October 1, 2005 Wind farms may have an impact on local weather patterns. As environmental engineers have discovered, wind farm propellers create a lot of turbulence in their wake, mixing air up and down with effects that can be detected for miles. But more efficient rotors may significantly reduce this problem.
DURHAM, N.C.--You've seen the prices at the pump go up and now home heating costs are on the rise. And scientists are looking to the wind for a much needed alternative to fuel.
They're the things that fuel our lives, but what fuels them is running low. Scientists may have found an answer with wind farms. Somnath Baidya Roy, from the department of civil and environmental engineering at Duke University in Durham, N.C., says, "It's very clear to everybody that we have to move away from conventional fossil fuels like coal and oil and look at alternatives."
With a new power source comes an impact to our environment. Roy says, "Large wind farms can significantly affect local meteorology." He studied these massive machines and believes wind farms can actually impact our weather because wind turns the blades of the turbine around a rotor, which helps generate electricity the blades create a lot of turbulence in the wake.
Roy says, "It's something like the wake from the propeller of a boat. Now this added turbulences mixes air up and down and creates a warming and drying effect near the ground." He says the affects can be felt for miles and could have an impact on air conditioning costs and more money may have to be spent on irrigation of nearby crops.
He believes the solution is simple -- create better rotors. "We found that low-turbulence rotors are more economically efficient, they tend to generate more electricity than conventional rotors," he says.
Wind farms tend to impact the weather more at night, which is when the wind is usually stronger and the most energy is generated.
BACKGROUND: Wind farms are growing in popularity as an alternative energy source, but an increasing number of critics are concerned about possible negative impacts on local weather. Researchers at Duke and Princeton Universities used computer modeling to determine any possible adverse impacts of a large wind farm in the Great Plains region.
WHAT THEY FOUND: Large groups of power-generating windmills could have a small influence on a region's climate. All large wind turbines disrupt natural airflow to extract energy from wind. During the day, the effects from the disturbed airflow are negligible, since natural turbulence mixes the lower layers of the atmosphere. But the researchers found that in the predawn hours, when the atmosphere is less turbulent, a large windmill array could influence the local climate, raising temperatures by about 2 degrees Celsius (about 4 Fahrenheit) for several hours. The rotating blades could also redirect high-speed winds down to the Earth's surface, boosting evaporation of soil moisture.
WHAT IS WIND: Wind is a form of solar energy, caused by the uneven warming of the earth's surface. This is why air masses have different temperatures and pressures, and are constantly moving to find a balance. The higher the difference in pressure, the swifter the air moves and the stronger the wind. Mankind has used wind energy for thousands of years, using it to pump water, grind flour, press olives, and even to explore the world in wind-driven sailing ships.
WHAT ARE WIND FARMS: Wind farms use windmill turbines to generate electricity by converting the kinetic energy of the wind into mechanical energy. The wind's force is gathered by the long blades of the turbine, causing them to rotate (mechanical energy). This rotation starts a generator, which produces low-voltage electric energy.
BENEFITS: Wind power is a renewable energy source that requires no fuel to operate and does not produce any emissions that are harmful to the environment. Wind turbines are made of plastic and metallic materials, so they don't have any radioactive or chemical impact either. Wind farms take up much less space than conventional power plants, and they also don't produce noise pollution.
DRAWBACKS: Electricity produced from windmills generally costs more than that produced from traditional sources like natural gas and coal. At best, wind farms produce electricity at an efficiency rate of 30 percent, compared to a 70 percent efficiency rate from natural gas and coal. Wind energy is also unreliable. Electricity can't be stored: it must be produced on demand, yet wind is inherently unpredictable. Back-up generators are needed to make sure enough electricity is available to meet demand.
The Institute of Electrical and Electronics Engineers, Inc., and the American Society of Civil Engineers contributed to the information contained in the TV portion of this report.