Author Topic: A thought I keep kicking around  (Read 7293 times)

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Deveak

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A thought I keep kicking around
« on: June 28, 2016, 06:27:47 PM »
Is it possible to do a direct drive 240 volt AC water wheel and keep it regulated enough that you get 60 hz without electronics or fancy resistor loads?
A waterwheel puts most of its energy in torque and not rpm. So it seems like it would be more stable. Is it possible to have enough torque and gear it up just up above 60hz unloaded that it settles pretty close to it and holds frequency through shear torque? How could it be mechanically and cheaply regulated? I see it costs a pretty penny even for basic resistor regulators. No gen head exists right now so it would have to be an axial PMA. Not sure about the quality of the sine wave though. Pretty much no chance of overspeed though in a larger diameter waterwheel as long as its geared right and the unloaded speed is lower than what the charge controller can handle. Thoughts? Regulation is one thing that keeps me up at night for any pma driven power source. A lot of neat charge controllers exist for batteries but the pma has the risk of burning them up if its not protected with expensive resistive loads machines like the midnite classic clipper. A nice 8-12 foot water wheel seems like an rpm stable power source.

tanner0441

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Re: A thought I keep kicking around
« Reply #1 on: June 29, 2016, 12:00:38 PM »
Hi

I see an 8/12ft water wheel as being quite slow turning and large, where as your 60 Hz PMA would be by comparison quite small and a need to spin up  very fast. Gearing up would give you the speed but a slight variation in speed of the wheel would mean the variation at the PMA would be magnified. You don't actually mention the size of the PMA. I did see a commercial system some years ago and that had a degree of regulation by controlling a bi-pass valve but that was a 30,000 to 50,000 W system.

You could look at the Daf/Ford varimatic drive that has two variable diameter pulleys.

Brian.

mab

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Re: A thought I keep kicking around
« Reply #2 on: June 29, 2016, 01:17:57 PM »
the speed stability of the water wheel is more an illusion that real I think - it's hard to see the difference between slow and a bit slower.

The question is: what do you want to use the power for? Or, how close to 60hz/240v do you want to stay?

I've got a pelton wheel system with and induction motor generator (keep meaning to go PMA but haven't had the time) which unloaded goes to about 1.8 times full load volts, and Hz in a similar ratio, give or take. However, with a simple battery charger load (transformer & rectifier) connected to my main battery bank I can vary direct connected a.c. loads on the generator substantially, and the battery holds the generator volts to within 30%. I.e. the battery and battery dump load regulator effectively regulate the generator. - Hz I'm not so sure about but my direct connected loads are not too picky (even the charger transformer doesn't care as long as you don't exceed the designed Volts/Hz ratio).

If you don't have a battery that wont work for you, but even without active regulation, resistive and transformer loads can be quite tolerant of volts/Hz variation.

Johann

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Re: A thought I keep kicking around
« Reply #3 on: June 29, 2016, 07:04:04 PM »
Use a centrifugal governor. that could apply or release a break or a extra load to speed the wheel  up or to slow it down. It could open or close a adjustable belt pulley to regulate speed like the ones used on riding lawnmowers to regulate driving speeds.
Very old mechanical technology.
See Wikipedia https://en.wikipedia.org/wiki/Centrifugal_governor

Interesting.....yes.
Cheaper.........probably not, unless you have some recycling centers in town to make your own.

On the other hand, why do you need to keep the frequency at 60 hz ?
Most items would run above or below that 60 hz. The only thing would be that some of your clocks would not hold the right time. Europe has 50 hz and you may even use and run some of their 50 hz designed items right now at 60 hz.

joestue

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Re: A thought I keep kicking around
« Reply #4 on: June 30, 2016, 11:16:48 PM »
wouldn't supprise me if a typical waterwheel has a 2 or 3:1 ratio of unloaded to loaded rpm.

Flux

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Re: A thought I keep kicking around
« Reply #5 on: July 04, 2016, 09:35:39 AM »
As long as you have enough power for any expected load you can use  a hydro controller that dumps excess power over that you are using. By maintaining near constant load the wheel speed will be near constant . This is the control used with pumps as turbines in 3rd world countries.It is a simple thyristor or triac dump load sensing speed or voltage may do if frequency is not critical.
This doesn't work unless you have water to spare.

