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Old 04-21-10, 07:38 AM   #11
jwxr7
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So, how does this work?
The plan is to wait for a calm day, then drive down my usually deserted country road. I will record speed, current, and voltage at given load resistances. Basically I want to gather data to make a power vs wind speed curve for the wind turbine. Thru bench testing, I have already made a power curve for the generator, so I know what it is capable of and I know the load resistance that should give the maximum power at any given rpm. Now I need to see if the blades can turn the generator well enough to make that power and how much wind speed they need to do that.
Testing will show me the minimum wind speed required to meet the minimum power and voltage required to start a grid tie inverter. Information can be gathered to help me decide when I want the turbine to furl. I can then put the proper weighted tail fin on and test the furling with the test rig. With the test rig I don't need to wait for big wind to see if these blades are a good match for the generator, I can observe it under controlled wind speeds to be sure it performs safely and properly overall.

Since there should be minimal wind on test day, I will use the truck speedometer for the as-tested wind speed. This is as good as I can do it without a good anenometer mounted up stream of the turbine. I have a cheap hand held wind speed meter, but I don't trust it's accuracy.

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Old 04-21-10, 07:50 AM   #12
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I forgot to explain the orientation of my test rig.

Researching test rigs I saw many ways of doing it. The ones mounted all the way out front seemed the best for clean wind. I couldn't think of a good temporary way to do that. I saw alote mounted with the rotor near the front of the cargo bed and above cab height. That seemed like a good way to go , except the air coming over the cab is going to mess with things. Then I started seeing other people testing with the rotors back near the tailgate and up high. I tried looking at the way the air travels over a truck, and it seems to me like the farther back the better as long as it's up high. So that's what I'm going to try. The vertical support will be up against the tailgate. It's not perfect, but I believe I can obtain useful data using this set-up.
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Old 04-21-10, 08:52 AM   #13
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I hope you have someone to help you take the data or do the driving.
Hopefully there aren't any low hanging limbs or wires to worry about, on your test route..

Maybe you can mount a camera in back of the cab, looking up towards the blades,
maybe get some video of the action as the truck gets up to speed.

Good luck and stay safe..
Rich
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Old 04-22-10, 09:32 AM   #14
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With it mounted on your roof how are you going to brace the building to handle the wind load? a turbine prop is, from a load point of view seen as a solid disk or sail when the wind is hitting it, that can be alot of force.
Also the basic rule of 50 feet above anything within 500 feet treats the top of the roof as you would treat the ground level, just like if you put a turbine up in a forest you need to be 50 feet above the top of the tree line, otherwise you get turbulence and enough variation in wind speed that the machine will rip it's self appart, why? a 1mph difference in wind speed at 12mph is almost twice the force pushing on the blades, so if the top tip is seeing 12mph and the bottom tip is seeing 11mph that top tip, at 50 feet in the air this is not uncommon to see, at 10 feet in the air I can't say exactly what the difference is going to be but I'd like to see a video of it.
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Old 04-22-10, 10:41 AM   #15
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I still need to finish bleeding my brake system before any testing can start.

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I hope you have someone to help you take the data or do the driving.
I will probably have my wife help collect the data. I have my resistor bank and 3 phase bridge rectifier mounted and wired. The only data I really need to write down is mph and voltage for each load resistance, then I can calculate the amps and power. This probably could be done solo.

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Hopefully there aren't any low hanging limbs or wires to worry about, on your test route..
I'm investigating this currently. It looks like I'll have problems in my driveway but the roads look pretty good. Most semi trucks have trailers around 14' which is at least a foot taller than my set-up, so they keep the branches above that range.
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Old 04-22-10, 10:48 AM   #16
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With it mounted on your roof how are you going to brace the building to handle the wind load?
I plan to involve several of the adjacent roof trusses to spread the load. My initial thoughts have been to furl near 25mph. At 25mph I've calculated around 27 lbs of turbine thrust. If I decide to furl around 30mph, forces are around 40lbs. Furling will then tend to have a governing effect on most of the turbine thrust.

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Also the basic rule of 50 feet above anything within 500 feet treats the top of the roof as you would treat the ground level
That maybe ideal, but isn't practical for me at this time. Eventually a tall tower out in my back field will be great.

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Old 04-22-10, 11:24 AM   #17
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Quote:
Originally Posted by jwxr7 View Post
Most semi trucks have trailers around 14' which is at least a foot taller than my set-up, so they keep the branches above that range.

Just remember, many times branches will drag across the top of trailers,
without causing any problems..
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Old 04-22-10, 02:15 PM   #18
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Originally Posted by Xringer View Post
Just remember, many times branches will drag across the top of trailers,
without causing any problems..
Very true, I will ride the route on my bike and use a fiberglass pole as a way to check the heights of low hangers.
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Old 04-24-10, 05:03 PM   #19
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I trimmed the trees in the driveway and drove the route with a fiberglass pole that extended a few inches taller than the turbine would. There was good clearance on the road from what I could tell. I put the turbine on the test rig in the back of the truck this morning. It has been sprinkling all day, so I wrapped the head of the turbine in a plastic bag since it hasn't been weather proofed yet. It's been breezy so I haven't tried any testing while driving. Click image for larger version

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I have done a few preliminary tests. I aimed it into the breeze with no load (open circuit) and took a few voltage measurements against my handheld anenometer. It starts turning with a 5-6mph breeze. It reaches 12volts dc at 9-10mph. The highest wind I gathered data from was 12.5mph, where it put out 19volts dc. Keep in mind, these numbers give no real indication on power output. I didn't do any loaded testing since the winds were so sporadic.

The grid tie inverters I've been most interested in, require 10.5 volts minimum and around 10 watts to start feeding the grid.

I will try getting some driving numbers when conditions permit.
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Old 04-25-10, 12:06 AM   #20
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That's one neat looking test rig! Try not to speed!

Wind load can cause damage pretty quick. Once I had some 4'x8' paneling on a roof-rack,
and only got up to about 30 mph when I hear this loud snap.. Then it was 4x6 panels...

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