Overview

More than half of the world's population—three billion people—cooks their food indoors using open fires or rudimentary stoves. Indoor burning of solid fuels releases toxic pollutants including particulate matter and carbon monoxide. These harmful cooking practices cause an estimated 1.9 million premature deaths annually (Global Alliance for Clean Cookstoves, 2010). As the household members most likely to cook family meals, women and children are most affected. The reliance on biomass fuels in developing nations has put considerable pressure not just on the safety of families, but on the environment as well, increasing both deforestation and greenhouse gas emissions.

In Sudan's war-torn region of Darfur, women must walk for hours to find firewood, risking attack every step of the way. In 2005, the U.S. government asked Dr. Ashok Gadgil, Deputy of Lawrence Berkeley National Lab's Energy Technologies Area, for a solution to this grave problem. His team designed a fuel-efficient cookstove which is tailored to Darfur's climate and cooking. The Berkeley-Darfur Stove requires less than half the fuel of traditional cooking methods, decreasing women's exposure to violence while collecting firewood and their need to trade food rations for fuel. (2011 BERC Symposium poster)

Building on this work, the Lab has extended its cookstove research and development to other regions as part of a larger effort to develop affordable and appropriate technology for the world's poorest households.

Research Areas

Efficiency

Researchers use comparable quantities of firewood and food to compare the efficiency of improved cookstoves with the traditional cooking method in the majority of developing countries, the three-stone open fire. In each stove test, researchers cook a fixed quantity of food on a three stone fire and the improved cookstove to compare fuel usage between the two. Efficiency tests allow researchers to compare different design alterations to estimate impact, predict the reduction in firewood use, and determine the carbon emissions reductions that will result from substituting an improved cookstove for a three-stone open fire.

How much less wood does a Berkeley-Darfur Stove or Berkeley-Ethiopia Stove use than a three-stonefire?
Researchers use comparable quantities of firewood and food to what is available in local context to compare the efficiency of the stoves with the traditional three-stone open fire. In each stove test, researchers cook a fixed quantity of food on both the three-stone fire and the Berkeley-Darfur Stove or Berkeley-Ethiopia Stove to compare fuel usage.

Efficiency tests allow researchers to:

Predict the impact that the stove will have for women. The more efficient the stove, the less wood the women will need to collect or buy for cooking.
Determine the carbon emissions reductions that will result from substituting the stove for a three-stone open fire.
Compare different design alterations under consideration so that we can estimate the impacts of each change on the stove.

Emissions

How much soot does the Berkeley-Darfur or Berkeley-Ethiopia Stove produce compared with the three-stone fire?
Researchers are currently characterizing the particles emitted by the traditional three-stone fire and the stoves and comparing the results. The results of these tests will be used to examine if the widespread implementation of advanced stoves such as the Berkeley-Darfur Stove and Berkeley-Ethiopia Stove might reduce undesirable impacts on climate change while also improving public health in developing nations. Black carbon and other soot particles emitted by cooking fires may be contributing to climate changes such as reduced precipitation and the melting of glaciers. See an evaluation of the Berkeley-Darfur Stove's emissions and efficiency here.

Reducing CO₂ emissions: Each stove saves a little over 1.5 metric tons of CO₂ per year. According to the US Environmental Protection Agency, the average US car (traveling 12,000 miles per year and getting 20 mpg) emits 5.2 metric tons of CO₂ per year. With stoves lasting an average of 5 years, each stove in the field reduces more CO₂ emissions than removing an average US car off the road for an entire year.

The World Health Organization estimates that 1.9 million people die prematurely each year from exposure to indoor smoke from burning solid fuels.

Stove Use

How much are the stoves being used and how efficiently are the cooks feeding the firewood?
Efficiency tests allow researchers to understand how much firewood the stoves can save under ideal lab conditions; however, it's also important to measure efficiency and use in the field. LBNL is studying small devices called Stove Use Monitors (SUMs) and plans to mount these small self-contained devices on Berkeley-Ethiopia Stoves to monitor and log stove temperature over several months of use. Periodically, a researcher in the field using a PDA or laptop computer will retrieve this information. The SUMs will enable LBNL to have a better understanding of how cookstoves are used. Information collected will be used to analyze the frequency of stove use, the "burn time" for each use, and the rate at which cooks are feeding firewood into the stove. Likewise, the data will help quantify the reduction in greenhouse gases resulting from the use of improved cookstoves.

Combustion

How can we optimize how fast the stove gets hot?
The heating rate of the stoves is controlled by many factors. These include the type of wood used to fuel the stove, the size of the pieces of wood used, environmental factors like humidity levels, and how the wood is fed into the stove, among others. Researchers are working towards quantifying how these variables change the heating rates of the stove. These findings will help users of the Berkeley-Darfur Stove and Berkeley-Ethiopia Stove better control heat, make more efficient use of their fuel, and optimize stove functioning.

What portion of the heating energy in the wood is transferred to the pot?
Comparing the total potential heating energy in the wood to the amount of heat affecting the cooking pot ultimately helps researchers determine the efficiency of stoves. This research is being conducted with the help of a Bomb Calorimeter. These devices determine the amount of heat released through combustion of a small amount of wood fuel burning inside a sealed vessel (called the bomb). Oxygen is used to ensure complete combustion of the wood. The heat from this bomb vessel is then transferred to water that surrounds it on all sides. Very sensitive thermometers are used to measure the temperature rise of the water and determine the amount of heat released though the combustion process.

Stove Modeling

Supported through a Federal doctoral fellowship, graduate student Jennifer Jones is working to incorporate computer generated stove modeling into stove design testing. Most stove literature to date has focused on experimental testing on stoves to learn about stove performance to obtain necessary data. We are excited to launch this new component to our work and hope to build a computational stove model that guides stove design and can be used to determine tradeoffs between increased stove efficiency and reduced emissions.

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