[Stoves] Simple Modifications to Traditional Wood Cookstoves - Rocks and Clay Grates

Thu Apr 25 14:25:00 CDT 2019

 List and ccs

	See below:


> On Apr 25, 2019, at 4:03 AM, Crispin Pemberton-Pigott <crispinpigott at outlook.com> wrote:
> 
> Dear Friends
> 
> The two-pot, one-fire stove is a staple in places like Sri Lanka. There is a helpful Practical Action video in English showing the production of the common product:
> 
> https://www.google.com/url?sa=t&source=web&rct=j&url=https://m.youtube.com/watch%3Fv%3Dz8oGUHDEDpY&ved=2ahUKEwix4YaQ9-rhAhUO2FkKHbGNDKYQwqsBMAB6BAgJEAU&usg=AOvVaw1xLbIsxqNtadxTnvxMKzJo <https://www.google.com/url?sa=t&source=web&rct=j&url=https://m.youtube.com/watch%3Fv%3Dz8oGUHDEDpY&ved=2ahUKEwix4YaQ9-rhAhUO2FkKHbGNDKYQwqsBMAB6BAgJEAU&usg=AOvVaw1xLbIsxqNtadxTnvxMKzJo>
> 
> I hope that link works. It looks messy. 
> 
> The layout is efficient and the diagonal chimney is creating the draft needed to keep the smoke away from the first pot. 
> 
> Note that the first pot seals the hole at cooking station one. 

	[RWL1:   This Sri Lankan thrown clay 2-pot stove is interesting - and I think I have seen similar elsewhere.

	The difference is that example is quite different from Kevin’s.  The two Sri Lankan cook-pots are in parallel.  In Kevin’s design they are in series.   It appears that a 3-cookpot series design can possibly be even more cost effective.  The succeeding pots are utilizing flame energy that was missed at the first (or first and second) cook-pots.  So the question remains - any other examples of two or three cook-pots in series (and especially at different heights - so draft improves)?


	Most of the remainder below is what was described in my first message a month ago - on air flow control.   Kevin’s work is also emphasizing the use of the (air improvement) rocks as energy storage components.   Still hoping for other examples of both the air and storage elements of rocks (all the rocks involved).  Again - because the cost can be zero.  Who else is doing that?
	One more topic (the last of Kevin’s four being explored) below.

> 
> What Kevin is exploring is the better combustion of the wood. There are a number of ways to do this. The oldest I know of is the traditional Ugandan trench stove that was tested in Uganda in 2008 as part of the USAID project that convinced them to drop stoves altogether. 
> 
> It is shown in the project photos and essentially tried to introduce some air below the fire. If combined with a grate of some kind (which it was not) it would be fire. The problem is the free grate. 
> 
> Kevin has been promoting an interesting extremely cheap set of three. Bent reinforcing steel bar wood supports that hold the tips of the wood above the ground when they are burning. Obviously this has limitations because wood is not infinitely long but clearly it saves fuel by was burning some of the smoke, and the char that is often left on the ground at the end. 
> 
> Elevating the char itself is the trick. If the stick is elevated at the burning point, the char attached to it is getting "under air" and burns cleaner.  Char can be elevated and aerated by many methods, including, as Kevin has demonstrated, putting a perforated clay disk, or a layer of round stones on the ground between three stones that support the pot. It is functionally the equivalent of the wedge-shaped metal insert being promoted in India that has holes through the upper surface. Some readers may recall that being shown on this channel a few years ago. 
> 
> It is also the main function of the two-part tilted grate demonstrated in the SAE Stove and Keren Super in Central Java which was developed in the WB's Indonesian Stove Pilot Project. 
> 
> There are variations on the theme demonstrated elsewhere. What Kevin shows, I think, is that using the very inexpensive clay grate (which identical in appearance to the grate in the Indonesian Jolento and Anglo (Thai bucket) stoves) produces much better results than a three stove fire in terms of fuel consumption, combustion temperature,  smoke and CO. 
> 
> The cook will notice higher cooking power, faster lighting and less smoke. 
> 
> Having spent some time experimenting with various ways to elevate the fire enough to get air under the fuel at the centre, Kevin demonstrated that round stones placed on the ground in the centre, either between the pot-supporting elements. 
> 
> This could be added to any stove with a flat floor on which the fuel burns, in that any grate (passing air under the fire) is better than none. The clear advantage was measured recently in the Cambodian lab and at the SeTAR Centre in Johannesburg. 
> 
> A rocket stove's overall fuel performance can be improved by adding a grate under the tips of the wood, or between the wood and the floor under the fuel support, or on the floor of the stove. Tossing in a layer of round stones that sits on the floor in such a way that it elevates the char and doesn't interfere with the primary air supply to the wood will also produce that result: better and hotter combustion of the char normally left sitting at the bottom of the stove. 
> 
> There are times when one doesn't want the char to be burned in this fashion. There is a two-station traditional stove $are in one province of Indonesia that provides for the char to be produced under a pot and has a flat platform protruding from the front of the fire chamber. The char is raked back onto this platform and meat or vegetables is roasted over it.
	[RWL2:  Crispin:   Seems to be a typo with "$are” in the first line.  Can you correct?  (Just delete?)

