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diesel generator fuel consumption?
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| Can someone post their actual fuel consumption for their diesel engine
and generator? The chang-fa site lists SFC at 270 g/KWh. I assume this
means 'specific fuel consumption and grams/KW hr' but it would be nice
to have one other data point. Trying to compute an efficiency based in
power out/power in. I've heard 40%. Trying to run the numbers.
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| Pete C. 2005-08-24, 5:21 pm |
| BobG wrote:
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> Can someone post their actual fuel consumption for their diesel engine
> and generator? The chang-fa site lists SFC at 270 g/KWh. I assume this
> means 'specific fuel consumption and grams/KW hr' but it would be nice
> to have one other data point. Trying to compute an efficiency based in
> power out/power in. I've heard 40%. Trying to run the numbers.
Efficiency of a generator is very dependent on the load placed on the
generator. At light loads the efficiency is much worse than when
operated at close to rated capacity. A generator that consumes 1 gal/hr
of fuel at full load may still consume 3/4 gal/hr at half load.
Additionally the efficiency can be higher if you are able to capture and
utilize the waste heat from the generator (DHW or house heating for
example).
Try the Kohler or Onan sites where you'll likely find more comprehensive
and readable performance data than the Chang-Fa site.
Pete C.
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| Thanks Pete... the kohler site gave .45 gal/hr for their 7hp diesel. I
have a 3250W gas generator I ran for several days during the hurricanes
in central Florida last year. I'd add 3/4 gal every 2 hrs.... so I was
getting .375 gal/hr. Both of these figures work out to about $.23/KWhr,
and the grid in cen Fla is about $.12/KWhr, so I'd have to invent some
way of DOUBLING the efficiency of the motor and generator before I
could start saving money on electricity.
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| Harry Chickpea 2005-08-25, 11:21 am |
| "BobG" <bobgardner@aol.com> wrote:
>Thanks Pete... the kohler site gave .45 gal/hr for their 7hp diesel. I
>have a 3250W gas generator I ran for several days during the hurricanes
>in central Florida last year. I'd add 3/4 gal every 2 hrs.... so I was
>getting .375 gal/hr. Both of these figures work out to about $.23/KWhr,
>and the grid in cen Fla is about $.12/KWhr, so I'd have to invent some
>way of DOUBLING the efficiency of the motor and generator before I
>could start saving money on electricity.
More accurately, you would probably have to quadruple efficiency or
more. You probably weren't using 3250 watts, so anything over what
you actually used and below the capacity of the genny has to be added
into the equation. You also have to amortize the generator, include
the cost of oil, include the cost of getting gas to the genny, include
a small amount for your time, etc.
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| Hey Harry... I'd like for you to meet a buddy of mine... Don
Lancaster..... you two would probably get along great
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| Pete C. 2005-08-25, 12:21 pm |
| BobG wrote:
>
> Thanks Pete... the kohler site gave .45 gal/hr for their 7hp diesel. I
> have a 3250W gas generator I ran for several days during the hurricanes
> in central Florida last year. I'd add 3/4 gal every 2 hrs.... so I was
> getting .375 gal/hr. Both of these figures work out to about $.23/KWhr,
> and the grid in cen Fla is about $.12/KWhr, so I'd have to invent some
> way of DOUBLING the efficiency of the motor and generator before I
> could start saving money on electricity.
The problem with that type of use is that most of the time the generator
was probably running at perhaps 25% load where it's at it's worst
efficiency. Larger diesel generators tend to do a bit better than gas
generators as well.
Some time ago I calculated that my 25kw diesel unit would cost about
half of the cost of utility power if it was operated at full load. With
gas you pay a lot in transportation fuel taxes, diesel you can get
untaxed for off-road / non-transportation use. One of the reasons you
see construction equipment moved on trailers is to save the cost of
registration and the cost of taxed on-road diesel.
For maximum efficiency you have to really do a full "co-gen" type of
configuration where the load is carefully matched and managed and the
waste heat is captured and utilized. You also have to worry about
emissions for a continuous use application like that as opposed to
emergency use. Continuous use also requires a genset designed for that
use, nearly all the small sets are intended for about a 10hr day at
most. Prime power rated gensets have larger oil and cooling systems and
some are designed so that maintenance such as checking and topping off
oil can be done with the set running.
Pete C.
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| nicksanspam@ece.villanova.edu 2005-08-25, 3:21 pm |
| BobG <bobgardner@aol.com> wrote:
>...the grid in cen Fla is about $.12/KWhr, so I'd have to invent some
>way of DOUBLING the efficiency of the motor and generator before I
>could start saving money on electricity.
Heat water for showers while running the meter backwards, as needed.
Nick
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