running generators/ alternators in series

loteklotek Solar Expert Posts: 65 ✭✭✭✭
Is it possible to run the power generated by a generator (wind, water, what ever) through several alternator, wired in series and powered in the same manner? Would this double the output with every additional alternator? It’s my understanding that an alternator doesn’t created electricity but doubles what is introduced to it.
Having only laymen’s knowledge of generators and alternators, I’m wondering if this would work, or what would result? Could generators be run in series? Would the resulting power production be any different than with all parallel wiring?

Comments

  • Solar GuppySolar Guppy Solar Expert Posts: 1,962 ✭✭✭
    Re: running generators/ altornators in series

    http://en.wikipedia.org/wiki/Perpetual_motion
  • GreenerPowerGreenerPower Solar Expert Posts: 264 ✭✭✭✭✭✭
    Re: running generators/ altornators in series

    Iotek,
    The short answer is NO. We can not have more engery out (electricity) than what's being put in (wind, hydro energy). And you can not parallel or series generators or series alternators. There are complications electrically.
    GP
  • BB.BB. Super Moderators, Administrators Posts: 30,051 admin
    Re: running generators/ altornators in series

    And, typical, mechanical to electrical conversion for a car type alternator is around 50% (losses inside alternator, V-Belt losses, etc.)...

    So, the power does not double, but about 1/2 is lost in the conversion process (i.e., to generate 1 HP of electricity takes about 2 HP from the car's motor).

    Adding batteries in Parallel or Series does not matter regarding power. From the equation:

    Power = Voltage * Current

    If you add two batteries in series (like in a 2 cell flashlight), the voltage doubles and the current remains the same.

    If you add the same to batteries in parallel, the voltage remains the same, but the current is doubled.

    So, in both cases, the Power of two batteries added together is 2x the power if the individual cell--regardless if which way it is done.

    When we make our solar arrays--we are taking solar panels that have a bunch of 1/2 volt solar cells in series to get a "useful" voltage (typically around 12-40 volts or so--depending on the number of cells in parallel)--then we connect each panel in parallel or series (or even series / parallel) to the whole array depending on the needs of the Solar Charge Controller or Grid Tied Inverter.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • loteklotek Solar Expert Posts: 65 ✭✭✭✭
    Re: running generators/ altornators in series

    perhaps I framed my question wrong, Im not trying to get more energy out than I put in.
    Im wondering if I can use a wind generators DC power, and run it to a wind powered alternator. As an alternators dosn't make power from scratch, it would need a source to multiply . IE: 20w DC to an AC alternator ( or 2 or more alternators) that is driven by the wind would produce x amount of power, hopefully AC power that is easier to run long distance without the current drop of DC. OR... am I beating my head against a wall trying to save money on wire.
  • FL SUNFL SUN Solar Expert Posts: 94 ✭✭✭✭
    Re: running generators/ altornators in series

    lotek,

    Trying to understand your question.

    Are you asking if you could take numerous wind generators with an output of 35 vdc, and string the dc (2 wire) outputs together like you string PV panels together and get higher voltage? Say 10 wind gennies together and get 350 vdc for a grid tie inverter? I actually want to know this myself as I've wondered if this would work.

    Or are you asking about the 3 phase AC output of a PMA type alternator (like a Windblue unit), and rectifying the 3 phase AC into 2 conductor DC far from your generator next to the batteries? This is a better solution because the same energy is traveling across 3 wires instead of 2.

    Or are you hung up on dc current and ac current losses being different for long runs? I believe the same rules apply for AC and DC voltage drop through like current carrying conductors. Amps is amps and wire is wire.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: running generators/ altornators in series

    I think I understand what lotek means (correct me if I'm wrong):

    You start with a low voltage generator which turns easily in a light wind but does not produce much power.
    The output from that is used to excite the rotor in an alternator, turning in the same wind. Its output would be higher voltage, which is then fed to the next alternator and so on. The idea being to increase the voltage at each succeeding alternator all being turned by the same relatively low speed wind.

    Right?

