April 22, 2008 was officially Earth Day,  so I am pre-announcing my Vertical Axis Wind Turbine  (VAWT) for the occasion. I have been working on this project for 6 months and I am currently testing out the performance of Prototype #8.  These units are initially designed to be built and maintained by hobbyists interested in experimenting with various Low Cost Green Technology Projects. Production VAWTs similar to Prototype #8 will be built strong enough for commercial use.

 

The picture above shows my 7th Prototype of a Vertical Axis Wind Turbine (#7 VAWT).  This unit was built on the $200 frame of a 4' x 4' trailer so that it could be simply pushed to a good wind spot or pulled behind my car to test its capabilities in the wind. I have had #7 out in winds up to 85 MPH ( I was doing 55 MPH on US-285 near Denver and hit a 30 MPH headwind gust!), and it kept right on running...very fast.   #7 was made from a pair of bicycle wheels spaced 28" apart, mounted on some 3/4" threaded rod acting as a central fixed shaft. The eight turbine blades were made from some 4" diameter thin wall PVC drain pipe, longitudinally cut into two 180 degree semicircles.  Outside of the turbine blades were 16 fixed circularizer blades which deflected the wind by 90 degrees counter-clockwise, directing the wind into the rotating turbine blades.    The 16 circularizer blades were four 33" long sections of  4" Drainpipe PVC cut into  four 90 degree sections. The circularizer blades were shoved into some precut holes cut into some 2" thick styrofoam. disks.  The styrofoam disks set the blade angles and blade placement. #7 was built in 3 days, a very quick and dirty approach to see how a real VAWT might function.  It functioned great!

The picture below shows a closeup of the bicycle wheels bolted to a 3' section of 3/4" threaded rod acting as the central shaft. The eight turbine blades are held to the rims with some copper straps used to hold copper plumbing. The sixteen circulator blades are inserted into curved slots in the upper and lower 2" thick styrofoam circulator blades holdesssrs.

1. The center non-rotating shaft is shown in gray. Attached to this shaft is a pair of 4 bolt flange bearings, in yellow. These two bearings are the only moving points subject to friction.
2. The main turbine section, consists of eight rotating 6" wide x 48" long semicircle (brown) blades. The turbine blades on the right are concave, and the turbine lbades shown on the left of the center shaft will be convex. (This turbine is designed for counter-clockwise rotation.)
3. The alternator(s) consist of :
1. A rotating steel plate holding the bottom of the eight turbine blades on one side, and 16 or more strong magnets (shown in orange) , equi-spaced around a 360 degree circle, on the other side.
2. A second rotating steel plate holding 16 more strong magnets (shown in orange) facing the other set of magnets.This plate is bolted along the outside perimeter to the other magnet plate attached to the turbine blades.
3. An insulated disk (green) between the two steel disks, holding 7 multi-turn non-rotating coils (pink) equi-spaced around a 360 degree circle.  These coils are fixed to the center shaft(light blue), and their 14 leads exit through an enlarged center hole in the lower disk.
4. A second alternator may be placed at the top of the turbine
   
4. The large lavender blocks are a set of large or small width x 48" long circulator blades which concentrate the wind from any direction into a counter clockwise pattern against the turbine blades. The 12 circulator blades are held fixed by top and bottom plates (dark red) held fast to the non rotating center shaft.

This VAWT is typically mounted solidly to some fixed stand. It can also be be mounted to a trailer for testing and demonstrations. Another option is to make a matched counter rotating pair of these VAWTs, mounting them on either side of a communications tower or power tower.

Design Principles:

• Magnets on a given plane are an even number, alternating in polarity. e.g. N S N S N S etc
• Opposing magnets have opposing polarity.
• Maximum energy field is obtained when the magnets are mounted on a piece of steel or iron
• Maximum energy is obtained when the coils are sized and shaped so that when one side passes through a N S field, the other side of the coil is passing through the S N field.
• The faster the coils move through the magnetic field, the more energy is generated.
• More magnets in the circle is equivalent to turning faster.
• The Stronger the magnets & magnetic field, the more energy is generated.
• The more turns of wire on a coil passing through the field, the higher the voltage.
• The thicker the wire, the more current the alternators could generate without overheating.
• Coils can be connected in series, parallel, in phase, or any combination.
  • A number of coils in series, in phase will produce higher voltage with higher effective resistance.
  • A number of coils in parallel, in phase will produce higher current with lower effective resistance.
• More phases = Smoother running. More magnets = smoother running.
• Phases can be connected together after rectification, and will follow the parallel connected rule.

General Principles

• The radius of the turbine inversely controls the speed at which the turbine will turn.
• The diameter and length of the circulators controls the amount of energy the VAWT can extract from the wind.
• The magnets are the most costly component in the system.
• The coils take the longest time to make (are the most labor intensive).
• The turbine blades are the trickiest items to adjust for evenness and balance.
• The circulator blades are the trickiest to adjust for maximum energy, but well worth the time spent.
• The bearings/turbine ease of turning set the minimum point of energy pickup. Adjust & lubricate for <1 foot/oz over the whole 360 degrees. I test using a digital fish scale.
• The bearings should be completely flushed and re-oiled with light low temerature oil.
• Any runout will greatly affect the minimum energy pickup speed.
• The alternator(s) should be matched to the VAWT. Too much energy extracted can overload the Turbine; Too little extracted is wasting the energy deriving capabilities of the turbine.
• It is better to design to slightly overload because the energy output from the turbine can be increase with larger circulators, or the excessive loading of turbine can be reduced by pulse width modulating the load.

I have been designing my VAWTs in mathematically linear progressive steps so that if you need more or less power, make a bigger or smaller VAWT

Some typical sizes and power expectations will appear soon.

