Small hydro system discussion

LucMan
LucMan Solar Expert Posts: 223 ✭✭✭
Recently I had the opportunity to visit a house that had a small hydro system to power 2 houses. The system consisted of a 3 phase 480v 1725 RPM centrifugal pump running in reverse to generate power ( water piped into the discharge of the pump). The owner is an electrical engineer and explained that he had a bank of capacitors connected to 1 leg of the 3 phase motor that was exciting the field. Now I remember learning 35 yrs ago that this changes the sine wave by shifting the phase but that's all I can remember.
Can someone refresh my memory on how this works?
Also any insight on sizing & wiring the capacitors ( formulas for capacitor selection) for different H.P. motors would be greatly appreciated.
How clean is the power generated with this alternator?
Does it also require filtering before final use?
Thanks

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Small hydro system discussion

    I am not sure that this makes sense to me...

    You can make a Grid Tied type system where the motor is driven by the water faster than it would normally turn--you would be "back driving" power to the grid--or, perhaps, sharing power with a local generator.

    If you wanted to start up the pump--and it was a three phase pump with only single phase available on site--then you could attach starting caps (through a switch/relay) to start the motor turning--and then open up the caps and allow it to pump (or back drive to the grid).

    I guess it could also be possible to use motor run caps to power the third leg--and not deal with the starting relay/switch (just a guess on my part).

    But, using a 480 VAC motor--those are usually pretty large. And what are your plans for a load?

    I have made 3 phase converters to power 3 phase mills and laths when only single phase 120/240 VAC is available. It does not generate ideal 3 phase power--but runs well enough that I have used a 5 hp "Y" wound 3,500 RPM motor to drive 5 HP laths off of 240 VAC single phase very nicely--both 3 phase induction motors and DC drive (I wired the electronics to pull their power from the one "Real 240 VAC" phase).

    But to wire something like this up for an off-grid Hydro installation... Not quite sure where this is heading. At best, this would work OK as a "Grid Tied" equivalent for a 1 or 3 phase grid connected powerhouse/home site (that I can see).

    Did the three phase motor have slip rings (synchronous motor running at 3,600 or 1,800 RPM)? You could excite the field in the rotating section and generate AC power through the stator (again to power AC grid tied, or through some sort of transformer/rectifier to a battery bank--sort of the equivalent to 1960's and earlier cars that used DC generators instead of alternators with field windings and regulators).

    -Bill :confused:
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • LucMan
    LucMan Solar Expert Posts: 223 ✭✭✭
    Re: Small hydro system discussion

    Did the three phase motor have slip rings (synchronous motor running at 3,600 or 1,800 RPM)? I don't know

    You could excite the field in the rotating section and generate AC power through the stator (again to power AC grid tied, or through some sort of transformer/rectifier to a battery bank--sort of the equivalent to 1960's and earlier cars that used DC generators instead of alternators with field windings and regulators).


    That is the system.

    This was not tied to the grid, the owner connected to the grid manually by turning off and on a large double pole double throw contactor, so he was either on hydro power or grid power. The hydro system supplied enough power for the 2 houses when the water flow from the stream was sufficient to spin pump motor. The owner constructed what looked to me like a eel wier that channeled the water to a catch basin with a 6" pipe at the bottom, this pipe then dropped about 250-300 ft down to a pump house where the pipe was connected to the discharge of the pump. All the water pressure and velocity spun the pump backwards generating power. The suction side of the pump was piped back to the stream at the bottom of the hill.
    I did see a transformer in the basement of the house so I'll assume that the power generated was 480v and then stepped down to 240v at the house.



    The reason i'm asking about this is I have some 3 phase motors laying around maybe one can be hooked to my wife's bicycle :roll: to generate some power!
    Basically I'd like to understand how this system generates power, and how to duplicate it. As this was not a commercial hydro generator but home made.

    The load could be a hot water heater element.

    Thanks
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Small hydro system discussion

    Here is a thread on a home made bicycle power system:

    generator bike system

    You are only going to get a 100 watts or so out of your wife--so don't try overdoing it with a large alternator/generator.

    If the hydro system was an older one (say out of the first half of the century)--then I would guess it was some sort of synchronous 1 or 3 phase alternator system with a frequency regulator and such (before my time).

    The effort required to build a system with a 300' head and all of the support equipment sounds a lot like the systems that where spread around the Sierras and such. I would not call them a typical home hydro system.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Small hydro system discussion

    Many (not all) induction motors, when driven, will generate power fairly efficiently.
    Article here: http://www.qsl.net/ns8o/Induction_Generator.html
    and
    http://web.archive.org/web/20071117164801/http://www.microhydropower.com/staffpubs/staff4.htm
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • LucMan
    LucMan Solar Expert Posts: 223 ✭✭✭
    Re: Small hydro system discussion

    Thanks guys that's exactly what I was looking for.
    Now I can start my project of building a wood gasification power generator.;)
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Small hydro system discussion

    The article on adding the caps to an induction motor makes sense... The caps allow an off-phase current to flow through the motor to support the rotating magnetic field and induction into the rotor (no current flow in the windings, no magnetic field, no induction in the rotor).

    Using the residual flux in the rotor to self-excite--if the rotor is demagnetized, "flashing" AC or DC current through the motor windings can magnetize the rotor enough to self excite.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset