Wind Turbines for the Layman

7/30/2019 Wind Turbines for the Layman

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We strive to preserve natural resources to the maximum extent

racticable b develo in sourcin and commission of the latest

technology and solutions for efficient use of such resources. In expressing

this concern as part of our daily activity and in acting upon this premise,

We strive to educate and impart a partnership to save the environment

to live a world better than what we found for our children.

"Something from Nothing",

"Treasure from Trash" and"


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WIND TURBINE


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nemome ers : s essen a oknow the real wind speed in any wind

generator installation, commercial or

Build your own anemometer: We built

an accurate anemometer for under Rs

500 using plastic Easter eggs. See it.the machine is performing correctly,and extremely high wind speeds mightbe a clue that ou should shut the mill

here! It counts frequency with a simple

circuit, and can be adapted to use with

computer data acquisition equipment.

down for the duration of the storm. Ifyou plan on investing significantmoney in wind power, a logging

Logging anemometer kit: This ingenious

kit is from Australia and costs less than

anemometer might help you decide ifyour local wind resource is worth the

investment. Commercial anemometers

s rac s w n spee an

direction, and logs data to its own

memory, including average and peak

expensive, but can be found with aquick Google search...you can also try

. ,

PC...your wind data can import live

right into a spreadsheet!


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First, figure out the direction from which

the prevailing winds in your area usually. u y

observation during wind storms, and bylooking at the trees near your site. Trees

and that have branches mostly on oneside of the trunk are a good indication ofprevailing wind speed and direction.Local airports and weather stations cansometimes provide you with this

information.

*** A Logging anemometer that also records winddirection can be useful here too, though expensive.


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the ground is like mounting solar

panels in the shade! Your windgenerator s ou e ocate at

least 30 feet above any

obstruction within 300 feet in any

directionmany sourcesrecommend even more. Short

towers in turbulent locations

cause drastically reduced power

output, and extreme physical

tower.


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generator and your batteries can

also be a problemthe closer the

,

wires and to keep the wire size

required down to a reasonable

c ness an cos . vo

systems are the worst for power

transmission lossesyou end up

needing very thick wire. A 24v or

48v battery bank can save you big

money on wire!


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Tower

Check out our TOWERS page for somehomebrewed solutions that are cheapand easy to fabricate, plus lots of details

and pictures. There's also lots of tower,available by Searching the Other powerdiscussion board for 'towers'.

Your tower must be extremely sturdy,wellanchored, and tall enough to getabove obstructions. We've seen 1.5 inch

mph winds, underneath a wind machinewith only an 8foot rotor. Some windenergy guidelines tell you to plan onspen ng a as muc on yourtower and power wiring as on the windgenerator itself!


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tower are the TiltUp and Stationary. A

stationary tower is the most sturdy and

,

install, maintain or remove the wind

machine.

A crane is often used for installation, anexpensive propositionthough you can do it

yourself by climbing the tower and moving

a gin pole up it as you add each new

section. If climbing towers disagrees withou o for a tiltu . Then all maintenance

can be performed while standing safely on

solid ground.


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against mounting a wind generator on yourroof. The winds near rooftop level are very

slow and turbulent, and power output will.types of wind turbine, not just ours. Again,your turbine needs to be mounted at least30 feet above anything within 300 feet in

. .

Though the manufacturer says it works, wehave observed firsthand the vibration andno se ur ng a w n s orm n wo erenroof installations...it is VERY noticeable andirritating. And keep in mind that the verysmall unit (only a 1.3 meter prop) that

...be unbearable, and possibly dangerous toyour house itself.


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**

oug e manu ac urer says wor s, wehave observed firsthand the vibration andnoise during a windstorm in two different

roof installations...it is VERY noticeable andirritating. And keep in mind that the verysmall unit (only a 1.3 meter prop) thatmakes very little power...a larger mill

,

dangerous to your house itself.Most commercial and homemade windgenerators don't make much physicalnoise, but some vibration is unavoidabledue to the nature of permanent magnet

alternators. Listen to the vibration ofWard's 7 foot diameter windmill

** (12 second .WAV file, 140K) and hearwhy we don't recommend roof mounts!


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ROTOR


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e s a spee s a very cruc a ac or n atypes of alternator and generator. The unitneeds to make higher voltages at lower

RPMs, otherwise it is not suited for windpower use.

