Value of true-sine generator?

bentherebenthere Posts: 109Solar Expert ✭✭
I've gathered that true-sine inverters are better for efficiency, reliability of appliances, and ability to run all kinds of appliances.

Fair enough. No argument here. I'm going true sine.

Interestingly, I've not seen this argument as it applies to generators. It seems to me that the same arguments would apply.

So, is the power from a generator, while used for battery charging, somehow conditioned by the PV system inverter or how does that work?

Are the Honda inverter-series generators better than standard generators for more than the ability to vary the RPMs according to load?

Thanks!

Comments

  • EcnerwalEcnerwal Posts: 101Solar Expert ✭✭✭✭
    Re: Value of true-sine generator?

    Standard generators make a pure sine wave, the old fashioned way (by spinning wires in a magnetic field produced by other wires, generally). In that sense, they are actually better (or purer) than inverter generators. Where inverter generators are good is by being able to vary speed to match load, while a standard generator must maintain constant speed to keep output frequency stable. Particularly with gasoline powered units, this makes a big difference in fuel consumption at partial load, and noise level.
  • BB.BB. Posts: 27,550Super Moderators admin
    Re: Value of true-sine generator?
    benthere wrote: »
    I've gathered that true-sine inverters are better for efficiency, reliability of appliances, and ability to run all kinds of appliances.

    Fair enough. No argument here. I'm going true sine.

    True enough--the "cheap" way to make inverters is to make a simple On/Off switch--and the result is pretty much a "square wave" which can cause damage/issues with some devices (the old 80/20 or 90/10 rule--80-90% will work OK, 10-20% will have some sort of problem).
    Interestingly, I've not seen this argument as it applies to generators. It seems to me that the same arguments would apply.
    A decent/properly sized generator will generate, pretty much, a true sine wave.

    The problem with a generator, it it is pretty difficult to get the frequency within 5-10% on smaller units. Again, many devices will not have a problem, some will.
    So, is the power from a generator, while used for battery charging, somehow conditioned by the PV system inverter or how does that work?

    Gets a little more complex here... The most fuel efficient is to have an inverter with a transfer switch--that can either run AC utility power, AC Generator Power, or Inverter Power. No losses with piping the generator AC through the inverter to the protected load--and many inverters include an internal battery charger--and will suck a little power on the side from the generator to recharge the battery bank.

    Or, you can power the battery bank directly with the generator (DC output or AC to DC battery charger power conversion). You now have extra losses (dc charger to battery and battery to ac inverter). Nothing wrong with this method--and can give you very clean AC power (continuous conversion AC to DC to AC is used by many for computer backup, no power glitches when the AC mains fail and the Inverter turns on).
    Are the Honda inverter-series generators better than standard generators for more than the ability to vary the RPMs according to load?
    The little Honda euX000i family uses the inverter to support rock solid frequency and to support power sharing (can plug two generators to power one larger load).

    And, with the inverter, they can throttle back the generator to power smaller loads with the engine spinning slower (and wasting less fuel).

    Many of the $299.99 5kW noise makers will have the same kWhr/gallon of fuel at full load (or even slightly better than the euX000i family). However, these generator frequently reach minimum fuel flow around 50% output (any further reduction in output does not use any less fuel). The eu2000i for example, will reduce fuel flow down to ~25% load (or even a bit less?).

    For many people, they only need the high power to run the occasional heavy load. And many loads in an emergency are just a fridge, a few lights and a TV/radio. So keeping the average loads low--results in fuel savings (gallons per hour) with the inverter generators.

    One drawback is that when running with "Eco Throttle" ON, the generator may have problems starting heavy motors (like a small window A/C system)--so you may have to turn eco throttle off to get these larger loads started (and use more fuel vs the eco mode on--you may be able to turn eco throttle on when you get the load started).

    In any case, using as small as genset as you can and matching its loads in an emergency can get you down to a couple gallons a day--vs the 4-10 gallons a larger/non-inverter genset costs you.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • bentherebenthere Posts: 109Solar Expert ✭✭
    Re: Value of true-sine generator?

    That makes things clearer.

    Thanks!
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