Have you been thinking about building a wind generator? If that’s the case, you’ll need to know just how much power you’ll have the ability to create with your finished system. In the following paragraphs, I am going to explain precisely how much available power is in the wind. Then I am going to show you what amount of that power can in fact be harnessed, and, lastly, I will use real DIY wind generator examples to describe just how much power can be created with standard do-it-yourself wind power systems.
The Amount of Energy in the Wind
The energy in the wind is measured in watts. The formula is:
Watts = (.5) (rho) (A) (V^3)
Now, just what does all of this mean? Well, it’s less complicated than it seems. “Rho” stands for air density, and, at sea level, one cubic meter of air weighs 1.23 kilograms: therefore, we insert 1.23 for “rho.”
“A” in the equation represents what is called swept area. Swept area is a representation of the amount of area your wind generator rotor blades cover-longer rotor blades = more swept area. To figure out your particular wind turbine’s swept area, use this formula, A = pi x r^2. Or, to keep matters uncomplicated, A = 3.14 (length of a single turbine blade squared).
“V” in the equation represents the velocity of the wind. In this space, you would insert the average wind speed where you want to install your wind turbine.
So, simply, 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 Power You Can Get From the Wind
The above formula demonstrates how much energy is in the wind. It doesn’t explain how much power you’re able to extract from it. It is only possible to extract 59.26% of the power available in the wind. I won’t go into the details at this point, but you’d like 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 produce power.
Okay, what’s the bottom line? The bottom line is that utilizing a modest, well-built DO-IT-YOURSELF 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 power is your own personal DO-IT-YOURSELF wind turbine going to produce? Let’s say that you’re planning to construct a 6-foot wind generator, meaning each of your blades is 3 feet long. The wind in your area blows at 12 MPH. Before we do anything at all, we must convert our numbers into metric numbers. Our rotor blades are 3 feet long, which equals .914 meters. 12 MPH must be changed 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 be able to draw out approximately 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’d create 2088 watts daily, or about two kw (kilowatts).
Exactly 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 laptop, 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 really 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 significantly, there are wonderful things known as battery packs that we can use in order to hold the power our wind turbine makes.
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, after sunset, for example, we can make use of that stored up power to watch TV or search the Internet. How much 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.