I'am totally confused

[johnbfl]

I'am confused i d'ont understand the difference or advantages of a 48 or 36 or 24 volt system compared to a 12 volt system volts x amps = watts it makes cence  that u would want to have a system with higher volts seeing that its a primary multiplier but do u use higher voltage system because u are in an area with a higher wind speed average and you have a higher average rpm or just for the fact of charging more batteries to accommodate your consumption.confused higher volts thinner wire more resistance with higher voltage more rpms more heat totally confused can't get my little mind rapped around this one totally new trying to figure out what would work best been reading this forum since jan 08  any help would surely be appreciated like wind mill math for dummies thank you.    

[Bruce S]

john;

  It can be all of the above or none of the above :-()

Mostly though its due to line loss. See when trying to push power through wire at long distances the resistance of the wire times the length causes losses.

Doing the math, a higher starting voltage will result in a lower end loss at the point of the batteries or whatever it may be.

This is also the best reason to have the wild AC coming down the windmills and being recitifed at the controller rather than changing it to DC at the pole.

AC by its nature will have less line loss over longer distances than DC.

The higher DC voltages incoming to inverters, water heaters, etc. means less line loss and or better use of the incoming power.

Hope this helps

Bruce S

[racer]

From my own scrap yard of math with many thinks to others on this board and beyond.

Its just a beginning

Wind Turbine

and

Generator

Formulas

for

Dummies

To find Voltage

N x A x R x B x P = V of each coil

N = number of turns of wire

A = area of one magnet in square meters (square inch x .000645 = sq meters)

R = revolutions per second ( 60 =1, 120 =2, 180 =3, 240 =4, etc..)

B = strength of magnet in Tesla (gauss / 10000) ( Neo in .5 - .7 est)

P = Number of magnetic poles

Three phase wire set ups

Multiply coil output by;

 1.732 to get voltage output in Star

 1.000 to get voltage output in Delta

To convert AC output to DC output

Multiply AC output by 1.4 to get DC voltage and then subtract 1.4v for bridge rectifier loss (real world equation seem to be more like ACv x 1.25 to 1.3 = DCv). Loss increases as voltage output increases.

Total equation (three phase star setup)

N x A x R x B x P = V x coils per phase = phase V x 1.732 = AC stator output x 1.3 or ( 1.4 then - 1.4v) = DC voltage est. output of generator

How much power is in the wind?

P = .5 * AD * (D^2 * .7854) * V^3

P = .5 * AD * A * V^3

P = .5 * AD * (sq. feet * .0929) * V^3

Where:

P = power in watts

AD = air density (RHO)( typically 1.22 at sea level )

D = Diameter of prop ( in meters )

V = Velocity of the wind ( in meters/sec )

A = swept area in square meters

Then (P) has to be Multiplied by blade eff. and generator eff. to get estimated useable wind power. P * BE * GE = WW

where;

BE = blade eff.

GE = generator eff.

WW = Windmill watts

If you know what your alternator/generator will do in watts, this one will help determine the size prop you will need to run it....

D = (P / ( Cp * rho / 2 * Pi / 4 * V^3 )) ^ 0.5

Where

D = Diameter of prop in meters

P = power in watts

Cp = overall efficiency ( typically .15 to .20)

rho = air density ( 1.22 at sea level )

V = velocity of the wind in meters/second

If you have a prop you plan to use, this one will determine the power output you can expect...

P = Cp * rho / 2 * Pi /4 * D^2 * V^3

To find the TSR ( tip speed ratio ) of a prop at a given output...

TSR = rpm * Pi * D / 60 / V

To calculate the rpm at a given TSR...

rpm = 60 * V * tsr / ( Pi * D )

Good idea

Adding a capacitor in line after the rectifier bridge to store power spikes so the battery has the opportunity to absorb the power made from the generator better.

Centrifugal Force:

.000341 * W * R * n^2

Where:

W = weight of outer ring

R = Radius in feet

n = RPM

Other formules to find wire turns per phase

17,000 x (System voltage + 1.4v) / (desired cut in speed RPM) / (strength of flux in Tesla) / (total area of magnet faces in square inches) = turns per phase

[SparWeb]

On the other hand...

You have to consider cost.  The cost of buying the 48V equipment must be justified by the alternative expense of buying heavier wire to carry the greater current around the 12V system.

For example, a 12V inverter rated at 1000 Watts is pretty cheap, say, 200$.  The 48V version will be hard to find, and you may have to pay 400$ for it.  Then you realize that the batteries have to be a long way away from the inverter, so you need to run 10 feet of wire to carry that 1000 Watts.

In the 12V system, the wire must carry 90 Amps.  Think double-Naught wire sizes.  The typical auto parts battery cables will do, but at 10$ per foot, over 10', that eats up a lot of your savings on the inverter.

If you opted for a 48V system, the current is about 20 Amps, and you can use 10 gauge wire, easily available at Home Depot for a few bucks.

Okay, that's over-simplified, but the point I'm getting across is that you should choose the system voltage based on your approach to the system.  If it's "One Big Job" and when it's done, you will tinker with it minimally, then you might as well go for 48V or at least 24V up front.  The efficiency will be higher.

If you are endlessly going to fiddle with this part or that, changing connections, adding loads, testing ideas, then you might prefer to start with the 12V stuff.  It will be much easier and cheaper to find at the auto supply store the bits and pieces you need for your "invention of the week".  

