How Do I Modify Deep Well Submersible Pump to Operate as Turbine

Whoa!

First, obtain the relevant consents to inject water into deep level reservoirs. It may affect water abstraction for drinking purposes across the region!

Yes, I know that, frst conditio is to inject only clean water...but I have problem whith electrical part, I want to know is it possible from electomechanical point of view! What you think?

If the consent isn't there, the rest is academic.

In my country (Montenegro - South East Europe) we have special procedure for consent, but before consent we must done Preliminary Design and other documentation. In order to create Preliminary Design, I must know how to execute main problems.

Ok, we can theoretically discuss about this topic! Are You electrical engineering?

Look - there is no point in abstracting water from one well and then injecting it into another just to make electricity. It just isn't done; there isn't a need. It's easier to stick a waterwheel in a river and use that if all that is wanted is a source of cheap power!

That part is not problem, but my problem is how to modify pump to work as turbine. You are right, sometimes is very hard to find appropriate location for this kind of "mini mini power plants", but is possible in special hydrogeological conditions.

So what about the local aquifers?

The water pump or wet end part on that submersible pump cannot work in reverse as turbine , you will have to design a new unit all together.

A worthwhile assignment for a university project.

JS

This project sounds interesting, but as PWS said you need to first check on the abstraction and discharge points. You don't give your location so I can only say that in the UK if you abstract water from a watercourse you have to pay the water authorities a fee, even if you return the water to the same course at a lower point.

As to keying the shaft that is dependant on the pump used you will have to contact the manufacturer. To be honest the pumps you suggest would be so inefficient as to make this a waste of time, yes a pump will run in reverse but I'll leave it to others to explain.

Yes, we also need concession and other permissions for water use or injection. Now I am at least easier when I know that this is possible, and I hope somebody will give me a detailed explanation. Thanks!

Please describe the type of motor.

I am sanding the characteristics of 6'' pump (detailed in the catalog http://www.pedrollo.co.uk/water-pumps/borehole-water-pumps/6-inch-borehole-water-pump.html):

Flow rate up to 330 L/min (19.8 m³/hr)
Dynamic head up to 390 m

This new series of submersible pumps is fitted with a patented anti-seize system (ensuring pump operation, even after being left idle for long periods),and a water filled motor with removeable cable connector.

OPERATING LIMITS

Maximum fluid temperature + 35°C
Maximum sand content: 100g/m3
Maximum Depth 100m
Starts: max. 20/hr

PEDROLLO borehole pumps feature a patented design giving them a high tolerance of entrained sand.

PUMP INSTALLATION AND APPLICATIONS

These pumps are suitable for pumping water with a sand content of up to 100g/m3. Their high performance and dependability make them suitable for use in civil, agricultural and industrial fields, for the automatic distribution of water, for irrigation, washing and pressure-boosting systems, and for fire-fighting purposes etc.

6SR pumps can be installed in wells with a diameter of no less than 6" (100m max immersion depth). The pump is lowered into the well by means of the delivery pipe until it is completely immersed. (min 50cm) and at least one metre from the bottom of the well. Care should be taken to ensure that the pump remains submerged as pump operation may cause the level of the water in the well to fall. The pump can be installed either vertically or horizontally. When installed vertically it is advisable to secure the pump by using a stainless steel or nylon cable connected to the special holes provided on the discharge head.

PERFORMANCE

6SR pumps combine the advantages of a submersible pump with the performance of a centrifugal pump.
As submersible pumps, they assure reliable operation even with considerable water depth.
As multistage pumps they assure high flows, high heads, stable performance curves.

