vertical axis wind turbine

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vertical axis wind turbine

Postby LostSkillsPodcast » Tue Jul 01, 2014 12:07 pm

does anyone have any experience building a vertical axis wind turbine ? i have been wanting to build one to power my outdoor wood stove. i think a combination of wind and solar would be sufficient to power my stove, all it has is a aqua-stat, a solenoid and a 145 cfm blower on it .i was thinking of something similar to this.

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Re: vertical axis wind turbine

Postby Comrad » Thu Jul 10, 2014 8:19 pm

To be honest, I don't have a lot of experience with a vertical axis wind turbine, I did look into them a few years ago, but never built one, so I can't say anything first hand about them. However, I do work as a power production engineer, with one of the fields being large scale industrial wind turbines, and in my opinion, they're more trouble than they're worth. Obviously things are different changing from small to large scale, and all things are not equal, but I would really suggest focusing more on solar than wind.

I know you listen to The Survival Podcast, and like the Stephen Harris episodes, and he has a reputation for beating on photovoltaics, and for the most part, he's correct. They're one of the most expensive initial start-up costs, and their efficiency goes down significantly with a change in angle based on your latitude and part shade coverage ( 20% shade doesn't mean 20% efficiency loss, its a geometric scale based on the inverse square law). However, they're the simplest possible power sources ever. Photons hit the cell, causing the silicon to shed electrons, and creates a current. No moving parts, no fuel consumption, no wear, almost no maintenance (except for cleaning the panel every now and again).

Wind, however, is often very troublesome. It has the inherent issues of any mechanical device, and often has gearbox issues. In the commercial wind farms, they use a decent sized planetary gearbox system to ensure an appropriate rotational frequency for the generators (commercial turbines spin at about 17 RPM compared to the 3000/3600 RPM of a gas turbine depending on whether you use 50 or 60 HZ power) Smaller vertical axis wind turbines obviously spin much faster, but with little to act as a flywheel, don't really have any inertia, so whilst they might whip by with no load, under load they can really struggle. Now, thinking about your gearbox, the way a turbine works is to convert linear motion into rotation motion, which puts the rotor and gearbox under radial strain and bending causing unavoidable gear issues such as poor meshing, alignment and wear over time. In steam and gas turbines, the blades and vanes are encompassed with supports on the outer circumference, giving greater strength which wind turbines seldom have. I've included a photo of one of the wind farms I work on which had a failure, and tore itself apart (once the brakes let go, there's nothing you can do to stop them from destroying themselves aside from hope the wind stops blowing)

Its irrefutable that wind power works, and can be effective, and more importantly to me, it just looks cool when you have a little wind turbine at your house. However, for sheer practicality, I'm not sure I would recommend it, it will require much more maintenance, and fail much more frequently than any solar system would. If you want to do it just for something different, and to have some fun learning about new power sources, then by all means, have a go, its a lot of fun. But you're more likely to get a better economical and more reliable system by running a good PV array with some good batteries.

I don't know much about your wood stove, but I would guess that since its just using a solenoid, thermostat and fan, you could just get by using a DC system, so you wouldn't need an inverter, which would keep the cost and complication down.

I'm sorry if I seem like a kill-joy and I'm putting down your idea, that really not my intention, I used to try a lot of little projects like this, which was a lot of fun, but seldom super effective. Now that I've had some exposure to the industry, I'm learning the limitations of the systems. If you had any more specific questions, let me know and I'll try my best to answer them.
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Re: vertical axis wind turbine

Postby LostSkillsPodcast » Mon Jul 28, 2014 12:03 am

I was thinking I could mount the motor under the turbine,maybe direct drive or with a belt and pulley system to overdrive the motor. Conrad,do you know if you can use a dish washer motor to produce electricity? My dishwasher started leaking but the motor was still good.
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Re: vertical axis wind turbine

Postby Comrad » Mon Jul 28, 2014 8:20 pm

You can use any motor to produce electricity. Michael Faraday discovered a relationship between electricity, magnetism, and relative motion. In an open loop system, if you have a device with a magnetic stator and rotor, and you apply a current to it, the device will spin. If you physically spin the device, it will produce current. Any generator can be a motor, and any motor can be a generator. In fact, in larger gas turbines, they need a lot of rotational momentum to get started, so the generators will draw about 6 MW of power from the grid, and act as a huge motor until the turbines are able to achieve their own firing inertia, and start turning the generator itself to produce electricity.

