Archive for June, 2010

Wind Power: Cool Breeze or Hot Sirocco?

Jamie Bull brought to my attention a paper saying that land based wind turbines are likely to create a small degree of earth surface warming.

Jamie was concerned that there might not be a net surface cooling, even once the effects of reduced greenhouse gas emissions were taken into account. He did some calculations, and showed that the net effect of wind power on surface temperatures was still strongly negative.

He need not have worried. An understanding of the mechanism of this surface heating, and the conservation of energy make it clear that the surface heating effect of wind is smaller than the surface heating effect of thermal electricity generation such as coal, gas, nuclear, and Concentrating Solar Power (CSP) on a per kWh basis.

Conservation of energy tells us that all the energy in wind is eventually dissipated by friction, creating heat. The effect of wind turbines is to take some of this energy that might have become heat in the atmosphere, and create electricity, which will eventually become heat on the earth’s surface, and some will become heat in the turbine itself.

The net heat added to the Earth by wind turbines is zero: heat that would have been created in the atmosphere is now created on the surface instead, and the net effect is zero.

Now consider thermal electricity generation. When a fossil fuel is burned, or when a nuclear power plant or CSP plant makes steam, heat is either created from a fuel or captured from the sun, reducing the amount that would reflect back into space. All this heat is dissipated at some point near the earth’s surface, creating more surface warming than wind power, and also creating net warming where wind power creates none.

The direct surface heating effect from wind is likely to be only a fraction of the direct surface heating effect of thermal electricity, even before the effects of greenhouse gasses are accounted for.

Solar PV and Solar CSP capture heat from the sun that might otherwise reflected into the atmosphere, so more precise calculations are probably needed to determine if their net effect is negative before the effects of greenhouse gasses, but wind is clearly cool by any thermometer.

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