[racer]

Also print out this web page http://www.interfacebus.com/Copper_Wire_AWG_SIze.html

I use the 200 Cicular mils per amp to calculate max power before burnup. As you will see after a while SPACE is the limiting factor.

Also find wire size charts round,flat,and others

[racer]

Need to add in this formula

DC voltage est. output of generator - battery clamping voltage / resistance = Amp output x battery clamping voltage = wattage output

[johnbfl]

let me explain my son lives on lake michigan he is the president of the condo association. the building is 25 stories high and they were looking at putting a solar system on the roof to cut down on cost of maintaining lights for hallways and video monitoring all that stuff. being from the windy city myself i told him it would probably be more efficient to think wind. he did a wind speed test and at that hight gives average wind speed of 23 mph with gust to 60 . there is no real tower issue the wind mill can be set up on 20 ft poles the roof can accomidate 4 wind mills from wind mill to batteries is  about forty feet the biggest issue is birds  they are talking about installing a cage of sort around each wind mill and doing solar and wind powerand selling it back  to power comp and sharing the revenue  with the association. seems like a lot of investment but all members of the building are helping finance and our trying to bring this concept of green to the big city . I'm just doing my best to help my son w/ research and all info is appreciated  could just turnout to be a idea but they seem very serious so it sounds like a 48 volt system may be best here to get the highest pwer from the alternator thanks again in advance bruce  

[ghurd]

I was going to say that.

Plus, if it is a small system, then chances are the uses are small.

Laptop computer, LCD TV, maybe a CFL light and a cell phone charger?

Can do that with a $30 12V inverter.

Try to find a 48V inverter suited to low power uses.

A small 12V system can use 2 golf cart batteries with great results.  48V needs 8!

I can't understand 24V at all, except for the endless supply of free 24V UPS.  Seems like 24V has all the problems of 12V and 48V, with few of the benefits of either.

G-

[electrondady1]

a very informative thread.

one thing to note is if they intend to do a grid tied system

won't the  alternator voltage be dictated by the equipment for used for grid tie

[commanda]

I can't understand 24V at all

24 volt inverters for trucks are almost as common as 12 volt inverters. Plus, 78xx regulators will run directly off a 24 volt battery for DIY electronics, but not off a 48 volt system. I think it's a nice compromise.

Amanda

[SparWeb]

24V - It's also the standard system voltage of airplanes.  I work with aircraft, so speaking for myself, I'm more comfortable with the currents and wire sizes typically used in 24V systems than anything else.  I still use 12V at home, but a switch up will come soon, once my new barn is built, new shed is located properly, etc. etc....

[Bruce S]

John;

  With the added detail, you can see how many different ways you can go.

Couple things: Birds, unless they're on the endangered act, don't worry too much about them, they'll learn real fast not to even bother being around the blades. Some birds might hit it but most will just fly around them. Your worst would be the ones who see it as a place to rest when the wind isn't blowing.

I lived for a very short couple years on a 7 acre grape farm in South West MI (Lakeshore,MI) and the wind always blows.... At 20= MPH you're sure to get a good solid output, but I'll leave that part to the blade gurus on here :-}

Since you're wanting to in the beginning start with hallway lighting and monitors;

Have your son take inventory of ALL the power requirements for the total of the lights and monitors.

Most of these lights will be mounted to a single circuit at the mains. The monitors are a different duck.

These we'll need to know the types. Newer ones use CCD cameras and they're DC powered anyway. They'll have the power requirements on them, beware of some of the units out there, they use the power lines to push the video/sound through AC and have a DC disconnect at the VCR or computer that then strips the video/sound (most lost prevention places uses this type especially with color micro and wide angle cameras).

Once you have the power requirements, then it could be as simple as a few windmills with PV panels for redundnacey along with batteries and inverters.

Selling back to Con/Ed? might be okay , might not be worth the extra install/fees.

Memory serves me right MI still has at least one Nuke still going which makes for cheap power( whatever cheap is these days).

It will be the power requirements IMHO, that will deside the rest of the design.

Hope this helps;

Bruce S

 

[ghurd]

"24 volt inverters for trucks are almost as common as 12 volt inverters."

Not here in Michigan and Ohio.

Last 110VAC small one (50W to 500W class) I tried to get was from UK.

Yes, a 120VAC inverter from UK is strange.

I never did find a decent one.  Added a 2nd 12V controller, 2nd battery, a $100 4PDTCOw/detent toggle switch, and a $25 12V inverter.  LONG story.

There just doesn't seem to be a 50W to 500W class 24VDC to 120VAC 60HZ inverter, from a name brand, or semi-name brand.

I do like the 78xx idea and didn't think of that angle.

I can't think of anything common here that needs over 12VDC.

[finnsawyer]

People think they can add weight to the roof of a building with impunity.  Not so, as an example that showed up on "Engineering Disasters" showed.  I believe that was in Korea.  Your son should talk to the building's architects about any proposed modifications.  There is also the issue of noise from the wind turbines penetrating the building as well as stresses from the forces on the turbines.  If the building is of masonry construction it will not take well to the constantly changing forces.  I think they should forget the wind and stick with solar.  

[spinningmagnets]

I haven't built one yet, but...

It's my understanding that if you mount a wind-gen to the roof of a high building, the wind will be better, but the vibration will send an annoying hum through the structure. I've even heard that if the vibration frequency hits a sweet spot, it can do a lot of damage.

"I know it works in real life, but does it work in THEORY"? -PhD