Project Table of Contents
- What kind of energy should I harvest?
- City ordinance and neighborhood considerations
- Installing the tower base
- Building and securing the tower (this article)
- Building and installing the wind turbine
- Wiring up the electrical connections
- Preventing “reverse flow”
- Regulating and controlling the charge
- Dump Loads
Building and Securing the Tower
This is arguably the “biggest” part of this project, and potentially the most dangerous. Great care should be taken during construction, erection, and anchoring of the tower.
Before we get into all of that, it’s vital that you have a solid foundation upon which you’re going to place your tower.
Before acquiring the parts that I needed to build the tower, I had to determine how much tower I’d need to build. Ideally, you’d accomplish this by conducting a lengthy site-survey using anemometers at varying heights (10-foot sections would be ideal) to measure the speed of the wind at your location. This survey would ideally be held over 2-3 years to get an average at each height so you could choose the height that is most efficient through the year. This data would then be used to determine the type and length of blades on your turbine, as well as the motor/generator that you’ll be using. Obviously that’s a time consuming activity, and one that I didn’t have the time nor the resources to accomplish.
Instead, I took the rule of thumb that “the wind is faster and more constant the higher up you go.” This rule goes hand in hand with “there’s less interference the higher up you go” or “the wind is cleaner the higher up you go.” Basically, you want to get above buildings, above roof-lines, and above trees and other obstructions (hills, signs, etc.). Trees hundreds of feet away can divert wind and rob your turbine from spinning. My house is the tallest in the neighborhood by about 10-feet and I don’t have any trees or buildings anywhere near that could potentially “steal” my wind.
Local ordinance says I can’t build any structure taller than 7-feet above the tallest point on my roof. Obviously I want to maximize that, so I climbed up on my roof with a tape measure, laid along the uppermost part of my roof, and dropped the tape down. I had one of my children hold it against the ground while I took my measurement.
To that measurement I added 7-feet (to maximize my height), then subtracted the following:
- the height of the blade to the center of the motor (2.5-feet)
- the center of the motor to base of the mount (1.5-feet)
- the height of the ground to the top of the nipple and adaptor of the tower-base (2-feet)
The resulting measure was right around 30-feet. I purchased three 10-foot sections of 1.25-inch pipe and 3 couplers, and had the body of my tower.
The Tower Base
The tower base (which we talked about in the last article) carries the vertical weight of the tower and the turbine, and holds the whole assembly in place. With this type of tower it does not do much at all regarding the horizontal stresses from the wind pressing against the turbine, that job is for the guy wires.
Preparing for the Worst
You want your tower taller than the surrounding obstructions, which means it’s going to be the highest point around. Due to that fact you need to take lightning precautions because you’ll basically be building a giant lighting rod.
There are a couple things to keep in mind here. First, you need a good ground! I opted to isolate my system from my houses electrical system, because of this it needs its own ground, and no, cementing the base into the ground isn’t enough to be safe. I purchased a 1/2-inch grounding rod from my local home improvement store for less than $12. The thing is basically an iron rod coated with copper, and beveled at each end. Oh, and it’s 8-feet long! Yikes! Make sure you have a post-driver handy, you’re going to need it.
Your grounding rod needs to be close enough to the tower to easily reach with your grounding cable, but far enough away from the tower (and any other sub-terrain cement) to make it 7.95-feet into the ground. Since my tower is relatively close to my house I had to make sure I was far enough out not to hit the house foundation or footer (about 2.5-feet from the house and about a foot from the tower base).
The easiest way to get this monster into the ground is with a post driver. If you don’t have one, it’s worth renting or borrowing. It will get you down to a couple feet above-grade, at that point it’s time to whip out the hand 3 to 5 pound sledge. Keep the top of the rod out of the ground about 1 to 3 inches, or as required by code. Don’t cut anything off, you want all 8-feet (minus the few inches to make your attachments) in the ground.
Connect a grounding cable to a grounding nut and install on your grounding rod, then connect this to a grounding saddle attached to your tower (above the base). This will ground your not only your tower but the turbine (once connected).
It’s important to run this grounding cable down your tower as well, even if your wind turbine doesn’t have a grounding line coming out of it, you can’t trust the turbine mount to make a good, conductive connection to the tower, meaning if lightning were to strike your turbine, it very well might follow the power cables down and fry your equipment, bypassing the grounded pole entirely. If your motor/generator doesn’t have a ground-line, attach the ground cable to the mount or to the motor directly. This will provide a path for any lightning or static electricity to flow safely to ground.
Make all your grounding connections BEFORE you raise your tower!!!
Assembling the Tower and Running the wires
Since my base uses a 1.5-inch tee around 1.25-inch pipe as a pivot, I need to adapt the 1.5-inch tee into 1.25-inch pipe.