	Your “raked back ”  reference is indeed interesting.  Any Indonesian technical literature anywhere on that?  The amount (both in kg and %)  that can/must be removed for roasting?   

	Obviously the char could alternatively be raked out from ANY cook-fire - then spread to extinguish and saved for placement in soil (biochar).  Or sold as a way of maybe even making money during each cooking session.

	Anyone else have data on removing char in this way?   (This was part of what we might call Kevin’s item 3b below from yesterday).

  End

Ron
>  
> 
> Adding a few round stones to the centre of any fire, a bit smaller than a hen's egg, is a very low cost way of improving the performance of the stove. Not in Northern Moçambique near the coast, of course because there are no stones, but in many places there are. 
> 
> In Yogyakarta we made a set of tools for making a clay grate with no holes at all, but instead a set of upside down feet each of which looked like one bump on a civil engineering "sheep's foot roller". This allows air to enter the fire sideways just under the fire while the char is elevated just enough to burn properly with the wood instead of afterwards. 
> 
> I commend Kevin for his continued interested and innovations. 
> 
> Regards 
> Crispin 
> 
> 
> 
> 
> 
> From: rongretlarson at comcast.net <mailto:rongretlarson at comcast.net>
> Sent: April 25, 2019 12:02 AM
> To: stoves at lists.bioenergylists.org <mailto:stoves at lists.bioenergylists.org>
> Reply to: stoves at lists.bioenergylists.org <mailto:stoves at lists.bioenergylists.org>
> Subject: [Stoves] Fwd: Simple Modifications to Traditional Wood Cookstoves - Rocks and Clay Grates
> 
> List:   cc Kevin M
> 
> 1.   This is to bring you up-to-date on Kevin McLean’s “zero cost” stove work - that I have learned in the last 4 weeks..  This today is on three (mainly one) new concepts (despite keeping the thread name).   It has applicability especially to those working with Rocket stoves - but I am pretty sure he/we can find ways to work also with TLUDs.  
> 
> 2.  After Kevin sent me 3 short videos a few days ago,  we agreed there could be great benefit to his and everybody’s stove research to get this early work out for discussion.  So this is to ask everyone to view Kevin’s annotated 2 minute video on an approach I have not previously seen:
> https://drive.google.com/file/d/1EJQEKKkMTQbcKn3kBC1YZ50oqtZPsbym/view <https://nam05.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdrive.google.com%2Ffile%2Fd%2F1EJQEKKkMTQbcKn3kBC1YZ50oqtZPsbym%2Fview&data=02%7C01%7C%7C39647a26ff924621097708d6c932d5b0%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636917617497762873&sdata=YoLqMafxKJpPjFGK4NFlKlVeC05A5XaMexKenR94ZUQ%3D&reserved=0>.   
>   I am amazed that so much energy gets to the second pot (and he may develop a 3 pot design, that also looks well worth the relatively small added extra cost).  No metals anywhere.
> Anyone seen this before? 
> 
>   3.  I will try to report soon on two other new (to me) very low cost stove improvement areas on which Kevin has also been working - and which I am unaware of any others pursuing: 
> -   adding energy storage using movable hot rocks or bricks (headed to hay baskets maybe?)
> -  making char while cooking (and NOT with TLUDs)
> Can anyone give a lead to these storage and char-making areas?
> 
> 4.   The 4th area of our discussions since the message below still seems brand new:
> 
> - improved air flow with 3-stones - using "rocks and clay grates” to elevate the fuel.
> 
> 5.  Since Kevin is adamant on zero costs to users (and minimum costs allowable when payback time is short), these ideas are not amenable to most companies looking at the 3-stone-user market.  Accordingly, Kevin will not be patenting any of this - all 4 areas will be open source.
>   
> 
> Anyone working on any of these 4 areas?  Or know of past results from anywhere?
> 
> Ron
> 
> 
> 
>> Begin forwarded message:
>> 
>> From: Ronal Larson <rongretlarson at comcast.net <mailto:rongretlarson at comcast.net>>
>> Subject: Re: [Stoves] Simple Modifications to Traditional Wood Cookstoves - Rocks and Clay Grates
>> Date: March 29, 2019 at 3:01:27 PM MDT
>> To: Discussion of biomass cooking stoves <stoves at lists.bioenergylists.org <mailto:stoves at lists.bioenergylists.org>>
>> Cc: K McLean <info at sun24.solar <mailto:info at sun24.solar>>
>> 
