[Stoves] Rotary project question

Mon Nov 27 08:36:40 CST 2023

Dear Paul

As I am presently designing large cooking stoves for Uganda the question is relevant and I may be able to provide a couple of insights.

The schools use stoves up to 300 litres, in the main, not larger as is often the case in Rwanda next door.  So the first question is: what is the pot capacity?

There are a great many boarding schools in Uganda so it is likely that the places mentioned are boarding schools which use far more wood than day schools.  High mass institutional brick stoves are common and using them is quite fuel efficient at low power which covers a lot of meal preparation.  Meals are heavy in beans and posho which are longer cooking meals than rice (usually). Is it a boarding school?

Durability is a huge issue with rural institutional stoves.  In Rwanda it is common to see a school budget of $200-$500 per term for rebuilding cracked and broken stoves.   Is there any sort of warranty about working life in hours or months that the producer is willing to guarantee?  We normally require 2 years free maintenance.

Fuel consumption:  Fuel saving is a loose term and it should be expressed either as the hot stove fuel efficiency (protocol available from me) or the cooking of two disparate meals such as rice and beans (very short and very long).  What is the proposed design and has it been tested by outside parties for evaluation?   Comparisons are available for checking the fuel consumption per student.  That is a good gross metric.

Pots: At that price the stove should include a modern pot with lid and handles, sealed into the stove with no leaks around, and a chimney. The pot should have a 3mm bottom at least, and 2mm wall thickness, at least.  The bottom corner should be radiused so food does not stick in the bottom corner. All internal welds have to be smoothed and there must be a pair of handles for easy removal.  The pot material must be a food grade SS304 or better.   The pots will be approximately 1/3 the price of the stoves you describe.

It is quite unnecessary to have a fan and solar panels to make a high performance wood stove in Uganda.  There are designs available to you for the asking.  Avoid the designs promoted by the Ministries as they are essentially 1990's Rocket Stoves.

There is available for download a presentation made last on exactly the designs you require.  You can have the detailed design in the size you require, from 50 to 300 litres (6 sizes).  The link is on my website:

https://www.newdawnengineering.com/website/library/Papers+Articles/CAU/CAU_FREPDC%20_2023/

Warning - it is a large PPT because it contains a lot of videos.  Just click on the link and chose where to save it. If someone has a design they want to simulate contact me directly.

A fan is a substitute for a properly designed chimney.  As a school there is usually enough space to have a chimney - about 4.2m tall.  A major advantage of a chimney over a fan is that the system is likely to run the combustion at a negative pressure, so there are few leaks from the stove into the kitchen, if any.  If the chimney is effective at removing the fumes from a fan-driven fire, it is likely it would work even better without the fan.  Almost all fan-drive fires have too much air entering and exiting the fire without doing anything useful.

If such a fan stove exists, I would be interested to see the gas emissions measured at the exit from the stove body.  In particular I want to see the CO and oxygen concentrations over the period of a high power heating and lower simmering run, typical of many food cooking sequences.  If the O2 is generally over 12% it is losing heat for nothing, and if it is under 8% it is starving and will be smoky.  These guidelines apply whether it is at high or low power.

Heat distribution: as you will sees in the videos, there are serious problems encountered with getting heat distributed over large pots when the combustion chamber is constrained.  Does the proposed stove have a "combustion chamber" or just an open or large cylindrical space below the pot?

Charcoal: Charcoal is a different fuel altogether from wood and requires a different type of combustion chamber and air supply.  It is rare to find a stove that burns both fuels "well".

You may be able to get the Forestry College in the West or CREEC lab in Kampala to evaluate the emissions from the proposed stove.  It can be done in the field.  If you fail in that regard, I can test it when I am there next.

In the meantime I would be happy to review any drawings or photos you have been given to estimate what they are trying to sell.

Best regards

Crispin

Past Sergeant-At-Arms, Malkerns Rotary Club, Eswatini

Senior Technical Advisor to ESMAP and the Clean Cooking Fund

crispinpigott at outlook.com

PS I cannot see the video as I am in Beijing at the moment but in the coming days I will look.

________________________________
From: Stoves <stoves-bounces at lists.bioenergylists.org> on behalf of Paul Arveson <paularveson at gmail.com>
Sent: November 27, 2023 8:57
To: Discussion of biomass cooking stoves <stoves at lists.bioenergylists.org>
Subject: [Stoves] Rotary project question

I received this from a friend and would appreciate your comments:

"I received the email below from a Rotary member in Ithaca New York.  She has put together an $11,620 project (attached) to pay for Vron Engineering of Kampala, Uganda, to build four fuel-efficient stoves at schools in Gulu, Uganda, enhanced with a PV-powered fan to regulate the cooking temperature.  Vron Engineering claims their unit reduces firewood or charcoal use by 80%.   https://www.youtube.com/watch?v=4SyWCc-EGis.  The Rotary presentation is very professional, but my unscientific mind is skeptical.  I know that clean cookstoves reduce firewood use, but it seems doubtful that adding a PV panel, battery and fan would further reduce fuel use.  And without the PV panel, it seems excessive to spend $11,000 to demonstrate that clean cookstoves (with stovepipes) actually save fuel—something everyone already knows.  Your thoughts?"

Paul Arveson
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