No More Carbon? 

The popular Jiko stove, photo by AIDG on Flickr

With carbon prices low and support apparently shifting, perhaps thinking about market-based improved cook stoves is increasingly interesting?

In the Millennium Villages studies, a high-end retail price of something like $10 was recommended to sell stoves directly into the market. (Adkins, Tyler, al, 2010)

What can be accomplished in stoves already being sold without raising prices?

  • For instance, the pot supports in the Jiko shown above can be too high for optimal heat transfer efficiency 
  • The door needs to be tight fitting to effectively simmer food
  • Perhaps the combustion chamber is too big, wasting fuel?
  • Small changes in the refractory ceramic material used in the combustion chamber can double durability
  • A low cost pot skirt effectively reduces time to boil and fuel used to cook

On the other hand, Rocket stoves or even forced draft TLUDs could theoretically be made for ~ $10, if metal was replaced by refractory ceramic or similar materials.

ARC is looking into this.  

Sound interesting to anyone?

 “To him that will, ways are not wanting.” (George Herbert, 1640)

ARC Assists CSIR-Ghana in Capacity-Building 

In the first week of October, ARC Research and Development Engineer Jaden Berger visited CSIR-Ghana for capacity building training. The Council for Scientific and Industrial Research (CSIR) is the foremost national science and technology institution in Ghana.

The main focus of the visit was to teach them how to perform field testing using various sensor suites. CSIR was especially focussed on learning to perform KPTs (Kitchen Performance Tests) while using EXACT sensors from Climate Solutions Consulting. We also used other sensors CSIR already had: a PEMS (Portable Emissions Monitoring System) with a portable hood, an IAP (Indoor Air Pollution) meter, and an air quality sensor along with performing UCETs (Uncontrolled Cooking Efficiency Tests) during cooking to determine the efficiency of the stove.

Making observations of how cooks are using stoves.

Setting up a PEMS with a portable hood to measure stove emissions.

Testing was done at a secondary boy’s boarding school in Accra. The school cooks breakfast, lunch, and dinner for 3,000 students using a variety of improved and unimproved stoves. The stoves identified as the least efficient and highest emitters were the 12 wood stoves and 4 palm kernel stoves. (Palm kernels used to be considered agricultural waste from palm oil production but are now commonly used as fuel.) Several design meetings were held to determine a design that would increase efficiency, clean up emissions, and remove emissions from the room the cooks were in.

Palm kernel stoves in use for breakfast.

Weighing wood for three 24 hour-long KPTs.

Performing UCET measurements.

The next step is for CSIR to finalize a CAD model of the design along with some CFD analysis to predict if the prototype will work. ARC will then virtually meet with CSIR and their manufacturer to finalize the design and begin creating prototypes.

During the second week of the visit, ARC and CSIR worked on wrapping up older projects. This included gathering final data for a charcoal conversion efficiency study, creating a draft of the charcoal conversion efficiency protocol so that it can be published, and developing and using a durability protocol that is more applicable to conditions a stove will have to withstand in Ghana.

Taking measurements for creating a new durability protocol.

Overall, a successful trip with good progress made toward improving health and cooking conditions in Ghana.

Heat Transfer Efficiency!

Heat Transfer Efficiency!

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Wow, heat transfer efficiency is easy to understand! 

Read on…

Raising the Temperature of gases flowing next to the heat exchanger (the pot in a cook stove) is probably the most effective technique in a Rocket stove to increase heat transfer efficiency (use less wood for cooking).

Doubling the Temperature of gases doubles heat transfer efficiency.

Doubling the Area exposes to the gases doubles heat transfer efficiency.

Doubling the Velocity of gases ~doubles heat transfer efficiency.

Doubling Radiation increases heat transfer efficiency to the 4th power.

Increasing the view factor helps, too! That’s the proportion of the radiation strikes the bottom surface of the pot.

A 6mm to 7mm channel gap pot skirt increases heat transfer efficiency by ~ 25%.

Simmering at the needed low firepower can save a lot of fuel, too.

Appreciating Local Expertise

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Cooking over an open fire in Ghana. (Photo: Global Alliance for Clean Cookstoves)

Cooks are experts!

Community organizers often say that to be successful the solution has to come from the folks with the problem. Another important factor is to appreciate the culture and long evolved expertise in their technical and social solutions. The women at Rancho San Nicolas, where I lived for eight years, were incredibly skillful at cooking on an open fire and were understandably proud of their abilities when cooking perfect tortillas, fish, beans, soup, etc. At a fish camp, guys who were not cooking every day, had a lot of trouble making anything close to a succulent home cooked meal.

Along with the hundreds of technical skills that made ranching fun, culture made life easier and more beautiful. Ranch culture was at least half of competency and expertise. Laughing at life’s problems made overcoming them much more likely. Religion, nature, the beauty of living outdoors and liking the slow pace were strengths in my friends that I grew to envy and attempted to emulate.

Bringing innovations started with lots of failure. The first Rocket stoves became flowerpots. The first solar cookers became toilet seats and windows. Eventually, ARC appropriate technologists made prototypes that were simply put on public display. Of our many attempts to introduce ‘helpful’ technology, cement rat proof boxes were the biggest success.

We learned a lot more than we taught, starting with listening to our expert hosts. The shorter and higher firepower Rocket stove that has gone viral was created by women in 18 villages in Southern India. Dr. Winiarski had the idea and the cooks made it practical.

Over the Moon

A couple of weeks ago, Claudia Truesdell and Shane Washburn from Google’s X – The Moonshot Factory visited us for the day. We made lunch on an earthen Rocket stove and on a metal pot skirt stove with Jet-Flame while doing a field test that generated some numbers. Google’s X was interested in what we have learned since 1976. 

Our staff had various things to share. I found myself explaining how to improve fuel efficiency in high mass stoves. Maybe ~95% of biomass stoves in use are high mass (?), made from earthen mixtures. 40% clay and 60% sand works well, especially when a relatively dry mix is pounded into a form. Metal is hard to find, expensive when purchased, and even stainless steel doesn’t last for a very long time near the fire. Improving earthen stoves might help lots of people.

When we did seminars with the Partnership for Clean Indoor Air, we showed that fuel use could be reduced by a minimum of 30% by:

  • Moving the flame further away from the mass walls.
  • Lowering the pot closer (but not too close) to the fire to increase the temperature of gases contacting the pot .
  • Using a constant cross sectional pot support to increase heat transfer efficiency to the bottom of the pot.
  • Adding an adjustable pot skirt that, especially when tight, forces the hot gasses closer to the sides of the pot.
  • Nowadays, we suggest adding a Jet-Flame to improve both heat transfer and combustion efficiency.
  • Most importantly, as recommended by Mahatma Gandhi, adding a functional chimney!