    Won't work.
    As the voltage goes up, so does the strength of the electromagnetic field, requiring greater mechanical power to spin each consecutive alternator. The 'higher up the string' you go, the more wind would be required to turn the alternator. Even with the electrical losses and all, one of the alternators might get enough field strength to lock up, and the ones beyond that would simply freewheel (for having no voltage to excite their rotors).

    Or I've completely mis-understood the question. :blush:
  • mike95490mike95490 Solar Expert Posts: 8,612 ✭✭✭✭✭
    Re: running generators/ altornators in series

    Someone has given you wrong information in that "It’s my understanding that an alternator doesn’t created electricity but doubles what is introduced to it."
    Wrong

    Alternators create Alternating current (AC) Generators create Direct Current (DC)
    The mechanical motion of a magnetic field across a wire, generates power.

    Placing 2 in series, just adds more bearing losses and sync problems.

    What do you have on hand, and what are you trying to do? We can help.

    (keep the receipts for the stuff you already bought, you may want to return it)

    Here's a construction page of a "alternator" made of a disc of coils, and 2 disc's of magnets that spin around it, like a Oreo cookie
    http://www.forcefieldmagnets.com/catalog/product_info.php?cPath=22_30&products_id=188&osCsid=bgprlrue1toi0qt2um1h1d69b6
    it's a sales page, but you can see the basic idea, wire & magnets. Just move one relative to the other.
    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 ,

  • loteklotek Solar Expert Posts: 65 ✭✭✭✭
    Re: running generators/ altornators in series

    I think Coot was closest in his description of my desires. ” You start with a low voltage generator which turns easily in a light wind but does not produce much power.
    The output from that is used to excite the rotor in an alternator, turning in the same wind. Its output would be higher voltage…”
    I was trying to figure a way to run AC power through the electrical lines though, I may be wrong (often) but I believe DC creates much more heat as it runs through wires and so requires larger gauge’s to run the same amps???
    And if Im reading Mike correctly , his thoughts revolve around energy losses do to friction in multiple units.
    Now.. I have nothing in the works, except my mind ( working overtime) I have seen , on Ebay DC permanent mag electric bike motors in 24,36, and 48 volt models. I was considering using several on them to make 5 rooftop vertical axis windmills out of 5” pvc pipe cut in half and put together like an S . I live in what is typically a low wind area 3/5 mph average. But that’s because of the calm days with lots of sun. I see many stormy days with winds in excess of 10. During tropical storms Make that a lot higher.
    Sun will be primary power supply but it would be nice to have some recharge ability during those stormy days.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: running generators/ altornators in series

    If you're doing this as an experiment/learning experience, go ahead. But don't expect serious power; small-scale wind is notoriously inefficient because there really isn't that much mechanical power in the wind. The losses incurred in converting it to electrical power are significant. So on a large scale losing "X%" in conversion leaves you with lots of power. On a small scale you end up with milliwatts, as it were.

    But skip the "generator feeding generator" idea. If you have several turbines producing low current at a similar voltage you can increase the current by paralleling them on the DC side.

    Couple of other notes: AC transmission has less loss than DC for the same voltage/distance/wire size. Technically, generators (as in old automotive type) also produce AC: it is 'rectified' by the positioning of the brushes on the commutator. In a generator, the field is excited by a low-level current and the power is produced in the spinning armature. Lots of sparks, wear, and inefficiencies in the brushes/commutator. In an alternator, the armature, aka rotor, is excited through slip rings (fewer problems than the generator set-up) and the power is produced in the field windings and then converted to DC by solid-state rectifiers. Auto-type alternators actually produce 3-phase current internally. Some people have replaced the rotor windings with permanent magnets, taken out the rectifiers, and sent relatively high voltage AC 3-phase along the wires to the point of use, then rectified it to DC for charging batteries.

    Just some thoughts for you to consider. It can be fun building your own wind turbine, and in the end is probably a better deal than buying some of the over-hyped absolute junk sold by certain commercial outfits.

    You might want to check out the DIY windpower guys at Otherpower: http://otherpower.com/
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