Lenz2 wind turbine

This instructable will show you how to build a Lenz2 wind turbine from materials you have around the house.

The design was developed and tested by Ed Lenz of Windstuffnow.com:
http://www.windstuffnow.com/main/lenz2_turbine.htm

The Lenz2 VAWT (Vertical Axix Wind Turbine) is 4 foot tall and 3 feet in diameter. It is a basically a Savonius style turbine but with the refinement that the three wings are shaped to provide lift as well because or their teardrop configuration. In the above link Lenz describes how he placed an ananometer inside the stational turbine and showed that the windspeed picked up passing past the solid portion of the wings. This turbine is more efficient than a pure Savonius in that it provided both drag and lift.

In my design I scaled down the diameter to approximately 18 inches and the height to 21 inches. (In hindsight, I should have made the height 18 inches so that there would be more of the center axis free on both ends for flexibility in mounting.)

I was able to use materials I had on hand to build the turbine. When I tested it in a 15 mph wind, it worked so well that I was afraid to stop it for fear of getting injured. The only downside of what I produced is that it seemed to produce very little electricity. This is not due to the design of the turbine but to the nature of the DC motor that I had it attached to. The emphasis in this tutorial will be on how to construct the turbine itself. Full credit for the design and some of the instructions goes to Ed Lenz.

[Note: Since this instructable was published, I learned more about how the wings should be shaped. The construction details for the lenz2 provided in this instructable still hold but the dimensions of the wing in Step 2 should be substituted for those given in the newly inserted Step 3.]

Step 1 Materials needed

The materials you will need are listed below. Substitute alternatives freely if you think they will work.

Materials
Plywood (quarter or half inch)
Steel strapping with holes in it (other alternatives are possible)
Nuts and bolts
24 inch allthread rod (half inch diameter)
.5 inch nuts that fit on the althread rod (about 6 of them)
Roof flashing, thin sheet metal, or even some sort of flexible plastic
9 pieces of lumber, .5" x 1" x 18"
Hardware for mounting your turbine (you will have to design this)

Tools
Drill and drill bits
Tin snips
Jigsaw
Wrenches

Comments

[Robert_13]

Oops! That last part of the math expressions should have read:

1/2.618034 = .3819661, 1 - 0.3819661 = 0.618034

[Robert_13]

I wonder whether this design was arrived at empirically first and then tweaked to conform to the interesting mathematics of it, or the reverse. I notice that the proportion of outside degrees of arc corresponding to vanes and to the open spaces between them is right on the Golden Mean (1.618034 or its reciprocal, 0.618034). The angle of the vanes with respect to a tangent to the circumference has a tangent very close to 0.618034 (3/4.9 = 0.612, or a 0.9% difference).

I would think the rationale behind this is that the Golden Mean has very interesting self-referential and scale invariant properties. Since air is essentially scale invariant macroscopically at low wind speeds, I would expect the self-referential nature of the Golden Mean to produce a high probability of self-reinforcing aerodynamic behavior. (1/1.618034 = 0.618034, 1.618034^2 = 2.618034, 1/2.618034 = 0.381966 = 1 - 1.618034, etc.)

[DeanC993]

hi are Vawts less efficent than Hawt's?

[rhackenb]

I'm not an expert on this but I think VAWTS are less efficient but they tend to have a lower cut-in speed. This means that they start producing power at lower speeds. That's important because they can be mounted lower to the ground where you can get to them for maintenance. You can also mount them on the top of commercial building and not worry about an ugly tower that will ruin the architectural appearance.

[Robert_13]

Sorry! This next-to-last sentence:
This both controls optimizes efficiency speed and offers a relatively loss-less way to control speed. Other advantages are simplicity and the resulting low cost,

...should have read:

This both optimizes efficiency and offers a relatively loss-less way to control speed.

[Robert_13]

The Lenz has lift, which your reply seems to ignore. Lift is a big game changer. I've designed a different, but also 3-blade turbine that has even more lift than the Lenz and maintains some of its characteristics in terms of the Savonius or drag aspect.

I can put wind on either side of my VAWT and it will spin in the same direction. The lift pulls it forward on the side moving into the wind, although very slowly. That's better than simply neutral and way better than just less drag on the side moving into the wind as in the Savonius. There is much stronger lift that pulls it toward the side moving with the wind even before it gets to 90 degrees to the wind. Then it takes off like a rocket and pours wind into the next blade forward as well. The wind through the turbine wraps way around the back side so you can channel a fan into the most productive side and feel the wind coming out about two thirds around from a normal to the front facing the wind.