Deveak

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Re: A thought I keep kicking around
« Reply #6 on: July 21, 2016, 08:14:27 PM »
Yeah honestly a resistor slowing it down sounds a lot easier than gearing it up to just the right ratio and seeing if it falls in the right rpm range to run. I did find some math equations that figure out how much rpm loss from a given load but they are a bit over my head. My grandpa was telling me about a 555 circuit. I think thats what he called it. Basically you use a magnet on the driveshaft to generate an AC signal. The circuit turns it into DC with varying voltage that can drive a linear dc motor back and forth and hold it depending on the speed of the drive shaft. I suppose it could be possible to use a variac or some other form of control to vary a large resistor. Replace the knob with a sprocket and use a flat gear that spins the knob as it extends. He said you can use a POT on it to adjust the sensitivity and rpm range you want. A bit over my head, I am not well verse on electronics. It would be cheap though, he says 100 bucks for the whole thing if that. I think he used them for instruments in airplanes, he builds small airplanes as a hobby/side business. The only other problem I have run into is gearing. The lowest rpm generator I have yet to find is 1800 rpm or a pto generator which is just hooked up to a gearbox. Waterwheels are SLOW, so its gonna take a hefty gearbox to get it high enough. Finding one that can handle 10-20 HP and a high ratio is expensive and hard to find. Pulleys are cheaper but you lose a lot more power in them.

skid

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Re: A thought I keep kicking around
« Reply #7 on: July 22, 2016, 04:21:07 PM »
The lowest rpm generator I have yet to find is 1800 rpm or a pto generator which is just hooked up to a gearbox. Waterwheels are SLOW, so its gonna take a hefty gearbox to get it high enough. Finding one that can handle 10-20 HP and a high ratio is expensive and hard to find. Pulleys are cheaper but you lose a lot more power in them.

I have a 50 rpm 7.5kw generator for my water wheel. I'm using a 5:1 pulley system to bring my rpm up from 10 to 50....

Deveak

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Re: A thought I keep kicking around
« Reply #8 on: July 28, 2016, 10:35:46 PM »
Where id you get it? Is it one of those axial flux PMA's? If it is does it make a good sine wave?

joestue

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Re: A thought I keep kicking around
« Reply #9 on: July 29, 2016, 05:27:52 PM »
IIRC he said it weighs 850 pounds.

skid

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Re: A thought I keep kicking around
« Reply #10 on: August 01, 2016, 07:26:42 PM »
Where id you get it? Is it one of those axial flux PMA's? If it is does it make a good sine wave?

I got it from China. The attachment has the info for both a 5kw and 7.5 kw generator. The 5kw is ~550 lbs. and the 7.5 is close to 1000 lbs... They were designed for a wind turbine but will work well with a pulley system too. They have SKF bearings...



Ungrounded Lightning Rod

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Re: A thought I keep kicking around
« Reply #11 on: August 03, 2016, 07:43:49 PM »
wouldn't supprise me if a typical waterwheel has a 2 or 3:1 ratio of unloaded to loaded rpm.

Pelton wheels have a 2:1 ratio between unloaded and optimally loaded.
A jet of water is reversed in the spoon as it pushes it.  Optimally loaded,
the rotor moves at half the speed of the jet and the water leaving just
"falls down".  Unloaded, the rotor moves at the speed of the jet.

Other wheel types may have other characteristics, depending on geometry.
But figure that they do something similar:  Loaded, the water leaves with
negligible energy left in it, and the rotor was moving slowly in a way that
cushioned its exit.  Unloaded, the water leaves with all the energy in it
that it had to start with, which means it's moving faster, so the rotor is
also moving along a bunch faster.

2:1 is a bunch of difference for frequency sensitive devices (though higher
frequency is generally better than lower, so it's not "saturate the transformer
cores and start a fire" nasty).

Trying to use a dump load to regulate the speed means keeping it fully
loaded all the time.  That means the load is disappating as much energy
when the load is tiny as the full power of the mill.  Think of that many
kilowatts of space heaters and you have an idea of how much power
your dump load must dissipate.

If your load isn't inherently adjustable to match the need, it seems to me
it's better regulate the incoming water with feedback to keep the rotor
at a particular speed, use some kind of transmission, or use a voltage
and frequency converting device and let the rotor speed and generator
voltage be "wild".

Warpspeed

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Re: A thought I keep kicking around
« Reply #12 on: December 25, 2016, 03:48:45 PM »
Take a look at a real full sized Francis centrifugal hydro turbine, with the control vanes on the inlet.
These can be speed and load controlled to first sync up to the grid, and then control the amount of load by tweaking the vane angles.

Something like that would be impossible to duplicate in a small enough size for a do it yourself home hydro turbine.
Just the complexity of the scroll and turbine blade shape, then there are the control vanes.
But take a look at this:



Yes, its a variable vane turbocharger exhaust turbine.  It works just like the enormous Francis hydroelectric turbines. Its identical in every small detail.
Exact same principle, exact same geometry, but small enough to hold in your hand.  And available from auto junk yards at minimal cost if you hunt around.  Stainless steel rotor and vanes, and high nickel cast scroll housing none of which will rust.

Turbocharger technology has made great strides in recent decades, a huge amount of technology has gone into perfecting scroll and blade designs for highest efficiency. You reap all of that from a junk yard turbo.  A big advantage of the Francis turbine is that every blade supplies torque throughout the full 360 degrees of rotation, unlike a Pelton wheel where only one blade is actually working.  So the Francis can develop enormous torque from a large volume of comparatively low pressure head water. It should work at very usefully low rpm, because water is so much more dense than the hot air it was originally designed to work with.

