[Stoves] K Smith Article in Energy for Sustainable Development

rongretlarson at comcast.net rongretlarson at comcast.net
Mon Nov 29 18:18:33 CST 2010


Otto (and 2 ccs) 

Thanks for the quick response. I now understand a little more - but not yet enough. Is there any more technical description anywhere? (any drawing?) 

Also I had a series of later questions interspersed with your remarks - that you apparently did not see. Getting at those might help. 

The biggest surprise below is where you said in response to my 3c: 

"There is no seperation of the secondary and primary air apart from the combustion chamber wall and the outer sylinder, as I see it. " 

This is what I would expect rocket stove proponents to say, but not those claimed to be TLUDs . Also the mention of red glowing grass late in the process is a sure indication that the char is now combusting. Do you have a sense of how much smoke is produced when the pyrolysis front reaches the bottom? It would be a help to see a video of operation over the two full tome periods you describe. Can you describe how the char is extracted? 

Ron 

----- Original Message ----- 
From: "Otto Formo" <formo-o at online.no> 
To: rongretlarson at comcast.net,. 

"Otto Formo" <formo-o at online.no> 
Cc: "Discussion of biomass cooking stoves" <stoves at lists.bioenergylists.org>, "biochar-policy" <biochar-policy at yahoogroups.com> 
Sent: Monday, November 29, 2010 2:51:13 PM 
Subject: SV: SV: [Stoves] K Smith Article in Energy for Sustainable Development 

Ron, 
find my comments below. 

> From: rongretlarson at comcast.net 
> Sent: 2010-11-29 20:27:47 MET 
> To: Otto Formo [formo-o at online.no] 
> Cc: Discussion of biomass cooking stoves [stoves at lists.bioenergylists.org], biochar-policy [biochar-policy at yahoogroups.com] 
> Subject: Re: SV: [Stoves] K Smith Article in Energy for Sustainable Development 
> 
> Otto (cc "stoves" and "biochar-policy") 
> 
> 1. Thanks for the reminder to look at the three You Tube videos, which were given by you on the 7th as: 
> 
> http://www.youtube.com/watch?v=amaUDK6VyRg 
> http://www.youtube.com/watch?v=gi3Xx7NtTGw&feature=related 
> http://www.youtube.com/watch?v=dsfuVGBi4fc&feature=related 
> 
> 2. I had seen the first two - but not the third. They all emphasized the use of grass - and I think this is wonderful. I have never tried grass in these stoves - although I have mostly used thin twigs and the same fuel orientation and shape. I have to say I am dubious of a general proposition that 1 kg of grass can replace 5 kg of wood. This must be comparing with a very inefficient wood stove. 
> None of the videos mention charcoal production . Is this guaranteed or an option? 
> 
Paal has always focused on household energy and this was "long before the biochar area", but the TLUD ND produces charcoal. 
The straw to be used was well prepared in bundels and gave an open flame for about 45 mins (temperature around 700 C in a TLUD ND of the size of 3-4 litre). After a while the straws started glowing in a "standing" manner in the combustion chamber even increasing the temperature up to 900 C for another houer. 
This will very well compete with any improved wood or charcoal stove, I belive. 


> 3. I find I still do not know the geometry and especially the hole sizes and placements. So I have these questions (need a cross-section diagram, optimally, as well): 
> 
> a. Is there any attempt to control (during cooking, so as to be able to control flame height and power output) the size of the lower holes? If not, I suggest that would be an important added feature for the convenience of the cooks, and justifiable economically in fuel savings.. 
> 
This are details Paal are the one to ask, but I know that the size of holes and pattern are very delicate and of great importance. 
The idea is to "tune" the stove to be most efficient and clean burning without any regulation during cooking. 

> b. It is not clear whether the space between the inner and outer cans is used to preheat secondary air. Can you clarify the air flow pattern in that space? Regardless, I think two concentric cans probably pays quickly for that extra metal in (possibly important) captured and otherwise wasted radial heat loss. It might even pay to have three concentric cans. But these cans are not needed for TLUD operation. They are needed for Nat Mulcahy's TLOD design - which I am pretty sure is not going on with Paal's design. 
> 
The secondary air is preheated at the upper part of the sylinder and I cant see any point haveing a third can or sylinder unless you are very much focusing on biochar, like the "Anila" stove. 
Three cans, higher cost, yes. 

