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
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..
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..
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..
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..
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..
RE: Hydropower from water mains..
The pressure drop was the only concern....
cheers, thanks for your input....
vin
RE: Hydropower from water mains..
I expect this would not be a common occurance.
RE: Hydropower from water mains..
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..
RE: Hydropower from water mains..
vin
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. The water system will also have probably tunneled to avoid the need for the lift in the first place.
RE: Hydropower from water mains..
Also apperently the lift isen't as great as the fall.
RE: Hydropower from water mains..
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..
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..
RE: Hydropower from water mains..
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Hydropower from water mains..
However, the answers by some good engineers were very good in this case.
rmw
RE: Hydropower from water mains..
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
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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..
RE: Hydropower from water mains..
RE: Hydropower from water mains..
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..
Again, Thank You
RE: Hydropower from water mains..
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..
But by blending the rates of the turban, and the bypass, you can control the total flow rate.
RE: 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..
RE: Hydropower from water mains..
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..
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..
But with green power, the electricity can be sold for a higher cost that other generation.
RE: Hydropower from water mains..
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..
RE: Hydropower from water mains..