>> List,  cc Kevin
>> 
>> This is to encourage this list to view the two “Sun24” links given below.   Because I was so impressed when I viewed those, I had a nice phone conversation with Kevin yesterday.  A few things I learned:
>>   Kevin is a retired lawyer.  Retired for only a year, but already in contact with stove-knowledgeable NGOs in many countries.  Through them, he is offering - for free - improvements in 3-stone use of doubled efficiency, and improved emssions.  Working also with some low-cost rocket designs.  Not yet working on TLUDs - but knowledgeable about them, and supportive at the right price.  Has stove modifications measured in multiples of 10k, I think (in only a few past months).
>> 
>> His emphasis on major stove improvements at zero cost (better air delivery), with local NGO support, is something we have been mostly missing in our stove development efforts.  Emphasis zero cost - described at these two sites given below.
>> 
>> Ron
>> 
>> 
>>> On Mar 28, 2019, at 9:24 AM, K McLean <info at sun24.solar <mailto:info at sun24.solar>> wrote:
>>> 
>>> Sun24 and its partners operate at the primitive end of the cookstove spectrum.
>>> 
>>> We have found that both rocks (or broken clay bricks) and a clay grate improve open-fire wood cookstoves' efficiency.  Here are examples of rocks and a clay grate in a three-stone cookstoves:
>>> <Rocks in 3-stone.jpg <http://3-stone.jpg/>>
>>> <Clay disc grate in 3-stone stove.jpg <http://stove.jpg/>>
>>> SNV tested <https://nam05.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdrive.google.com%2Ffile%2Fd%2F183kPF5DrwIR5mdDhE7xC9AaNJLaorGZt%2Fview%3Fusp%3Dsharing&data=02%7C01%7C%7C39647a26ff924621097708d6c932d5b0%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636917617497772879&sdata=QHVmk6eMWsJNjJMSBsb%2BKnaXTIAW0fb55Cu9hrN7Qf0%3D&reserved=0> the rocks and clay grate in its open-fire stove.  Here are SNV's results:
>>> Rocks vs unmodified open fire
>>> +30%    Thermal efficiency
>>> -27%     Wood fuel used
>>> -53%     CO 
>>> -57%     PM 
>>> Clay grate vs unmodified open fire
>>> +52%    Thermal efficiency
>>> -47%     Wood fuel used 
>>> -57%     CO 
>>> -58%     PM 
>>> 
>>> Early user feedback suggests that rocks in traditional charcoal cookstoves also improve efficiency.  We are expanding our informal field testing and hope to test in the lab soon.
>>> 
>>> Since rocks and broken clay bricks are free and ubiquitous, we only need to disseminate the idea, not a product.  We are rapidly disseminating the idea with success in Kenya, Uganda and India by training women group association leaders to train others who then train at the local level.  In Kenya and Uganda we are working with the Catholic and Anglican Churches.  In just a couple months and at low cost, we have trained tens of thousands of women to use this simple modification.  The trainers' feedback is that the users love it.
>>> 
>>> Here is our occasionally-but-not-frequently-enough updated Cookstoves Overview <https://nam05.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdocs.google.com%2Fdocument%2Fd%2F1ZryS7gQ1q3zKLZPM2KcXdtIHbOYQp4PbloPqMvrlZ5Y%2Fedit%3Fusp%3Dsharing&data=02%7C01%7C%7C39647a26ff924621097708d6c932d5b0%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636917617497792895&sdata=VD%2FiHyZlmTpggeXVKI2i96lE6%2FYjalfl%2F6bX%2BT7ORd0%3D&reserved=0>.
>>> 
>>> These cookstove modifications are a transitional first step but they are important.
>>> 
>>> All suggestions are welcome and appreciated.
>>> 
>>> Kevin
>>> 
>>> Kevin McLean, President
>>> Sun24
>>> https://sun24.solar <https://nam05.safelinks.protection.outlook.com/?url=https%3A%2F%2Fsun24.solar%2F&data=02%7C01%7C%7C39647a26ff924621097708d6c932d5b0%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636917617497802907&sdata=BhKuWGSogPLC6vJzVqc3CJ5vkQp%2FICnhJwPoBF%2BAKZs%3D&reserved=0>  Sun24 Cookstoves Overview <https://nam05.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdocs.google.com%2Fdocument%2Fd%2F1ZryS7gQ1q3zKLZPM2KcXdtIHbOYQp4PbloPqMvrlZ5Y%2Fedit%3Fusp%3Dsharing&data=02%7C01%7C%7C39647a26ff924621097708d6c932d5b0%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636917617497822923&sdata=8Lj4zcfxkXdWbUJJpDn7oenMu5ylVMI5XAJQhQJxZ%2Bk%3D&reserved=0>
>>> Tampa, Florida, USA
>>> +1 (813) 505-3340 <tel:+1(813)5053340>
>>> 
>>>                      
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