Small scale domestic hydro power generation project

[HughF]

Banki/crossflow would be my go-to for this low a head. Do you have anywhere on your land where you could build a sluice and make a feed pond?

[SteamyTea]

It is easy to see why we do not have much hydro power in the UK.  We just don't have the topology for it.

[ProDave]

16 minutes ago, HughF said:

Banki/crossflow would be my go-to for this low a head. Do you have anywhere on your land where you could build a sluice and make a feed pond?

Care to explain what that is?

 

I don't want to do any engineering work as such.  the burn as you see it now is it's docile summer flow.  It can get quite excited in winter spate and don't want any obstructions.  Any water wheel or other generator will have a means to retract it out of the way when in spate.

[HughF]

21 hours ago, ProDave said:

Care to explain what that is?

 

I don't want to do any engineering work as such.  the burn as you see it now is it's docile summer flow.  It can get quite excited in winter spate and don't want any obstructions.  Any water wheel or other generator will have a means to retract it out of the way when in spate.

I’ll write a better response this evening when I’m in front of my laptop…. If I forget then @mention me

[ProDave]

So I have been tinkering with my collection of "stuff that will come in handy one day"

 

Anyone reading beyond this point has to make a promise not to laugh, at least not out load.

 

So put together a test water wheel entirely from bits you have to hand:

 

The business side, that will collect the water.  Yes that is a bicycle wheel, and the trial set of "buckets" that will go around the outside to collect the water and so cause it to rotate, are indeed baked bean cans.

 

 

Looking at the other side, that is the pulley and belt from a dead washing machine.  It is driving a little DC servo motor as my trial generator candidate.  Initially I tried the pulley from the washing machine motor, but that only gave a 9:1 ratio, I felt it wanted more, so I made a very much smaller pulley for the servo motor and I have got to about a 17:1 ratio.

 

 

The whole lot is mounted to the end of a length of aerial pole.  The shaft is a length of M12 threaded rod and the bearings are old idler bearings left over from a previous cam belt change on my car.  They mount to the aerial pole with a heavy duty aerial pole clamp set.

 

The proposal is to mount the aerial pole pivoted about it's mid position giving somewhere for a counter weight and easy height adjustment.

 

 

And since the motor is right in the "splash zone" it will have a plastic cover to keep it a bit dry

 

A similar one will will also be fitted over the bearings

 

 

We need to eat some more baked beans before there are enough cans to give it a water trial.

[Onoff]

Love it! 👍

[ProDave]

Okay, we have eaten enough beans / soup / rice pudding and today was the day to "give it a splash"

 

So I had driven a post into the burn to support the wheel, and rigged up, with bits of wood and G clamps, to hold the delivery pipe and give it a go.

 

I had set this up to rotate "with the flow" that is the bottom of the wheel would be travelling in the same direction as the burn.  I had expected to feed it with the water feed pointing downwards making ir a breast fed water wheel.  That proved not to work and gave very little rotation of the wheel and a lot of splashing.  I found the best results were feeding right at the top, making this on overshot water wheel.  Of course it is set up completely wrong for that and the feed pipe is actually delivering it's water upstream in this test.  If this goes any further I would re jig the wheel to rotate the other way.

 

The other finding was i needed the water to exit the pipe as a clean stream, the raw end of the pipe made too much of a broad spread of water.  A rummage in the "plastic pipe" bits box found part of an old sink trap that made a good reducer and gave a clean water flow.

 

So this is the trial.

 

I will post again later with some technical analysis

 

 

[ProDave]

So the technical analysis.

 

The wheel is rotating at 32 rpm, so with the 17:1 gearing my motor / generator is doing 544 rpm.  At that speed it is generating a disappointingly low 3 volts.  I didn't attempt a proper load to measure what power it would produce as I know it would be tiny.  If I short circuit the motor, the wheel does slow down slightly, but not as much as I would have thought.  I think (certainly for this speed) the motor I have is a poor candidate as a generator, but it was the only one I had.

 

My flow rate looked poor to me, so I re measured it.  I am getting barely 1 litre per second.  But it's not a pipe blockage or lack of water, that is all it will deliver at that height.  Drop the pipe down to the bed of the burn and it's back to 2 litres per second.

 

Baked bean tins are poor "buckets" for this application.  Roughly 50% of the time the delivered water hits the side of the tin rather than go in it, which will add nothing to the rotation of the wheel.  conventional square buckets are what's needed with any overspill just dropping down onto the bucket below.

