[Stoves] Fwd: 2015 Stove Camp at Aprovecho Research Center

Mon May 18 21:32:33 CDT 2015

Dear Dean

I read the WHO 1document that describes the leakage from the stove into the room (a model actually, no measurements) and they use 10%. What has no connection to anything that I can find is where their total emission number comes from. In other words what stove was used to guess the leakage.  Just about any modern stove will meet the 10% leakage rate standard so that is not a problem. The 25% figure is the average of the range used for conducting the Monte Carlo analysis, and had nothing to do with ‘average emitted mass’ or leakage or anything that I can see. It is an average of the model limits for that parameter, not the emissions or leakage or the number for the modelled emissions of vented stoves.

Very odd. I suggest you keep an eye on that because the current model uses 10% and that is far more likely to be their model of emissions (assuming no one is interested in the actual emissions of various improved stoves).

With respect to the 1.75 mg target, does that include ignition emissions, and if not, from when is the measurement started?

I hope everyone noticed that the stoves submitted to the CSI-Indonesia project were under 0.7, not 1.7. To tell you the truth I don’t think they are optimized. There is still room for improvement.

Because I am not listing names, I can give the following achievements for PM2.5 for 13 of the stoves submitted:

  1.36 mg/minute (This is an ND stick burning side-fed stove)

  1.89 

  1.33 

  1.63 

  2.08 TLUD with wood

21.01 

  8.78 

  7.71

21.63 

  3.84 

  0.67 TLUD with pellets

  0.69 Another TLUD with pellets

  5.58 

There are only 5, not 7. I mis-counted from a large sheet. One fan stove not listed was about 1.0 with pellets and 1.63 with wood.  I expect there are already 10 stoves on the open market that will reach the 1.75 mg target consistently. The fuel was 14% moisture Teak, the pellets were 6-8% moisture Albasia.

For additional reference, the very cleanest coal stoves in Ulaanbaatar achieved a performance of just under 0.21 mg/minute however the tests are at higher power (a penalty) and much longer which spreads the ignition emissions over more hours (a bonus). Those are chimney stoves so 10% of that is about 0.02 mg/minute. After being well-lit they have zero emissions, actually cleaning the ambient air then runs into the stove and emitting nothing detectable.   We frequently see this happening in the TLUD’s. Depending on the stove, after pyrolysation is finished they emit no particles at all because they are really hot and there is only coke left.

There is virtually no leakage into the home for any of the stoves. When the pot is lifted, the fire dies suddenly and air rushes into the pot hole (assuming they are cooking over the hole not the stove top) and up the chimney. All the accepted stoves run at a negative internal pressure. They don’t leak anything out operated normally.

I think the best performing mass produced stove on the market is the Mini Dul which reached 2.03 mg/minute with an average fire power of 6.3 kW (3 hours). 

The problem with a metric like mass emitted per minute is that it is not tied to a power level, so burning less fuel reduces the mass emitted. Reducing the fire power to 5.4 kW would reduce the PM2.5 to 1.75 mg/min and there you have it. In short, you can game the rating system.

Here is further encouragement from Ulaanbaatar where 175,000 greatly improved stoves have contributed significantly to reducing the city’s air pollution (issued May, 2015):

This achievement is far better than the prediction made by Berkeley last year (their ‘best case’ scenario) which conditioned their (higher than current) predicted PM number to be achieved in future after an as yet undiscovered ‘breakthrough technology’ plus processing the fuel. What has been achieved now was done without changing either the fuel or the processing of it. Just the stoves, and they are not optimized yet either. 

The air quality inside the homes is far better than outside (multiple studies) showing that leakage from chimney stoves into the room is very low even with horrific outdoor air quality.  The PM2.5 reduction (blue bars) is about 65% for the whole city while the population continued to increase (green line). A combination of factors is expected to have made a contribution, but the only hardware intervention were the 175,000 stoves (red line) and a few apartment building boilers (in the dozens?)

So stoves are making significant impacts in several fronts. Keep them burning clean!

Regards

Crispin

Dear Crispin,

I think that the WHO figured on only 75% going out of the room up the chimney.

The thinking is that the smoke comes back in the windows, the stove leaks into the room, especially when the pot is removed, or from back drafting, etc.

I've seen some of this in kitchens but it is strange to me that "Indoor Emissions" is used for a measurement of CO and PM2.5 out of the chimney.

The biomass stoves that scored less than 1.75mg/min PM2.5 in the Indonesia tests are so great! If an inventor sends one to Stove Camp it will very probably win and he or she wins the $250 prize!

We'll pay for the shipping!

Best,

Dean

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