Hydro-electric generator problem

[Mac of Cygnet]

You can easily run a house on 7 HP.

 

Exactly. That is the intention. Although the engine of his present diesel generation setup is I think rather more than that.

[Justme]

As a temporary measure he is now using the water wheel to drive a 12v alternator with a 900Ah battery bank and inverter to produce 3KW of usable power (and using it), until he can get a new generator with voltage regulator.

 

It appears that some of the figures for amount and flow of water required quoted here are not accurate. He has a flow at the wheel of 11000 litres per minute producing what I have just quoted, rather different from the 14000 litres per second mentioned here. In fact I have actually seen successful domestic hydro schemes (in Iceland) using the same order of magnitude of water flow as he has.

 

Do you mean 3kwh of power cos 3kw would need a 250amp alternator running at FULL power & would produce 72kwh per day.

(or is the 3kw bit from the inverter & not what the alt is making at all so in effect not relivent?)

 

Whilst 3kwh (per day) only needs a 10amp (125watts) alt if running 24 7.

 

Water flow depends on available head. Your lower flow could be due to the much lower power you are getting than you think (3kwh not 3kw).

Edited August 19, 2009 by Justme

[Mac of Cygnet]

Do you mean 3kwh of power cos 3kw would need a 250amp alternator running at FULL power & would produce 72kwh per day.

(or is the 3kw bit from the inverter & not what the alt is making at all so in effect not relivent?)

 

Whilst 3kwh (per day) only needs a 10amp (125watts) alt if running 24 7.

 

Water flow depends on available head. Your lower flow could be due to the much lower power you are getting than you think (3kwh not 3kw).

 

You are quite right. The 3KW is from the inverter, but not irrelevant! It allows that much power to be used at any one time, but of course that would not be needed 24/7. As a matter of interest I looked up our own usage (2 bedroom house), and we use 15kwh per day average. My neighbour lives in a residential caravan with lower requirements, so say 10kwh per day. So the alternator would need to be at least 35amp working 24/7to keep the batteries charged up - I'm sure there are other considerations which would require something bigger, but I'm quite happy to be told this. I'll ask him how big his alternator is. In fact this may be a better way to go, as a normal household would not need 5KW all the time, which is what he was aiming for.

 

Edited to add that he is using a 75 amp alternator, so easily adequate for the purpose.

 

Cheers

 

Mac

Edited August 19, 2009 by Mac of Cygnet

[Gibbo]

To get 7HP from 11000 litres per minute of water flow will require an actual fall over the water wheel of almost 20 feet. You said he had a low headl. So how is he going to get the water to wrap its way round a 20 foot diameter waterwheel?

 

You read that bit about efficiency of belt drive on a website owned by someone who sells belt drives It's cobblers!

 

Gibbo

[nb Innisfree]

To get 7HP from 11000 litres per minute of water flow will require an actual fall over the water wheel of almost 20 feet. You said he had a low headl. So how is he going to get the water to wrap its way round a 20 foot diameter waterwheel?

 

You read that bit about efficiency of belt drive on a website owned by someone who sells belt drives It's cobblers!

 

Gibbo

 

Toothed belts as used on camshafts would be a much better option.

[Chris Pink]

To get 7HP from 11000 litres per minute of water flow will require an actual fall over the water wheel of almost 20 feet. You said he had a low headl. So how is he going to get the water to wrap its way round a 20 foot diameter waterwheel?

 

You read that bit about efficiency of belt drive on a website owned by someone who sells belt drives It's cobblers!

 

Gibbo

 

It would be nice if just for once you contributed positively rather than your usual "it won't work but i won't tell you why" stance.

 

Presumably, given the figures above you must be able to come up with some approximation of available power.

[Gibbo]

It would be nice if just for once you contributed positively rather than your usual "it won't work but i won't tell you why" stance.

 

Presumably, given the figures above you must be able to come up with some approximation of available power.