This goes for all power units...even motorsuse as generators an a ternators s ou e

rated for low RPMs. This is also why vehiclealternators are not suited for wind poweruse.

Most commercial wind generators cut in at8

12 mph. The generator's low

speed

voltage performance, the design of the rotor(the blades and hub), and the wind behaviorall factor into where cutin will occur.


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Rotor

A win generator gets its power rom s owing own t e win . T e a es

slow it down, and the alternator collects the power. BOTH must be correctly

designed to work together and do this efficiently.We are not experts at blade design...we sort of started in the middle with a

functioning design, and made changes from there. Really, you could make a

they would work JUST FINE! But to really tune in the performance of yourwind generator, it's important to pay

attent on to a ew actors. p ease org ve us w en we s p up an re er

to the rotor as a "prop" or

" ro ellor"

it doesn't propel anything! Rotor is the proper term, not to be confused with

the rotor of an armature. But we slip up sometimes...


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ar p pee s s e w n spee awhich the rotor starts turning. It should spinsmoothly and easily when you turn it by

hand, and keep spinning for a few seconds.Designs that 'cog' from magnetic force orthat use gears or pulleys to increase shaftspeed will be poor at start up. A good design

at 7 mph.CutIn SpeedA wind generator does notstart pushing power into the battery bankuntil the generator or alternator voltage getshigher than the battery bank voltage. Higher

shaft speed means higher voltage in allenerators and alternators and ou want totry and get the highest shaft speed possiblein low winds without sacrificing highwindperformance.


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Current (DC), and use the term Alternator to describe a machine that producesAlternating Current (AC). However, the term Generator is also used generically to

describe any machine that produces electricity when the shaft is spun.

OptionsThe alternator or generator is the heart of your wind machine, and itmust be both properly sized to match your swept area, and produce the right type

. ,

commercial or surplus products than can be easily matched to a set of blades forbuilding a wind turbine. It's MUCH more practical to build your own alternator thanto try and adapt a commercial unit that was designed for a completely differentpurpose. you try t at anyway, converte n uct on motors, generators,brushless PM motors, vehicle alternators, and induction motors are options...but

are marginal performers at best.

ApplicationWindgenerated electricity can be used for battery charging and forconnection with the power grid. All of our designs and information are aboutbattery charging at this time, since we all live 12 miles from the nearest power line.


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.

Single Phase vs. Three Phase3 phaseoffers some advantages over single phasein most alternators. Most smallcommercial wind turbines use 3 phase

,to DC (direct current) for chargingbatteries. When building an alternatorfrom scratch, single phase seems

understand. 3 phase is not really anymore difficult.

Goin 3 hase allows for s ueezin morepower from a smaller alternator. Itsignificantly reduces line loss, and it runs

with less vibration. Older single phase

(and make more noise) than 3 phasemachines.


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An alternator that uses man windin s of thin wirewill have better lowspeed performance than one thatuses fewer windings of thicker wire, but higherinternal resistance. This means it will becomeinefficient more quickly when producing higheramperage as wind speeds and power output rise.

The formula used to calculate power wasted frominefficiency is AMPS^2 * RESISTANCE = Power wastedas heat in the alternator windings (in watts).

A ternator Des gn FactorsMa ng PM a ternators

from scratch is sort of a "black art"

there are manyfactors that enter in to it, we try to discuss some ofthem below. And then, you must add in anotherimportant factor, the design of the blades. We discusst at e ow a so. e n t start u ng w n m s analternators by doing a bunch of math...we just jumpedright in, made lots of mistakes, and eventually wound

up with a satisfactory design by observingperformance and changing one variable at a time. Thecu t part s gett ng t e est matc etween t e

blades and the alternator.