So lift is a big deal and potentially increases efficiency a lot over a straight Savonius or drag-based turbine. Other huge advantages, besides not having to swivel windward to maximize power, combine to favor VAWTs. Examples are no gears and the potential for magnetic levitation (maglev) and the lower losses to friction that brings.

Maglev can simply be a bi-product of a generator built right into the turbine. Ideally the coils and magnets should be placed just inside the outer edge where the maximum speed exists. The stator can use speaker magnets (very powerful ones available). The coils can pass over the statro magents underneath or potentially even through C-shaped magnets placed on the outside of the bottom rotor rim. You can even wire the coils so at low speeds you use only half or a third of the coils (evenly spaced) and cut the others in as wind speed increases. This can be built into a control system and optimized for the specific power versus wind speed curve of a particular design implementation. This both controls optimizes efficiency speed and offers a relatively loss-less way to control speed. Other advantages are simplicity and the resulting low cost,

[vikolord]

ok im agree with you when you say " that they start producing power at lower speeds" but i'd like to know how many rpm does your VAWT need to generate power? i mean.. your 24DC motor...

[DeanC993]

Thanks i like the design of the lenz 2 i like the way the Vawts dont need a tail fin

[mhkabir]

Derrius-type Vawts do need a kind of complex tail fin

[macrumpton]

Actually that is not entirely true. The original Darrius turbines with eggbeater type blades are fixed wing devices, but other VAWTs like the Gyromill and Cycloturbine change the angle of their blades using a tail fin.
http://en.wikipedia.org/wiki/Darrieus_wind_turbine#Cycloturbines

[Heygalicious]

That's they're beauty, they don't need to be pointed at the wind! Great build by the way, i'm building something slightly similar myself hope to have it finished and up here in a week or two.!

[trike road poet]

One thing to consider is making the wings out of Styrofoam with a PVC 'axle' tube glued down through the foam. (if you're not sure how, check with RC fliers in your area, many make their own wings with a hot wire cutter and can make such a shape easily.) 

Add plastic bushings for easier rotation, and consider an upper frame to hold the top bearing end of the center axle rigid, so the energy lost in the wobble at speed is regained. (such a frame will be outside the circle through which the wings move. It ought not to affect the wind to the rotor assembly.) 

[stackerjack]

What you say is correct, BUT, if you haven't got enough torque, the turbine will not be able to drive the generator at the desired speed.

[kat49242]

Why notch them at all? Would it still work if you just glued & screwed the wings on top & bottom of the ribs?

[stackerjack]

If you move the wings further from the central shaft, the shaft will rotate more slowly. Imagine a wind speed of 10 ft/sec, then, the wing, in theory, will move 10 ft. in 1 second. If this corresponds to a circumferential dimension of 10ft. then the speed of the shaft will be 1 revolution per second.
If the circumference is 20ft., then the shaft speed will be only 1/2 revolution per second.
It will however have more torque, because the arms will be longer.

[rhackenb]

What you say is correct but if you are building a very simple turbine, you will want a non-geared generator.  Generally, you want the rpm to be as high as possible to increase the voltage output.

[Bitty]

Very nice, thanks for posting this. I'm at the drawing stage of a smaller version of it myself. After seeing the concept in action, it looks like I won't have to spend all that time building a proof of concept first. :oP

[rhackenb]

Thanks, Bitty. What do you plan to use in terms of a generator?

[Bitty]

I'm going to be building off his idea for a scratch built axial field generator. I'm also playing around with designing a star-delta switching circuit to more efficiently collect the power. The big challenge right now is deciding what to use for bearings. I want to mount the thing on a single pole (like the hub of a bike wheel with the pole being the axle).

[rhackenb]

I've played with the idea of extending the axle of a bicicyle wheel for the axis. There are some aspects of that approach that I haven't solved in my head. How do you get some kind of axle that is long enough and also how do you mount it to the bottom frame? You really have to get the whole axis straight vertical so that there is no wobble. The threading on a bicycle wheel is fine and I think it would be hard to get a fine-threaded bar long enough for what you want to do with it.

The http://www.instructables.com/id/Wind-turbine-with-bicycle-wheels/
instructable gave me some ideas but it will require using both wheels for support. It also has the advantage of fixed gears on one of the wheels. That could be used to an advantage for getting higher RPM.

[freddysserpent]

use pipe with  bicycle wheel nuts tacked  or puddle welded in place

[macrumpton]

It seems like with a little metal bending to close the back of the "D" on the blades you could do away with the framework except for the end plates.

