Dear Phil
Because a TLUD is so easy to make from cement, clay or metal, it is probably an option you want to consider. Experimenting is cheap. You may not have to make briquettes at all. You can also mix all sorts of fuels into the chamber – it does not have to be a ‘pine needle burning stove’. It can just be a stove. The cross-sectional area burning to produce the gas sets the power level (factored a bit for the fuel type). The hole that brings flames and smoke together (which can be a flat plate or a cone) is one way to have more assurance that the flame will be stable. If the physical distance from the burning flame to the fuel is short, there is more likelihood that the flame will help the burning of the fuel below (positive feedback). This enhances flame stability. The Peko Pe has such a short gap and you could start with that. The Vesto uses a clearly split chamber that has a primary air and fire section below and a secondary air section above with holes below that are uncovered progressively as the fuel burns down. The TLUD’s tend to have all primary air supplied through the fuel, 100%. In both cases the primary air is far less than needed to completely combust the fuel which is deliberate. In principle the fire is controllable by varying the primary air supply. The secondary air (usually a ring of holes or an annular gap like a POCA charcoal stove) provides enough air to complete the burn. Care is taken not to allow in more air than is needed because excess air cools the flame. If you get the primary/secondary ratio wrong the result (smoke) is pretty obvious. There is far less primary air required than most beginners would think. Most stoves had huge, pointless amounts of cold air running through them. It is the main reason they are so smoky (chilled flames go out). I think you should take up Paal’s offer of a design for the Peko Pe and start with that to see if there is any enthusiasm for a stove that cannot really be re-fuelled. It is a batch stove. There are places where they will work. With practise, the amount of fuel needed is learned. If you need to refuel it several times, then you would go to a more Vesto-like construction where the air is controllable and you can set it to the prevailing conditions. The name comes from Variable Energy STOve. If you mostly have char remaining in the box you open the primary air (it needs a different pri/sec split). I like the idea that you have easy access to verbal distribution channels! If it works, talk it up! Regards Crispin +++++ Or illegal to gather. (Clearly another detail I left out in the post.) In 1991, Nicaragua created national Reserves. I happen to live in one of them. The way this was done was large areas of privately owned land were included into the reserve. Restrictions were placed on land use but landowners were compensated by replacing a property tax with a "management fee" that the government pays the landowners. (The tax and the fee are both very small but it does seem to make sense.) One of the restrictions is that you cannot cut a tree over 100cm in diameter without a permit. As you might expect, most people ignore that law. My thinking is that rather than stepped up enforcement (which is virtually impossible and just creates hostilities), it seems like the right time to introduce some "solutions". In some parts of the reserve, including where I am, pine needles present a real fire danger. For example, about a year ago, 9 hectares burned on the property just north of us. Had there not been a road separating the properties or had the wind been stronger the fire would have continued on to our property. Thus, it seems like a good chance to address fire danger, illegal logging and inefficient cook stoves all together in a fashion that is a win for all. I am not anything more than a "creative Gringo" here (composting toilets are my other "project") but if I can come up with something which is accepted than there are NGOs that would probably be willing to run with the idea. The right solution has the local acceptance issue as well as how practical something is. My advantage is that I live here, I know the people and I see their transportation options. For many, transportation means walking 2-10km to get to the closest road. While someone external (and that could include the government) could come in, study the situation and come up with an approach, I am here. To take but one possibility, I can get a TLUD, feed it pine needles and if it works, show my neighbor. A week later, 100 people will know about it. If it gets accepted it is something easy to carry/deliver by horse. Building an enclosure with adobe uses existing skills and so on.
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