<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">Dear Crispin,<div class=""><br class=""></div><div class="">When we would turn for the night we would find the largest pieces of wood to add to the stove that would last a longer time. So that would be less surface area = slower burn. </div><div class="">I have wondered if pellets are made of different sizes? From the ones I have worked with they all seem to be the same size. Reason? If adding larger pellets having a bulk mass with less surface area might work for night.</div><div class=""><br class=""></div><div class="">Also; water is used a lot to store heat and release it slowly. A large (try large) pot filled with water on top would heat up during the day (perhaps insulated) and slowly give up its stored heat into a room at night (insulation removed). </div><div class=""><br class=""></div><div class="">Regards</div><div class=""><br class=""></div><div class="">Frank</div><div class=""><br class=""></div><div class=""><br class=""><div class=""><br class=""></div><div class=""><br class=""><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""><div><blockquote type="cite" class=""><div class="">On Dec 4, 2015, at 5:26 PM, Crispin Pemberton-Pigott <<a href="mailto:crispinpigott@outlook.com" class="">crispinpigott@outlook.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class="">
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Dear Frank</div>
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I think you may be on the right track. There are two different modes of use: brief heating of the room of water (cooking is often done with LPG or electricity if it happens to be on at the time) then "heating mode" which is hours long. </div>
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The social situation is quite complex. Except in Pamir, the rooms are heated one by one with a stove in each (that is a generalisation but close enough). So there are frequently multiple stoves with multiple cooking fuels in an extended family home, multiple
generations and because of ethnic diversity, many cooking behaviours and biomass fuel use patterns. </div>
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The major considerations looking at the stoves are: no provision for secondary air, general lack of chimney draft control and indistinct primary air control, ie no precise settings of anything. </div>
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Inserts for different fuels were my first guess before coming and I am leaning towards that at the moment. If the room is a bedroom and it is only heated at night, why not a TLUD coal insert? If it is rapid water heating with wood, remove the insert to make
room for the fuel (no one wants to chop wood into little fragments). </div>
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Today we will test a few stoves that have been tried in the field. Bread baking is very popular with each home having a tandoor. It consists of a purchased oven built into a classic form by the home owner using clay and hand tools. It is heated with small wood.
When it is reduced to coals the coals are covered with a metal tray and the dough is slapped onto the surfaces (it is cylindrical, either horizontal or vertical) and left for a few minutes. </div>
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The dough sticks there and bakes, basically using retained heat. It is pulled off after a few minutes. </div>
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I say a small shower room (bathing room) with a small stove in it that is only lit when in use. The stove heats the room and the bathwater. The chimney was shorter than the ones in the house. My estimation of the water heating efficiency for these stoves, including
the ones in the house is 3-15%.</div>
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Regards </div>
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Crispin </div>
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<div class="" style="word-wrap:break-word">Dear Crispin, Stovers,
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<div class="">Wondering what is left after the coal has done what it is going to do?</div>
<div class="">Are there clinkers? </div>
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<div class="">One idea might be to add a night time insert. That would look like a
<u class="">IIIIIIII</u></div>
<div class="">with baffles that go almost to the base. The base has fuel spread across the bottom. You lite the one close to the door and that burns up quickly but it takes longer to ignite the second baffle and even longer for the third and so on……</div>
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<div class="">Well you did ask for ideas.</div>
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<div class="">Frank</div>
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<div class="">Frank Shields</div>
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<div class="">On Dec 4, 2015, at 2:01 AM, Crispin Pemberton-Pigott <<a href="mailto:crispinpigott@outlook.com" class="">crispinpigott@outlook.com</a>> wrote:</div>
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Dear Friends</div>
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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.</div>
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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.</div>
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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.</div>
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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.</div>
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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.</div>
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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.</div>
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There is no obvious capacity to produce pelleted or chipped fuel. There is no energy available to do that mechanically.</div>
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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.<span class="x_Apple-converted-space"> </span></div>
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Homes frequently have one stove per room and only light them when the room is used.</div>
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Regards</div>
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Crispin</div>
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