I prepared a 12” 1.5-inch nipple by drilling a 1/2-inch hole near the bottom, just above the threads. Into this hole I will insert a length of PVC conduit, this will help transition the wire inside the pipe through the hole to the outside, and help prevent wear or fraying of the wire as it exits the pole.
I attached this nipple to the tee. Next I need
to reduce the pipe from 1.5-inch to 1.25-inch. I was unable to find a female-to-female reducer in that would accomplish what I needed (which I would have preferred). Instead I connected a 1.5"-inch coupler, and into that an 1.5-inch to 1.25-inch male-to-female adapter.
At this point my son and I laid out and assembled each of the three segments of the tower (pole to coupler) taking care to tighten each segment as much as possible with our pipe wrenches. Once we had three assembled sections we ran our cable from what would become the uppermost section through the pipe, and into the next section, and so forth, then out the hole we drilled earlier. Once that was complete we connected the first segment to the base, tightening with pipe wrenches as we went. Then we connected the two upper segments, starting with the segment closest to the base, and finally the upper segment.
Now that the tower was complete on the ground we could begin the first erection.
Raising and Securing the Tower
Safety is the bottom line here. Your tower is going to be heavy, and the leverage you’ll need to lift it will be substantial. You have to take precautions and make preparations before you start lifting your tower into place.
First, you’ll need some way to pull the tower up, no you’re not going to be able to push it, trust me. For this application I screwed an eye bolt into the eve through which I ran a nylon rope. This rope ran back down to the lowered tower at the bottom of the upper-most section. I tied a clove-hitch around the pipe just above the coupler, and another clove hitch just beneath the coupler to prevent slippage.
I then pulled the rope taut on the other end and fastened it to a fence post. Next it was time to bring in the helpers. I’d recommend older kids or adults to do this.
In my installation I only had to worry about getting the tower upright and keeping it there. Once the tower is up it will “fall over” toward the house and the house will hold it there. If your tower is going to be free-standing you’ll need to affix a rope to the opposite side to keep the tower from falling over. You may also want to affix and anchor your guy wires at this time.
I had my helpers pull on the rope, but they couldn’t raise the tower, which put me in harms way – right beneath the tower. This is the most dangerous place to be. If the rope breaks, your knots slip, the anchor gives way, the helpers lose their grip, etc. the tower will come right down on top of whomever is underneath it. KEEP THIS AREA CLEAR UNTIL THE TOWER IS TEMPORARILIY SECURED!
Once I got the tower to about 20 degrees off the ground, I couldn’t push up any more. I re-fastened the end of the rope to the fence post, securing it until I could devise a way to push raise it higher. I found the longest “toobafore” (2” by 4”) I had readily available and cut a U-notch into the end to use as a “pusher.” This “pusher stick” helps support the middle section of the tower while it’s being raised, and really helps with the raising process. You’ll need this when you attach the turbine to the top of the tower, since that will add quite a bit of weight to the end of the tower.
Once the tower was all the way up I tied off the rope and secured the tower to the spacer-block and bracket attached to the eve. This spacer block is nothing more than a 4-by-4 secured to the eve using long lag-screws. In the center of the block I attached a 1.5” bracket lined with a length of old bike-tire to help with electrical and vibration isolation. My turbine is approximately 15-feet above this point, too far up to let it free-stand, so I’ll need to install some additional support by way of…
You might not like the look of guy wires (I’m right there with you) but the cost difference in towers that will support the stresses from the wind pressing on the turbine are prohibitive for most backyard wind turbine projects. Even a 4-inch stand-pipe will need to be guyed (one of . Unless you’re going to put up something like a telephone pole, you’re going to need guy wires.
I used 3/16” galvanized wire rope (a 125-foot spool cost me less than $50 at my local Home Depot). I bought six clamp-and-thimble sets (3 guy wires times two ends).
If you don’t know, a clamp is used to hold the wires together and a thimble is used to keep the wire from kinking and subsequently fraying. Three clamps and one thimble per end. Remember, “the saddle portion of the clamp assembly is placed and tightened on the opposite side of the terminal end of the cable.” (“Don’t saddle a dead horse” rule)
These I connected to the tower about 5-feet below the turbine (the blades are 2.5-feet long, so I’ll have plenty of room from them to sweep without worry of hitting the wires (or interfering with the wind).
The anchor ends of the guy wires I’ll refer to as my “turnbuckle assembly.”
n the eve (on two sides, into the edge of the roof (and into the eve) on the third side). I heavily caulked these anchor points to keep water out of the holes.
To the anchors I attached a quick link (pictured), then the turnbuckle (you’ll want two eye-bolts on your turnbuckle, not a hook and eye) then the “thimbled” guy wire.
Wow, that was a lot of information to digest, but possibly the most important part of your wind turbine installation.
So now, if you’re following along with me, you should have a 30-foot grounded and guyed tower standing against your house, seated on a pivoting base (to help you raise and lower the tower), and a means of securing the tower when erected.
All that’s left now is the actual turbine and the electrical!