Small scale domestic hydro power generation project

[ProDave]

This is going to be a long / slow thread as it's not an imminent project but one that is on the "to do" list but I have been encouraged to start the thread anyway to get some thoughts and ideas.

 

As many of you know a small burn runs through our garden.  The plan is to experiment with small scale hydro power generation.  This is more of a project / fun thing as it won't be generating significant power to make any real impact on our energy use.

 

2 pictures:

 

the first has been posted before, the more or less straight run the burn takes through the garden.

 

And the second one that has not been posted before, where the burn enters our garden

 

 

As the burn enters our garden from next door, it makes a rapid S bend, briefly forming the boundary between us and next door.  The fence line in the middle of the picture is the boundary, left of the fence is our garden, right of the fence is next door.

 

Initial thoughts are to experiment with an undershot water wheel in this section of the burn for the following reasons:

 

This is probably the fastest flowing section of the burn as it runs down a slope.  The rocks in the foreground under normal flow create a constriction concentrating the flow in a narrow space.  So a waterwheel just a little narrower than that gap between the rocks and the right hand bank would get the best flow.

 

It is close to the shed for power connection for batteries / inverters or whatever stuff needed to make it work (solar PV inverter is already in that shed)

 

It is upstream of next doors septic tank discharge that you can just see as the burn turns left as the fence starts.

 

This burn comes up drastically when in spate, so the plan would be to mount the waterwheel essentially on a float pivoted upstream, so as the water level rises the whole waterwheel would float up.

[markc]

Interested project, as a burn there is very little ‘power’ available but it is constant so worth exploiting. Some experimenting will be required with paddle surface area and gearing to the generator to find a happy medium that will work with a low flow rate and no head of water

[ProDave]

I considered a more conventional capture and into a turbine, but end to end on the plot there is barely 1 metre fall.  Creating a headstock to capture water, then piping it the length of the burn would be a lot of work and a lot of pipe to bury and then technically you need permission to extract water (even if all of it goes back) and there are the issues of not restricting the flow in spate and not wanting the headstock to silt up etc it would be far too complicated.  Hence the waterwheel idea which I know will not produce much power.

[SteamyTea]

38 minutes ago, ProDave said:

barely 1 metre fall

Is there anywhere lower i.e. other side of the road.

 

Worth playing Pooh Sticks to calculate the mass flow rate. 

Then you will find you have one less project to do.

[Radian]

1 hour ago, ProDave said:

I considered a more conventional capture and into a turbine, but end to end on the plot there is barely 1 metre fall. 

Are you talking about a Pelton Wheel here?

[ProDave]

33 minutes ago, Radian said:

Are you talking about a Pelton Wheel here?

Possibly.  More typically you see a Pelton Wheel used in an enclosure as a low velocity turbine from a piped water supply (from a higher heater pond) but that article suggests it is an efficient way to extract power from moving water as a better alternative to an undershot wheel.  So it looks like a good contender.

[Radian]

I was just thinking that if you were to create a barrier (dam) and have a hole for a jet pipe then you can set the top of the dam at an appropriate level and automatically provide relief (overtop) when in full spate. The Pelton wheel is probably the most efficient energy harvester you can build.

[SteamyTea]

The type of 'wheel' is not going to affect the the overall energy extraction.

Like most energy generation, larger is best.

[JohnMo]

Bunch of calculations here for working out the potential.

 

https://www.renewablesfirst.co.uk/hydropower/hydropower-learning-centre/how-much-power-could-i-generate-from-a-hydro-turbine/

 

This link tells you to determine the head available, which from looks of will be quite low.

 

https://www.renewablesfirst.co.uk/hydropower/hydropower-learning-centre/what-is-head/

 

But a system that generates a few hundred watts, will cover the house base load all year.

[TonyT]

Kris Harbour on you tube has begun 3d printing these. He lives off grid with initially hydro and added solar and homemade wind turbine.

 

he’s started a business selling equipment based on his own experience.

 

lives in the middle of no where and builds everything himself, former lift engineer who turned his back on the 9-5 life

[SteamyTea]

1 minute ago, TonyT said:

former lift engineer

Wonder if he was the chap that could not be bothered to come to Lakeside Shopping Centre, Essex, when I was stuck in the lift and having an cleithrophobia episode.

[jamieled]

Peltons are normally used in high head situations. For lower head applications kaplans are typically the preferred choice.

[saveasteading]

7 hours ago, ProDave said:

a small burn

That is  technically a wee burn.

[Radian]

4 hours ago, jamieled said:

Peltons are normally used in high head situations. For lower head applications kaplans are typically the preferred choice.

 

Sure but a ducted turbine is going to get even more stuff stuck in the duct! Also tricky to home-brew a decent screw compared to buckets.

 

[saveasteading]

 I know more about hydraulics than electronics. A bit.

Therefore before this discussion gets even more technical here is my input.

 

I would select a suitable wheel that can run at a steady speed to feed your fairy lights,  then create the waterflow to suit.

 

Hence a spillway that feeds water from the burn into a full pipe, and then along the line of the burn or bank to the 'power station', gaining clear height.

Then an outfall from the pipe onto  the wheel which is above a small catchment and thence flow back to the burn.