Curve tolerance according to ISO 2548

STRUCTURAL CHARACTERISTICS

• UNI ISO 228/1 gas thread DISCHARGE HEAD in brass (up to 2.2kW discharge head, check valve and motor bracket in AISI 304 stainless steel).
• Techno-polymer, high resistance CHECK VALVE enables the weight of the column of water to be dispersed without stress to the impellers and diffusers, thus ensuring long pump life.
• Lexan General Electric technopolymer IMPELLERS.
• Noryl GFN2v technopolymer DIFFUSERS
• AISI 304 stainless steel BOWL.
• AISI 304 stainless steel EXTERNAL SLEEVE.
• AISI 304 stainless steel PUMP SHAFT
• Brass MOTOR BRACKET built to NEMA dimensional standards.
• AISI 316L sintered stainless steel TRANSMISSION COUPLING
• AISI 304 stainless steel BOLTS
• AISI 304 stainless steel FILTER
• AISI 304 stainless steel CABLE GUARD
• 6" SUBMERSIBLE MOTORS: water filled motor with removeable cable connector.
• PROTECTION IP 68 for Pedrollo motor
• FE4DM/T submersible SUPPLY CABLE. Supplied standard with 1.5m of cable (4" motors).4m of cable (6"motors)
• CONSTRUCTION AND SAFETY STANDARDS in compliance with EN 60034-1 (IEC 34-1, CEI 2-3).

Not the pump. The motor.

It's already looking as though the pump, as an asset, is too valuable to be butchered for use as a home-brew power generator at this stage.

MOTOR: Pedrollo 6" submerged electric motor(from 4 to 30 kW)
6SR: three-phase380¡Â415 V - 50 Hz.

OK. If the motor is to be used as a generator, how is a magnetic field to be provided in the stator windings?

I am not expert for electromechanics but I found that motor can be modified to generator by adding excitation capacitors to the motor leads to allow it to operate in reverse direction (Gregory M., 2007).

That would be the solution then. It doesn't solve the aquifer injection issue, which remains outstanding at this reader's unsubscribe point.

<unsubscribes>

Water injection in well is not problem, we can abstract water in low price tariff, store water in reservoir, and inject in high price tariff. Also, water from reservoir we can use for irrigation etc.

Could you detailed explain me how to add excitation capacitor to motor lead and how to know which type of capacitor is appropriate?

MR, I understand that tariff for irrigation by pumps is low for the farmers in your country and many other countries. You are thinking of generating power and selling at higher tariff may be for industrial or other applications. Firstly it may not be legal. If it is legal then I suggest you should buy turbine and alternator for generating power instead of using pump for multi purpose. Firstly pump is pump not a turbine also motor is motor not a alternator. There are basic design limitations.

Could you suggest me type and characteristic of turbine and alternator for well or borehole? I want to inject water from ground to the deep of 30m in well, and I can inject about 50 l/s.

Sorry, I am not able to understand your project. Firstly you want to use pump to lift water and store in reservoir at ground level. Again you want to pump back the water in the 30 m well. It will be better if you can explain in details your purpose of pumping out water and re injecting in the well. Water will go in the well on its own due to gravity if there is space in the well, in process you can generate power. If it is the same well then you can install turbine and alternator in parallel to pump but you have to install valve to close turbine when pump is in use and another valve to close the pump when turbine is in use.

Regarding selection of turbine and alternator better to contact local dealer who will give you proper suggestion. You will have to provide him necessary information such as size of pipe, water pressure, volume etc. For alternator you will have to inform him about voltage and frequency, out puts required by you.

Is it possible to install only turbine in well. That is the best solution but I never hear for that product. I am trying to modify pump, because its diameter is appropriate (4'' - 10'') for well installation. How to insatall submersible turbine, I think it is too wide for wells? If you know anything, please sand me link or catalog. Thanks!

I think it's a non-starter for basic reasons. The pump appears to be a typical radial-flow centrifugal. If this is driven backwards, it will not pump in reverse, it will still give flow in same direction, but the performance curve is much reduced. Nor will it rotate backwards if water goes through it in reverse direction.

An axial-flow pump will pump backwards (though usually at lower efficiency). Impeller is similar to a ship's propellor which reverses thrust on reverse rotation. It can in principle be used as a turbine. But axial-flow pumps are high-flow, low head. You don't say how many stages your pump has but to give 390m head it isn't going to be axial flow.

Codey

Yor comment is very usefuol for me...Pedrollo prodact both semi-axial and radial pumps. Please, see that catalog http://www.pedrollo.co.uk/water-pumps/borehole-water-pumps/6-inch-borehole-water-pump.html) and tell me is it semi-axial 6" pump appropriate. Thanks in advance!

Had a look at that and there is a ref to semi-axial impellers (as well as radial). But the type nos are confusing and I can't tell which impeller is in your pump. If it works at all in reverse flow or rotation, I think the efficiency would be poor. Why not ask the manufacturer? Please tell us what he says. If you do want to run it in reverse flow, you need to remove the non-return valve.