 

I am unsure if I will take this further, it does at the moment seem like it's never going to be a source of useful power.  I might look at turbine ideas instead?

[joe90]

Love it Dave 👍, if I remember correctly Dick Strawbridge when he did a water wheel in cornwall (many years ago) had an 80:1 gearbox but had a much heavier wheel and more head.

[Roger440]

Good work

 

Surely, aside from changing the buckets, just double or quadruple or whatever the number of wheels? If you have 6, then it will generate 6 x more power. Plus effiecency improvements from new buckets and a better geberator.

[SteamyTea]

27 minutes ago, Roger440 said:

Surely, aside from changing the buckets, just double or quadruple or whatever the number of wheels? If you have 6, then it will generate 6 x more power.

Not if the mass flow rate is the same.  That is where the energy is, not the wheels.

1 litre a second is very low.

Edited June 14, 2022 by SteamyTea

[Roger440]

31 minutes ago, SteamyTea said:

Not if the mass flow rate is the same.  That is where the energy is, not the wheels.

1 litre a second is very low.

 

Why would the mass flow rate be the same?

[SteamyTea]

8 hours ago, Roger440 said:

 

Why would the mass flow rate be the same?

If that is all the stream is delivering, or all the pipe can deliver.

 

[joe90]

16 minutes ago, SteamyTea said:

If that is all the stream is delivering, or all the pipe can deliver.

 

But lots of water is flowing past the pipe 🤷‍♂️ More pipe will collect more water. @ProDave you need a dam 🤯

[ProDave]

I need more / larger pipe.  The availability of that will determine if this moves forward.  To just go out and buy it would cost far too much so I am "searching"

 

 

[joe90]

When reading about the fountains at chatsworth house the water come from a lake above the house and the pipe starts large then gets smaller till it produced a 300ft plume. I think this is the same theory with hydro.

Edited June 15, 2022 by joe90

[ProDave]

7 hours ago, joe90 said:

When reading about the fountains at chatsworth house the water come from a lake above the house and the pipe starts large then gets smaller till it produced a 300ft plume. I think this is the same theory with hydro.

I think that is certainly true if you are trying to increase the pressure to get a small high pressure jet to drive a turbine or pelton wheel type device.  For an overshot wheel that I am experimenting with I don't think it would make any difference.

[ProDave]

Thinking about @joe90 suggestion, A quick rummage amongst my various bits,. cobbled together a quick set of different size pipes of reducing size to gauge the effect.

 

The final bit of "pipe" in that contraption is a bit of flexible conduit with a bore of about 20mm

 

It definitely increases the velocity (measured by how far will the jet of water reach) and I lose about half a second on the time to fill the bucket test.

 

So next experiment is try and cobble together a mini turbine to see if this has any merit.

[joe90]

Interesting stuff, no idea how to do it but I guess what’s really needed is a smooth  reduction in diameter to stop turbulence at the “steps” 🤷‍♂️. 

[Radian]

27 minutes ago, joe90 said:

Interesting stuff, no idea how to do it but I guess what’s really needed is a smooth  reduction in diameter to stop turbulence at the “steps” 🤷‍♂️. 

Go out and nick a traffic cone.

[Onoff]

3d print conical reducers. Easy.

[Onoff]

...may have had a little drinky but you get the drift. 45deg or larger is good.

 

 

Could print it standing up with no supports and no sharp corners to create turbulence...

[ProDave]

I took the reduction experiment one step further (literally) reducing to a bit of 20mm mdpe which has a bore of about 16mm.  That really killed my flow rate to less than half, and put immense back pressure on the fittings that made up the reduction forcing one to blow apart.

 

So I think my sweet spot for reducing the size is 20mm bore.

 

I am currently eyeing up an old radial air fan for equipment cooling (sometimes known as a snail fan)  Thinking it would be easy to swap the present ac motor for my little dc servo motor.  The challenge would be making a suitable impeller (candidate for 3d printing?)  I will do a sketch if @Onoff fancies a challenge?

[dpmiller]

@ProDave I dunno if that servo motor is the best choice tbh, they can be very delicate. What's the I reckon you've got enough power for something a bit meatier- a 380 RC motor or a pillaged small cordless tool motor maybe?

[Onoff]

57 minutes ago, ProDave said:

I will do a sketch if @Onoff fancies a challenge?

 

My lad will have a go of course. 

 

Elsewhere "we", that's me and nerds from another herd, are on the brink of investment casting in brass from an original 3D print so that's (brass impeller) a possibility for the future.