Wind farms are an important source of renewable energy. They generate electricity by removing energy from the wind. A switch from fossil fuels to wind energy could help reduce greenhouse gas emissions and subsequent global warming they cause. But wind farms also modify local climate and affect the transfer of energy, mass and moisture within the air. Therefore, large-scale wind farms can also lead to significant climate change.
Renewable wind energy is experiencing rapid growth around the world as it is cheap and abundant. Currently, wind energy accounts for 6.3 percent of electricity generation in the United States. A new research from Harvard University suggests that the full transition to wind or solar power in the U.S. would require five to 20 times more land than previously thought and such large-scale wind farms would warm average surface temperatures over the continental U.S. by 0.24 degrees Celsius.
“Wind beats coal by any environmental measure, but that doesn’t mean that its impacts are negligible,” said David Keith, the Gordon McKay Professor of Applied Physics at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS). “We must quickly transition away from fossil fuels to stop carbon emissions. In doing so, we must make choices between various low-carbon technologies, all of which have some social and environmental impacts.”
In a previous research, David Keith and his colleagues modeled the generating capacity of large-scale wind farms and showed how these wind farms would impact the climate system. But that research lacked factual data to support the modeling.
In the latest effort, they used latest data from U.S. Geological Survey and quantified power density of wind farms operating in the U.S. during 2016.
“For wind, we found that the average power density – meaning the rate of energy generation divided by the encompassing area of the wind plant – was up to 100 times lower than estimates by some leading energy experts,” said lead author Lee Miller. “Most of these estimates failed to consider the turbine-atmosphere interaction. For an isolated wind turbine, interactions are not important at all, but once the wind farms are more than five to 10 kilometers deep, these interactions have a major impact on the power density.”
Wind farms do have local effects on heat, humidity and other factors that drive the climate in the region in which they are situated. Since wind farms will continue to expand as demand increases, interactions and associated long-term climatic impacts cannot be avoided.
“If your perspective is the next 10 years, wind power actually has — in some respects — more climate impact than coal or gas,” said Keith. “If your perspective is the next thousand years, then wind power has enormously less climatic impact than coal or gas.”