Wednesday, February 16, 2011

How an Alternator Works & how to make it work for you!

More and more people are now using alternators to make generators for renewable energy purposes.  I have my truck outfited with multiple alternators and 750aH battery bank so if my house ever loses power (no sun or wind for a few days), I can simply plug my truck into my house system and roll off of that.

Many people (including myself) are using older GM alternators to make small wind turbines, and they do work pretty well and parts are cheap!

OK- so you wanna' know how they work, and how to make em' work with your renewable energy setup.

We'll cover a few areas here.
1. General How It Works stuff
2. AC Power & DC Power
3. How to make it work as a wind turbine
4. Making a backup generator with an alternator

1. How It Works
An alternator is nothing more than a small generator. The alternator in your car is a 12v alternator and has an internal voltage regulator. Your average alternator consists of a few components..
A rotor, a stator, a voltage regulator, a bridge rectifier, and diodes. It's a very simple design. The rotor spins inside of the stator and creates an electrical field. This field is carried out of the stator via 3 phase AC into a bridge rectifier which converts the 3 phase AC (alternating current) into DC (direct current). The DC is regulated by the voltage regulator which is usually preset to 12v (14.2v charge rate).
This is hooked to your battery and viola - you have a 12v charging system and all your accessories like radio/wipers/climate control all work off the alternator while your car is running. An unregulated alternator can make 120v DC - but this would be bad inside of your vehicle - things would sizzle for sure. Most stock alternators used on a vehicle are anywhere from 80amps - 150amps depending on the application.  It is very possible to modify most alternators to produce anywhere up to 320 amps by changing a few of the components. This is commonly done to accommodate large stereo systems, police & emergency vehicles, and any other application that requires a lot of amps/current.

2. AC / DC - im not talking about the band!
Alternators make 3 phase AC. You can actually make your car alternator run more efficiently and last longer by running 3 phase to an external rectifier before your battery. When using the DC output post on the back of an alternator, you must use have gauge wire - depending on the application, it may be 1ga, or even 2/0 ga which is really expensive these days. The further you have to pull the DC, the heavier gauge wire you must use or it will create resistance and that creates heat -end result- your going to burn something up. Thats why the wires on your car battery are so thick.  Lets say you hook up a beefy car audio amplifier in the trunk and you have some crazy boom boom car stereo. You will need a heavy gauge wire to run to the back so you do not have any loss.
OR- you can tap the 3 tags of the stator, run a a smaller gauge extension cord and an external rectifier and this will be a lot cheaper, and your alternator will love you more for it. Then you would not need as much heavy gauge wire.
3. How to make an alternator into a wind turbine
Most commonly used today is the GM 10si and 12si series alternator.
If you just took your alternator out of your car and put it on your roof and slap some blades on it - it aint' gonna' work! There is a little modifying you must do first. First, you will need to gut the alternator. Take it completely apart. You must change the stator first because you want to hit system voltage at a much lower RPM. Stators are available online that will produce 12v in as little as 125rpm.
Next - the best practice would be to remove voltage regulator and bridge rectifier from the picture completely. Tap the 3 output tags from the stator- this is your 3phase output.  You can use a 10ga extension cord to carry the 3 phase AC- it will be a lot cheaper this way and its actually better for the alternator. So now you have an alternator with 3 wires hanging out of the back, and a heavy duty  extension cord going to where ever you need it to go. At the other end of the extension cord (where your batteries are) you will then hook up (a little beefier) bridge rectifier to convert your 3 phase into DC. A voltage regulator is NOT needed in a configuration like this. The batteries that you are charging will regulate the turbine.  Lets say you have a 12v system. When the turbine is spinning, it will start to tighten up (harder to spin) at 14.4 volts - thats when the magic happens and your batteries start to charge because you are now producing amps/current to force into the batteries.

