[Stoves] ND-TLUD Burners at ETHOS -- What Works Best?

[Ronal W. Larson]

Julien, List, Tom:   (This also to be considered the last of the ETHOS series.)

	Thanks Tom.  I’m writing on flight home from Aprovecho, so will take a first crack at this  (giving credit to Kirk Harris who drove me to Eugene and we discussed this a bit).  I hope others will jump in.

	1.  My view is that we have not had any real “breakthroughs” in the stove world - but are making good progress.   If we likened our path to going to school - the stove world is perhaps in middle school - lots still to learn in High School and College ahead of us.  In this I am restricting myself to your interest (and most short-termers at Apro) - in TLUDs.  I see little new information likely to occur with charcoal-using stoves and Rockets (they are mature technologies).  At Apro, ALL the testing (and advance?) was with TLUDs this time;  no charcoal-using stoves or Rockets  (but plenty around to look at).

	2.  I think more than half of the testing was with fans, including the previously mentioned Mimi-Moto (testing mostly by Paul Anderson.  But also testing with TLUD fan - stoves made in Portugal (excellent high quality factory workmanship), Ohio (very large, using rice husks), and one set from South Africa.   The first three and most fan stoves that I have seen have fans in the stove itself.  The one from South Africa (developed by Dave Lello) is the first I recall having the fan in a fixed base.  More important to future sales is that the fan electrical supply is a small addition (20-25%) of the solar panel coming with the stove - also supplying lighting and cell-phone recharging.  Considerable discussion with Dave about marketing using PAYGo principles (users can see money saved from day 1).

	3.  This last (“Lello”) stove was being tested with the normal (outer) secondary air hole locations, but also an alternative using an interior “column”.  This could be a wave of the future - because of the way this prevents the normal (too-laminar) central flame.  Good results (meaning low emissions, constant power, etc) were being obtained in the first testing over these last three days.

	4.  Several times at ETHOS we heard that the optimum ratio of primary air to secondary air was about .25 to .3  (or primary to total about 0.2 to .25).  [for emphasis -  secondary to primary at 3.5 to 4.)  Perhaps we should be thinking of controlling the larger (secondary) amount - and bleeding a little off for the primary.  I don’t know of anyone who is thinking or doing that.

	5.  With the real-time testing equipment available at Apro, it is possible to see “strange” events that we don’t see in normal operation.  Kirk Harris saw at least three still-unexplained happenings.  The CO level rose significantly in the early stages - a broad peak at first when first lit - maybe 10 times as high as during normal operation.  Perhaps due to the pyrolysis front not really having been established.  But then, after a good strong flame had been established, a very similar “bump” occurred as the 5 liter pot of water was added.  Reduced air flow?  Different radiation conditions?
	CO is not considered a major problem - except in charcoal-using stoves.

	6.  Kirk for the first time today noted that near the end of the run, the particulate count went below the ambient.  The stove was cleaning up the room air.  Why?

	7.  “Big” spikes for both CO and particulates - often (usually) appear as the pyrolysis front reaches the bottom.  - But not always. Why?

	8.   Every morning at Apro, there is a handout of all the previous day’s testing results.  Kirk noted that this year there were many more Tier 4 levels than he recalls from past testing. 

	7.  Kirk was testing for the first time a ‘radiant-fin-array-dome”.  As the gases exit the stove - this “dome” turns red and presumably helps in radiant heat transfer to the pot.  More to come from Kirk on that.  Dean Still reported at ETHOS the use of a special exhaust cleanup catalyst material - that turns white and should similar help with radiant heat transfer.

	8.  Some discussion on using the pot to limit airflow - for improving heat transfer.  We saw no aperture changes (o control power levels) during operation but this might be a future control mechanism.  Arnold Oliphant demonstrated 1 and 2 mm flame-exit gaps.

	9.  I saw some excellent looking new experimental and analytic material at ETHOS - mostly on TLUDs.  We will have to wait to receive the PPts to better understand if these were breakthroughs.  I saw several PPts that might be small breakthroughs.

	10.  Lots of discussion of fuels.  There seems sure to be increased emphasis on pellets.

	11.  I heard the word “biochar” more than previously.  More than “carbon negativity”; emphasis on soils, although the benefits are not in conflict.

Ron



> On Feb 4, 2016, at 9:12 AM, Tom Miles <tmiles at trmiles.com> wrote:
> 
> Julien,
>  
> Great question for the group that is at Aprovecho this week including Paul, Krista, Ron and others. I’m sure that they are still busy testing.
>  
> Tom 
>  
> From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org <mailto:stoves-bounces at lists.bioenergylists.org>] On Behalf Of Julien Winter
> Sent: Wednesday, February 03, 2016 9:02 PM
> To: Discussion of biomass cooking stoves <stoves at lists.bioenergylists.org <mailto:stoves at lists.bioenergylists.org>>
> Subject: [Stoves] ND-TLUD Burners at ETHOS -- What Works Best?
>  
> Hello folks who attended ETHOS
> 
> Were any important breakthroughs in natural draft, TLUD gas burners reported at ETHOS?  Is there a concensus developing on what works best?  
> 
> I would not be surprised if there is a different solution for pellet fuels as opposed to chunks of wood or large briquettes.  
>  
> Cheers,
> Julien
> 
> -- 
> Julien Winter
> Cobourg, ON, CANADA
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