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Pumping water

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eepee
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Pumping water

#226852

Postby eepee » June 4th, 2019, 3:03 pm

A rather late Xmas present happened last week - a visit to the 'Electric Mountain' (the Dinorwig Power Station).

Here is some idea of the set-up:-
http://www.sxolsout.org.uk/p21.html

Fascinating tour. However it is based on bus tannoy and headphone commentaries and there did not seem to be any opportunity in which to ask questions.

Needless to say, the tour raises a load on questions! However there is one that intrigues me.

With a water drop of over 100 metres during operation, the water is pumped back to the top reservoir during slack, none-generating periods.

This is done without staging. How can they do it? I always thought it was impossible to pump water upwards for more than about 30 feet in one go.

Regards,
ep

Imbiber
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Re: Pumping water

#226856

Postby Imbiber » June 4th, 2019, 3:16 pm

It is I think impossible to lift water more than 32 ft with a suction or lift pump. Pumping up higher is possible with pressure pump.

Itsallaguess
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Re: Pumping water

#226862

Postby Itsallaguess » June 4th, 2019, 3:25 pm

eepee wrote:
With a water drop of over 100 metres during operation, the water is pumped back to the top reservoir during slack, none-generating periods.

This is done without staging. How can they do it? I always thought it was impossible to pump water upwards for more than about 30 feet in one go.


Multi-stage pumps can offer performances into the hundreds of meters.

Here's just one example -

Image

https://www.sulzer.com/en/shared/products/2017/03/28/13/01/bbt-bbt-d-process-pump

I think Dinorwig uses Reversible Francis Turbine/Pumps, and this Wikipedia page suggest that they have a head range of around 40 to 600m - https://en.wikipedia.org/wiki/Francis_turbine

Cheers,

Itsallaguess

jfgw
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Re: Pumping water

#226926

Postby jfgw » June 4th, 2019, 6:01 pm

Imbiber wrote:It is I think impossible to lift water more than 32 ft with a suction or lift pump. Pumping up higher is possible with pressure pump.

With a lift pump, it is the external pressure that pushes up the water. If you have a long, vertical pipe dipped into a body of water at atmospheric pressure and you create a perfect vacuum at the top of the pipe, the pressure difference will push the water up the pipe about 10.3m. In reality, the maximum lift will be significantly less than this as no pump can achieve a perfect vacuum.

Julian F. G. W.

XFool
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Re: Pumping water

#227008

Postby XFool » June 4th, 2019, 8:41 pm

eepee wrote:A rather late Xmas present happened last week - a visit to the 'Electric Mountain' (the Dinorwig Power Station).

Here is some idea of the set-up:-
http://www.sxolsout.org.uk/p21.html

The problem I have with that website (it has an axe to grind) is that it seems to bang on about Dinorg being a (cheap!) 'Power Station' compared to say a nuclear power station.

But it ISN'T a generating 'Power Station' at all! It is a Power Storage system. Really a sort of energy time shift system. All very important, especially now with wind power etc. But it does not of itself originate any energy at all, indeed, it inevitably loses some.

Your question about water pumps has already been answered.

Dod101
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Re: Pumping water

#227023

Postby Dod101 » June 4th, 2019, 9:49 pm

This sounds very similar to the Cruachan Power Station in Argyll which has a lift of 1299 feet. It was built in 1959/60 by what is now SSE, then Scottish Power and I think it has been bought recently by Drax. All very clever. It takes power generated from a local nuclear power plant at off peak times and using that it transfers water up 1300 feet or so to be used to generate electricity at times of peak demand. So I guess that Xfool is correct in that these stations are not really power stations in the conventional sense but rather a power storage system.

I cannot answer the original question though.

Dod

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Re: Pumping water

#227204

Postby quelquod » June 5th, 2019, 1:44 pm

jfgw wrote:With a lift pump, it is the external pressure that pushes up the water. If you have a long, vertical pipe dipped into a body of water at atmospheric pressure and you create a perfect vacuum at the top of the pipe, the pressure difference will push the water up the pipe about 10.3m. In reality, the maximum lift will be significantly less than this as no pump can achieve a perfect vacuum.

Julian F. G. W.


Well, a bit less certainly, but perhaps not significantly.
A few people have been caught out by this. I remember visiting a McDonnell Douglas semiconductor plant where they’d installed lift pumps overlooking the >>10m height from the basement to the factory floor. They had to replumb of course - oops!

eepee
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Re: Pumping water

#227520

Postby eepee » June 6th, 2019, 4:07 pm

Yes the system is a peak demand buffer. Its appeal is its ability to come online to full power within seconds.

Somebody has written to me to point out that, the pumping back of the water is not very demanding so long as the system can withstand the water pressure of the column, because the pipe(s) are always full of water. Think of it as pushing marbles through a tube that is already full of marbles.

Makes some sense. However I am not clever enough to work out the physical forces this would require!

Regards,
ep

swill453
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Re: Pumping water

#227542

Postby swill453 » June 6th, 2019, 5:10 pm

eepee wrote:Somebody has written to me to point out that, the pumping back of the water is not very demanding so long as the system can withstand the water pressure of the column, because the pipe(s) are always full of water. Think of it as pushing marbles through a tube that is already full of marbles.

You still have to lift a whole column of marbles though. Pushing water into (or the first marble into) an empty pipe would be much easier, so the fact that the pipe starts full doesn't help.

Scott.

Itsallaguess
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Re: Pumping water

#227553

Postby Itsallaguess » June 6th, 2019, 5:39 pm

eepee wrote:
Somebody has written to me to point out that, the pumping back of the water is not very demanding so long as the system can withstand the water pressure of the column, because the pipe(s) are always full of water. Think of it as pushing marbles through a tube that is already full of marbles.

Makes some sense. However I am not clever enough to work out the physical forces this would require!


Dinorwig uses 33% more energy to pump the water back up than it produces from the water on the way down....

Pumping back up is done using off-peak power, however, which is cheaper.

Cheers,

Itsallaguess

twotwo22
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Re: Pumping water

#228837

Postby twotwo22 » June 12th, 2019, 8:01 am

An interesting alternative to pumping water

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


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