Wind Power: Coming Soon to Hardware Stores

[Kingfish]

Posted on Reuters this morning: Wind Energy Coming Soon to Hardware Stores

The part that is interesting…

The new turbines have moved the power-generating magnets to the tips of the blades. The benefit of doing this comes from the increased speed of the blades at the tips. Increased speed equals more power generation, and less wind is required to start generation. The turbine starts generating power at 2 miles per hour (mph) and continues to generate up to 45 mph.

So instead of gearing the axle the angular velocity is apparently tapped at the source. It would be interesting to see what sort of configurations this would blossom.

~KF

[vanilla ice]

Its got spokes like a bicycle wheel!
http://www.earthtronics.com/pdf2/WND-01 ... s-Full.pdf
MSRP $6500
"produces on average of 1500 kWh per year"

[Kingfish]

Touché Vanilla! Perfect for recharging my ebike

Hopefully no birdies will be harmed.

Hey, what about an eggbeater design? Same principle, different shape, longer period of rotation, possibly more blades. The magnets could be on the blades, or a wheel attached to the axle. Bird-friendly.

Tweet, tweet. KF

[vanilla ice]

Hopefully they can apply this new design to improve the efficiency of larger units. I'd love to get a small personal gen like this to charge batteries too. And I love the new efficient hub-less design, but from reading the pamphlet I think the economics of it don't work out? At ave output all year it puts out 1500kWh.. so I'll save less than $20 per month on my bill, or 30 years to pay its way. That can't be right?

[Kingfish]

Agreed. Let’s think about this:

We have hubs & rims; why not DIY? Gots to be cheaper than the $6,500 they are charging!

Wound-up, KF

[torker]

I even downloaded a pdf reader so I could check this out. That is a good looking design. Making it work well in really low wind is super important I think. Especially for close neighborhoods where houses are 30 ft. apart. Low rpm will make a lot less vibration too enabling to possibly mounting on a house/maybe. Although I would probably still want it on a separate structure. Ok Guys/gals I am ready to see some ideas for the diy crowd.

[Jeremy Harris]

The snag with edge driven designs is that the wire losses are high, as there is a hell of a lot more copper distributed around the periphery of the ring. My guess is that this probably offsets the advantage of not having to have a gearbox to increase the shaft speed.

The idea of using ebike motors to make wind generators is a good one though, a direct drive hub motor is already likely to run at around the right speed. Using one with a suitable turbine blade set up should give reasonable performance, I'd have thought. If you don't want the hassle of making blades, then buying a realtively cheap adjustable pitch propeller might be a good start. The cheapest, reasonably light adjustable pitch props that I know of are Ultraprops, like these: http://www.competitionaircraft.com/ultr ... parts.html You need adjustable pitch to match the blade to the generator for best efficiency, otherwise you could just try a cheaper fixed pitch prop.

Jeremy

[John in CR]

Touché Vanilla! Perfect for recharging my ebike

I love alternative energy, but if the $6500 pricetag is even close to the actual price for this 6ft diameter wind turbine, then it's the kind of thing that provides ammunition to naysayers. That may not even include the tower and installation, which should be the main cost in any domestic size turbine.

I currently pay about $.17/kwh for electricity, so that's a 25 year recovery period using a 0% interest rate with no tower to get up where the wind is, and no grid tie and/or storage capacity.

If you want to fly a turbine that makes economic sense, you've gotta be frugal. I fear these kind of MSRPs are like the several thousand dollar ebikes, and are intended to desensitize us to prices that may be lower in the future but still way too high.

[vanilla ice]

I forget who it was that pointed it out before, but it bears repeating- as prop diameter doubles you get SOOOO much more than twice the power. And looking at those graphs as size goes up, the cost doesn't rise nearly as much as the power output. That is the huge downer for these small home wind units.

[Kingfish]

Actually, Force or Torque increases linearly with the radii

Doing the Math

Calculated, KF

[amberwolf]

So essentially it's the generator version of the more recent PC cooling fans I've run across now and then, that use the coils on the frame and magnets in the blade tips, with a good bearing in the center on the axle. They don't seem to wear out like the ones with the motor in the middle tend to, but it might just be that all the ones I have seen were by one manufacturer, and the crappy clones haven't shown up yet. They are also quieter (the PC fans) than their motor-core cousins.