 

The leaves are kept out by angling the spillway so that leaves flow by but water trickles over, and then a small settlement area where sinkers and floaters are kept away from the pipe, with another weir and/ or gauze divider.

Then a gauze over the pipe as a precaution in case of remaining bits.

 

Presumably you would be  far enough down the burn that the turbine is above spate level.

 

All the above speaking as the student who caused the weir experiment to overflow onto the PhD student designing a wave energy machine below our mezzanine.

 

 

[SteamyTea]

26 minutes ago, saveasteading said:

PhD student designing a wave energy

That was lucky. Wave machines have proved to be failures so far, but it was seeing Dr Salter's Ducks, back in 83, that got me interested in the whole RE field.

[Radian]

Handy chart from Science Direct

[saveasteading]

5 hours ago, SteamyTea said:

Dr Salter's Ducks,

I think that was him.

[Dillsue]

20 hours ago, saveasteading said:

That is  technically a wee burn.

Is that because the neighbours septic tank runs into it🙈

[ProDave]

4 minutes ago, Dillsue said:

Is that because the neighbours septic tank runs into it🙈

That would make it a sh1t burn. (at times it can smell that way)

[ProDave]

So i had some time on my hands this morning.  Time for a paddle around in my wellies.

 

The only bit of "hose" of any size I have is a left over length of mvhr ducting, about 70mm diameter from memory.  So I drop that into the burn at a high point, finding a good place that is a natural bit of a "header" and roll it out down the burn.

 

The bit of pipe I have is nowhere near long enough. So at it's lower end the water I have collected has a head of about 0.5 metre.  If I extrapolate that to the full length of the burn (assuming the fall is constant, it's not far off) I would get to a little over 1m head, perhaps 1.5 if I get creative with where I take the water at the upper end.

 

The flow rate coming out of my pipe at 0.5m head is 2 litres per second (it takes 6 seconds to fill a 12L bucket)

 

So if I plug those optomistic figures of 1.5m head and flow of 0.002 m³/s into here https://www.engineeringtoolbox.com/hydropower-d_1359.html I get 29 watts.  That's before you even think about generator efficiency.

 

Now obviously if i could find a nice long length of some form of hose that was a much larger diameter, I might get better flow rate, or even 2 lengths of this pipe might bet me up to just over 50 watts.

 

Clearly this is never going to be a serious amount of power and is in the "fun" category if ever I actually do anything with it.

 

About the only thing I could say is perhaps catching and piping water like that might work with a breastshot water wheel at the bottom.

[SteamyTea]

2 hours ago, ProDave said:

Now obviously if i could find a nice long length of some form of hose that was a much larger diameter, I might get better flow rate, or even 2 lengths of this pipe might bet me up to just over 50 watts.

A constant 50W could be useful.

But 100W would be very useful.  2 kWh a day is my non E7 usage.

[ProDave]

So I have done some more.  I remembered where there was a spare coil of black electrical ducting, not ideal but good for my test work.

 

So we have:

 

Spare length of mvhr ducting collecting the water at a bit of a natural header pond right where the burn enters my land.

 

 

that goes round the S bend in the burn.  Where that runs out, it joins to the black electrical duct, a bit smaller and a tight fit inside the mvhr duct

 

 

That black duct then runs as far as it reaches which is only a couple of metres short of where the burn departs our land

 

 

At the end of that we still get most of the flow I had before, perhaps 6.5 seconds to fill the 12L bucket so say 1.8 litres per second.

 

The head is now 1.4 metres

 

So putting that into the page linked before gives a grand total of 24 watts

 

I bet you would be lucky to actually get 15 watts of electricity from that.

 

The only way to do this I think is is to treat is as a fun project and make a large water wheel for the water to run over as a garden feature and any power you get from it is purely a bonus.

 

Or find a cheap / free very much larger length of pipe to increase the flow rate.

[saveasteading]

Apologies before I start as I will give an opinion with the benefit of ignorance, which is always easier.

Hydraulics yes I know a bit , turbines no, I leave it to you.  And there seem to be mill experts on BH.

 

Might it be possible to dangle a turbine into the fastest flowing part, that flows reliable all year? Create a channel if necessary. Perhaps on a float so that it follows the water level. Then you could have multiples of that if wanted, and they can all be different using various salvaged motors.

It would (or could)  be fairly discrete and keep the charm of the burn. 

[ProDave]

I think what this has done is show how much water you need and how much head to get a useful amount of power.

 

My initial thought was just an undershot water wheel at pretty much that constriction in picture 1 above where the red pipe presently starts from.  Although the flow is fast there, the same equations apply and the power you get out is proportional to the flow in litres and the head it falls.  An undershot water wheel at that point would deliver in minute amount of power because the head is only what it self creates to turn it..   But yes you could put a whole load of them along the burn.

 

I won't just leave the pipe like that, it will be buried somehow.

 

I have one low power candidate motor so I might just rig up a "Blue Peter" water wheel and try flow I have from that pipe and see what I actually get.

 

It seems odd that 2L per second at 1.3m head only generates about 30W.  Why do I feel if I was asking the question, what power of pump do I need to pump water uphill by 1.3m at a flow rate of 2L per second, the answer would probably be a lot more than 30W?