[Stoves] Dushanbe Stove

[Crispin Pemberton-Pigott]

Dear Friends

 

Continuing the conversation about the stoves in Tajikistan, here is a photo
of the most popular stove I could find. I visited a factory where these are
produced and was able to test one for about an hour.

 



 

The house in the photo has a very long horizontal chimney – perhaps 7 or 8
metres – which enhanced the efficiency quite a bit. The exit temperature was
under 100 C in the early and late/low power sessions. In other words it has
a condensing heat exchanger.

 

We tested one using a standard 4.2 metre tall chimney 110mm in diameter,
using a standard 2 kg load of local coal with kindling wood under it. The
average space heating efficiency, give or take, was 30%. This is the result
of having a high chimney gas temperature, high excess air and no control
over the air flow at any point. Late in the fire when there was a lot burn
rate, the efficiency dropped to 18% and was still sinking when I packed it
in.

 

The CO/CO2 ratio was steady at 21% during the late burn, something that can
only be achieved by ‘forcing’ the burn using retained heat and having no
secondary air in a usable form.

 

So this is the baseline. The stove is not used for cooking, only heating the
rooms and heating water. It is quite well made, the doors seal quite well if
closed. The welding quality is good. The main material is recycled 6-7mm
thick steel pipe.  If you want to think about the burn rate and how to
improve this, the required burn rate is about 300-500 g/hr. The target
energy efficiency will be 70% and remember it has to heat water.

 

The available materials are steel sheeting up to 6mm thick, and water pipes
in standard sizes from 4” to 16”.The chimney height will be 3-4 metres in
most cases. People are very familiar with the concept of ‘banking down’ a
stove for the night. The typical fuel load will be 4-8 kg of coal depending
on the altitude. In some places the winter temperature is below -40°C. All
stoves have to be able to burn wood as well at least part of the time.

 

There is no obvious capacity to produce pelleted or chipped fuel. There is
no energy available to do that mechanically.

 

Ideas are welcome – I am not developing products, just holding a discussion
for those who might. I will introduce the cooking and cultural complexities
later. First think about how to burn wood and coal at a low power – 3 to 5
kW – overnight. 

 

Homes frequently have one stove per room and only light them when the room
is used.

 

Regards

Crispin

 





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