the estimated power necessary to run earth's power grids in 2030.

"We've seen some papers out there that have been somewhat annoying or confusing because they had very low estimates of the total potential of wind energy," Archer says. "We decided to run our own model and we found wind is very abundant—we feel very strong these previous studies were incorrect."

Archer and coauthor Mark Jacobson, of Stanford, ran several different models—including one in which virtually the entire earth was covered in turbines, to determine that earth could support enough turbines to satisfy about half of the global power demand.

According to Archer, about 4 million turbines would be an optimal number—once more turbines are added, each individual turbine begins to generate less energy. Previous studies suggested that adding more turbines would create diminishing returns to a point where wind power wasn't worth utilizing.

"Four million turbines is a lot, but it's not impossible. We have to decide whether we want to do it. The benefits are immense—we'd have a clean economy and we'd be getting rid of pollution," Archer says. "If society wants to do it, the technology is there—it's not like we have to invent cold fusion from scratch."

In the United States, about 3 percent of all energy is generated with wind turbines, but the Department of Energy released a report in 2008 suggesting that by 2030, about 20 percent of America's energy could be generated by wind.

On Monday, Reuters reported that China plans to order its electrical companies to source up to 15 percent of all of its power using wind turbines.

Archer says that while wind energy could one day provide the world with much of its energy, wind's drawbacks will keep it from becoming the earth's primary power source.

"Wind is no constant—sometimes it blows, sometimes it doesn't," she says. "There are reasonable concerns about wind power, and we're not saying it should be the only energy source."

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Wind Farms May Have Warming Effect

                    Area over large Texas wind farms shows temperature rise

Large wind farms might have a warming effect on the local climate, research in the United States showed on Sunday, casting a shadow over the long-term sustainability of wind power.

Carbon dioxide and other greenhouse gases from burning fossil fuels contribute to global warming, which could lead to the melting of glaciers, sea level rise, ocean acidification, crop failure and other devastating effects, scientists say.

In a move to cut such emissions, many nations are moving towards cleaner energy sources such as wind power.

The world's wind farms last year had the capacity to produce 238 gigawatt of electricity at any one time. That was a 21 percent rise on 2010 and capacity is expected to reach nearly 500 gigawatt by the end of 2016 as more, and bigger, farms spring up, according to the Global Wind Energy Council.

Researchers at the State University of New York at Albany analysed the satellite data of areas around large wind farms in Texas, where four of the world's largest farms are located, over the period 2003 to 2011.

The results, published in the journal Nature Climate Change, showed a warming trend of up to 0.72 degrees Celsius per decade in areas over the farms, compared with nearby regions without the farms.

"We attribute this warming primarily to wind farms," the study said. The temperature change could be due to the effects of the energy expelled by farms and the movement and turbulence generated by turbine rotors, it said.

"These changes, if spatially large enough, may have noticeable impacts on local to regional weather and climate," the authors said.

MORE RESEARCH NEEDED

But the researchers said more studies were needed, at different locations and for longer periods, before any firm conclusions could be drawn.

Scientists say the world's average temperature has warmed by about 0.8 degrees Celsius since 1900, and nearly 0.2 degrees per decade since 1979. Efforts to cut carbon dioxide and other greenhouse gas emissions are not seen as sufficient to stop the planet heating up beyond 2 degrees C this century, a threshold scientists say risks an unstable climate in which weather extremes are common.

The Texas study found the temperature around wind farms rose more at night, compared with nearby regions. This was possibly because while the earth usually cools after the sun sets, bringing the air temperature down, the turbulence produced by the farms kept the ground in their area warm.

Previous research in 2010 by other U.S. scientists found wind farms could make the nights warmer and days cooler in their immediate vicinity, but those effects could be minimised by changing turbines' rotor design or by building the farms in areas with high natural turbulence.

That research was based on evidence from two meteorological towers over a six-week period.

Although the warming effect shown in that study and the latest research is local, and small compared to overall land surface temperature change, the findings could lead to more in-depth studies.

The authors of the study released on Sunday said: "Given the present installed (wind farm) capacity and the projected installation across the world, this study draws attention to an important issue that requires further investigation."

"We need to better understand the system with observations and better describe and model the complex processes involved to predict how wind farms may affect future weather and climate."

Commenting on the study, Steven Sherwood, co-director of the Climate Change Research Centre at the University of New South Wales in Australia, said: "Daytime temperatures do not appear to be affected. This makes sense, since at night the ground becomes much cooler than the air just a few hundred metres above the surface. The wind farms generate gentle turbulence near the ground that causes these to mix together, thus the ground doesn't get quite as cool." (Edited by Pravin Char)

By Nina Chestney@Reuters