[Stoves] Vesto emissions - TLUD with Pellets

[Crispin Pemberton-Pigott]

Dear Friends

 

Although the stove has been around for 10 years, there is never anything
heard of the emissions performance of a Vesto so I have decided to send a
little to the group.

 

I found a really old Vesto (2004) at YDD in Yogyakarta a couple of years ago
and ran it as a TLUD with locally produced wood pellets to see how it
worked.

 

This is Prianti Utami holding the sample tube.

 



 

This is the steady state combustion: 

CO2 5.6% (by calculation)

Excess air ?290%

CO concentration 183 ppm

CO/CO2 ratio 0.03%

High power heat transfer efficiency ?35%

Low power heat transfer efficiency (burning remnant charcoal) >60%

 



 

The combustion chamber has a lever-controlled primary air supply with free
flowing secondary air plus a portion of the primary air is preheated and
supplied as secondary (sorry, but it is complicated). 

 

In later years the secondary air supply holes were reduced in number by 25%
which limits the excess air even further.  It reduces the high power limit
but improves combustion generally.

 

Note to Saloop and others: This stove architecture with descending preheated
primary (and/or secondary) air has proportions that are dictated by the % of
oxygen in the atmosphere, the density and the thermal mass of air. In other
words, the entrance heights and primary/secondary air split follows a set of
ratios dictated by The Earth which taken together with the oxygen content of
the fuel itself, show where the optimum performance lies.

 

Here is a picture of the flame from a Vesto burning switchgrass pellets in
TLUD mode (it can also burn in a regular updraft mode):

 



Note the complete absence of any central spire of flame. 

 

Solid fuel combustion regulations often seek a CO/CO2 limit of 2% in part
because it is (apparently) not considered dangerous given 'standard' air
turnover rates and also because it is achievable. Lately the performance of
wood-fired heating stoves and cooking stoves have greatly exceeded these
standards when using pellets (processed fuel).

 

Given that may 'high end fuels' like LPG and kerosene and ethanol are highly
processed, it seems reasonable that the wood burning community demand 'equal
treatment' meaning that there is no sound reason for solid fuels, as a
group, to be rejected as 'modern fuels' as has apparently been done in the
Nov 2014 WHO document which basically claims they are inherently unable to
burn cleanly.  There is mention repeatedly in documents that 'only stoves
with a fan' can burn biomass cleanly which is disproven by this one
measurement (if it was necessary to demonstrate it at all - there are lots
of other examples).  The biomass stove community as a group needs to
understand this and its implications, and demonstrate how these widely
available, inexpensive and low cost fuels can be applied safely and
consistently to cooking and heating tasks.

 

Regards

Crispin

 

 

Crispin Pemberton-Pigott

 <mailto:crispin at newdawn.sz> crispin at newdawn.sz 

Managing Director

New Dawn Engineering

 <http://www.newdawnengineering.com/> www.newdawnengineering.com

 

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