Codey

Ok, I will ask manufacturer, and I will advice you.

Just spotted one thing in the pump specification. The filter will have to be removed and some form of filtration fitted to the abstraction point. Otherwise the pump will retain any detritus in the pump body.

Yes, that is useful comment! Could you also explain me how to add exciting capacitor to motor lead and which characteristics of capacitor are optimal?

Dear Mr, I complement you on your patience.
If no one on this site can help you, there are other sites that may be able to help you.

Good Luck
Carl Pugh

Dear Carl Pugh, Could you propose me some anather site? Best regards, MR

I am out of my league on this subject, but would it not be simpler to get out the check book and buy what you need instead of all the hassle you are describing?

How to buy whan submerceble well turbines are not in manufactores? I heve to buy classic submerceble pump and modify it.

I'm a little surprised reading through this entire thread that nobody has simply linked to this Wikipedia site. It explains everything about calculating the capacitors for an induction motor to be converted to a generator with a fixed load. Now a residual magnetic field must exist in the rotor for an initial excitation, but almost always the residual hysteresis from the motor being driven once will be enough for the dragon to start chasing its tail.

Now having said this I don't like the premise of putting a well pump at the bottom of a well so that water can be pumped into a well to obtain power. The underground region will accept water at only some maximum water flow going up or down depending on the density and fracture structure of the surrounding earth. Additionally there's the complaints that several people here have mentioned that most centrifugal pumps are designed for efficient fluid flow in only one direction regardless of the pump adding power to the fluid flow or extracting power from the fluid flow.

What you appear to be proposing is not a very a complete, well thought through concept. You have your immediate question answer at the link. However, I believe your idea is doomed to failure.

For other sources of information on motors used as generators you could Google "Electrical Engineering Forum". A couple of other popular forums are
http://www.physicsforums.com/forumdisplay.php?f=102
http://www.eng-tips.com/threadminder.cfm?pid=238

Thanks!

I am not sure about what you are doing really. Submersible pump usually is multistage centrifugal type. I can not somehow realized by reversing the flow, you can have the medium driving the motor shaft.

But, it is possible somehow for the motor to drive motion as a driver and induct electrcity as it is driven by motion.

That technology is already on the market. Elevators such as OTIS Gen2 Regen use this type of set-up, where there motor is a permanent magnet type and uses IGBT rather than BJT diodes.

Ok, I have found something but I want to hear what you (everybody) mean. I am thinking about variance, If I need only turbine, is it better for me to search for submersible turbine or to try to modify pump. Below is a quote from the thesis (Gregory M., 2007) where he explaining well pump/turbine system:

"2.3 System Components

2.3.1 Water Pump-Turbine Motor-Generator

The core of the aquifer UPHS system is an integrated pumpturbine/
motor-generator unit. As the name suggests, this single unit
performs the functions of both pumping water using electrical power
and generating electricity from water power. This type of integrated
machine exists commercially for large pumped hydroelectric
installations, normally employing a Francis reaction type turbine
coupled to a synchronous AC electric machine. A unit sized and
designed for the proposed aquifer UPHS application is not
commercially available. In this section, the important design
considerations for the integrated pump-turbine/motor-generator unit for use in the aquifer UPHS system are described.

2.3.1.1 Pump-Turbines

Reaction type turbines, such as Kaplan or Francis designs, are
capable of accomplishing both pumping and turbine functions at
efficiencies that increase with the unit's size. Kaplan or propeller
style turbines are used in low head, high flow applications, while
Francis turbines and "pump-as-turbine" designs are applied in high
head, high flow situations. Typical efficiencies for very large
Francis turbines can approach 95% [2]. For smaller sized units,
lower efficiencies in the range of 70% to 90%, depending on head,
flow and specific speed, can be expected. In standard Francis
turbine designs, the water enters or leaves a scroll-shaped vane
housing that is at a right angle to the rotation of the drive shaft.
This characteristic may pose a design challenge in installing such a
unit in a vertical shaft well.