One thing I do see with this wind generator type is you'll need a stronger tower and/or guy wire system, because there will probably be more wind resistance than the same generator built using the traditional way, due to all the outer framing and such. And that resistance won't be generating power, either, just adding drag to the wind, and tugging at the guy wire system and tower.

Also, if I read their power curve chart in the PDF right, it isn't outputting much useful power until 12-15MPH, where it gets up to 250W. I don't remember enough of what I once studied on regular wind generators to know how that compares to them.

[Jeremy Harris]

Actually, Force or Torque increases linearly with the radii

Doing the Math

Calculated, KF

Yes, but the energy in the wind is proportional to the swept area.

If you double the blade length, you quadruple the energy available.

Jeremy

[Jeremy Harris]

Also, if I read their power curve chart in the PDF right, it isn't outputting much useful power until 12-15MPH, where it gets up to 250W. I don't remember enough of what I once studied on regular wind generators to know how that compares to them.

That seems similar to other wind generators. The power that could theoretically be delivered by the wind from a given swept area of a wind turbine's blades is given by:

P = 0.5 x Rho x A x V^3, where P is the power in watts, Rho is the air density (1.225kg/m^3), A is the swept area of the blades (in m^2) and V is the wind velocity in m/S.

Because of the cube law relationship between velocity and power, all wind generators perform badly at low wind speeds and much better at higher speeds. The secret is getting the efficiency up over a wide range of wind speeds and rotor rpm. If the turbine is optimised for low speeds, then it may over-speed or over stress the mast at high wind speeds. If it's optimised for high wind speeds then it will only deliver low power at low wind speeds, or it may not even start up until the wind is blowing quite hard. A really good wind domestic size wind turbine might have a total efficiency of around 50%, so a 6ft diameter one might be able to extract around 70 watts from a 10mph wind speed.

The answer to linearising the efficiency curve is to have variable pitch blades, as the big turbines do, but the cost and complexity of this is too great for a domestic system. I've toyed with the idea of making a 6ft turbine, as I have a spare 6ft carbon fibre adjustable pitch prop in my "may come in handy" store. I reckon it would match well to something like a Crystalyte 400 series motor used as an alternator. Where I live at the moment is in the bottom of a valley, though, so it's not worth doing until I move house.

Jeremy

[Harold in CR]

Marcellus Jacobs started out experimenting with the typical "Water Pumper" wind mill. He lived in the Dakotas and was famous for developing the "Jacobs" Wind Turbine. He established quite early, that there was no viable output in low wind areas.

In the real world, you MUST get the Turbine, AT LEAST 30 feet above ANY object within 300 feet of your machine.

I live on top of a nice hill, and, I still need at least a 90 foot tower to get in an UNinterrupted wind stream. Anything less, and the machine will be constantly yawing, looking for the steadyness in the turbulent wind pattern. I was in the Business for several years. A tower is $$$.

As far as the variable pitch blades, I made such a system, in 1979. It had a fixed blade angle of attack, and, as the winds and blade speed increased, the blades would twist to allow the tempering of the winds and governing of the generator. The 4KW machine I built, would start up in 7.5 MPH winds, but would not produce power until + or - 10 MPH winds. As is said here a lot, "it depends". It would run at 250 RPM's max, with a 15' dia. span.

I have started another variable pitch hub, to fly a 2.5 + or -, Wind machine. It's for possibly selling the system to a neighbor. I have Solar Cells for 3 panels, and a small stream for Hydro. ALL 3 systems will be minimal output, and houses and neighbors are not even a player where I am.

Except for my wood shop, we are VERY frugal, and might be nearly off grid, But, I probably won't be able to keep a big battery bank up to snuff, even with all 3 systems. It ain't so easy, and, i DO have enough experience from those 7 years, living in the country, in Arkansas.

In my humble opinion, that $6500.00 would be better used to start a fund to develop an Organic Rankine Cycle Refrigeration-Generation System. There are several people, on other forums, coming close to having a working system. That's what I'm studying, right now, along with Electric Drives, for my, one day, 3 Wheel Moto-car type vehicle.