[Digestion] Rép. : Re: Electricite generation

Wed Sep 5 10:35:41 EDT 2007

Hi François.
What do you mean by "energy efficiency"?
Are you looking for electricity production for an off grid home and greenhouse?
Because in that case, most ICE (internal combustion engine) are more efficient that those Capstone turbines. They average 26-27% at 70-80 Deg F air intake temperature (electrical efficiency). 
As of the internal combustion engines, the ones that are used in Germany by ag digesters, the average 29-33% electrical efficiency. However, you will not see the same figure for a small modified conventional gasoline engine wit a natural gas conversion kit. You might even have to mix it in with pipeline NG. Too complicated. And it could be easier to run on low quality biogas with a modified diesel engine (dual fuel), similar to the Schnell CHP kit in Switzerland, or a Martins Machinery CHP that uses oil and gas engines or old Cat engines, again with modified ignition systems. Might be too much capital cost for your project however... Are you looking for a grant right now? In which country do you reside?
Your boiler idea seems great, but how are you planning to light the greenhouse in the startup or end of season. Maybe you don't have too, but in Canada it is different.
Don't know anything else for turbines. Someone will have to bump in here. There is a researcher in Agriculture Canada in Lenoxville, Quebec that has ASBR for pig manure. They are hooked up on boilers because he could never have a good steady biogas production and quality (and for obvious reasons). His name is Dr. Daniel Massé. He might be able to explain his systems. You might find his larger scale projects under Bioterre.
There is someone in Calif. selling some Capstones for 18K US$, but the website is pretty old and he doesn't offer a warranty. I am sure you have looked the net already.
Good luck.
Terrence Sauvé

>>> francois chartier <francoischartier at yahoo.com> 05/09/07 5:02 >>>
Hi Bruno,

THanks for the input. 
For now I am only at the conception phase. I have
actually found a gaz turbine from Capstone in CHP
which has a high energy efficiency but will be
expensive you are right.
the idea to reuse the exhaust heat is not to have a
never ending motion - don't worry. No the reason why I
would like to reuse the heat is 
a - there will be no valorization for the heat
generated possible other than this way
b - that heat can be used to preheat the water inflow
to the boiler so that there is less energy used to
heat the water to the desired heat and pressure from
your biogaz. Just a question of energy efficiency.

Can you tell me more about what you wrote?
your biogas
> into an adapted motor ( ICE), that is coupled to a
> generator,
I am not familiar with this system

cheers
Francois 
--- "Bruno M." <brunoM1 at telenet.be> wrote:

> Maybe you need ( already) to rethink your endeavor,
> 
> If I understand it correctly you have biogas from a
> digester( CH4 + CO2 )
> you like to blow that in a boiler to produce steam,
> then you gonna blow that steam into a expensive
> turbine,
> that drives a generator that makes electricity ( 
> for your own use or selling to the grid).
> And you think blowing the rest steam of the 
> turbine back into the boiler will help?
> 
> To expensive and to complex i believe, on every 
> conversion you gonna loose energy.
> so leave out the boiler and the expensive turbine
> and blow your biogas
> into an adapted motor ( ICE), that is coupled to a
> generator,
> find a use for the waste heat from the ICE, e.g.
> heating a greenhouse
> ( than you can also use the CO2 containing exaust
> gas as fertilizer),
> or heating your digester.
> 
> Also, in your proposed setup there will be no 
> real gain by blowing the turbine exit steam
> back into the boiler.
> Why?
> Let say you make 10 bar wet steam ( = 184°C ) you
> blow that steam
> in the turbine, you will get energy out as 
> rotation of the shaft to run your generator,
> what comes out of your turbine is steam ( and 
> water droplets) with a temp lower than
> 184° C. How you gonna heat y colder? ( wile your boiler is 
> working the water will be constant on 184°C,
> and al heat input will then be used to convert 
> water from 184°C to steam (-vapor)
> of the same temp; so there will be no real use 
> (gain) for a fluidum with a temp below 184°C
> to help (pre-)heat the boiler.
> 
> Maybe you can start with telling us about your
> system you already have
> ( how much gas a day you produce now, and whats the
> quality) ,
> and what your future needs are ( electricity and
> heat ).
> 
> 
> grts
> Bruno M.
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> At 12:22 3/09/2007, Francois wrote:
> >Hi all,
> >
> >I am looking for a system to produce electricite
> out
> >of biogaz - most likely a cogeneration steam
> turbine
> >that reuses the exhaust to preheat the boiler for
> max
> >energy efficiency.
> >Does anyone know of trade marks, sellers etc.
> >Cheers and thanks
> >Francois
>
>==================================================================
> 
> 
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