[Stoves] Key differences of performance test protocols for household biomass cookstoves

[Crispin Pemberton-Pigott]

Dear Otto

 

The claim, if presented as a comparison between the energy that goes into a
power station compared with the fuel burning in a stove is an apples and
oranges comparison because the energy that went into making the wood is not
considered.

 

It is presented of course in a patently misleading manner as if an open fire
is 'efficient'. It depends on how much of the tree is wasted in the field,
how much is lost during ignition and how much is left smouldering after the
cooking is finished.

 

It is this sort of thing that gives stoves projects a bad name.

 

As for time to boil, a Vest stove will boil water at a rate of 3 minutes per
litre measured from the time of ignition, i.e. light the match and start the
clock, and it will boil 2.5 litres in 7.5 minutes. That is much faster than
anything on the chart. I wonder why it is not included as it has been
available for 10 years. The Peko Pe has been available much longer.

 

The way to really misrepresent the performance of a stove in terms of its
fuel consumption is to calculate the energy used in the fire rather than the
energy that was standing in the forest when the fuel cycle started. Then
compare it with the energy in the ground that needs to be dug up to make
electricity.

 

The numbers quote for an induction cooker are clearly wrong. Yixiang Zhang
and I looked at every model available in a Chinese mall and none were less
than 88% efficient. So even the worst of them, from, power station to hot
water, is more efficient that the most perfectly operated open fire not
counting forest losses and burnout.

 

And that's enough of that.

Crispin

 

From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of
Otto Formo
Sent: Saturday, July 05, 2014 1:02 AM
To: Stoves Bioenergylist
Subject: Re: [Stoves] Key differences of performance test protocols for
household biomass cookstoves

 

Dear stovers,
 
I do not know what kind of gasifier unit the Low Tech Magazine, are refering
to and have tested, but for sure, the ND Peko Pe, will boil 2,5 L of water
in less than 10 mins, using wood pellets from Pine. (Woodchips or almost any
type of dry biomass, moisture content less than 15%, will do the same).
That should indicate a different result, mentioned in the diagram, where the
gasifier came third.
 
The efficiency of the Peko Pe, tested in Copenhagen in 1996, varied from 25
- 29%, depending of the type of fuel.
 
How the Rocket stove can reach a therminal efficiency up to 54%, is to good
to be true.
 
Have a Nice summer.
 
Otto
 

Dear Crispin - thank you for sharing this,  

 

Have you (or anyone else) by any chance read this article
http://www.lowtechmagazine.com/2014/06/thermal-efficiency-cooking-stoves.htm
l 

 

It a real mind turner to say the least.... I would be very interested to
hear some of your thoughts on this matter. To quote one of the opening
paragraphs - 

 

''In fact, an electric cooking stove is only half as efficient as a
well-tended open fire, while a gas hob is only half as effective as a
biomass rocket stove. And even though indoor air pollution is less of an
issue with modern cooking stoves, research indicates that pollution levels
in western kitchens can be surprisingly high.'' 

 

The author then follows that article up with this one -
http://www.lowtechmagazine.com/2014/07/cooking-pot-insulation-key-to-sustain
able-cooking.html

 

What do you think? I think I need to double my forestry efforts. 

Kind Regards, 

 

Teddy 

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