Improved Biomass Cooking Stoves

Andrew J Heggie June 2002

Here I post pictures which may help to explain the evolution of what I was trying to do with my steam aspirator. I have had it successfully running but whilst it sustains combustion in a device that self extinguishes in the absence of a fan, it needs much more fettling. In fact the steam content very much modifies the flame, such that I do not think my monotube boiler and nozzle are at all matched to the task.

I now think it would probably better suit when used to provide only primary air or as an eductor. In essence I must be achieving very poor mass and power ratios on the aspirator, such that Ken Boak's mechanical propeller could well have better conversion of the steam to air motion.

I have also now bought some other tubes with which to demonstrate.

Andrew Heggie

andrew.heggie@dtn.ntl.com

My initial monotube coil (made from ~2.5m of cunifer brake pipe) producing steam in the flame of my small (2.5 litre table top demonstrator) cook stove being powered by a small electric blower.
	Monotube Coil
The same with a view of the pressurised water reservoir and a propane burner nozzle attached.
	Pressurized Water Reservoir with Burner Nozzle
6mm coanda nozzle operating on low pressure compressed air prior to being attached to the steam coil.

Paul Anderson February 21, 2002

This is my report on the February 2002 developments with the Juntos (Together) stove.

(Paul S. Anderson) Jan 31, 2002

We are making some progress on the Juntos stove.

Yes, I do have a two-stage fire (or 2-level fire) or fires on each of 2 levels. Or maybe even could be called three (3) levels:

Pyrolyser with Horizontal Burner Alex English March 24, 2000

The following three images relate to single experiment. The goal was to set up a forced air burner for the gasses from a top-down pyrolyser. This is a concept which could be scaled up for firing a conventional boiler, kiln or __________(you fill in the blank).

Mike Bess, Energy for Sustainable Development, UK

Selling Lakech Mercato Addis Ababa

Alex English March 25, 1999

The testing was done with the boiler induced draft fan running constantly. It normally cycles to meet demand. The fuel was unseasoned Red Maple slab wood.

CO2 and CO % dry volume basis. 0 CO means less than 1000 ppmv.
Stack temperature in degrees F.

Alex English (Dec 18/97)

Check out a Thesis by Grant Ballard-Tremeer which promotes the use of vent hoods for the testing and evaluation of rural cooking stoves. http://www.ilink.co.za/~grantt/

After reading his thesis I was motivated to try and apply it to the testing of the One-Can Charcoal Making stove.

T. B. Reed and Ron Larson

*Presented at the "Developments in Thermochemical Biomass Conversion" Conference, Banff, Canada, 20-24 May, 1996.

Introduction -

A.The Problem

Since the beginning of civilization wood and biomass have been used for cooking. Over 2 billion people cook badly on inefficient wood stoves that waste wood, cause health problems and destroy the forest. Electricity, gas or liquid fuels are preferred for cooking - when they can be obtained, but they depend on having a suitable infrastructure and are often not available in developing countries. In the last few decades, many improved wood stoves have been developed (the Chula, the Hiko, the Maendeleo, the Kuni Mbili, etc.), but the new wood stoves are often more difficult to manufacture, often more heat goes to the stove than to the food, and they do not offer good control of cooking rate. They are not always accepted by the cooks for whom they are developed.[1] Because of the problems of wood cooking, people often cook over charcoal. However, charcoal manufacture is very wasteful of energy and very polluting, so the problems of the wood stove are externalized but not solved.

A.THE SOLUTION

Gas is preferred for cooking wherever it is available. Gas can be made from wood and biomass in gasifiers developed in this century, but these gasifiers are generally too big for home use. A downdraft stove for domestic cooking is now being manufactured in China.[2] We have developed a new "inverted downdraft gasifier" stove shown in Fig. 1. It operates using only natural convection. The rate of gas production and heating is controlled by the primary air supply to the gasifier. As an option, the gasifier can make charcoal with a 20-25% yield. The wood-gas stove consists of an "inverted downdraft gasifier" (shown in Fig. 2) plus a burner to mix air and gas and burn cleanly (Fig. 3). These sections are discussed below. The stove has been started and operated indoors with no exhaust fans and no odor of burning wood. However, we believe that there is still much work to be done in optimizing the stove for various fuels, adapting it to various cooking situations and developing other uses. For that reason we are publishing our preliminary results and hope that others will help adapt these principles to improve world cooking and wood conservation.