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, .and stronger your magnets are, themore power you can produce in a

smaller alternator. NeodymiumIron

Boron ("rare earth", NdFeB) are by farthe strongest permanent magnetsknown to man, and are ideal for

alternators. Many older designs callfor strong ceramic magnets, this wasmainly because of price. We do sell

, that are suitable for alternator use,but in practice NdFeB magnets willgive over 4 times as much power int e same space t an ceramics. P us,prices on large NdFeB magnets havedropped dramatically since they werefirst invented in the 1980s.


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' ' .Generally when building an alternator we need aseperate magnet for each pole. The faster that

alternating north and south magnets poles pass the, .surface area is important as well. If we have a verynarrow magnet (required for using many poles), thefield strength would be much weaker over a distance

.

wind turbines, there is a compromise to be made.

We choose a number of poles that allows forreasona y s ze co s an a goo s rong magne c ethrough whatever airgap we wind up with. It mustalways be an even number. For a 3 phase machine we

like 4 poles for every 3 coils, although there are. ,

a 3 phase machine we'd have somewhere between 8and 16 poles (magnets) unless perhaps the machinewere to be very large.


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This is the distance between themagnets and the laminates in a single

ma net rotor desi n or between twomagnets in a dual magnet rotor design.The smaller the distance, the better thealternator performs. This means it's

possible, and to make the armature fitvery precisely near the stator...if it isnot perfectly square, the air gap will bearger on one s e o t e a ternator

than the other, and performance will

be compromised. Halving the airgapives 4 times as much ma netic flux.


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Bearings--

e opera ve wor ere s .Besides having to withstand vibrationand high rotation speed, there is a

bearings from the wind, and it increasesgeometrically as the prop size increases.That's wh we've moved to usin

standard trailer wheel bearings in ourdesigns, they are tapered and designedto take the thrust loads. The frontbearings in our converted AC inductionmotors have so far held up well, but

they are not designed for that kind of.

especially vulnerablethe front bearingwill eventually fail dramatically in high


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en co s are connec e n ser es,the voltage increases and so does

resistance. When connected in,amperage increases and resistancedecreases. Also, parallel connections

flow where you don't want it to,called 'parasitic losses.' The correct

depends on many factors.

Windstuff now's 3Phase Basics Page

3phase, star and delta. We wire allof our alternators in Star.


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Enameled magnet wire is always used for winding the stator, because the insulation is very thinand heatresistant. This allows for more turns of wire per coil. It is very difficult to strip, use a

razor knife or sandpaper, and be sure to strip each lead thoroughly! Choosing the gauge of wire is

for lowspeed cutin, but using longer, thinner wire gives higher resistance and therefore the unitbecomes inefficient faster at high speeds.

.

are said to originate at one pole and return to the other, just like a battery. Air is a poorconductor, both for electric and for magnetic lines of force. In order to make best use of a magnet(and our copper wire) in an alternator, we need to have the strongest possible magnetic field. Justlike co er is a ood conductor of electricit steel is a ood conductor of ma netic fields. A oodmagnetic circuit involves steel between the poles with a gap (the airgap) where we need to utilizethe field. In an alternator, our wires should occupy the airgap, it should be no wider thannecessary, and every other part of the magnetic circuit should be of steel.

We can either use steel laminates (laminated steel reduces eddy currents) or we can havemagnets on each side of the coil(s) moving together with steel behind them. Again, look at ourvarious wind turbine experiments to see. It should be said that some of them, like the woodenalternator and the all wooden windmill have very poor magnetic circuits.


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BLADES:


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Wood is really an ideal material for blades. Itis very strong for its weight, easy to carve,

inex ensive and is resistant to fati uecracking. Choose the best, straightest, mostknotfree lumber you can find; pine andspruce are excellent. Hardwoods are generally

.

much too heavy and prone to fatigue cracking;sheet metal would be a poor choice, andextremely dangerous.

Cast reinforced Fiberglas blades are verystrong, and are common on commercial

windmills

but the mould making process

of blades from wood, and there would be littleor no gain in strength.


