Sunforce 45444 600W Wind Turbine

I purchased this windmill to augment a solar panel I use to charge a 12 volt battery bank. I have a solar powered well system for watering cattle, and the solar was not keeping up during times of low light. I intend for this unit to be an augment to my current system, not the only source of electrical current. I purchased this unit because it was 200 more watts output than the most popular sun force mill, but I was sort of disappointed that it is not made in USA like the 400 watt model. It is made in Taiwan. I guess this is ok, as Taiwan is an ally of the USA, so at least it was not made in PRC.

The package arrived quickly, and everything was in order and exactly as described. I assembled the unit in just under 30 minutes. There was an extra set of screws, nuts, and bolts included, and this could be handy for fumble fingers like myself. The fasteners are of good quality, and they were all present and accounted for. I did not have to use any of the extras (yet). Also included is a electro brake switch which I am not planning on using.

I first tried to mount the mill on a 21 foot piece of chain link fence top-rail, but it buckled over in the middle. I opted for a heavy piece of tubing from the chain link fence wholesaler, and it works great. I used #10 SOJ cable for my electrical connections. The mill started turning even before I had it hoisted all the way up, and it makes a pleasant enough sound as it turns. There is some small noticeable vibrations that may be due to a small imbalance in the rotor blades or something, but nothing that seems detrimental to the mill.

I made all the electrical connections without any trouble. The charge controller seems to be a fairly substantial unit, but could have been labeled on the back a little more clearly about which color wire goes to which screw, but the instruction manual cleared this up and there were no problems. The controller has a switch on the front that brakes the rotors to keep them from turning. I have not tested this in a stiff wind, but it stops the rotors in 8-10 MPH winds. Also included is a 30 amp panel meter to plumb into the electrical system in case you want to monitor current flow going to your battery bank.

The mill turns pretty much most of the time, although the charge light on the controller will only illuminate when there is a fairly good gust of sustained wind. This intermittent charging will work fine for me as this is supplemental to my solar panel, and I expect to get the most charging on cloudy days and windy seasons when the sun doesn't tend to shine so much. The unit is located in North East Oklahoma. I can readily see that another 21 ft of tower length would increase the output due to more undisturbed winds, but for now this is working pretty good, and I didn't have to use guy wires as the pole is attached to the side of the well house.

I am satisfied with this unit.

***** The Caveat ******

After reading so many negative reviews on this same product, I feel I must amend my review so that I am disclosing everything. Now pay attention: This unit requires wind to work! That's right, I know this is surprising, but this baby doesn't do a thing without wind! And even when it is working at max speed and full power, it will not replace your utility company, your neighbors will not be buying power off of your grid, and you will not be getting a fat rebate check from the grid. They won't be shutting down 3-mile island just because you have a wind turbine in the back yard. Hope this helps alleviate all the disappointed folks looking to start selling wind power and offering free rides to the moon.

The "Product Features" summary incorrectly states that it starts to "operate" at 4 mph, implying it's producing power. If you read the manual, there is a diagram that shows the turbine starts producing at 4 m/s that's 4 meters per second, or about 9 mph, and then the power production is small. It does not produce 600W until you get up to about 30mph. That's a **lot** of wind!

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I bought this from Fry's electronics years ago. i installed this after a lot of effort. it really is hard to get something that high and stable at the same time. I suggest that you set up the pole first before you buy the turbine. Finally, after many tech support emails later, i could only get a trickle of a charge. After everything looked good, Sunforce said that i did not have enough wind! I found that was not true, because I tested it blowing as fast as possible, and I still get the same trickle charge. i'm just too tired of spending more time and effort on this turbine. It is now way past the return period, and it would be hard to prove that their product is defective in small claims since i'm not an engineer. I don't buy any sunforce products now. Neither should you. Also, i suggest that you try to turn the turbine with a drill first to see if you get a charge before installing. I should have done this first myself.

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"OK, I'll take your bait and do the math.

The stated rotor diameter was 2 ft (2/3.28ft/m = 0.61 m or 0.3048 m radius) and the stated power was 600 watts. We'll assume air density to be 1.25 kg/m^3, and the coefficient of performance = 0.4. The Betz Limit of coefficient of performance is 59.3% and is the theoretical maximum Cp.

The basic equation is

P = rho/2 * area in m^2 * (velocity in m/s)^3 * Cp

The area is pi *r^2 = pi * 0.3048^2= 0.2919 m^2. (For reference, 1ft radius^2 * pi = 3.14 ft^2.)

Rearranging the equation, the velocity through the rotor must be

cube root of (P / (rho/2 * A * Cp))

Cube root (600/(0.625 * 0.2919 *0.40))

= Cube root (8222) = 20.18 m/s (1 m/s = 2.24 mph)

Regressing to the English mph, that's a windy 45.14 miles per hour.

Did I do that calculation right? Think I did. However, in such a small aperture, flow throttling likely would occur slowing the wind speed from that outside the turbine influence. The conclusion is that the 600 watts is a maximum rated power value. If the speed is cut in half, the power is one-eighth. So 22.5 mph yields 75 W, 11.25 mph yields 9 W, so this turbine is good for trickle charging a battery (just like a small solar module.)"

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This wind turbine will make good yard art and a good plaything, but if you really want energy output you need a real wind turbine, and you need to put it up high in the sky where the speedier and non-turbulent wind is.

And as long as you are going to the significant expense of putting up a decent-sized tower, you might as well purchase a heavy-duty turbine that has enough output to pay for itself.

Oh yes, and none of this is worthwhile unless you have a good wind resource, and that can only be determined by measurement and/or careful and pro-level observation.