[Stoves] New document from ESMAP

Fri Jul 31 07:30:05 CDT 2015

Dear‎ Philip the Kerosene stove tester

I want you to clarify first which efficiency you are referring to so we are looking at the same result.

For the entertainment of the Group, Philip and I are both ‎on the ISO Working Group that is compiling a list of definitions of terms and there are many 'efficiencies'. An efficiency is a good ratio, a fraction, so there are lots of choices of what to put on top and bottom.

In the meantime I will have a look for some tests including the one mentioned below and something closer to the pressure head you describe.

On another note, a pressure head that is glowing red is far too hot to work properly. Even considering the delta T across the thickness of the material, being cooler on the inside, it will be impossible to avoid the decomposition of the fuel leaving free carbon in the gas. Once free, it deposits in sharp surfaces, grows, breaks off in the flowing gas stream and ‎blocks the nozzle. That's why pressure stoves and lanterns have a 'pricker' which is a thin wire used to unblock the nozzle.

I had not noticed a ‎relationship between the really hot evaporators and the overall efficiency. I did notice that the stove which had a pumped air bladder had a tendency to overheat the fuel with radiant heat from the head. I 'aged' the top surface by making it black, as if burned food had accumulated here and there. This changed the reflectivity and raised the fuel temperature well above the legal limit.

Is this radiation a large portion of the heat loss?‎ If so it would be easy to fix.

I'll get back to you soon‎ with example(s).
Thanks
Crispin

Dear Crispin

You say "A good kerosene stove is going to be above 45-50% efficient." I
have yet to find one doing above 42%, and a good average value was 35%.  The
better ones were pressure stoves; wick stoves were invariably poorer.

The interesting question is where all the losses come from. In the wick
stove it is outward radiation from the heater, which glows red-hot in
operation to provide the energy to evaporate the kerosene from the wick.
But the loss of efficiency in the pressure stoves really puzzles me.

Prof Philip Lloyd

Energy Institute

Cape Peninsula University of Technology

PO Box 652, Cape Town 8000

Tel:021 460 4216

Fax:021 460 3828

Cell: 083 441 5247

From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of
Crispin Pemberton-Pigott
Sent: 30 July 2015 10:23
To: Stoves
Subject: [Stoves] New document from ESMAP

Dear Friends of Big Reports

There is a document you can get at

https://openknowledge.worldbank.org/bitstream/handle/10986/21878/96499.pdf?s
equence=1

which is from ESMAP

It makes for very interesting reading, from great observations to howlers.
It appears to have been written mostly by policy makers but makes many
technical claims as well.

Some points are really worth debating here:

"LPG is a clean, non-toxic fuel that emits little particulate matter and
burns efficiently. Compared

to kerosene, it delivers double the heat for the same quantity used."

Which quantity would that be? Certainly not per $.  Mass? LPG has about the
same energy content per kg as kerosene so this claim surprised me. A good
kerosene stove is going to be above 45-50% efficient, fuel heat to pot heat.
LPG is about 65% efficient on a good day. I would say that is 30-45% better.

Maybe they meant LPG with a modern good condition burner compared with an
old wick stove. In that case if could be more than double. If we compare
really good kerosene stoves with LPG there is no difference. Peak efficiency
at, say, 1.25 kW is comparable though I have seen a cheap wick stove from
China that outperformed a new LPG stove at that power level (71% v.s. 65%).

Why is anyone so certain kerosene is such a bad fuel? Is it perhaps bad
stoves that cause the problem?  The long term answer is low pressure stoves
because they avoid all sorts of pressure-related problems and does away with
wicks at the same time (they lose effectiveness over time). We need some new
inventions.

One of the objections raise against kerosene compared with LPG in South
Africa was from the fuels industry. With LPG they control the distribution
right to the last mile. With kerosene, all sorts of people are involved in
micro trading fuel in plastic bags (!) and bottles.

Unlicensed people! Ordinary folks!

Anyway, have fun reading. There are contributions from all the usual
suspects. There are lots of great charts you can cite.

Regards

Crispin

PS I see they once again have omitted the stellar performance of the
super-clean TLUD coal stoves rolled out in Ulaanbaatar, the most expensive
and most successful externally funded stove project ever.  It is also the
first time a city's air pollution has been substantially improved (-63%)
without changing the fuel. Eat that, London.

This email has been protected by YAC (Yet Another Cleaner) http://www.yac.mx
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