4. Making a backup DC generator from an alternator
There is many ways to go about this. Some people use an old lawn mower or small gas motor mounted to some sort of chassis. As I mentioned in the beginning, I have made one out of my vehicle.
I added an additional alternator and batteries. If my house batteries ever die, I can plug my truck into my house and run from batteries as well as charge the dead battery bank simultaneously. This might not be that practical for the average homeowner,  so some people will make a scaled down version. You must use an alternator setup like a wind turbine for an application like this, but may want to go with a "high wind" model or build one with a higher rpm stator. Lets say you have an old lawn mower laying around and it still runs and you just cant bring yourself to toss it to the scrap heap. You make some sort of chassis to bolt the motor and alternator to, thro a belt on it and youre spinning! Obviously you cant just plug this into your panel and expect electricity- you would need a couple batteries and an inverter for that. Pulleys play a vital part in this as well. If you have a decent size pully on your motor and need to drive the alternator harder/faster, you want to use a smaller pulley on your alternator. In the automotive world, this would be known as an overdrive pulley. Making too much power and need to slow the alternator down? Do just the opposite and put on a larger pulley.
There are many ways to this and I could type for days, but this is a general idea to get the ball rolling.

As always - any questions, please feel free!

Be one with your Batteries!

Your system is ONLY AS GOOD as Your Batteries and Inverter!

Deep Cycle Batteries have a different plate design and are made to run low and cycle charges.
A Car Battery - Different animal!! These batteries like to be topped off all the time- fully charged and ready to go for the one funcion they have in life- to start your car!! Thats why your alternator has a built in voltage regulator - so it doesnt over charge your battery and all your 12v accessories run from the alternator, not your battery - but that will be in a different blog entitled how an Alternator works.
If you were to run a car battery on your system - you "might" get 3 charge cycles before the battery is ruined and could possible overheat and explode.

Deep Cycle Batteries are rated by Amp Hours (aH).
Car Batteries are rated by cranking amps (CCA).

When it comes to off grid applications, Dont spring for cheap batteries - you DO get what you paid for.
12v Walmart Marine batteries are good and cheap, but an expensive Rolls Surrette will run circles around that Walmart battery and probably last 5-8 times as long!

Make sure you have enough amp hours (aH) in your system to last you.
Insulate your batteries if you live in a region that has cold winters! A cold battery does NOT like any kind of load on it and will last 1/3 (or less) of your normal runtime.
Vent your batteries if they are conventional Lead Acid batteries. If you batteries are not sealed (lead acid or AGM), then they DO produce hydrogen as you charge them. That bubbling you hear means hydrogen is being produced and will need to be vented. Enough hydrogen could cause an explosion and nobody wants that. The make special vents for this. Just some plain ol' fan with exposed brush motors could ignite hydroden - so spend the money!!! Its worth the extra couple dollars!

Higher voltage systems - Like 48v and above - WEAR RUBBER GLOVES!!!! If one of those things bite ya', your gonna know about it and you wont like it!!!! 12/24v systems isnt much of a worry, but something could still bite! Always wear eye protection when handling your batteries. I have seen these thing explode and it aint' pretty what the electrolyte solution of a battery can do to exposed skin, much less an eyeball (plus the shrapnel can get ya).

Maintain your batteries!
Get into  the habit of checking your batteries at LEAST once per month.  If you have sealed/maint free batteries, then only some of this applies to you.
Check water levels - very important - no water and charging means your going to damage a cell, or two, or three...
Desulphate your batteries - Over time, your batteries will produce sulphur and this sticks to the plates.
This needs to be rattled off and this will extend the life of your batteries. Some inverters and charge controllers will allow you to "Equalize" your batteries which is more or less the same thing. The Equalization of your batteries is done a little differently though, but more or less serves the same purpose.  A desulphator works slower and over a period of time. Some people actually leave them on all the time (which I wouldn't do personally), but some people swear by it.

Any questions - feel free!

Tuesday, February 1, 2011

What blades to use on your small wind turbine.