 

It would be nice if, just for once, you stopped being rude (and I'm far from being the only persion to mention your obnoxious manners) instead of just running round the forum looking for things to have a go at.

 

If you can't interpret my post as meaning "there is insufficient head or water flow" then there isn't much hope for you.

 

Gibbo

 

Toothed belts as used on camshafts would be a much better option.

 

Absolutely. They are much better.

 

The problem with normal V belts is that they rely entirely on friction. And in order to get sufficient friction the tension has to be high. That creates unwanted friction as the belt enters and leaves the pulley which simply wastes energy. Plus the extra friction in the bearings.

 

Gibbo

[Chris Pink]

"there is insufficient head or water flow"

 

for what exactly?

 

and an unhelpful rhetorical question like

 

"So how is he going to get the water to wrap its way round a 20 foot diameter waterwheel?"

 

that's not rude?

 

I am interested in a completely disinterested way but i don't know why the OP bothers with the trite answers you give.

 

Why not say something along the lines of

 

"given the figures you provide i calculate you can get x power using a transmission designed like this"

 

and thus contribute usefully to the issue?

 

it is not me who said "As a piggy in the middle, I rather feel they are flying through me! "

Edited August 19, 2009 by Chris Pink

[Gibbo]

for what exactly?

 

Duh, for 7 HP

 

Why not say something along the lines of

 

"given the figures you provide i calculate you can get x power using a transmission designed like this"

 

Because we still have not been told what the head is other than "it isn't much" or words to that effect. Therefore the question cannot be answered.

 

Gibbo

[Chris Pink]

Because we still have not been told what the head is other than "it isn't much" or words to that effect.

 

Fair enough. Eyes turn towards Mac of Cygnet for this vital piece of information.

[Mac of Cygnet]

Fair enough. Eyes turn towards Mac of Cygnet for this vital piece of information.

 

Fair enough. It's p***ing down outside at the moment, but when it stops I'll go and have a look.

[nb Innisfree]

Lads, lads, lads, come on.

[Mac of Cygnet]

Lads, lads, lads, come on.

 

Isn't electricity supposed to generate sparks?

 

Anyhow, here are some answers to what people were asking.

 

The head is approx 2 metres. This site allows calculation of the amount of electricity which can be generated from a given volume of water at a certain head, and using the figures available (190litres/sec and 2metres head) this gives 3.7KW hydraulic power (= 4.9HP) which can be turned into 2.2KW electricity, at 60% efficiency) . This is rather less than the 7HP claimed by my neighbour (who is called Dick, by the way, and no stupid jokes - I will refer to him as such from now on), but rather more than calculated by Gibbo. Both, however are in the right order of magnitude, unlike Gibbo's earlier statement about 14000 litres per second at one metre head being needed. (this, using the calculator mentioned, would have produced 82KW of electricity, BTW, enough to power a small street).

 

However (and this is where I reserve judgment) Dick claims, after several years of trials, to have designed a much more efficient undershot waterwheel than previously used, incorporating ball race bearings and specially shaped cups, and which is up and running at this moment. Whether it lives up to his expectations remains to be seen, but at least he has hands-on experience in this field, which I don't suppose many of the contributors here have (including me).

 

The original query, about the generator, seems to have been resolved, but feel free to argue about the rest!

 

Cheers

 

Mac

[Gibbo]

Yes there was an error in my figures. I got a decimal point in the wrong place. The figures then agree with the other poster who knows just how little power is got from water wheels. Your friend's numbers are still miles out.

 

How do I know?

 

Because I have built several. And believe me I know just how physically huge a 7HP water wheel is.

 

I await the results with fascination.

 

But you did say he had actually measured the output at 7HP. Is that not, in fact, the case?

 

Gibbo

[Chris Pink]

Requires a bit of calculus to compensate for the falling head but at the start of emptying a wide lock with 6' there is about 750 litres per sec coming down the paddles.