Also that turbine looks like it would go twice as fast if the shaft were not so wobbly.

[dimovi]

This is really cool.
Can you provide the cad drawings?
I want to have it laser cut

[batonas]

eweryone are useing sheet metal for wings, can it be replaced by thick chelophane or plexy plastic ?

[Roy smith]

Instead of the "u" shaped metal strap just have one 1/2"(.5) coarse thread nut welded to a 1/2"(.5) fine thread nut! Much stronger and more simple (maybe)! Thanks for Your hard work!!! Roy.

[clafever]

Nice project. I just love how people do totally inappropriate stuff in their pristine carpeted living rooms :) When lifting the generator up after taking pictures I would probably have a huge grease ring on the carpet :) Good Luck!

[conntaxman]

Isn't the width of the wing to wide for the length?when making a large wind turbine isn't the Diameter to large? say the diameter of the wind turbine is 8 foot. that would mean the dia. of the wing is 18 inches.and the length is only 38.4 inches.Isnt the "bucket" diameter of 18 inches too large to cut through the wind? Im wondering which is more important,the length or the bucket. tks Johnny I had made one that is Y i ask.very low rpm,.Mine was 3 blade,hight of blades were 54" length 46" Bucket diam was 19" Next I want to make a 5 blade one and trying to figure out a smaller diameter bucket so it would cut through the on comming wind. Yes it did have alot of tork

[boognishmofo]

Cool!! I was looking at another one thinking of using its design, but I think this will be much better. I was pondering the idea of "trying" this out of almost all recycled aluminum cans. Do you think this would be possible. I was thinking of coffee cans for the top and bottoms of the wings and support bars and soda for the actual wings. Just thinking cheap, durable, light, and recycling in the same time. Would you need several of these for a car alternator?Any help would be greatly appreciated.

[rhackenb]

Sounds like it would work if you can get enough material from a single can for each wing. You don't want to get into trying to bond two cans together. Give it a try.

[-Aj-]

pvc piping from the hardware store works well. just cut it out to the desired cup depth.

[stncilr]

What if you built the wings with balsa wood and mylar sheets, of carved out foam? cound that reduce the weight and make them spin easier.

[rhackenb]

Sure, that would work. However, I wonder about the durability in rain and strong wind. It would make a good demo model, however.

[thewoodcarver]

Very nice I will use this with a student at sons school scaled down to fit a small electric motor for his science project ...he is testing sail designs for windmills

[rhackenb]

I'm thinking of scaling this down to about half the size and finding something better than metal flashing to use. You definitely want to avoid metal flashing for a school project. It's difficult and dangerous to work with and once it's spinning, there area lot of sharp edges that can cut people who try to stop it with their hands. I keep thinking there is some sort of plastic laminate that is relatively sturdy but flexible enough to bend around the round part of the wing.

[tornadoboy]

You could try making them out of fiberglass cloth and resin, if done right it should be relatively light and extremely durable

[tornadoboy]

In fact if you wanted to get cute, and could skip using wood for the ribs and just mold them out of fiberglass right onto the wings, then they would REALLY be strong!

[rhackenb]

I have been in contact with Ed Lenz and he pointed out that I don't have the right shape for the wing. The way it is right now, it won't get the lift he designed into it. I will make a change to the the instructable but here is the critical change: The plywood endpiece of the wing is now shaped like an icecream cone. The two sides leading to the pointed end are currently of equal length. What needs to be done is to have the the side that that is covered with sheet metal be at a right angle to the diameter line of the half-circle. In the current posting, that angle is less than 90 degrees. If you draw it at 90 degrees, it will make the other side (the open scoop side) to be at a much more accute angle and for the open side to be longer to the closed side. I will make changes to the instructable as soon as I can.

[kahles77]

Nice job, been thinking of trying to make one of these for a while now.

[3thumbsup]

This is just too much! I have been mulling this idea around my melon for months, and here I find like minded thinkers. The concept is the same with just a few tweeked parrameters. I have a realy rough drawing I did on paint, but it suffices. However the scale is about 10-fold. As soon as I get a proto, I will show. Tks

[explosivetron]

general DC motors are very inefficient at generating electricity, ii have learned from experience that proper dynamo's are a lot more effective because with one I had at home and stuck a fan on the shaft I was able to achieve about 8-9 volts with a hair dryer (pointless i know generating electricity with electricity) but anyway... here in aus i get them from dick smith's but in USA i think it would be radioshack? just ask them