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allfoden
05-26-2005, 10:38 AM
I have a 5KW water cooled Kubota diesel generator that I use for primary power and am considering upgrading to a 14KW water cooled Isuzu generator. About 90 percent of the time the generator runs about half power (2.5KW)
Would the 14KW unit consume more fuel running under the same conditions because of the larger engine on the 14KW unit?

jfsmith
05-26-2005, 11:25 AM
I have a gasoline generator and it has an idle control, so it is not always running full out. But diesels like to run at one speed and they do that very well.

Here is the webpage for what I have:

http://houseofgenerators.com/gen_port.html

It's the 15Kw model and worked really well for me at the shop and on the job site.

Jerry

Carl
05-26-2005, 02:42 PM
The efficiency of diesels increases as the level of load decreases. This is because as the load dercreases the air/fuel ratio increases (less fuel mixed with the same full cylinder of air). The larger engine should operate at a higher efficiency level since the load on it will be at a lower percentage of maximum. Whether or not it uses the same or less fuel for a given load will probably depend on the thermodynamic efficiency and frictional losses of that particular model of engine.

wierdscience
05-26-2005, 10:25 PM
Well it has to run either A 1800 rpm or B 3600 rpm to gen 60cycle power,so idling down is not an option.

14 divided by 5 is 2.8,you have 2.8 times the genset you did previously.Assuming a no load situation it will use 2.8 times the fuel the other one did.

This isn't a scientific way of factoring the increase,but the laws of physics are still in effect.It's possible you may get away with 2x the fuel,but I doubt it.

chief
05-27-2005, 03:09 AM
I would not recommend running any diesel generator at less than 80% load unless maintenance cost are of no concern. Carl is right to a point but as the load decreases
accelerator mechanical problem problems occur,excessive carbon build up, fuel dilution and general wear. In transportation diesels the industry agrees that one hour of idling is equal to seventy miles of road wear.
On the other side of the coin maintain a clean air filter and change the oil and filter on a regular basis with quality oil and strip the water from your fuel tank daily.

JRouche
05-27-2005, 09:03 AM
Can't you use a DC generator along with batteries and an inverter? I have always kicked around the idea of going off the grid.

I though folks who used generators did it this way instead of using AC gen. sets.

For efficiency the DC system seems the way to go.

You figure out how much power (watts) you need then figure out how many hours a day you want the gen. running. Say you only want the engine running eight hours a day you can determine how large a gen you need and how much storage (batteries) you need.

For example, a 14kw gen. set feeding a given amount of batteries, (say for numbers purposes 20) for eight hours a day theoretically should be equivalent to a 7kw gen. set running for sixteen hours a day into 10 batteries (less batteries because the gen. set will be running more hours a day so there will be less reliance on long term storage of power, the fewer batteries will be continually recharged).

What's nice about a DC system is it can be fed from different sources (solar, wind, hydro).

Problems are high cost...

OOOpps, gotta go to work, sorry for the ramblings. JRouche

Kansas_Farmer
05-27-2005, 09:55 AM
I'm thinking that steam would be the way to go for me.

A multi-fuel boiler for burning trash, wood, coal, waste oils, whatever really.

200 psi working pressure with a 10"x10" 2 cylinder engine with a belt pulley and a clutched shaft setup. Belts for running line type shop equipment and the shaft for turning a dc genny.

After the Steam is used in the engine, it heats the house/shop, is condensed and the water is reused.

Also, a steam powered air compressor would be a neat setup with this idea in place.

operose
05-27-2005, 06:11 PM
check out http://www.green-trust.org ... the guy there uses a diesel generator run on WVO (waste vegetable oil.. fryer grease..) for his electricity

DancingBear
05-27-2005, 08:06 PM
<font face="Verdana, Arial" size="2">Originally posted by Kansas_Farmer:
I'm thinking that steam would be the way to go for me.

A multi-fuel boiler for burning trash, wood, coal, waste oils, whatever really.

200 psi working pressure with a 10"x10" 2 cylinder engine with a belt pulley and a clutched shaft setup. Belts for running line type shop equipment and the shaft for turning a dc genny.

After the Steam is used in the engine, it heats the house/shop, is condensed and the water is reused.

Also, a steam powered air compressor would be a neat setup with this idea in place.</font>

I'm pretty ignorant about steam, but it seems to me the biggest problem with it is that when it goes bad it goes *really* bad! Most steam systems (at least those of yore) were extremely high-maintenance (as in daily), which would be a drawback if you ever wanted to go on vacation and leave the heat on...