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Hydropower from water mains..
7

Hydropower from water mains..

Hydropower from water mains..

(OP)
Given that water is pumped from the reservoir to the town,
is it feasible/practical to use the kinetic energy produced in the pipeline to drive turbines installed along the mains waters, for electricty generation??

how would one calculate the potential generation ??

With standard hydro calculations they use flow rate and head... but in this case head wouldn't apply??


cheers
vin
 

RE: Hydropower from water mains..

2
If the water is pumped, any energy you extract with your generation would have to be supplied by the pumps.  Add in the inevitable losses and the additional energy into the pumps will exceed the energy out of the generation.

Where the water flow is entirely gravity powered there are already locations that use turbines for pressure reduction and generate power in the process.

RE: Hydropower from water mains..

Any energy in this system is provided by the pumps, unless there is a net elevation difference between the reservoir and the town.  So any electric energy generated would come from the electric energy used to run the pumps.  Add in the losses, and you will be using more energy than is being produced.

I once worked on  a project to install a small hydro turbine on the outfall of a sewage treatment plant.  In that case, the elevation difference between the plant and the ocean provided the necessary head to run the turbine.   

RE: Hydropower from water mains..

Wizeguy

Both davidbeach and dpc are correct, the arrangement you're discussing uses more energy than it produces.  However, having a reservoir run a turbine under peak power conditions and then refilling the reservoir under low power conditions can be economically viable.

Look up "pumped storage" in Wikipedia.  You might also want to do a search on TVA's Raccoon Mountain pumped storage unit.

Patricia Lougheed

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RE: Hydropower from water mains..

(OP)
Thanks for the replies....

I understand that energy is used to run the pumps, and that any energy extracted would be less than what is used to run the pump etc.

However this is how I was looking at the concept....

Water is being pumped to my house right now, through the local councils water mains pipeline, it has been for the past 30 odd years and will be for another 30 + years. If that water is fed through a series of turbines before reaching my taps, it could generate some electricity to feed into the grid.

The idea was to have a number of turbines along the pipeline. If  pumps are needed after each turbine to maintain pressure, then yes the system would be worthless.

The idea was to use the kinetic energy that exists in the water mains system to generate some more electricity.

vin
 

RE: Hydropower from water mains..

That would reduce the pressure being delivered.  If you don't need the pressure it probably wouldn't be being provided.  There are exceptions; I have to have a pressure reducing valve on my water service since the houses 150-200 feet higher up the hill need some water and the mains are pressurized sufficiently to supply those customers.  In theory I could generate power while producing that pressure drop.  Not enough volume, nor nearly continuous enough to make it worth while.

RE: Hydropower from water mains..

(OP)
The turbines would have to be between the pump and the township.... it wouldn't work on a per house or per street basis, as you've said not enough volume or continuous supply.

The pressure drop was the only concern....

cheers, thanks for your input....

vin

RE: Hydropower from water mains..

Actually there might be a good reason to use a hydrogeneration following a pump station, and that would be if the pump was needed to pump the water over a high pass and on the other side a pressure reduction was required. The hydrogeneration could be used to recover some of the pumps energy. (Stranger things have happened).

I expect this would not be a common occurance.
 

RE: Hydropower from water mains..

(OP)
Ok then.... so the major flaw in this system would be the reduced pressure after passing the turbine?

If the issue of loss of pressure was "resolved" then this system maybe worthwhile?? (a big if I know!)

I suppose it would depend on how much pressure was lost after passing through the turbine/s, and how much energy is required to return the pressure back to "normal"?

(obviously the energy produced from the turbines collectively would have to be significantly more than what would be required input to bring the water pressure back to normal)

How would you calculate the water pressure lost through the turbine?

Which brings me back to my other question of.... how would you calculate the potential energy generation from the water pressure in a pipeline?

vin

RE: Hydropower from water mains..

You can do the math wizeguy, delta p time mass rate = energy.  You'll see tha you either need lots of delt p or a lot of water.

RE: Hydropower from water mains..

(OP)
is this where the Tesla turbine or Tesla pump might be employed? or the Wolfhart Willimczik pumps?

vin  

RE: Hydropower from water mains..

Energy is energy.

Cranky, in a sealed pipe the water going down the other side will tend to reduce the work necessary to lift the water up the hill.  The water system will also have probably tunneled to avoid the need for the lift in the first place.

RE: Hydropower from water mains..

You are correct. The example I was thinking of has a lake between the pump station and the hydrogeneration.
Also apperently the lift isen't as great as the fall.
 

RE: Hydropower from water mains..

"wizeguy"

I believe that you are persuing a device of the "second kind".

http://en.wikipedia.org/wiki/Perpetual_motion
 
Additionally, the comments stated above are good advice.

Also, please remember that, in any municipal water distribution system some energy must be "left on the table" because there is a minimum system pressure required for the "folks that live on the hill" that is not required by the "folks that live in the valley"

Wize, do you have an engineering background ????

-MJC

   

RE: Hydropower from water mains..

"Cranky, in a sealed pipe the water going down the other side will tend to reduce the work necessary to lift the water up the hill."

Yes, that is called a syphon.  Only works to 32 feet or so, then the water column on the downhill side cavitates.

But, a tunnel under the pass avoids the issue altogether.

RE: Hydropower from water mains..

