Coupling a turbine with a pump 5

[nilsadams]

Hello,

I would like to combine a turbine with a pump in order to lift water up to the pump position. I am considering two options:

Either (1) using a turbine pump
Or (2) using a turbine and then connect it to a pump

From financial and technical point of view, which one is a better option ?

I want to lift water up to the pump (turbine) position, which is 3 meters (bellow the pump position) using a discharge of 2 m3/s. Just beside to the pump position, there is a cannal where the pumped water needs to be discharged. The idea of using a turbine is because I have a water fall of about 6 meters to the pump (turbine) position with a flow rate of discharge of 0.9 m3/s.

Thanking in advance,
Nils

 

[Warpspeed]

Have you considered using a Ram Pump ?

These operate on the principle of allowing a column of water to (gravity) flow down a long pipe, and then abruptly shutting off the flow at the discharge end.

The very high inertia of the heavy moving water column will then produce a pressure spike that can push a small volume of water to a surprising height through a non return valve.

The pump pulses by itself and would probably do what you require, but the efficiency will not be terribly high. The advantage is low cost and high reliability.

Well worth thinking about, because these types of systems are frequently lost or destroyed in flash floods. Something more exotic may be damaged beyond repair. But a simple Ram Pump can often be dug out of the mud and recovered miles down stream and put straight back to work.

 

[Warpspeed]

Something like this........

http://www.lifewater.ca/ram_pump.htm

 

[thewellguy]

I would need more info on the specific application. However, look at Gould industrial pumps, Berkely Ag pumps, or American Marsh to get an idea if this will work for you.

 

[nilsadams]

I thank you all.

Warpspeed: Well, the discharge to be lifted up to the pump position is higher than that hitting the ram pump. As I said, the water fall has a discharge of about 0.9 m3/s, head of about 6 m. On the other end, I have a discharge of about 2 m3/s to be lifted up a height of about 3 m. If I understood about the mechanism of the ram pump, it releases a discharge lower than the discharge entering the pump. But I need the inverse, i.e. using the power of a lower discharge to lift a higher diacharge. Will the ramp pump appropraite in this situation ?

thewellguy: can you give me the links ?

Regards,
Nils

 

[Warpspeed]

nilsadams,

I appreciate the problem, that you need to convert a relatively high available pressure head into a much greater flow, rather than just pumping a small proportion of the available flow volume much higher.

Another less elegant idea would be a giant water wheel. Theoretically it could be the most efficient system of all, and would work over a reasonably wide flow range. It should be very tolerant of silt and debris, be self staring and self regulating, and it too has a rather appealing simplicity about it.

See what the turbo pump manufacturers say, but I would expect their turbines and pumps to stop working, or become very inefficient if the available flow rate falls much below the optimum design figure.

 

[waross]

Reality check.
Not doubting or dispariging, just putting it in perspective.
The water wheel will require 2 cubic meter buckets passing at the rate of one bucket per second.
A cubic meter weighs a metric ton.
A 50 gal. oil drum holds a little over 400 lbs of water.
That means over 5 oil drums a second.
It's do-able, and a water wheel will probably be quite efficient but BIG.
respectfully

 

[Warpspeed]

I did say a GIANT water wheel, and it would probably need to be at least 8 metres diameter, the required buckets would not be completely out of proportion.

And I totally agree it is not exactly space age technology. I just mentioned it as one possible alternative.

 

[BRIS]

Turbine driven pumps used to be quite common. The turbine is usually a reverse flow pump and efficiency is low maybe 50%. The usual situation is a large flow dropping through a small head used to lift a small flow through a large head. Common application are at drops on irrigation schemes, rivers etc where the turbine pump is used to supply village water supply.

You have a flow of 0.6 m3/sec dropping 9m and you want to lift 2 m3/sec by 3m. You can’t do it.

The maximum flow with an efficiency of 50% is

Q = 0.6m3/sec x 9m x 50%/3m = 0.9 m3/sec.

You simply need to bolt two suitable pumps together.

 

[nilsadams]

I appreciate the contribution of all of you !

As to the waterwheel, I have very complex site that doen't allow me thinking that. In addition, if I go with that much size, I will face problem with the hydraulic head of the outlet head, which is connected to a big river.

I could go with only a single turbine for the larger flow (2m3/s) and connect the outlet to the river end. The problem, the construction cost will be huge due to the need for tunnel works and displacement of several electronic installation on the way. The option I had thaught was to couple the discharge with another pump, in ch the latter can be driven by another fall (with lesser discharge), to discharge it to the existing pipe to the river.

When I calculate the max position of the pump to lift the higher discharge, it won't be more than some centimeters. Technically as well as financially less attractive.

I am still wondering what kind of options I should think of : ....

 

[BRIS]

I think I have lost the plot!. 1) you cannot get out more energy than you put in: you can't lift 2m3/sec by 3.0m. from an input of 0.6m3/sec dropping 9.0m and 2) you need to consider the economics: construction of tunnels etc. to recover 30kw of electricity may not be cost effective.

 

[nilsadams]

BRIS:

The plot goes like that:

There are two water fall sources. one for bigger discharge (2 m3/s) with a fall of about 3 meters and a second with smaller discharge (0.9 m3/s) with a fall of about 6 meters. with this setup there is an existing combined discharge to a river at about 2.9 m3/s.