 

According to reuk.co.uk this gives 8.8 kW available.

 

If it was a linear curve then there would be 4.4kW available for 10 minutes or just over 0.7kWh or 58Ah at 12V

 

hydro electric battery chargers on locks just has to be the way to go.

[Mac of Cygnet]

Yes there was an error in my figures. I got a decimal point in the wrong place. The figures then agree with the other poster who knows just how little power is got from water wheels. Your friend's numbers are still miles out.

 

How do I know?

 

Because I have built several. And believe me I know just how physically huge a 7HP water wheel is.

 

I await the results with fascination.

 

But you did say he had actually measured the output at 7HP. Is that not, in fact, the case?

 

Gibbo

 

What do you mean by physically huge? This wheel is 11ft in diameter and 5ft wide. And here it is! The rain finally stopped so I could go along and take a picture. The water is turned off, as he was working on it.

 

 

As for HP, well I asked him this (because I knew you would, and because I'm getting quite interested in this myself) and he said he calculated it from torque and RPM, so I found an engineering site to let me do this myself and got:

 

HP = rpm x torque/5252 i.e. HP = 15 x 3000/5252 =8.5 He allowed for transmission losses to arrive at 7HP at the generator.

 

Believe me, I also await the results with fascination. This has been a long-term project, and it may be a while before he can get hold of another suitable generator, but he says he is looking for a brushless electromagnetic type - that leaves me behind, but of course not you.

 

Cheers

 

Mac

[Gibbo]

Now we're getting down to the nitty gritty.

 

Where is the 2 metres of head (note, the head is the amount of water fall through the water wheel.) That looks more like he might have a foot or so at the most.

 

Gibbo

[Justme]

Where is the 2 metres of head (note, the head is the amount of water fall through the water wheel.) That looks more like he might have a foot or so at the most.

 

Gibbo

 

 

For wheel yes but for turbines no. Then "head" is the height above the turbine that the level of the top water storage point is.

 

Yes that pic looks like about 1 foot of head. To make that wheel work well the water needs to be filling the containers entering from the left of the pic & just going over the center point & filling the lower one that is painted green (or the highest patchy painted one from this side) on the outside (3 from the top). Would be better yet if you could fill the top one but the containers would need to be rotated a fair bit to do that & not be the shape they are.

 

How is he measuring the torque?

[Mac of Cygnet]

Now we're getting down to the nitty gritty.

 

Where is the 2 metres of head (note, the head is the amount of water fall through the water wheel.) That looks more like he might have a foot or so at the most.

 

Gibbo

 

I think you are talking about an overshot wheel, where the water fills the buckets from above. This is an undershot wheel, which normally have simple blades and are very inefficient (about 20%) Here the water is diverted from the river about 100 metres upstream through (I think) a 50cm pipe, with a 2 metre head, and is directed precisely at the upper part of each trough with great force as it reaches the bottom of the wheel, curves round the trough while (presumably) releasing its energy, and exits over the other lip. Believe me, this is the latest of several prototypes, and he thinks he may have reinvented the waterwheel. But as he says himself - time will tell.

 

Edited to answer Justme. See my answer to Gibbo, above. The torque? Ah, yes, this is where I have my doubts, as he has not measured the torque directly but calculated it from the weight and force (some assumptions there!) of water in the troughs and distance (5ft) from the axle. I wasn't convinced by this, but there was enough force to buckle a 10mm thick steel plate and sheer a 20mm steel pin in the drive shaft at the generator end when the generator suddenly ground to a halt. Too vague I know, but as I (or rather he) said, time will tell.

 

Mac

Edited August 20, 2009 by Mac of Cygnet

[Gibbo]

For wheel yes but for turbines no. Then "head" is the height above the turbine that the level of the top water storage point is.

 

Agreed. But as this is a water wheel and not a turbine I'll stick with my definition.

