[Stoves] K Smith Article in Energy for Sustainable Development

Sun Dec 5 16:45:51 CST 2010

Paal (and 2 lists) 

Thanks for the two nice responses (below) sent a few days ago. I have combined them here to improve readability. Your associate (?) Otto Formo has done a nice job of explaining the background. I hope you can add more on the charcoal output mechanism and produced-char uses (the Biochar side) - as well as the following questions. 

A. The second message (almost same timing as the next) said: 

Crispin 

To your infomation if Dean dont' have the exact figures by hand the TLUD-ND I made at Stove Camp 2009 had the following settings. 

The combustion chamber had a diameter 150mm and was 180 h 

    • 55 mm free space from concentration lid up to the pot 
    • 105 mm hole in concentration lid 
    • 6 mm split between concentration lid and top of thee combustion chamber - 4x15mm for the stand for 2 nd air 
    • 5 five mm holes 75 mm up from the bottom on the side of the combustion chamber 
    • [RWL1: Was the fuel always loaded below this level? If not, then what is the need for these holes? How deep was the fuel load for the test results given below? Some of next questions apply here also depending on how high the fuel loading is/was.] 
    • 5 five mm holes 25 mm up from the bottom on the side of the combustion chamber 
    • [RWL2: The purpose of these I also don't understand - believing the 13 (next) could do the full job for supplying primary air (if you want to make char). I would think that secondary air entry at these holes will quickly consume all the char above them and make it harder to combust the still-upcoming pyrolysis gases from below. On the other hand, maybe this is useful in some cooking tasks (such as a water boiling test). ] 
    • 13 five mm holes at the bottom plate for 1 st air 
    • 15 mm space between combustion chamber an cover for preheating of 2 nd .air 
    • [RWL3a: Not quite understanding this last. I'd rather see secondary air being heated as it rises rather than being drawn down - holes at the bottom for this? As for some of the first dimensions, a small cross-section diagram would be helpful on this detail. I think you show much larger dimensions for some of the air entries in the several videos listed below. Perhaps you can explain any differences and reasons for same. Which is the newer design?] 

B. Few more below on your first of the two messages. 

----- Original Message ----- 
From: "Paal wendelbo" <paaw at online.no> 
To: "Til: \"Discussion of biomass cooking stoves\"" <stoves at lists.bioenergylists.org> 
Sent: Friday, December 3, 2010 4:17:32 AM 
Subject: Re: [Stoves] K Smith Article in Energy for Sustainable Development 

When I started my work on simple cooking stoves late 1980ties I did not know any thing about the concept of TLUD-ND apart from the fact we used it making smokeless fire when we stayed in the forest during the 2 nd ww Illegal hunting. By coincidence, after a lot of trying and failing I happen to make a perfect simple cooking stove tested at Copenhagen Technical high school in 1988 and found completely clean burning. .It was introduced in Malawi in 1998 with stamped grass as fuel. In Mozambique in 1990, with cashew nut peals as fuel. In 1989 in Ghana, with chopped slabs as fuel. In Tanzania in 1990, in Uganda in 1994 with straw and chopped wood as fuel, where it was given the Acholi name Peko Pe (no problem), in Ethiopia with briquettes of cowdung and straw as fuel, In Senegal with compressed grownut peals as fuel. with chopped wood and in China in 2003and In Zambia 2008 with chopped wood All places the same stove locally made by local tinsmiths with the tools they had and from plane metal sheets or scrap metal sheets. All working perfect without any smoke and little soot.. 

At Trade Fair exhibition in Kampala 1997 we were selling 500 stoves in two days at market prise That time 5$. 

At Aprovecho Stove Camp 2009 I made one by memory of a 3 litres tin and some leftover sheets, it was tested and found clean burning and given the Kirk Smiths Award 

[RWL3b: And presumably the same as the numbers given below and above?] 

Fuel to Cook 5L 

(8 50/1500) g 768.8 

[RWL4: I don't understand the first (8 50/1500) numbers. I presume the 768.8 grams somehow took account of char produced? (In 28 minutes?) 

CO to Cook 5L (20) 23.0 

[RWL5: the "20" means?? The 23 is grams ? Out of 768.8? Same questions for particulates data (1500? 223.1?) next - which latter must be in mg?] 

PM to Cook 5L (1500 223.1 

15,000/25,000mkJ 

[RWL6: why two numbers above? The units aren't familiar. For almost anything biomass, I would expect about 17 MJ/kg; with your input kg, I expect more like 12 MJ. Anybody measure fuel moisture content?] 

Energy to Cook 5L 14,807 

[RWL7: Units probably kJ?] 

Time to boil 5 litres min 28.1 

[RWL7': This can be converted to an average (using my estimate) of (12,000 kJ/ (28.1 minutes * 60 seconds) = 200/28.1 = 7.1 kW. It would be helpful if this number was part of any stove data. I feel this number is too high for normal cooking and simmering - but it depends a lot on the heat transfer efficiency (about which we know nothing in this test)] 

CO2 to Cook 5L708.6 708.6 

[RWL8: If you consumed 768.8 grams of fuel, I would expect the CO2 weight to be much higher than 708.6 grams - unless there was a lot of char produced. Hope you or Dean can explain this number. I am thinking you probably didn't use this much fuel - and that char production hasn't been properly accounted for (since I think Dean should know the CO2 exhaust gas content pretty well. How often is a CO2 measurement recorded? Your (anyone's) thoughts?] 

Biochar has entered the arena and made the discussion about cooking stoves a bit more interesting. And Dean Still is right when he says by TLUD-ND you can choose between energy for simmering or biochar. Just by stopping cooking process when flame is ended you will have about 150-200 gram of biochar. 

[RWL9: Which must come into play in your above data - but I don't see how it was handled.. I have not liked the way char production is handled in the USAID formulas from 20 years ago. Can you give the formula so I can re-raise that topic?] 

Peko Pe which mean “no problem” according to the Acholi tribe women have a problem and that is infrastructure on fuel. Fuel, stove and user is one unit which can not be separated, If you don’t have the fuel to an appropriate price you will not manage.. 

Fuel and stoves is a part of the social life in a community, a part of the commerce and the communication in the society.. 

The charcoal business is the key to a successful approach. They have the full infrastructure intact and can easy change from charcoal to alternative biomass for cooking. [RWL10: I hope you are right on this. My hope is that today's charcoal sellers (or someone maybe helping them) can supply wood/grass/pellets/briquettes and receive back about 25% char in exchange - and later handle all the paper work for getting carbon credits (after assuring the char made into into the ground). Do you think that could happen?] 

. The local tinsmiths have the tools and the knowledge for production. They need only some guidelines, a template and customers for this simple technology. 

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 

[RWL11: It seems to me that in both the videos and the description by Dean Still of TLUD testing that there has been no means of varying your primary air. This is fine in a speed test to bring 5 L of water to boil - but is missing a valuable feature of TLUDs (or any modern stove). Can you clarify whether you have been varying primary air magnitude in any way? 

Thanks in advance for any more data. Ron 

With regards Paal W paaw at online.no 
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