Now, for me, the 2m3/s scheme seems attractive if I find some technical solution to increase the head from 3 m to possibly 5 or 6 meters. If I do that it means I have to dig down, thus I will be below the level of the combined chanel.

Ok, then le me think of this but then I have to lift the water back to the level of the combined channel. To lift water to the combined channel, I then took the option of using a pump. But a pump will consume energy to run and eventually my solution may not be feasible. I then thought how about a turbine pump that uses the 0.9 m3/s scheme (6 m fall) as energy source so that it may help me lift the water from the turbine of the 2m3/s scheme.

Unfortunately, the energy source with the 0.9m3/s scheme turbine-pump cannot help me lift water at (2m3/s)more than some centimeters (<1m). It means, with the current set up, I can increase the head of the 2m/s scheme only by a few centimeters (i.e, head=3.xx m). The other option I left is to go deep up to 6 m but then think of all the heavey construction work (tunnels, displacemnt of some existing installations and utility lines, .. with lots of messy stuff). Honestly, it doens't sound feasible but the client want to see the turbine installed through some technical solution. So, am wondering and wondering and wondering what kind of technical solution to bring to my client.... I hope you got it. True, a picture worth a thausand times of words..

 

[waross]

Gentlemen, I have used pumps called turbine pumps, but from some of the responses I am wondering if we are talking about a reaction turbine close coupled to a pump, or if there is a special arrangement of pump and turbine combined in one case that is able to divert some of its flow at a higher pressure than inlet pressure?
Have I misunderstood or am I about to learn something new?
Thanks

 

[Warpspeed]

It is difficult to visualise the complex topography of your project without the aid of a map or a photograph.

But you mention that an expensive tunnel on the outlet side may be a solution.

Rather than tunnel through obstructing high ground, would it be possible to go over the top with a siphon ?

A small volume turbine pump could then be used to fill the pipe and displace the air up to the high point. A natural siphon would then begin, resulting in a massive flow increase for free, and away it would go all by itself.

The required drive turbine and pump could be fairly small, and overall efficiency would not be an issue, it would only need to generate the necessary very high head pressure to fill the ascending pipe and get the siphon started.

 

[Warpspeed]

A much less violent way to start the siphon might be to first slowly fill the ascending pipe, that was sealed against draining back, by a submerged swinging check valve at the intake.

The discharge end could be sealed off with a large gate valve. Once water reached the high point, it would then begin to fill the descending pipe. An open air vent at the highest point allowing all the air to be purged.

When the entire pipe is completely filled, close the air vent. If the gate valve at the discharge end is then slowly opened, flow can be allowed to very gently build up to any desired level. Flow could be automatically modulated to pump almost the entire river volume without pumping the suction intake dry.

The turbine machinery is only required to initially fill and start the system. It could be comparatively small in size, and should last forever because of the low usage.

 

[BRIS]

For low head low costs turbines the solution is a reverse flow pump but they have relatively low efficiency. I still don't understand the objective of increasing the drop in the 2m3/sec stream if you then have to pump it back up into the tail race. This must be less efficient than generating power from the available head and flow of the two streams.
For such schemes the most feasible solution will be achieved with minimum capital costs which will preclude solutions using tunnels and siphons. Your most cost effective solution would likely to be to provide turbines on the two falls with minimum civil works. I suggest however that a basic cost estimate comparison of capital and o&M costs against the value of producing +/- 30kwhr will demonstrate the project not to be feasible. It doesn't sound feasible to me.

 

[Artisi]

I think you need to explain a little clearer what you are trying to do and what the installation will look like. 2m3/sec at low head is not a problem - many of the larger pump companies could do this with axial flow or mixed flow vertical pumps.also check round the pump companies that are involved in flood irrigation etc.

can you put a sketch / drawing onto a website somewhere so we can look at it.


Naresuan University
Phitsanulok
Thailand

 

[nilsadams]

I thank you all again.

I will be glad to show a sketch but don't know how where to present it.

Ok, let me try a bit with some thing visual. Look at the following points. Join ACDE. Then Join AD. AC is with 2m3/s, 3m scheme. BD is 0.9m3/s, 6m scheme. DE is combined drainage to a river which is about 4 meters below D. On top of DE, there are several constraints : roads, pipelines, other electro mechanical installations serving the industrial site. Between D and E, there is also property line limitation. It means I cannot install F beyand some boundary.

I plan a turbine at C. But I still have a head of more than 3 m between C and E. So, I want to lower C to F to get a total head of 6 meters. But if I go to discharge through FE, I will be forced to use a tunnel. To avoid the tunnel works, I had taken the option of using BD as a hydropower source to install a turbine (or turbine pump ?) at D in order to lift the discharge from F to D and then use the existing drainage pipe DE.

It sounds that using BD doesn't seem sufficient to lift the 2m3/s discharge from F to D. So, I am now thinking either to connect FE with a tunnel or I don't know if a siphon option can work with this confugration without losing some head.

*B

*A
\
\
\
\*C *D




*F
*E (River)

 

[nilsadams]

I mean "Join BD"

 

[BRIS]

Ok got it.

There is little point in your original proposal of using the head B to D to pump back from F to D. Even if there was sufficient energy, which there is not, it would be more effecient to use a turbine generator on each fall.

Why do you not simply pipe from A to C to E and from B to D to E and place your turbines at E ?.

Using a siphon on the downstream side of the turbine(s) is possible but it is simpler to locate the turbines at the lowest point (E).

Are A to C, B to D, C to D and D to E all pressure pipes?