[Digestion] Sucessful small engine Conversion experience?

[Michael Barnett]

Thanks a million Jim for responding.
There is a wealth of info here that I will be digesting and experimenting 
with.
I am thinking of 5-10 kw, as we run a welding training shop too.
What percentage of diesel do you think I could reasonably replace running 
biogas in the arrangement you mention?



Mike
JAMAICA

----- Original Message ----- 
From: "Jim and Amy Rankin" <ajrankin at westal.net>
To: "Michael Barnett" <dreadlox at cwjamaica.com>; "The Digestion Discussion 
List" <DIGESTION at LISTSERV.REPP.ORG>
Sent: Monday, May 05, 2008 11:41 PM
Subject: Re: [Digestion] Sucessful small engine Conversion experience?


> Hi Mike,
> The biogas conversion would be easier on an engine that is already setup 
> for propane vapor or Natural gas use.  then it's a matter of opening the 
> gas adjustment on the vapor mixer/carburetor to account for the %CO2 
> that's mixed with the biogas compared to pure LPG vapor or natural gas.
>
> If you are likely to need more power than your biogas can supply, you 
> might want to supplement a diesel engine (maybe like one of the Lister or 
> "listeroid" generators) with biogas.  These engines are very long lived 
> and reliable running on diesel, biodiesel or vegetable oil and many are 
> used around the world for the only source of power as opposed to the 
> common small portable backup/emergency set which probably will not ever 
> run more than 10's of hours before neglect and age result in it being 
> junked if it doesn't fail on it's own while under load.
>
> Supplementing a diesel engine can be pretty simple if the load is stable, 
> you adjust the flow of biogas into the air intake of the diesel engine 
> after it is started, running at the desired speed and the load applied. 
> As the biogas comes in, the diesel governor will cut back to keep RPM from 
> rising. If the biogas runs low or load increases, the governor will feed 
> more diesel fuel and attempt to meet the demand.  If the demand for power 
> is greater than the engine can supply,  it may overheat since it's 
> essentially being overfueled even though the diesel injection system may 
> not have reached it's set fuel limit.
>
> This works well on a fairly constant load maybe like a battery charging 
> setup but would not work where load varied down.  If load is allowed to 
> decrease, there has to be some way to cut back on the biogas so the diesel 
> doesn't overspeed.  I expect it could be done with a separate governor 
> that just metered the biogas into the diesel intake as opposed to the 
> normal spark engine governor that controls the throttle plate.
>
> You would have the expense of the diesel essentially running at idle speed 
> just to ignite the biogas, but you get a heavy duty/continuous duty 
> engine, backup fuel capability and the ability to burn very low % methane 
> biogas if that were to be an issue.   If you use a spark engine, you 
> probably should oversize it by about 100% compared to one that is rated on 
> gasoline or LPG.
>
> You don't mention what size generator you are considering.
>
> Jim
>
>
>> I am considering an environmental proposal in a few months that could 
>> give our property more power through a hybrid arrangement in tandem with 
>> an existing solar energy system.
>>
>> Can anyone tell me of their experiences converting a small generator to 
>> run on biogas, and maybe of the modification experience on a standard 
>> "off the shelf" genset?
>> I would appreciate any papers, documents and other info on "real life" 
>> exercises.
>>
>