Entries by Kim Still

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Aprovecho Announced as a Winner of the Wood Heater Design Challenge

The U.S. Department of Energy (DOE) Bioenergy Technologies Office (BETO), in collaboration with Brookhaven National Laboratory (BNL), Lawrence Berkeley National Laboratory (LBNL), and the Alliance for Green Heat, today announced the winning teams for the Wood Heater Design Challenge (WHDC).  Aprovecho Research Center, from Cottage Grove, Oregon, came in second place and won $25,000 with a novel burn pot, airflow configuration, and sensor package for pellet heaters. […]

Biochar Goals

A few years ago, on another series of hot summer days, Aprovecho hosted a seminar on biochar. About twenty enthusiasts from all over the US joined us for a biochar summer camp, lighting a lot of stoves and scaring the safety advisors. We needed more spark screens. At the closing event, we created a list […]


H.R.6316 – Clean Cooking Support Act

Following the COP26 international climate conference, Senator Susan Collins (R-ME) and Senator Dick Durbin (D-IL), have introduced a bill to accelerate access to clean cooking. Here is the opening text of the section defining the activities directed in the bill. H.R.6316 has been referred to the Subcommittee on Energy: SEC. 5. CLEAN COOKING PROGRAM. (a) Department Of […]


A Short History of Cookstove Durability

Tin can stove by Katska on Flickr The Problem with Metal It’s great to start making stoves and testing ideas with tincanium (cut up tin cans). Making new prototypes from tin cans is a quick, inexpensive way to start the design process but tin cans only last for a limited amount of time, depending on the […]

Predictive Testing of Cars and Wood Stoves

Testing a car on a dynamometer Written decades ago, the lab based tests for both biomass heating and cooking stoves were designed to achieve statistical validity by controlling variables. Because many real world variables were removed from the heating and cooking stove protocols, the results were known not to predict real world performance. Automobiles are […]

Reaching 50% Thermal Efficiency

Adjustable pot skirt, ssmstoves.com For good thermal efficiency, be sure that as much heat as possible is being transferred to the outside of the cooking pot. The temperature of the hot gas flowing past the surface of the pot is increased by 1.) Creating as much flame (1,100C) as possible in a low mass, insulated […]


Combustion Chamber Heat Loss

Illustration from Biomass Stoves: Engineering Design, Development, and Dissemination “Lightweight walls have the intrinsic potential for much higher performance than massive walls due to their lower thermal inertia.” –Baldwin, Biomass Stoves: Engineering Design, Development, and Dissemination, 1987 After about 80 minutes, the earthen mass wall in the illustration above gets hot enough to equal the heat […]


Emission Testing: Tuning a Stove Like a Race Car

Yesterday, two fine fellows who manufacture stoves in southern Oregon visited our lab. One of the very competent guys had just installed a Corvette engine in a Jaguar, for fun.  We quickly got on the same page when the ARC staff showed them how an emission hood (with both real time and gravimetric measurements) enables […]

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Watching a Rocket stove or a pellet stove (as above), it becomes obvious that metering the fuel is a primary factor in achieving close to complete combustion. When too much fuel is introduced into the combustion chamber, the emissions of smoke increase almost immediately. For the clean burning of biomass, the controlled metering of fuel […]

Clean Combustion Needs More Than Just Heat

Dr. Larry Winiarski wrote the ten rocket design principles We have been having a lot of fun doing a modern literature search: Surfing YouTube. YouTube is often years ahead of the slower, but probably more accurate, information in peer reviewed journal articles. I suppose that many people are looking at both. A shared misunderstanding seems […]