How Much Energy a Wind Turbine can Generate
Have you been planning on constructing a wind turbine? If so, you’ll need to know how much power you’ll be able to generate with your finished product. In this article, I will show you just how much available power is in the wind. Then I am going to make clear just how much of that power can in fact be harnessed, and, finally, I am going to use real DIY wind generator examples to describe how much electricity can be created with typical do-it-yourself wind power systems.
How Much Power is in the Wind?
The energy in the wind is measured in watts. The formula is:
Watts = (.5) (rho) (A) (V^3)
Now, exactly what does all of this mean? Well, it’s simpler than it seems. “Rho” represents air density, and, at sea level, one cubic meter of air weighs 1.23 kgs: accordingly, we insert 1.23 for “rho.”
“A” in the equation symbolizes what’s identified as swept area. Swept area is a representation of how much area your wind generator blades cover-longer blades = more swept area. To find out your specific wind turbine’s swept area, work with this formula, A = pi x r^2. Or, to keep matters simple, A = 3.14 (length of one turbine blade squared).
“V” in the formula represents the velocity of the wind. In this space, you would insert the average wind speed where you intend to put your wind generator.
So, essentially, the power of the wind can be calculated like this:
watts = .5 X air density X swept area X wind velocity cubed
The Amount of Energy One Can Extract from the Wind
The aforementioned formula shows you how much power is in the wind. It does not tell you what amount of energy you’ll be able to extract from it. It is only possible to draw out 59.26% of the power available in the wind. I won’t go into the specifics at this point, but if you wish to learn more, you can research the Betz theory.
So, does this mean that we’re able to use a wind generator to draw out 59.26% of the total power of the wind, as described using the information above? No, it doesn’t. Why? Mainly because there are inefficiencies in wind turbine rotor blades and in the gears and motors used to generate energy.
Okay, what’s the bottom line? The bottom line is that using a small, well-built DIY wind turbine you should be able to extract about 30% to 35% of the energy in the wind.
Your Homemade Wind Turbine
Alright, let’s jump into what’s really important. Just how much electricity is your own individual DO-IT-YOURSELF wind turbine likely to generate? Let’s say that you’re planning to construct a 6-foot wind generator, meaning each of your rotor blades is 3 feet long. The wind in your area blows at 12 MPH. Before we do anything, we have to convert our numbers into metric numbers. Our rotor blades are 3 feet long, which equals .914 meters. 12 MPH needs to be converted into meters per second, which is 5.36 meters/second.
Our formula is.
Watts = (.5) (rho) (A) (V^3)
Let’s add the simple numbers to begin with.
Watts = (.5) (1.23) (A) (5.36^3)
At this point we need to get our “swept area,” (A). To accomplish this we use the very simple equation A = 3.14 x length of one blade^2. Our blades are .914m long, so to get our swept area we use the equation.
A = 3.14 (.914 ^2)
A = 3.14 (.835)
A = 2.62
At this point we go back into our original formula and put in 2.62 for the swept area (A).
Watts = (.5) (1.23) (2.62) (5.36^3)
Watts =(.5) (1.23) (2.62) (153.99)
Watts = (.615) (2.62) (153.99)
Watts = (1.61) (153.99)
Watts = 247.92
As you can see, there are 247.92 watts readily available for our wind turbine. Keep in mind, though, that your wind turbine is only going to manage to draw out about 30% to 35% of the power available. So, in reality, for your personal DO-IT-YOURSELF wind turbine.
Watts = 247.92 (35%)
Watts = 86.77
So, what you’ve got is a wind turbine rated at 87 watts. What does that mean exactly? An 87-watt wind generator produces 87 watts for each hour of operation. So, if the wind at your specific location blew 24 hours a day at 12 MPH, you would create 2088 watts daily, or about two kw (kilowatts).
What could this power?
The typical laptop computer uses about thirty five watts per hour. A CFL light bulb uses approximately 25 watts per hour. A 42-inch ceiling fan on low uses approximately twenty four watts.
So, if you sat in a room using a ceiling fan, a light bulb and a notebook, you would use up 84 of the 87 watts you were generating with your do-it-yourself wind turbine.
Needless to say, most people don’t actually live like this. Our wind generator won’t be rotating at 12 MPH for 24 hours a day, nor are we likely to be sitting in our home with a light bulb on and a laptop computer running for 24 hours a day. And, most importantly, there are wonderful things called battery packs that we can use in order to hold the power our wind turbine produces.
This means that while we are sleeping, or at work, or playing outside, we’re able to use our wind generator to replenish our battery bank. Then, in the evening, for example, we can make use of that saved up power to watch TV or log onto the Internet. How much electrical power does one have to produce to go off the grid? Well, that varies widely between households.
Come by our site and get loads of free and true information about how to make a wind turbine at home.
If you’re interested, you can also learn how to build your own solar panel.