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Mini hydroelectric scheme


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So anyone ever though about the following setup:

Solar PV water pump which runs during the day

The pump pushes water up from a low lying reservoir into a elevated reservoir 

During times when there is no daylight the reservoir water is emptied from the elevated reservoir into the low lying one

Slap some sort of "corkscrew turbine" onto the pipe joining the 2 reservoirs

This turbine would spin when the water flows down the pipe generating some power to charge batteries?

 

Or what if we all just connected a "corkscrew turbine" on the municipal water supplies to our homes (after the council meter) so whenever we open a tap we would be generating a bit of power?

 

I know it would be a very small amount of power generated but was just a pie in the sky idea

 

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Been down this train of thought a few years back because strong flowing water is the best way to generate electricity, if you are next to a river flowing all year round, and you are not hindered by regulations.

 

So I thought, using my pools water, all 28 000I of it, pumped say 20-30m higher ... the complication started with the power required for the pump to move that amount of water that high, after I figured out where to store 28 000l of water, that does not cost me a 2nd pool installation, then let it flow back to the pool at night generating enough power to power what I needed, before the sun comes up ... to start again, whilst powering what I needed plus the pumps kw required, not forgetting the pumps startup current ... or getting a sugar mommy to buy me a solar pump with panels.

 

So I thought, cheaper to get more panels, close the pool and get rid of the pump.  :D

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Dear all.

This is very interesting.

Please excuse my ignorance.

Could one over a course of a week. Pump water up to an elevated large resivor . Thus essentially creating a water battery.

When power is needed , gravity should run the water down into a highly geared water turbine, the force of the water and the back pressure (weight of water behind the head) should overcome the torque required to rotate the highly geared motor.

This is end can turn a alternator at very high rpm. I wonder how effective this is, vs storing power in batteries via "chemistry".

Essentially mechanical energy.

Sincerely

Jay

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Jay, yes, I believe you can, if the water is high enough, and there is enough water, you can create an awesome system.

 

Was looking at farms at one stage, with a) a waterfall or b ) a strong river or c) high up a mountain with a similar idea in mind, pump water daytime, use the power at night.

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Thanks so much, I really enjoy these threads.

What a great idea. We have very large resivors on the farm. I estimate the size of 10 jojo cans.

The height to them is about 40m, 4bar. I imagine one would require a very clever holding tank at the bottom and some type of electronic tap to shut the system off when your bottom holding tank is full up. I wonder how you could get around this? And keeping so much water at bottom requires a lot of volume?

Its a very exciting idea. Is a heavily geared water turbine availble? How do they operate?

I wouod also love to know the energy required to pump the water up vs what is gained on the down path.

I imagine pipe friction wont be in our favor on the up side. What a great water battery idea?

Thanks again guys very helpful.

Jay

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Hi Jay, someone much smarter than me would have to answer your questions ;)

Last night I had another thought, why not get a pressure vessel like on a air compressor, compress air during the daylight hours using PV and then release this air at night and spin a turbine?

Much smaller "vessel" required and no need to have a high lying and low lying area to allow for gravity feed between the 2?

 

I understand that efficiency and cost is always an issue with these sort of things but I still think having some sort of turbine on your municipal water supply is a good idea.

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I think a good head (40m plus) and a solar pump will do just fine to the the water.  Cheaper than a wind turbine, I would guess.

 

Pelton Wheel Design: 

 

Brazilian Video: Spanish but you will get the point

1.4kw per hour

Some divide the water stream and have a top and bottom jet OR send the divided stream to 2x Pelton Wheels.

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The volumes of water are enormous 

The potential energy (in Joules) is expressed as

 

Ep = mgh 

 

where m = mass of water (kg)

           g =  gravitational acceleration (a constant that has not changed, unlike Pluto)

           h = head (m)

 

(Don't you love the metric system. Try that calculation in imperial figures.)

 

Now 

       P(watts) = Energy(Joules)  /time(sec).

 

Working backwards for 500W we need to produce 500 J/s.

 

Therefore m= Ep/gh /s.

 

m = 500/ 9.8 x 40 (Energy the person's head in the example). 

 

m = 1.27 kg = 1.27 litres every second.

 

So we talking  just over 4500 litres/h.

 

This in the maximum possible energy. Pelton wheels can achieve 90% efficiency so lets say 5000l/hr. (2 Jojo tanks =48 Jojo tanks a day). 

 

One definitely could look at storage of part of one's requirement but if I was investing money in that sort of thing to my mind it should run 24/7.

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The volumes of water are enormous 

The potential energy (in Joules) is expressed as

 

Ep = mgh 

 

where m = mass of water (kg)

           g =  gravitational acceleration (a constant that has not changed, unlike Pluto)

           h = head (m)

 

(Don't you love the metric system. Try that calculation in imperial figures.)

 

Now 

       P(watts) = Energy(Joules)  /time(sec).

 

Working backwards for 500W we need to produce 500 J/s.

 

Therefore m= Ep/gh /s.

 

m = 500/ 9.8 x 40 (Energy the person's head in the example). 

 

m = 1.27 kg = 1.27 litres every second.

 

So we talking  just over 4500 litres/h.

 

This in the maximum possible energy. Pelton wheels can achieve 90% efficiency so lets say 5000l/hr. (2 Jojo tanks =48 Jojo tanks a day). 

 

One definitely could look at storage of part of one's requirement but if I was investing money in that sort of thing to my mind it should run 24/7.

I see it slightly differently...

 

Pump up to storage (or better still capture small catchment on top of mountain).

 

Solar for as many hours as possible - maybe with extra panels to drive pump.

 

Wait until battery bank drops to X SOC.

 

Open value and let pelton pump run to charge/cover load until sun rises.  So 8 hours per day.

 

This is really just a power storage solution (instead of more expensive batteries)

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Hi Mark

 

You might be on to something here.  A turkey nest dam with a liner should not cost a fortune and you could store tens of thousands of litres. Now to find out whether pumping water is more efficient that squeezing the last couple of Ah into a battery. I know that battery charging at lower states of charge are  nearly 1:1.

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  • 2 weeks later...

Generally, you need energy to produce energy. The biggest problem with this design, is how much energy is needed to pump said amount of water to the storage tank? And at what cost? At what point is it cheaper than buying extra batteries?

But the idea is a good one, albeit needs some decent R&D to get an efficient working model. 

But if you didn't have to pump water to a higher storage area, you could have some free electricity. For example if there's running river or you could install a turbine into a running water line - but this raises the question: " why has this not been implemented by municipalities already? Surely the water mains push through enough water/minute to produce some decent amount of electricity?

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7 hours ago, SilverNodashi said:

Generally, you need energy to produce energy. 

.....- but this raises the question: " why has this not been implemented by municipalities already? Surely the water mains push through enough water/minute to produce some decent amount of electricity?

Most municipalities have pump stations to maintain water mains pressure, so there is nothing to be gained for them. If the supply is gravity fed (Bloemfontein springs to mind) then inline would need to be geared so as not to reduce the pressure too much. One can get small inline generators useful for powering garden irrigation systems.

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