Comments on: Energy conservation as it relates to windmills? http://www.energy--talk.com/alternative-energy/energy-conservation-as-it-relates-to-windmills/95/ How Can We Be More Energy Efficient? Wed, 08 Sep 2010 13:40:14 +0000 http://wordpress.org/?v=2.6.5 By: pp_314156 http://www.energy--talk.com/alternative-energy/energy-conservation-as-it-relates-to-windmills/95/#comment-190 pp_314156 Tue, 09 Oct 2007 09:50:30 +0000 http://www.energy--talk.com/alternative-energy/energy-conservation-as-it-relates-to-windmills/95/#comment-190 Do you mean energy conservation, or the conservation of energy? The first wind turbine will extract power from the moving air stream, and since energy is conserved (neither created or destroyed), the downstream air will have less energy. The energy of the moving air mass is proportional to the velocity, therefore velocity (aka air speed) will decrease. The power available from a horizontal axis mill (they look like airplane propellers) is: Power in watts = (1/2) x (air density) x (swept area) x (wind velocity) cubed. Sorry, it isn't easy to type formulas in these boxes. air density is 1.23 kg/m3 at sea level swept are in square meters wind velocity in meters per second The theoretical limit to efficiency (called the Betz limit) is 59.26%. Real world generators will extract less energy than this. You could use this for the sake of example, and then work backwards to see how much slower the wind immediately behind the first would be. The energy in front of the mill = the energy extracted by the mill + the energy behind the mill. Have fun with the math. Do you mean energy conservation, or the conservation of energy?

The first wind turbine will extract power from the moving air stream, and since energy is conserved (neither created or destroyed), the downstream air will have less energy. The energy of the moving air mass is proportional to the velocity, therefore velocity (aka air speed) will decrease.

The power available from a horizontal axis mill (they look like airplane propellers) is:

Power in watts = (1/2) x (air density) x (swept area) x (wind velocity) cubed. Sorry, it isn’t easy to type formulas in these boxes.

air density is 1.23 kg/m3 at sea level
swept are in square meters
wind velocity in meters per second

The theoretical limit to efficiency (called the Betz limit) is 59.26%. Real world generators will extract less energy than this. You could use this for the sake of example, and then work backwards to see how much slower the wind immediately behind the first would be. The energy in front of the mill = the energy extracted by the mill + the energy behind the mill.

Have fun with the math.

]]> By: jjjcmzzt http://www.energy--talk.com/alternative-energy/energy-conservation-as-it-relates-to-windmills/95/#comment-189 jjjcmzzt Mon, 08 Oct 2007 02:24:01 +0000 http://www.energy--talk.com/alternative-energy/energy-conservation-as-it-relates-to-windmills/95/#comment-189 I'm guessing it would because the windmill is spinning when the wind hits it so ya i'm guessing it probably does slow it down. I’m guessing it would because the windmill is spinning when the wind hits it so ya i’m guessing it probably does slow it down.

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