> c. In my development of something similar in the mid 90's, I found it important to have a much taller secondary gas-combustion chamber above the fuel supply than I see in these videos - for two reasons. First was to get complete combustion before the flame hits the cookpot. But also to get more air flow (to get a lower pressure above the fuel). Has Paal or yourself investigated the impact of greater height above the secondary air holes (assuming there is separation of primary and secondary air)? 
> 
These are details of Paal`s knowledge, but I belive the distance in hight between the inner combustion chamber and the outer sylinder are vital and of importance. 
There is no seperation of the secondary and primary air apart from the combustion chamber wall and the outer sylinder, as I see it. 

> d. The use of three stoves in parallel was interesting, and should/could have some advantages. But I wonder if there has been any work on a larger single stove insert - which should be cheaper. I was able (sort of) to cook enjira in Ethiopia on a 60 cm ceramic griddle (magogo) with a pretty large single stove diameter of maybe 30 cm. 
> 
The TLUD ND can be scaled up into "any" size, but Paal mean its better to use more of smaler units and they can be replaced one at a time, which I think is a good idea, thinking about fuel cosumption and the feeding "challange". 

> Again, thanks for the reminder. Few more questions below. Ron 
> 
> ----- Original Message ----- 
> From: "Otto Formo" <formo-o at online.no> 
> To: rongretlarson at comcast.net, "Discussion of biomass cooking stoves" <stoves at lists.bioenergylists.org>, "biochar-policy" <biochar-policy at yahoogroups.com> 
> Sent: Monday, November 29, 2010 10:30:28 AM 
> Subject: SV: [Stoves] K Smith Article in Energy for Sustainable Development 
> 
> Dear Ron and all, 
> I hope you have had the chance to look at the videos linked to you from You Tube and then you will see that Paal was introducing the "GrassBurner" in 1994 in Uganda. 
> [RWL: See above.] 
> 
> About biochar, we have found it more easy to handle after the residue are made into pellets, not "only" because it burns so cleanly in the TLUD ND Gaisifier Unit. 
> [RWL1 This implies that Paal is always obtaining char. Is the ratio of char weight out to grass weight in about 25%? Wood char can be pretty tough stuff to break up. Are you saying that the grass-char breaks up too much? ] 
> 
> Pellets made out of pinewood also gives a compact and clear surface of the char with a minimum of waste and dust. 
> [RWL2: Would there be a preference for either grass or wood pellets - forgetting cost? Can you explain "waste"? ] 
> 
> This will make it easier to transport and spread in the field thinking about coaldust and silicosis. 
> [RWL3: Are you expressing concern for the small size of char dust made from grasses? 
> 
> One type of fuel (pellets), preferable made out of agri-residue, for one type of stove (TLUD`s), can it be more easy? 
> [RWL4: Until this question, I was pretty excited about the use of grass as a fuel (which I repeat I have never used - as grass in Colorado is not like that shown in the videos). As big grass is abundant in many places, in surplus often, easy to grow, etc. , help me understand your emphasis on pellets here.] 
> 
> According to scientist working on biochar, the agriwaste gives the best or most suitable biochar for cornfields, but also smaller quantities than wood. 
> [RWL5: Can you give a cite? I don't recall any conclusion like this before. Also, not sure the meaning of the last clause - is that referring to Paal's ratio of 1 grass to 5 wood? (I need more convincing - I think both will give about 15-17 MJ/kg) - and maybe more for the wood.] 
> 
> We still prefer to use the forest and agri-residue as Household Energy, until further notice............ 
> [RWL6 : Otto - This worries me a good bit. I hope you are not on the side of those saying it is better to combust the char (assuming the Peko Pe makes a lot of good char) rather than to get the many advantages of placing char in the ground . My hope is that you are only saying here that "forest and agri-residue" is a better choice than fossil fuels. That I can agree with. ] 
> 
> Ron ] 
> 
> Otto 
> 
> > From: rongretlarson at comcast.net 
> > Sent: 2010-11-29 17:55:42 MET 
> > To: Discussion of biomass cooking stoves [stoves at lists.bioenergylists.org], biochar-policy [biochar-policy at yahoogroups.com] 
> > Subject: Re: [Stoves] K Smith Article in Energy for Sustainable Development 
> > 
> > Richard (cc two lists) 
> > 
> <snip remainder> 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.bioenergylists.org/pipermail/stoves_lists.bioenergylists.org/attachments/20101130/89e06994/attachment.html>


More information about the Stoves mailing list