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B a es t at are too s ort attac e to

a large alternator will not be able to

get it moving fast enough to makegood power. Blades that are too

large for a small alternator will

over ower and burn it u or

overspeed to the point of destruction in high windsthere's

available to collect the energy

coming in from the wind.


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infinite number of infinitely thinblades. In the real world, more blades

give more torque, but slower speed,and most alternators need fairly goodspeed to cut in. 2 bladed designs arevery fast (and therefore perform very

from a chattering phenomenon whileyawing due to imbalanced forces onthe blades. 3 bladed designs are very

choice, but are harder to build than 2bladed designs. Going to more than 3

blades results in many complications,suc as materia strengt pro emswith very thin blades. Even onebladed designs with a counterweightare ossible


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than the windspeed the tips of yourblades are designed to travel. Your

blades will perform best at this speed,but will actually work well over a rangeof speeds. The ideal tip speed ratiodepends on rotor diameter, blade

alternator, and wind speed. Higher TSRsare better for alternators andgenerators that require high rpmsbut

particular site will make a big differencealso.

If in doubt, start in the middle andchange your blade design depending onmeasured performance.


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,wider at the base and narrower at thetips, since the area swept by the inner

portion of blades is relatively small. Thetaper also adds strength to the bladeroot where stress is highest, gives anadded boost in startup from the wider

ideal taper can be calculated, and itvaries depending on the number ofblades and the tip speed ratio desired.

'book and his free Blade Design Notescontain the relevant formulas. Honestly,

though...if you simply take a look at apicture o a unctioning sma sca e wingenerator's blades and estimate thetaper by the eyeball method, you willcome ver close to meetin the criteria

and have a very functional blade.


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as c n ro uc on o a e es gn ancarving Pitch and TwistAs we've said before,a simple wind generator blade with a straight

5 degree pitch down the whole length wouldgive adequate performance. There areadvantages to having a twist, thoughlikewith taper, having more pitch at the blade

,

pitch at the tips improves highspeedperformance. The wind hits different parts ofthe moving blade 's leading edge at differentang es, ence es gn ng n some w s . ne oour common blade designs that's right in themiddle for design parameters is to build an

even twist of 10 degrees at the root and 5degrees at the tipbut the ideal solution willalso depend on your alternator cutin speed,efficiency and local wind patterns.


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T ere are great engt s t at you can

go to for designing an airfoil...NASA

has some great information andcalculations out there on the net. But

all an airfoil needs to do is maximize

lift and minimize dra . You will do fine

if you do like we did

find a likelylooking airfoil cross section from a

,

copy it. A power planer makes quick

work of carving it, and a drawknife is,

the deep cuts near the blade root.


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e a es mus e very we a ance oprevent vibration. This is more easilyaccomplished with a 2blade rotor than a

3 bladed one. But generally, we simply usea homemade spring scale to make surethat each blade weighs exactly the same,and that each has the same center of

.

rotor configuration can be made with anupright spike that sticks into a dimplepunched at the exact center of the hub.

xcess ma er a rom e eavy areas canbe removed quickly with a power planer.

You'll also need to balance the blade inlace on the alternator. It's wei ht

distribution can be adjusted by attachinglead strips to the blade root


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FurlingSystems


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" "describe a mechanism that turns thewind generator rotor at an angle out

of the wind, either horizontally orvertically, to protect the machine fromdamage during high winds. Ideally itwill keep power output levels near the

early wind turbine designs didn't usefurling systems, and we feel fortunatethat some of them are still flying.

w n tur ne t at ur s s a so mucmore gentle on your tower and guywiresthe force on an over speedingwind turbine increases as the windgets stringer.. There are a variety offurling system designs:


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e genera or s moun e o cen erhorizontallly from the yaw bearing. Thetail is also angled in this axis. The tail is

,hinged. When the wind force back onthe rotor is strong enough to overcomethe offaxis enerator makin it want toyaw and the angled tail trying to keep itfrom yawing, the tail folds up and turnsthe alternator away from the winddirection, forcing the wind turbine toyaw out of the wind. When wind speeds

drops, the tail is returned to normal, .Many commercial and homemadedesigns (including ours) use this system,


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n ea u ex reme y comp ca e so u onis to use blades which change pitchdepending on the wind speed....these also

have the advantage of keeping poweroutput at the most efficient point for thecurrent windspeed. During low winds, theblades are pitched for best startup.