I'm sure someone else did a complete evaluation some years ago.

RE: Hydropower from water mains..

Quote:

With standard hydro calculations they use flow rate and head... but in this case head wouldn't apply??
I am afraid that you have to leave "head" in the equation.
 

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Hydropower from water mains..

I have to think that the OP doesn't have an engineering background.

However, the answers by some good engineers were very good in this case.

rmw

RE: Hydropower from water mains..

Will admit to being old and stupid but still interested in how things work!

Has this old coot followed accepted practices to  calculate the waterwheel  thingy?

Any help or comment would be much appreciated



http://en.wikipedia.org/wiki/Newton

http://www.ajdesigner.com/phphorsepower/horsepower_equation_rotating_horsepower.php

This is also posted at http://www.apakrat.com/American/Question1.html where the numerals can be highlighted and copied.
Thank Ya'll

RE: Hydropower from water mains..

my comment is that the more work you take out, the higher the water will rise behind the wheel, is there a place to allow the water to rise?

RE: Hydropower from water mains..

Thanks for the comment dcasco.  Still showing my ignorance, I suppose this build up would be in the Gulf of Mexico, when considering the little  thingy, about the size of 1/3 of a 55 gallon barrel, and supported by a raft anchored in the Mississippi River some where about Vicksburg.

RE: Hydropower from water mains..

apakat kinetic energy = 1/2 mv^2, not force. You'll need to know the width of the paddles

The torque will be the force acting on the paddle across the area.  The unit will slip and turn a lot slower than the 74 rpm's.

RE: Hydropower from water mains..

Appreciate the recommendations dcasto!  Been looking for a good reason for throwing in a 50% efficiency factor until further data from testing is available.  Just didn't know where or why to apply the reduction.

Again, Thank You

RE: Hydropower from water mains..

I don't think the idea is totally out of the question. Although fundamentally different I have seen these on raw water systems from reservoirs where the head is otherwise throttled to control the flow.

If the system is at the start of a long high pressure main then you may step down the pressure to branches, include pressure control strategies, design in back pressure in order to clear hills or maintain pressures in certain branches of the main.

It might just be feasible to replace these controllers with micro turbines that can control the pressure / flow.

However there are lots of whats and ifs surrounding the implementation of such ideas.
 

RE: Hydropower from water mains..

Sort of like a turbo charger, where the bypass can be partually opened to increase the total flow rate, or pressure. (I know the bypass in a turbo charger is to control the speed).
But by blending the rates of the turban, and the bypass, you can control the total flow rate.

RE: Hydropower from water mains..

Hydropower from water mains ???

Come-on guys. this can't be serious. Its candid-forum. They are going to post this thread on some campus billboard so the engineering students can get a good laugh to relax after a hydraulics 101 quiz.

RE: Hydropower from water mains..

there apparently are a few applications where a pelton wheel was used as a power generator- and I understand in some chemical refineries they have configured pumps to operate in reverse, to recover power as opposed to simply throttling across a pressure reducing valve. Noweadays one can automatically synchronize the small generator to the grid using teh same solid state technology as per Capstone turbine or small wind turbines.

RE: Hydropower from water mains..

The eazy way to synchronize a small Pelton wheel is to use an induction generator.
Pelton wheel power generation can be used to reduce the water pressure, and works well with drops greater than 1000 ft.
The issue as I've seen it is you have to drop the pressure before entering a treatment plant, where it is repressurized after treatment.  

RE: Hydropower from water mains..

From the original post:

Quote (wizeguy):

Given that water is pumped from the reservoir to the town,
is it feasible/practical to use the kinetic energy produced in the pipeline to drive turbines installed along the mains waters, for electricty generation??
No. In a well designed pumping system only enough energy is imparted to the flow to to give good service to all the consumers. If you were successful in extracting energy from the flowing water in a well designed system then the pressure and/or flow to the consumers would suffer.

Had you asked;
We have a mountain reservoir at an elevation of X feet above the highest user. We presently use a pressure reducing valve to maintain a lower pressure in the town. Can we use a turbine to extract energy from the water as we drop the pressure?
The answer would be a qualified yes. Even though you can easily calculate the expected energy, you may have controlability issues in smaller systems.
Mechanically feasible. Yes, with qualifications.
Electrically feasible. Yes
Financially feasible. Unknown. As the head increases and the flow increases the financial feasibility generally will improve.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Hydropower from water mains..

Financial Feasibility, Questionable. The issue as I understand it is the cost of operation of the pressure reducing valve. And the valve would be required even if the water were flowing into a pond.
But with green power, the electricity can be sold for a higher cost that other generation.

 

RE: Hydropower from water mains..

The pressure reducing valve would be replaced by the turbine. There is quite a bit of energy developed by a pressure reducing valve with a large differential pressure and a large flow.
The lost energy heats the water, but with a high flow and the relatively high specific heat of water the temperature increase is not often noticed.
Hint, multiply the flow times the pressure difference to get an idea of the amount of energy lost in a pressure reducing valve.
I remember an assignment from my school days.
A water fall is 100 feet high. What is the temperature difference between the top and bottom of the fall.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Hydropower from water mains..

all BS give it up.

RE: Hydropower from water mains..

dcasto, I agree power from water provider is BS. However power from run of pipe isen't. The difference is magnitude and CL2

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