Another option for the design of the aquifer UPHS pump-turbine is the use of standard centrifugal or "vertical turbine" well pump
in the forward direction for pumping and in reverse for turbine
operation [2]. Example images of these types of pumps are shown in
Figure 2-6. This use of the pump is referred to as a pump-as-turbine
(PAT) design. A first order estimation of the turbine efficiency of
a centrifugal pump is that it is the same as the pump efficiency
[3]. Although originally designed as a pump, a centrifugal pump may
be capable of operating in reverse as a turbine at efficiencies in
the range of 65% [4] to perhaps 85%. This method is proposed as a
preferred option for the aquifer UPHS situation because it uses
existing technology, is commercially available, and would be a low
cost solution. Because of the difficulty in predicting turbine
performance of a given centrifugal pump [3], testing is required to
characterize the flow capability, water velocity range, and turbine
efficiency. The selected centrifugal pump design will need to employ
a keyed shaft to accommodate shaft torque in either direction.
Centrifugal motor pumps are a common item used for pumping
water in many situations. They are available in submerged or non23
submerged designs. There are a wide range of available head ratings,
flow ratings, and power ratings for commercial motor pumps. These
units are commonly centrifugal or vertical turbine pump designs,
integrated with an AC induction motor. The industry standard
estimation of pump efficiency is 55%, however, with proper system
design, a centrifugal pump could run as high as 85% efficient. The
efficiency for either the pumping cycle or the turbine cycle can be
optimized, but not both simultaneously. In the case of aquifer UPHS,
the turbine efficiency must be optimized. The very rough range of
attainable turbine efficiency used in this paper is 70% to 85%, and
pump efficiency range of 65% to 80%. These numbers are estimates
adopted from research on modern PAT pumps, centrifugal pumps, and
turbines. Unfortunately no concrete data on the pumping and turbine
efficiency of a PAT unit was uncovered.

2.3.1.2 Motor-Generators

Motor-generator units that operate with relatively high
efficiency are a mature and available technology. As with pumpturbines,
the efficiency increases with size and rating. Some large
motor-generators can operate at greater than 96% efficiency. For the
application in question, efficiencies between 90% and 95% can be expected. Well motor-pumps commonly employ an AC induction motor or a
synchronous wound-rotor AC motor for larger machines. Although
commercial designs assume the unit will be used as a motor only,
modifications can be made to produce efficient operation as a
generator also. In the case of a synchronous wound-rotor AC machine,
an interface to the machine's rotor windings that provides
excitation current during generating operation is needed. It is a
relatively simple modification to implement with or without the use
of power electronics. If power electronic control of the winding is
used, the frequency of the generator output can be regulated.
For AC induction machines, perhaps the most common and simple
modification involves connecting excitation capacitors to the three
phase leads of the machine [5]. These capacitors provide excitation
current which is 90 degrees out of phase with the primary generation
current waveform. This excitation current induces currents in the
rotor of the machine which allow it to operate as a generator.
Another possible modification technique involves the use of power
electronics to synthesize this excitation current. In this case, the
same electronics used to drive the machine as a motor are used to
control excitation of the machine. To implement this method, a more
complicated control loop is programmed into the machine controller software.

For the aquifer UPHS system, a centrifugal well pump with an
induction motor is recommended. This option represents the least
cost solution, however, efficiency during the generating cycle may
not be optimized. For the final system design, a full-sized unit
should be procured and tested to determine the actual performance
capabilities. Care must be taken to select a unit that will operate
with the required flow and range of attainable water velocities."

Definitely, I should say, if its designed as pump-turbine system(generally for reaction type-impeller design). It can do dual pump-turbine operation.

However, what I meant above is for residential or commercial application submersible pumps for deepwell water. I don't think, this idea works since definitely both differ in design.

And to think, i can not figure out your installation set-up. I bet if that happens water will just come down to the well right after not being used. This is seem to be impractical. Both pumping the water from the well to tank and generating electricity when it will be back again to the well incurred pump & generating losses. I better be putting the water at the tank rather than letting it flow again at the well.

You see my point?

I agree, reversing flow through a multistage pump will be quite inefficient, suspect the OP will be far better off using engineered solution for this rather than using something not intended for this duty.

I also have concerns about the forces within the motor and pump. The throust bearings are designed for forces in one direction, not the direct opposite. Also the multistage pump may run on water lubricated bearings (most multistage pumps are), without the forces and water pressures in the right zones, the bearings won't be lubricated and highly likely to see a bearing failure in the short term.