Re: Any 24x7 Natural Gas Generator?

[m II]

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



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"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?

 

[Neon John]

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.

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.

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.

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

 

[m II]

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.

 

[[email protected]]

...
* 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
...
John

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.

 

[Guest]

wrote in message

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.

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

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

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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.

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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.