Car Alternator as Wind Generator?

[charliehows]

stupid question time but i've been pondering this for some time - why not set a car alternator up as a wind generator? Would it run too slow to be effective? too vulnerable to the exposed environment? wish there was a smiley with a dunce hat for this question... there ya go...

[anjou]

Unless you have a complex variable pitch prop, speed control is the issue.

If you have shorter blades with a shallow pitch, you wont get much power from it, ie, you cant load it enough to generate much current.
if you have longer blades with a correspondingly greater pitch, you need more wind to turn it and the tips so super sonic and are noisy

There are other reasons which I cant recall right now
Its a complex thing to get right.

[mrm]

Originally Posted by charliehows

why not set a car alternator up as a wind generator? Would it run too slow to be effective? too vulnerable to the exposed environment?

Basically you answered your question.
Exposure to environment can be dealt with quite easily, the other problem is more difficult. Alternators are designed to operate full power at approx. 10.000 RPM - no way to drive the shaft directly from a propeller - some sort of transmission is required.

[kellyp08]

For what it's worth, I don't think that your question is stupid. Car alternators are cheap, anything associated with a boat is not. I wonder whether the RPMs would be adequate (but I guess that could be regulated by having a very large pulley on the axle of the rotor and small pulley on the shaft of the alternator). Then there's the issue of exposure of non-marine spec equipment (the alternator) to wind and waves. Here one could fashion a water-tight fiberglass housing (with West system and fiberglass cloth) to surround the alternator. Nigel Calder has a nice section in his great book, "This Old Boat", on how to create fiberglass housings.

I hope you put such a system together. If it works - please let us know! I, for one, am just pee'ing in my pants to find out. (But not eager enough to do the work myself!)

[charliehows]

I think my car idles at about 700-900rpm and it spends a lot of time sitting in traffic - batt. seems to stay pretty well charged - cant see why 10000 rpm is needed. on the boat i putt along at 1200 rpm although the alt. is still charging at 700 when idling (needs a blip to 1200 to start it though) and the ratio wouldnt take it much more than twice that. Seems to me once the things are going above a minimum speed they're working ( my understanding is thats the basic difference between a generator and an alternator - the alt produces more at lower speeds). the charge rate shouldnt be a problem - if its producing anything at all multiply that by 24 hrs a day and you gotta be getting something. Give me time, im stupid enough to try it.

[mrm]

Originally Posted by charliehows

I think my car idles at about 700-900rpm and it spends a lot of time sitting in traffic - batt. seems to stay pretty well charged - cant see why 10000 rpm is needed.

Charlie, I wrote that 10000rpm is a typical point for full power.
A typical turn on/cut in speed for car alternators is in the 1300-1500rpm range. Once alternator cuts in, it will produce some power. For details on how much, google an alternator performance curve - for example from Bosch.

[charliehows]

Originally Posted by mrm

Charlie, I wrote that 10000rpm is a typical point for full power.
A typical turn on/cut in speed for car alternators is in the 1300-1500rpm range. Once alternator cuts in, it will produce some power. For details on how much, google an alternator performance curve - for example from Bosch.

ok, with ya there.

[anjou]

Dont forget that alternators have a pulley to gear it up so the car engine speed isnt the armeture speed

[charliehows]

yeah somewhere between 2 and 3 - 1 . How many rpms can you get out of a wind propeller of less than 1 metre dia. or span?

[mrm]

Originally Posted by charliehows

How many rpms can you get out of a wind propeller of less than 1 metre dia. or span?

Assume wing tip speeds below 0.95 of speed of sound.

[Reefmagnet]

The direct dc drive motors from Fisher & Paykel washing machines make excellent alternators for wind generators. There's plenty of information about doing this on the 'net. The diameter of the standard motor, which is about frisbee size, would probably be a limiting factor. Pretty easy to get hold of too, as the electronics of these washers are cleverly designed to destroy the entire machine bar the motors in the event of the slightest component failure. I've squirreled a couple away in the shed for another time when I finally run out of other projects.

[anjou]

And those washing machine motors are 7 phase, so they start up in lighter winds and run more smoothly

[cburger]

Originally Posted by charliehows

stupid question time but i've been pondering this for some time - why not set a car alternator up as a wind generator? Would it run too slow to be effective? too vulnerable to the exposed environment? wish there was a smiley with a dunce hat for this question... there ya go...

Just built up a GM 10si alternator that was given to me for free. Unit is making 14.5 volts at 700rpm. During the search for parts for this project I came across rotors for automotive alternators that were marketed as being used for building wind generators. My instinct is there are people out there doing it, just start searching the internet. The question that I have is that after you procure all the required components and engineer the housing and other related issues that won't be available off the shelf and figure in all the hours of time required would you really save that much money over purchasing a true marine wind generator and end up with an inferior product.

That being said it certainly would be an interesting project to be involved with.

[charliehows]

what got me thinking about this again was the boat i saw with a fixed - ie non-swivelling wind gen on their mizzen mast - if the boat is at anchor or on a swing mooring the gen doesnt need to swivel - the boat lines up into the wind. The work is in building a robust blade and gearing system, the alts. are a chuckaway part from the junkyard, no housings, just run em til they bust. But you're right about the false economy of wasting time and energy.

[anjou]

Have a read through this little lot, as I recall we discussed this topic here some time

Wind Turbines and associated systems