In my last post A Guide To Satisfying Electrical Demand With Wind Power, I calculated that around 670,000 5 MW wind turbines would be needed to satisfy electrical demand in the United States.
How much area, either on land or offshore, would be needed for this many turbines?
Wind turbines require a spacing of roughly 5 rotor diameters in the crosswind direction and roughly 10 rotor diameters in the downwind direction. If turbines are too close together their individual power output will decrease due to the “blocking” effect of neighbouring turbines. So a certain spacing is required to minimize these losses, while also maximizing the number of turbines on a particular area of land.
The Repower 5M has a 126 meter rotor diameter (ref: http://www.repower.de). It’s rated at 5 MW.
Therefore, 5 rotor diameters is equal to 630 meters, and 10 rotor diameters is equal to 1260 meters.
To help visualize how much area would be needed, have a look at the figure below.
Each turbine requires an area of 1260×630 square meters, or 0.7938 square kilometers.
Therefore, the wind turbines would occupy a total area of 532,000 square kilometers. This is an area larger than California but smaller than Texas. Very large indeed! However, a large percentage of this can be located offshore.
Also, keep in mind that land occupied by wind turbines is not wasted, and certainly not destroyed. It can still be used for other things like growing crops. And little or no wildlife is displaced since the “footprint” of an individual support tower is very small compared to the total area spanned by the turbines. They are for the most part “out of the way”.
Unfortunately, a real obstacle to something like this is of course NIMBYism (Not In My Backyard). Common complaints are that wind turbines are ineffective and that they kill birds. It’s true, they do kill birds, but to a small degree, roughly 1-2 bird deaths per turbine per year. The number of bird deaths can be minimized by choosing good sites.
To give you some perspective, if all the electrical generating capacity of the United States were to switch to wind power, the resulting number of bird deaths would be in the neighbourhood of 1-2 million.
Relatively speaking, wind turbines kill much less birds than vehicles, cats, transmission lines, and the grand-daddy of them all, windows. From these, the number of bird fatalities number in the tens, or hundreds of millions in the United States alone.
But vehicles, cats, transmission lines, and windows are part of an established structure which people have gotten accustomed to and which people need. However, people also need electricity, but at the same time they don’t want to breathe polluted air (such as from coal plants) or deal with hazardous waste (such as from nuclear plants). But that is already happening … so let me rephrase … people want electricity but they don’t want “eyesores” dotting the landscape, that can kill birds and lower property values. This doesn’t make a lot of sense, does it?
But honestly, which is worse?
If people want electricity, and they do, then tough choices will have to be faced. Compromises will have to be made. Not the least of which will be to cut down on consumption as a way to reduce the impact on the land.
It is my belief that renewables will force people to become more responsible and aware when it comes to their energy use. Because of the nature of renewables, the supply will often times be located close to areas of demand. Gone will be the days of the huge power plants that can produce and deliver power across very large distances. Out of sight and out of mind will no longer be an option.