[Stoves] RE Drying of wood

[Richard Stanley]

Good point Crispin.
However, AD's new method will markedly reduce the size of digester   
required – and the and the cost and kind of materials used.

Where we needed a 2.5 meter Ø  tank generator floating in a  3 meter  
deep brick and plaster lined reservoir, for our family sized cow  
biogas generator in Arusha in the late 70's, we can now get away with  
a 1.5 meter Ø x 1.5 meter deep tank reservoir and 1.5 -2 kgs of  
kitchen and yard wastes a day. This means using discarded rainwater  
tanks plastic or otherwise. It means that the ballast can be rocks  
wire-wrapped onto cross bracing at the bottom (open end ) of the  
floating generator to keep it upright and floating pretty much on  
center,  removing the  need for a center stabiliser pipe and sleeve  
and attendent pole and pipe  edge frame to hold same on center.

As far as heat loss is concerned, you are dealing with far less  
surface per unit of gas production.
  Seems therefore that in and of itself insulation of the new design  
would be far more efficient (%gas consumed  and  insulation cost  
invested)  per temperature maintained.  Will find out soon enough in  
our own prototype at our joint in little 'ole Ashland Oregon.

The problem is not so much technical with ADs new method and the  
reduced size and all that implies technically, It has much more to do  
with legality. The states is the last place you want to try it  
our ...piping a new gas into your house ....Its even apparently  
fraught with potential legal action by the local city councils here  
in Aus.

AD., you are more fortunate to have not only your mentioned more  
moderate climate: You seem to also have a more supportive (or  
possibly less –efficient –at–interfering)  government !

Richard Stanley



On Jan 8, 2007, at 16:43, Crispin Pemberton-Pigott wrote:

> Dear Richard
>
> I think he calculated on the basis of cost.  It was huge but very  
> cheap.  As
> you go deep it costs a lot more per mm of internal height.
>
> He did no excavation and it was made from cement block as I recall,  
> not even
> brick.
>
> Farmers tend to optimise for cost and use a lot of low cost labour.
>
> Regards
> Crispin
>
> ----- Original Message -----
> From: "Richard Stanley" <rstanley at legacyfound.org>
> To: "Crispin Pemberton-Pigott" <crispin at newdawn.sz>; "Discussion of  
> biomass
> cooking stoves" <stoves at listserv.repp.org>
> Sent: Monday, January 08, 2007 12:36 AM
> Subject: Re: [Stoves] RE Drying of wood
>
>
> Crisin,
> Ref the biodigester and heat loss,
>
> You say that he had a "massive digester only 1.5 meters deep...
> Optimum is to minimalise the surface area to volume ratio, defaulting
> to deeper, rather than larger diameter--if in ground heat retention
> is your concern. The last thing I should think, is that you want is a
> large top surface exposure to air as this is where most of the heat
> will go.
> Richard Stanley
>
>
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