The main difference comes down to whether the motor is an AC or DC motor. AC motors are generally simpler, so I would imagine that it would likely be an AC motor.

If you aren't sure, look for split rings near the brushes on the motor, this results in the polarity being switched as the shaft completes a half rotation making the load profile a varying amplitude DC (this is why small DC motors in RC cars and whatnot have little ceramic capacitors soldered directly onto the contacts - it creates a smooth output instead of a varying one). If you can't see any of that, and you can't see any markings for positive and negative, chances are you have an AC motor.

So, if you have a DC motor, just connect it to a charge controller like you would use for a Photovoltaic system, and use it to charge batteries. If you have an AC motor, you first need to put it through a bridge rectifier, which is really just an arrangement of 4 diodes to provide consistent DC power by only allowing flow in one direction. These are sometimes sold by power supply places as something much fancier than they actually are. They can be picked up cheaply from an electronics store, or you can simply make it yourself with 4 appropriately rated diodes. http://en.wikipedia.org/wiki/Diode_bridge this explains it a little more. After you've fed it through your bridge rectifier, simply connect up to your change controller like you would with a DC motor.

Hopefully that explains is properly, let me know if you want me to explain anything further.
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Re: vertical axis wind turbine

Postby Agcoach » Thu Nov 27, 2014 2:10 am

Been looking into peltier generators. May be ideal way to charge a battery to run the wood boiler?
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Re: vertical axis wind turbine

Postby Comrad » Sat Nov 29, 2014 12:26 am

Thermoelectric generators can be used to good effect on wood stoves. I'm pretty sure that there are even dedicated units designed for just that. They're also used on car exhausts, etc... They work pretty well, and they're very simple mechanically since they just work by the temperature differential between two metals, and the subsequent electron flow.

They usually don't put out a heap of power though. I reckon you'd be lucky to get 50 watts, which might be a little too small for Jeff's uses. Jeff, do you know the size of the motor on your blower?
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Re: vertical axis wind turbine

Postby LeeMorgan » Wed Dec 03, 2014 8:38 pm

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Re: vertical axis wind turbine

Postby LostSkillsPodcast » Sun Dec 07, 2014 3:33 pm

sorry i have been feeling under the weather lately and i got busy and forgot to check back. here is a link to all the specks on my blower motor. http://www.grainger.com/product/DAYTON-Blower-1TDP7?functionCode=P2IDP2PCP

here is a link to my pump http://www.menards.com/main/p-191375.html the pump runs continuously. where as the blower only runs when the system demands heat.the only other controls on the stove are an aquastat and a solonoid. thanks for the help

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Re: vertical axis wind turbine

Postby Comrad » Sun Dec 07, 2014 9:14 pm

At peak draw you'll probably use about 170 watts, with your pump drawing 90 Watts on peak. Not huge, but I think those thermoelectric wood stove generators produce about 70 Watts maximum (I haven't been able to open the link Lee sent, I don't know if it says something higher). The issue as well is that your motors are AC, so you'd have to put an inverter, and most cheap ones would have an efficiency of about 85% or so. If you take your average draw when both devices are running as say, 120 Watts, with your 85% inverter efficiency you'd still need about 140 watts being drawn. You might be able to recover some of the power to your batteries when the pump is running but the fan isn't, but I wouldn't bet on it. Your aqua stat and solenoid wouldn't really draw much at all.

Maybe if you combined your thermoelectric with a wind turbine or PV system you could make it work. Connect all the sources up to a single charge controller and run it to a battery and inverter and you should be right. You just need to do the sums now on how much you're paying for electricity to run the system versus the cost of a battery, charge controller, inverter, wiring, and the units, and see if you think the cost difference is worth it.
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Re: vertical axis wind turbine

Postby LeeMorgan » Mon Dec 08, 2014 2:04 pm

Here is the link again:

http://youtu.be/_fiV0Cii5RQ

There a bunch of videos about the VWAT

I think I sent a link attached to my YouTube account vs. a short link.
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