What blades will work best on your small turbine? How many blades should you use?
Well, just from personal experience, it depends on a lot of things, but we'll work with the 3 most common.
1. Average Wind Speed
2. System Volatge
3. Amps Required

Here's my formula based on the K.I.S.S. theory..
The Lower the Wind, The Larger The Blade.
The Higher the Wind, The Smaller the Blade.
The Smaller the Blade, the greater the RPM
The More Blades You Use, the More RPM's You Lose!

First - a little lesson on how this stuff works.
If you are running a PMA (permanent magnet alternator) turbine in a LOW WIND area, your system voltage plays a very important role. Lets use a 12v system for an example.  Low Wind areas are not very productive to be running a turbine, so you will want a turbine that can produce 12v at a VERY LOW rpm. Once it hits 12v (or what ever voltage your batteries are at), just like a car alternator, you will start producing amps/current when you reach a voltage of 14.2v or higher depending on your load or how dead your batteries are. The higher the amps, the faster you'll charge. When the PMA is charging, the shaft will get tighter and harder to spin as the amps increase. A small blade wouldnt be an efficient choice for this scenario.

A low wind / low voltage system is going to want A LOT of amps! So a larger 3 blade rotor with some pitch may be the way to go.You want to be able to create torque without things getting scary! Now you can run more than 3 blades in a low wind configuration. By adding blades, the PMA will cut in earlier and at a lower speed, BUT you may lose amps at higher speeds.

I run a 3x 35" aluminum blade configuration on my low wind PMA. It hits 12v at 130 RPM and it will produce about 12 amps in 15-20mph winds.. It will cut in (start to spin) in as little as 2mph winds.

High Wind areas may want to go with a smaller blade for a 2/3 blade rotor. You may also want to got with a higher RPM PMA that produces 12v at 250-450 RPM. This would yield a little better amperage.

You really do need to play with blade size and pitch because all areas are not the same. You may find that a 28" composite blade may work better for the higher wind areas. But this should give you a ballpark of where you need to be.  I'm happy to answer any questions you may have!

Free Solar Panels?? read the fine print!

Alot of these companies are now offering free PV systems for your home by locking you into and extremely cheap rate over a 20-25 year period. The company would collect your srec's to pay for the system. BUT- if you decide to sell your house 5 years down the road, you may have to pay for the remainder of the PV system (depending on the size, could be up to $80k or more!). make sure you read the fine print when exploring free PV systems.

Sunday, January 30, 2011

Small DC Wind Turbines - Wattage Myths

When selecting a small wind turbine, there are a few things you need to know before bolting one up to your house. The lower the voltage system you are running, the less amps the wind turbine will pump out. There are a TON of folks on ebay swearing by their PMA turbines being the most powerful, but in reality, there all pretty much the same. Though some may have a better design than others, the overall output may be the same.
Let's use a battery charging system for example. Most commonly used system voltages are 12, 24, 36, & 48v. Most home experimenters are using 12v systems because of 12v being the most affordable and parts can be purchased from pretty much anywhere from Walmart to your local auto parts store. If you basic OHMS LAW, a 500w turbine will clearly not put out 500w if used on a 12v system.
If you do the ohms law math - volts x amps = watts, you will see a way different number.
Unless you live inside of a permanent hurricane, your normal average wind-speed, blade size/length & pitch, and number of blades will determine your overall RPM of your turbine.

Lets say you have  average wind speed of 12mph. You are using a 4-500 advertised watt PMA turbine with 35" blades in 3 blade configuration. You are charging 12v batteries. You are only going to see up to 60 watts (which will charge a battery) and may be inefficient to charge larger battery banks. If wind is your choice of alternative energy, you may want to go with a higher voltage system, or multiple low voltage turbines. 

A low wind PMA that hits 12v at about 130 rpm, running a 35"x3 blade configuration yields approx 5-10 amps max. Cut in speed is about 2mph. If the blades config was 24"x3, the cut in speed would be higher - maybe 6-7mph, but output would be about the same if not a little less.

Im not the greatest writer, so I hope this sheds some light on the subject. Im happy to answer any questions.