 

Yes that pic looks like about 1 foot of head. To make that wheel work well the water needs to be filling the containers entering from the left of the pic & just going over the center point & filling the lower one that is painted green (or the highest patchy painted one from this side) on the outside (3 from the top). Would be better yet if you could fill the top one but the containers would need to be rotated a fair bit to do that & not be the shape they are.

 

Again, agreed. But it might be somewhat difficult persuading the water to run uphill to the top of the water wheel to create the two metre head which clearly doesn't exist

 

How is he measuring the torque?

 

He's calculated it from his calculated HP

 

Gibbo

[RLWP]

Agreed. But as this is a water wheel and not a turbine I'll stick with my definition.

 

 

Gibbo

 

Actually, from what Mac of C has just described, it sounds like he is running this as some kind of turbine (impulse or reaction or both, I can't remember). He's directing a jet of water into the trough and deflecting at around.

 

Not that he has reinvented the water wheel, just made a big, inefficient turbine.

 

What speed does it rotate at?

 

Richard

[Gibbo]

I think you are talking about an overshot wheel, where the water fills the buckets from above. This is an undershot wheel, which normally have simple blades and are very inefficient (about 20%)

 

They work exactly the same. The measured head (that is used for calculations) in an undershot wheel is the difference in height between the water leaving the wheel and the water entering it. It can be as little as half an inch or so. It depends how much water can leak round the outside and how much of the channel the buckets/blades fill. The problem for calculations is that the tighter the buckets fill the channel, the more it operates as a turbine.

 

Here the water is diverted from the river about 100 metres upstream through (I think) a 50cm pipe, with a 2 metre head,

 

That is not the head to be used in calculations. It is completely irrelevant for a waterwheel.

 

and is directed precisely at the upper part of each trough with great force as it reaches the bottom of the wheel, curves round the trough while (presumably) releasing its energy, and exits over the other lip. Believe me, this is the latest of several prototypes, and he thinks he may have reinvented the waterwheel. But as he says himself - time will tell.

 

Then that is working partly as a turbine and partly as an undershot water wheel. Not at all easy to calculate but......

 

If the dimensions given are correct, and it really does get 11000 litres per minute and assuming it's got about a 1 foot head then I'll hazard a guess at 0.5 to 1 HP absolute max.

 

Gibbo

 

Actually, from what Mac of C has just described, it sounds like he is running this as some kind of turbine (impulse or reaction or both, I can't remember). He's directing a jet of water into the trough and deflecting at around.

 

Not that he has reinvented the water wheel, just made a big, inefficient turbine.

 

What speed does it rotate at?

 

Richard

 

Yes your post crossed with mine. It would indeed appear that he has a cross between an undershot water wheel and a turbine.

 

Gibbo

 

I've just had a thought.

 

If waterwheels were the way to go, as opposed to turbines, why aren't boats still using paddles instead of these new fangled propellor/screw type thingies?

 

Gibbo

[RLWP]

You would think that he could buy something that was very efficient to work there: click

 

Richard

[Mac of Cygnet]

Actually, from what Mac of C has just described, it sounds like he is running this as some kind of turbine (impulse or reaction or both, I can't remember). He's directing a jet of water into the trough and deflecting at around.

 

Not that he has reinvented the water wheel, just made a big, inefficient turbine.

 

What speed does it rotate at?

 

Richard

 

15rpm

[Justme]

Actually, from what Mac of C has just described, it sounds like he is running this as some kind of turbine (impulse or reaction or both, I can't remember). He's directing a jet of water into the trough and deflecting at around.

 

Not that he has reinvented the water wheel, just made a big, inefficient turbine.

 

What speed does it rotate at?

 

Richard

 

That was my thought when reading the description & also looking at the pic.

 

He is either very very cleaver & has invented a new type or, well I'll leave the or up to you.

 

If I remember right under shot wheels are the least efficient & need the highest flows.

 

Justme