,

speed to the ideal RPMs for the generator.In extreme winds, they turn the blades evenfurther to protect the unit from damage.The problem is the complexity of making asystem work reliably...but it can be done!Large commercial wind generators use thiss stem exclusivel as do anti ue andmodern Jacobs turbines, and some oldWinChargers.


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In t ese esigns, t e generator o y

is hinged just behind the nacelle.

When wind speed gets too high, theentire nacelle, hub and blade

assembly tilts back out of the wind to

nearl vertical. As the wind slows

down, it returns to normal horizontaloperating position by either springs,

,

counterweight. Commerical wind

generators that use this method are

the buyout), the Windstream, and

many homemade designs.


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Simi ar to t e ur ing tai , ut t e tai

boom is fixed, with a hinged vane

underneath. Used on some olderWinchargers and homemade

designs, the disadvantage is that tail

and vane are more hi hl stressed

from wind force during furling, asthey still are sticking out there in the

.


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T e t eory is t at t e a es ex

both back toward the tower and

around their main axis, andtherefore protect themselves from

overspeeding. It does work if the

materials and details are

correct...for example, the bladesmust not flex back far enough to hit

,

flexing during cold weather too.

Slip Rings


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Slip Rings

tower to your power system. Since the actual wind generator must yawto keep pointed into the wind, the main power wires must be able tohandle this.

There are 2 options...

to simply use a length of flexible cable and a steel safety cable instead ofslip rings. Use the highest quality stranded, flexible cable you can findand attach it in a loose loop from the wind generator power terminals towhere your feed wire comes up the pole. Use a length of wire that allowsabout 3 or 4 wra s around the ole. Or run the wire down the center ofthe tower pipe and let it twist inside. Our experience is that while the

cord can eventually wind itself around the pole, it will also eventuallyunwind itself. Some of our models have flown for years with this kind ofsystem and required no maintenance. With a properly designed windturbine and furling system, you should hardly ever see the mill make a

egree yaw. e s mp e use a power p ug an soc et at t e ottom othe tower and unplug it once or twice a year to untwist the wire.

We've seen commercial turbines on 120 foot towers that successfully usethe pendant cable system.

Make or Convert Slip RingsSlip rings can be salvaged from old caralternators and converted to wind generator use, or built from scratchusing copper pipe, PVC pipe and graphite brushes. Home PowerMagazine has had articles in the past about both methods. We havenever felt the need to use them and they make for another potentiala ure po n , so we ave no exper men e w .


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ShutdownSystems


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T is is a manua contro t at

completely shuts the wind generator

down. It is not allowed to spin at all,and should be able to survive

extremely violent winds in this

condition. It can be electrical or

mechanical.Air BrakesNoisy and full of vibration,

.

used this system. Metal cups extend

from the hub from centripetal forceur ng g w n s, an no s y s ow t e

machine down; they retract back into

the hub when the wind slows.


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,simply shorting the main AC power output leadstogether should effectively shut down the windturbine. The problem is that when the machine is

s innin at hi h RPMs durin a windstorm theshutdown may be either impossible electrically(the turbine is performing too inefficiently forshorting the output to have any effect), or toodamaging to the alternator (the heat produced int e stator co s y s ut own at g spee s turns

the coils into molten slag.) Our normal method isto simply wait for a space between high windgusts to short the mill with a switch. We have

'was putting 30 amps into 12vdc...numerousshutdowns at 1020 amps of output have causedno vibration or problems. You can use a manualswitch, or simply a shorting plug to do this. Ourhomebrew deisgns have never had problems withrefusing to stop in high winds when shorted.


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T ese systems p ysica y ra e t e

wind generator, or force it out of the

wind by turning the tail parallel to theblades. Even the mighty Bergey Excel

10kW wind turbine has a mechanical

crank for emer enc shutdown.

