[Gasification] Question: Connecting a gasifier to a micro CHP unit

[doug.williams]

Hello Ian,

You Ask:

> This is my first time posting here, so excuse me if I seem out of touch -
> because I am. I was wondering though whether there had been any
> consideration given to connecting a gasifier to a small CHP plant like the
> one produced by Whispertech of New Zealand? It seems to me that anything
> which gets too hot to touch should really be mated with a stirling engine.

I guess in the context of how you phrase this question, you are looking at 
the waste heat that radiates from the casing, not use the gas made in the 
gasifier to run the Stirling. Personally, I have not heard of any systems 
set up like this, as it would require the Stirling engine manufacturer to 
get involved with the gasifier manufacturer, and that is not an easy 
marriage of technology to organize.

> The reason I mention whispertech is that they seem to have gotten the 
> round
> the wear problem in a closed cycle.

In 2004-5, I was asked by a third party to look at the requirement to gasify 
the WhisperTech, and the result was the Micro Class Gasifier that you can 
see on the Fluidyne Archive www.fluidynenz.250x.com     I had also worked 
with a German Stirling designer, and had discussions with other Stirling 
manufacturers about their engines need, by way of head heating, it was clear 
that producer gas had to be meticulously clean.  To date, I have not found 
any Stirlings that are actually operating with a gasifier in a commercial 
application.

Returning to the WhisperTech, I had the opportunity to see one opened up in 
June this year, and learnt more in a few minutes from the salesman, than I 
could extract through third parties over weeks! Their engine has a ceramic 
cover to the head, and this would make a huge difference to the problem of 
ash contamination. In fact, it is possibly the only way you could use 
producer gas for this type of application, in order to create the 
incandescent surfaces for heat radiation transfer.

> In any case given the high operating
> efficiency of CHP it seems to make sense to me that a gasifier should be
> part of something larger, rather like we have a camera in our handphones
> these days. So has this been considered?

In the end, it boils down to economy of scale. The WhisperTech puts out less 
than 1kWe/hr, and that takes 3kg of wood pellets at $0.10/kg to run, and you 
still have to deduct the power needed to run the gasifier The cost of the 
WhisperTech and gasifier, plus fuel pellets, is a long way from being 
economic, and even if really desperate, it would not be a good option with a 
gasifier. CHP is well proven with conventional engine generation systems, 
but also expensive, although in a DIY situation, you could clobber up a 
system that will work quite well at low cost.

Hope this helps.

Doug Williams,
Fluidyne Gasification.