One of those should easily generate a couple of horsepower at several hundred rpm if you have sufficient water.
The only real problem is the bearings need lubrication.  But you can pack the whole thing full of boat trailer waterproof grease.  As  its only running at fairly low rpm,  (and its water cooled ! ) grease will work just fine.

I live in the suburbs, so hydro is not possible for me here, but I  would really like to see this idea tried by someone.

This is the real thing:



This is a variable vane turbocharger turbine in action:

https://www.youtube.com/watch?v=kENxjxhoP24

Not too difficult to try I am thinking....

« Last Edit: December 25, 2016, 04:51:29 PM by Warpspeed »

mbouwer

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Re: A thought I keep kicking around
« Reply #13 on: April 10, 2017, 06:26:18 AM »
The subject inspires me and I am trying to make a turbine with active pitch.

mbouwer

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Re: A thought I keep kicking around
« Reply #14 on: April 11, 2017, 03:15:01 AM »
bottom view
In the ball I made six SS rods and swivel joints to twist the blades.

« Last Edit: April 11, 2017, 03:20:02 AM by mbouwer »

mbouwer

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Re: A thought I keep kicking around
« Reply #15 on: April 12, 2017, 07:04:02 AM »
This is the frame for the axle and the bearings. I want to prevent moisture touching this frame.

Warpspeed

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Re: A thought I keep kicking around
« Reply #16 on: April 12, 2017, 10:21:42 AM »
Were those parts made with a 3D printer ?

mbouwer

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Re: A thought I keep kicking around
« Reply #17 on: April 12, 2017, 02:52:00 PM »
No, it is just metalworking, welding and minium.
But I think it's an interesting question, because in 3D printing it would be easyer to shape the ball.

Warpspeed

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Re: A thought I keep kicking around
« Reply #18 on: April 12, 2017, 04:51:13 PM »
And 3D printing is ideal if you need multiple identical parts.
I rather like the turbo exhaust turbine, because its already all there.

mbouwer

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Re: A thought I keep kicking around
« Reply #19 on: April 13, 2017, 12:52:50 AM »
This is the kind of turbine I would like to make.

Warpspeed

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Re: A thought I keep kicking around
« Reply #20 on: April 13, 2017, 12:59:04 AM »
You mean like this :

mbouwer

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Re: A thought I keep kicking around
« Reply #21 on: April 13, 2017, 01:37:41 AM »
Do you think it's sufficient to regulate the number of rounds per minute only by the water inlet,
and what kind of generator would you choose?

Warpspeed

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Re: A thought I keep kicking around
« Reply #22 on: April 13, 2017, 01:59:23 AM »
A lot depends on the pressure head and the flow, and the physical size of the turbine.

george65

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Re: A thought I keep kicking around
« Reply #23 on: April 13, 2017, 02:19:19 AM »

I rather like the turbo exhaust turbine, because its already all there.

Are you aware of anyone using one?
I thought of this some years back but when I looked into it I found it had been addressed and people said it wouldn't work because the turbine setup and shape of the blades was wrong. There was more to it but I can't remember what it was now.

I think it would be interesting to see how a turbo fared in this application.  Perhaps for the flow and head it would be inefficent.  If it was cheap and water was not a problem, then could be a solution especially if multiple were used and hooked together with something like a small timing belt to give greater output.

I have a turbo here I can barely Lift.  I believe it was originally from a train engine. If using water instead of gas as the driving medium were viable, This mother would certainly keep the lights on!  :0)

MattM

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Re: A thought I keep kicking around
« Reply #24 on: April 14, 2017, 05:32:17 AM »
Seems like the turbine becomes overall heavier and less efficient.

joestue

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Re: A thought I keep kicking around
« Reply #25 on: April 14, 2017, 03:14:06 PM »
its better than nothing but gas turbines are designed for compressible air, not water.

for example, you can build an HVAC condenser fan that's 50% better than the competition if you can ensure that there is only 1/32" inch of clearance between the fan blades and the ducted air entrance. same kind of things go for water.

you can throw a ducted axial fan blade assembly made from bent sheet metal inside a pipe and get some power out of it. if you tilt the fan at 10 degrees you can have the shaft exit the pipe at a tangent and only lose maybe 10% of the power. it costs almost nothing but time to experiment with different blade angles.

while its easy to change the angle of the ducted blades at the inlet, its not easy to build a variable pitch kaplan style blade. but i don't think you need to for a 2:1 ratio of flow, if you're not concerned with the last 20% of available power. just change the inlet vanes and adjust the generator power curve.

dnix71

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Re: A thought I keep kicking around
« Reply #26 on: April 14, 2017, 03:50:46 PM »
Some of your blades look remarkably like vacuum cleaner fans.


This one is the impeller from a Hoover.