Generally, a cable is attached to ahinged tail, with a small hand winch

the operator.


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Wit atteryc arging win generators, regu ation o t e incoming vo tage is

accomplished by the battery bank itself, until it is fully charged. Though a PM

alternator or DC generator's open

circuit voltage might be 100 volts, thebattery bank keeps the wind generator circuit voltage at its own level. Once

the battery bank fills, system voltage will rise rapidly and something must be

done with the uneeded incomin ower.

Simply disconnecting the windmill is not an option

a windmill allowed to'freewheel' will quickly blow itself up from overspeed. The power must be

.


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This is the oldest, simplest and

most reliable method of regulation.

Problem is ou have to be there todo it. But by turning on house lights,

heaters, etc. that more or less equal

,

prevent the batteries fromovercharging, keep a load on the

voltage in the normal range.


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ese sys ems s mp y sense e a ery vo age an ver power rec y romthe batteries into heating elements (known as a 'dump load'), thus keeping a loadon the windmill while avoiding overcharging of the batteries. The very simplest

the batteries and connects it to some heating elements...just keep in mind thevoltage requirements of the heaters must be a good match to the alternator forbrakin to occur. Sim le s stems that divert all the incomin ower at once canbe built using Trace Cseries charge controllers or relays and voltage sensors.More complicated systems use power transistors or pulse width modulation todivert only part of the incoming power, or the entire amount, as charging needsrequire.

Both Home Power Magazine and Hugh Piggott's Website have plans and

schematics for building shunt regulators. Some commercial solar chargecontro ers can e set to unct on as ump oa contro ers, e t e Trace .controller intended only for solar power will NOT function with a wind turbine,nor will an automotive voltage regulator.


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. . .

.

A. No! No!! No!!! I am getting this question a lot and it really scares me. You need specializedequipment like synchronous inverters and transfer switches, and a licensed electrician, tointerface a wind or solar system with your house wiring safely and legally. Do not attempt to do it

necessary equipment and permits. In some areas some or all of the work may have to be doneby a licensed electrician. Check your local codes.

.

A.Probably not. This wind turbine only produces a few hundred Watts peak. It probably wouldn'teven do a very good job of heating one room, let alone a whole house.

Q. How noisy is your wind turbine? I'd like to build one, but I'm afraid it might be too loud.?

A.The wind turbine is not really very noisy. I do have it set up about 100 feet away from me, butit is not terribly noisy even up close. It isn't much noisier than the wind itself. Most of the time, in

a stiff wind, I can't really hear the wind turbine at all over the roar of the wind through the trees.e on y t me actua y not ce t e no se rom t e w n tur ne s w en t e w n as een

blowing hard and then suddenly drops off to almost nothing. Then I hear the whooshing of theturbine blades for a few seconds until they slow down.


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. . .

'.inverter or other appliance directly to the wind turbine?

A. The Voltage output from the wind turbine varies wildly with wind speed. You would bevery liable to damage the inverter or other appliance by running it connected directly to

e w n ur ne w ou a a ery an an c arge con ro er n e sys em. e oa romthe battery bank smoothes out the Voltage to something the inverter can handle, andprovides power during periods of little or no wind.

Q. Will a solar panel charge controller work for my wind turbine?

A. Unlikely. Most solar panel charge controllers simply disconnect the panel(s) from the

battery(s) when full charge is achieved. This leaves the solar panels opencircuited. This is

not a problem for solar panels. However, wind turbines need to be connected to a load atall times or they will overrev. When the batteries achieve full charge, the wind turbineneeds to be connected to another load, rather than opencircuited. It may be possible tomodify a solar charge controller to do this, but it would depend on the particular controller.I can't help you with selecting a controller or making modifications.

Q. Which direction does our wind turbine s in?A. When looking at the turbine from the blade side, (as opposed to the tail side), theturbine spins clockwise. So the motor shaft turns clockwise. The direction of spin is notreally all that important. A DC motor will act as a generator no matter which way it isturned. The olarit on the out ut will ust reverse if the direction is reversed.

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Wind Turbines for the Layman

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