Hybrid Car – More Fun with Less Gas

Any 24x7 Natural Gas Generator? - Page 5

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Posted by John Gilmer on August 9, 2011, 2:40 pm
On 8/6/2011 11:30 PM, W wrote:

THE problem with small power plants is that when run 24/7 they wear
themselves out in a year.   (The "life" before major tear
down/rebuilding maintenance is on the order of 6 to 8k hours.  The oil
might have to be changed once a week which is another problem.   Often
the schedule for small engines is to change the oil every 50 hours which
is every 2nd or 3rd day.   That get's old really, really fast.)

Larger reciprocating engines (like might be found on a railroad
locomotive or a medium sized ship -  1 to 2,000 kilowatts) have a "life"
on the order of 24,000 to 36,000 hours which is 4 or more years in
essentially full time service.

I happen to have a copy of my electric bill before me.   Of the "current
charges" of $13, some $4 is for fuel.   Generation and transmission
are, respectively, $02 and $1.   Local distribution is another $0.

If you DIY power generation, you distribution and transmission costs
will be ZERO.   Your costs are fuel and "generation."   NG will always
be more expensive than coal if only because it's cheap and easy to
substitute NG for coal.

So the "bottom line" is you keep your "generation" costs under $00
month for break even.   If you change your own oil, you may well be able
to change out your power plant once a year for, say, $00.

Posted by W on August 27, 2011, 10:50 pm

The "strategy" for minimizing utility bill cost should be to replace the
utility during peak use hours.   During the summer, that might mean running
the NG generator only from 11am until maybe 4pm.

What I cannot understand is why hasn't some vendor taken a 200K mile 4hp
engine like a Toyota taxi engine that they use on so many vehicles, and then
adapt that to use NG as a fuel?    These engines might run 100K to 200K
miles on gasoline, but natural gas is a much cleaner burning fuel, and the
same engine on NG might run 300K miles.

Rather than building a real workhorse of a generator around a proven
long-running engine, it looks like most generators are built around small,
maintenance-intensive, low-volume, and highly unreliable engines.   As a
result, those small generators are good for the occasional power outage and
nothing more.

Note that a key requirement for me was to use natural gas and not diesel.
NG is not only a much cleaner fuel, but strategically it is likely to remain
extremely cheap in the US for the next six years because of abundant shale
gas production.   I'm trying to ride that cost efficiency.


Posted by danny burstein on August 27, 2011, 11:24 pm

That's the case for "large" users, with the definition
of large being very different from utlity to utility.

In NYC, for example, the "peak usage charge" applies
(or applied - I'm not current, so to speak, with
the tariffs) for a customer pulling more than 50 kw.

Fiat had one of these in the 1970s (!) called the "Totem". It
otok one of their standard engines and hooked it up to a
line-synchronized generator. You also got to use the waste
heat (when applicable) for heating your building.

Knowledge may be power, but communications is the key
[to foil spammers, my address has been double rot-13 encoded]

Posted by Daniel who wants to know on August 28, 2011, 5:01 pm
The problem there is that vehicle miles can't really be converted to hours
very easily as it depends on what the vehicle is used for.  Take a 300k mile
engine in a car that averaged 30MPH over its lifetime, that is 10k hours. A
year is 8760 hours, so a single year of 24/7 would eat up almost its entire
lifetime.  Peak time usage only would stretch the lifetime out to maybe 6
years.  A taxi would be favorable here as it would have a lower average
speed.  It is also why used cars sometimes declare "all highway miles" as
that means higher average speed and lower hours.

Also never forget that for NG or LPG operation you really need to have the
head milled and/or get different pistons to up the compression ratio to

Posted by W on August 28, 2011, 8:34 pm

But for the five hours of usage per day during Summer that I envision, you
would would only need about five months of usage, maybe 900 hours, of engine

I just don't believe that someone cannot design a natural gas engine to run
900 hours without downtime.


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