Submitted by: Ryan Wiley
Building a wind turbine is a great DIY project, but how much power can one actually produce? When discussing how much power a wind turbine can produce, you have to understand three things: how much power is in the wind, how much of that power can be harnessed, and how much your particular wind turbine will be able to grab a hold of.
How Much Power is in the Wind
To find the absolute power inherent in the wind we use the following formula:
Power measured in watts = (.5) (rho) (a) (V^3), with “rho” representing air density, “a” representing the swept area of your wind turbine blades, and “V” representing the velocity of the wind in meters per second.
To find the swept area of your turbine blades, you must use the following equation:
a = pi x r^2, with “r” representing the radius of the circle made by your spinning wind turbine blades.
Let’s look at an example. We’ll say that we have an 8-foot wind turbine and 10 MPH winds (all figures converted to the metric system—meters/feet per second). Note: the radius (r) needed for this equation is easy to get—it is the length of one of your turbine blades.
Let’s get our swept area.
a = 3.14 (1.2192 m^2)
a = 4.666
Now we have the information needed to figure out the total power inherent in the wind using our specific wind turbine (the density of the wind [rho] is 1.23). We use the abovementioned equation.
Power measured in watts = (.5) (rho) (a) (V^3)
Watts = (.5) (1.23) (4.666) (89.338)
Watts = 256
So, we can produce 256 watts with our wind turbine, right? Wrong.
How Much Power We Can Really Get Out of the Wind
According to the Betz Theory, we can only extract 59.26% of the energy out of the wind. That figure, however, assumes that we have a perfectly efficient system, which we don’t actually have. How much of the wind’s energy can we extract? About 35%, if we build an efficient wind power system.
So, using the conditions outlined in our example above, we should expect our wind turbine to produce about 35% of our figure, which was 256 watts, giving us a total of 89.6 watts.
Important Facts to Consider
Did you notice that in the formulas above, wind velocity is cubed and turbine radius is squared? This is important to consider because making your turbine blades a little bit longer gives you the opportunity to harness much more of the wind’s power. Likewise, small increases in wind velocity mean much more power is available.
For example, it would seem, at first, that if the speed of the wind doubled, it would carry with it twice as much power. Look at these numbers, though.
Our original scenario was as follows:
10 mph winds gave us .5 x 1.23 x 4.666 x 89.338 = 256 watts.
Now let’s say we have 20 MPH winds.
20 mph winds give us = .5 x 1.23 x 4.666 x 714.708 = 2051 watts
That’s 8 times the power!
Now let’s see what happens when we double the length of our wind turbine blades.
Our original scenario was as follows:
10 mph winds and an 8–foot wind turbine gave us (.5 ) (1.23) (4.666) (89.338) = 256 watts.
Now let’s say we have a 16-foot wind turbine.
10 mph winds and 8-foot blades gives us (.5) (1.23) (18.664) (89.338) = 1025 watts
That’s 4 times the power!
As you can see, figuring out how much power your DIY wind turbine will be able to produce is not too difficult. You just use two simple equations and the radius of your wind turbine blades. For best results, complete a home energy audit to find out exactly how much energy you use throughout the year. Then use what you have learned above to figure out just how big of a wind turbine you need to build in order to satisfy all of your energy needs.
About the Author: Planning to make renewable energy at home? Be sure to stop by and check out my DIY wind Generator plans.
Source: www.isnare.com
Permanent Link: https://www.isnare.com/?aid=736642&ca=Home+Management
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