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Re: Any 24x7 Natural Gas Generator?

Discussion in 'Home Power and Microgeneration' started by m II, Aug 7, 2011.

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  1. m II

    m II Guest

    Why?
    The grid will always be cheaper and more reliable.



    --------------
    "W" wrote in message Are there any natural gas generators that are designed to run 24x7 for
    generating electrical for a small home? Most smaller generators I have
    seen are "standby" units.

    What should you expect to spend to buy such a unit? What is a typical
    annual maintenance cost?
     
  2. Neon John

    Neon John Guest

    My business partner who lives in San Diego has the same problem. Tier
    III rate is >25/kWh (can't recall the exact figure). We've been
    working on the same approach to a solution.
    Here are the problems.

    * Continuous duty generators that run on NG/propane in the 10kW range
    just don't seem to exist, at least not on the new market. The basic
    problem is that once the engine is ruggedized enough for continuous
    duty, it's so expensive that it can be uprated to make 20-30kW for
    almost no additional money. The few units I've found are invariably
    diesel powered.*

    * A generator synchronized to the grid MUST have
    anti-islanding/anti-backfeed protection. I've yet to find a unit
    designed for small single phase installations. Grid-intertie solar
    inverters come the closest but they require DC input and are very
    expensive per kW

    * Especially if you have an electronic meter, you will require a net
    metering setup. Your utility will require all UL-listed components
    before they will connect the outfeed to their grid. They may require
    a PE's stamp on the plans. I've run into that before.

    * There is one exception but it'll take some digging to find. That
    exception is a military surplus gasoline-fueled generator. The reason
    they're had to find is that several years ago the military unified all
    their piston engines to run on one fuel - diesel. Or jet fuel in a
    pinch.

    You have to be fairly particular about what vintage you buy. Up into
    the 60s the Army's trailer mounted 10kW machine used a side valve
    engine that was a terrible gas hog. Our ham club was given one but we
    couldn't afford to feed it.

    Later model units went to Jeep derived overhead valve engines that are
    fairly fuel efficient. If the gasoline fuel system is removed, a
    natural gas carburetor substituted, the head milled for optimum
    compression and more spark advance is dialed in (NG is a fairly high
    octane fuel) then it will have pretty decent efficiency.

    Even if you do find a mil surplus generator, the remainder of the
    above problems remain, particularly the anti-backfeed problem.

    There is another solution that he's looking into now. Do whatever is
    necessary, such as designating part of the house as a "mother-in-law
    apartment" to qualify for a second service entrance. Wire the MIL
    apartment to the second service, get it inspected and then rewire
    things to split the load evenly across the two services. This would
    prevent him from ever hitting the Tier III rate on either meter.

    John
     
  3. m II

    m II Guest

    To shave peak rate times there may be a profit in it but then that would
    involve 24x7 usage.

    Large units I have seen have not proven economical for commercial
    co-generation and have been abandoned in the past. OTOH: Some 1MW units
    that were installed for the purpose of creating steam have been quite
    profitable when the electrical outputs have been only a side effect. These
    were times when the 10 cent kWh (all taxes in) was common.

    Home Depot sells NG backup generators that island. The guy next door runs
    one and it is pretty quiet. I think it runs about 15kW. Self tests each
    month right off my deck (150') and unless I am outside I wouldn't know it is
    running.

    Rates are changing constantly and so are the economical balances created by
    any alternative scheme.

    -----------------------

    "W" wrote in message Over a baseline utilization level, electrical use on the grid in our area
    costs around 30 cents per kWh. With natural gas at all time lows and
    likely to stay depressed for many years because of shale gas discoveries, I
    thought it would be worth seeing if a natural gas generator could supplement
    grid to keep electrical usage from the grid under the baseline....
    For just the component of usage that is 30 cents per kWh, I wanted to see if
    a small NG generator could be operated at around 10 cents per kWh.
    The problem as I see it is that probably 24x7 NG generators are focused on
    higher end markets, typically small industrial production areas rather than
    home or small office level installation. But if the products exist for
    smaller applications and can run reliably, I would certainly want to run the
    numbers.
     
  4. Guest

    Just as a wild thought, if a suitable engine could be found, powering
    one of those inverters with a Faraday unipolar generator and possibly
    a small battery bank for overnight low loads could be a solution. The
    big problem is that you would have to make the generator from scratch.

    The close tolerances, relatively high speed, and high magnetic fields
    make it out of reach for most tinkerers. I have no idea of
    efficiency, even if you were able to construct it. On one hand, there
    could be hysteresis losses, on the other it is reputed to have great
    ability to handle changing and large loads with ease.

    I'm a little curious why popularity dropped in the 1920s and further
    use and development was relegated to high energy physics research.
     
  5. Guest

    Guest Guest

    wrote in message
    -------------------------------------

    I am on mains power and this below is part of my standby set up. The other
    stuff is a petrol 4.8 KW generator (single phase) and a 28 Kw diesel
    generator (Three phase). I have these as I am in a cyclone prone area, and
    we have been hit with severe cyclone twice in the last 6 years. We lost
    power for 24 hours in one cyclone and 4 days on the other, nearer the centre
    of the cyclone some were without power for around a month.

    With my set up the problem would be that running the diesel 24 hours a day
    would be very costly as it chews up around 73 litres ln 24 hours.

    Diesel currently coast $AUS 1.56 per litre here

    US gallons are around 4 litres to the gallon
    UK Gallons around 4.5 litres to the gallon

    -----------

    Battery/Inverter

    Deep cycle battery life would have to be factored into it.

    I have 4 x 6 volt Trojan T105 deep cycle batteries (24 volt), here in
    Australia they cost over 800.00 for the four. The first bank lasted around 4
    years and I am now on the second bank purchased after the first bank failed,
    they are now around 4 years old.

    I have a better set of charging parameters on this set. They hardly ever get
    used. I have set them up to go on charge every night for an hour. Currently
    the standing voltage is 25.7 volts. The way the first set were charged I
    think tended to reduce their life.

    The capacity is around 225 ampere hours at a 20 amp discharge rate. They say
    you can get 750 cycles out if them.

    IE discharge them to 50% and that us around 2 years life if they are used
    every day.

    Now I have a 2 door fridge freezer and if I run that on my battery/inverter
    set up it will run out of battery power over night. (Limiting the battery
    discharge to 50%)

    The fridge freezer draws about 2 amps at 240 volts, IE around 500 watts, now
    working at 100% efficiency which it does not, that means around 20 amps 24
    volts DC to drive the inverter. As we are only suppose to draw 50% out of
    the batteries that means under 6 hours running time with only my
    fridge/freezer running.

    Actually the inverter runs around 90% efficiency, which means it would drew
    more power from the batteries.

    If you discharge the batteries down to more than 50% then they have lesser
    life time.

    ------------------------------------------

    As for generators, in general terms they last longer if you choose a 4 pole
    genny rather than a 2 pole genny.

    2 pole 60 cycles runs at 3600 RPM
    2 pole 50 cycle runs at 3000 RPM

    4 pole 60 cycles runs at 1800 RPM
    4 pole 50 cycle runs at 1500 RPM

    US uses 60 cycle power

    Australia, New Zealand, England, Europe etc. use 50 cycle power .

    The cycles (Frequency) is controlled by the speed of the generator.

    It seems running the motor faster lowers its life.
     
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