Because I am designing and testing these low cost VAWTs at my home's 9000' altitude where the air density is 75% of the density at sea level, lower altitudes will see considerably more power output.

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The picture above shows my backyard with the 8th Prototype of a Vertical Axis Wind Turbine.  This unit was built upon the steel frame of a $200 Harbor Freight 4' x 4' trailer so that it could be simply pulled behind my car to test its capabilities in the wind.    # 8's center shaft was made from a 2 3/16" diameter x 6' long scrap piece of 2" electrical conduit. A pair of heavy duty surplus 4 bolt flange bearings support the magnet plates 48" apart. The bottom is held to the trailer by a standard 2" conduit holder, supported firmly upright by tubular turnbuckles from an old satellite dish. The 8 turbine blades were made from some hard temper (in fact, too hard) aluminum sheets cut to form twelve (4 spares) 9" wide by 48" long strips which were rolled to eight semicircles ~ 6" in diameter.  The turbine blades and magnet holding disks are ~21" in diameter made from some 3/16" thick steel scrap disks.  This shaft and turbine section could now be tested for various outcomes by either pulling behind my car or by putting the trailer mounted VAWT in front of my artificial wind test system. #8 is definitely not light, but it is a very heavy duty lifetime sytem with just a little WD-40 oil in the bearings occasionally!  I designed a small PIC microprocessor system to read and display the RPMs between 3.3 RPM and 6000 RPMs so that I can compare the turbine only readings to readings when the circulators are added to determine the energy capture gain. The PIC also reads and displays the wind speed in MPH from a small anemometer made from 1 1/2" PVC end caps, and the alternator output(s) in volts, amps and watts, all in real time. This can be sent to a PC by an RS-232 line or RF link, for storage and for further analysis.

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The picture above shows how I connect the Turbine blades  to the steel plates.  Since each of the eight blades forms a 6" semicircle, I cut some 1"  square aluminum tubing (found in a scrap box) into twenty 6" long pieces (4 spares)  Sixteen pieces of 1/4-20 threaded rod, each 6 3/4" long  with a shoulder washer and stop nut at each end hold the turbine blade firmly sandwiched to the 1" tubing pieces.  A 7" long 1/4-20  carriage bolt would be better, but the local hardwares stores did not have any that long! Sixteen 1/4-20 bolts, shoulder washers and stop nuts hold each steel plate to the turbine blades' ends.

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I added a 4' by 3 1/2' plate made from 3/4" plywood, finished with several coats of Polyurathane which protects the plywood from the weather, and the plywood protects the turbine from puddle splashes while traveling in wet conditions. Next, two 4' by 4' plates, made from 1/2" AC exterior plywood and finished with a couple of coats of Polyuraathane for temporary wet weather resistance, are used to to hold the twelve circulator blades firmly sandwiched between them.

My extensive collection of standard and deep throat C clamps was called upon to hold the circulator in temporary positions while I tested the amount of energy captured when I varied the wind injection angles and depth of wind injection.The picture above shows the 1" square aluminum tubing clamping system which is used to attach the twelve circulator blades to the top and botttom 1/2" plywood end plates. The Harbor Freight deep throat  C clamps are extremely helpful for setting and firmly holding precise angles while testing.  When the ideal locations, depths, and angles are determined, the twenty four temporary C clamps (top and bottom) are replaced by 48 bolts, washers and stop nuts.

 

I initially test my various VAWT designs by using the artificial wind system shown above. This unit has four big computer blowers which I found at a local surplus store for $25 each. The four blowers set upon a hydraulicly raisable and moveable table from Harbor Freight. The four blowers can be individually turned on and off and can be reaimed to provide many repeatable test setups.

 

Prototype #8 has the twelve circulators around the turbine nearing optimal angles now, and when a strong wind storm occurred recently, it really started spinning.  It was normally running around 40 RPM in a fair amount of wind..On one gust the speed increased to 137 RPM which is a power gain of the ratio cubed which is a power gain of 40 times more power! The wind was extremely fickle.  One second it would be blowing from the South at 40 MPH, and  a few seconds later dead calm, then instantly gust  to 50 MPH from the NW.  The best feature of a VAWT is that turbulent wind gusts that would destroy the big propeller driven Horizontal Axis Wind Turbines (HAWTs) cause no damage at all to a Vertical Axis Wind Turbine.  Highs winds that would result in the horizontals being locked down in safe standby will see the VAWTs spinning out more energy than ever!  My VAWTurbine turns at subsonic speeds, so it makes almost no sound except for a VERY slight noise from the bearings. It is difficult to see anything moving since the revolving turbine is inside the stationary outer circulator blades.   When a screen around the outside is added, this VAWT looks like a round air conditioner, except that it does not make any noise. It looks extremely "Critter Friendly" as my wife calls it.

Yesterday I readjusted all the circulator blades to about 20 degrees from 48 degrees shown in these pictures and this VAWT, turned by my artificial wind system picked up speed from about 70 RPMs to 113 RPMs - 4 times more energy recovered by adjusting the angles of the circulators.

I just took this VAWT out for a "Spin" behind my car this morning. It starts turning at about 10 mph, and looks like it is spinning fast enough some serious electricity output at about 20 MPH.  At 35 MPH it is going very fast.
I need to connect a longer line on my RPM measuring microprocessor input so I can read the RPMs while in the car. I hope to get the magnets and coils on the VAWT this week and then find out how much electricity it can really make.   I  tried slowing down the turning blades with my hand (very carefully) - the convex side of the turbine blades is moving forward.  They sure have a lot of power when they are moving at better than 50 RPMs.
 

 

to be continued with pictures and desciptions of the twin alternators used on this VAWT

and the microprocessor system which reads, displays, and stores the Turbine RPMs, Anemometer MPHs, and Alternators' Volts, Amps, and Watts being output.