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Still D.,Aprovecho Research Center | Bentson S.,Aprovecho Research Center | Li H.,Beijing University of Chemical Technology

The widespread adoption and sustained use of modern cookstoves has the potential to reduce harmful effects to climate, health, and the well-being of approximately one-third of the world’s population that currently rely on biomass fuel for cooking and heating. In an effort to understand and develop cleaner burning and more efficient cookstoves, 15 stove design and fuel/loading combinations were evaluated in the laboratory using the International Workshop Agreement’s five-tiered (0–4) rating system for fuel use and emissions. The designs evaluated include rocket-type combustion chamber models including reduced firepower, sunken pots, and chimneys (three stoves); gasifier-type combustion chambers using prepared fuels in the form of wood pellets (four stoves); forced draft stoves with a small electric fan (five stoves); and a single insulated charcoal stove with preheated secondary air. It was found that a charcoal burning stove was the only stove to meet all the Tier 4 levels of performance. Achieving over 40% thermal efficiency at high power was made possible by reducing firepower and gaps around the pot, although batch-fed stoves generally do not “turn down” for optimal low power performance. While all stoves met Tier 4 for carbon monoxide, only stoves equipped with electrical fans reduced respirable particulate matter to Tier 4 levels. Finally, stoves with chimneys and integrated pots were fuel efficient and virtually eliminated indoor emissions. It is hoped that these design techniques will be useful in further development and evolution of high-performance cookstove designs. © 2014, International Association for Ecology and Health. Source

Grabow K.,Aprovecho Research Center | Still D.,Aprovecho Research Center | Bentson S.,Aprovecho Research Center
Energy for Sustainable Development

Indoor air pollution from biomass cookstoves seriously affects human health worldwide. This study investigated the effect of increasing air exchange rates in a Test Kitchen. Opening the door and window in a Test Kitchen lowered the particulate matter (PM) 1-hour concentrations between 93 and 98% compared to the closed kitchen, and the carbon monoxide (CO) 1-hour concentrations were 83 to 95% lower. © 2013 International Energy Initiative. Source

MacCarty N.,Aprovecho Research Center | Still D.,Aprovecho Research Center | Ogle D.,Aprovecho Research Center
Energy for Sustainable Development

Improved cooking stove projects in the developing world have the potential to reduce deforestation, improve health, and slow climate change. To meet these requirements, stoves must be carefully designed through thorough testing and verification of performance. The systematic investigation of the heat transfer and combustion efficiency of stove design in the laboratory sheds light on what technologies work best and helps to ensure that stoves being disseminated are truly a significant improvement over traditional cooking methods.Performance of 50 different stove designs was investigated using the 2003 University of California-Berkeley (UCB) revised Water Boiling Test (WBT) Version 3.0 to compare the fuel use, carbon monoxide (CO) and particulate matter (PM) emissions produced. While these laboratory tests do not necessarily predict field performance for actual cooking, the elimination of variables such as fuel, tending, and moisture content, helps to isolate and compare the technical properties of stove design. Stoves tested fell under 7 main categories: simple stoves without combustion chambers, stoves with rocket-type combustion chambers, gasifier stoves, fan-assisted stoves, charcoal-burning stoves, liquid/gas fuel stoves, and wood-burning stoves with chimneys. A carefully made three-stone fire was also tested for comparison. Results showed that:. Stoves without well-designed combustion chambers may reduce fuel use in comparison to the three-stone fire but do not necessarily decrease and can potentially increase emissions of CO and PM.Rocket-type stoves can reduce fuel use by 33%, CO emissions by 75%, and PM emissions by 46% on average in comparison to the three-stone fire.Use of a pot skirt can reduce fuel use and emissions by 25-30%.When operating well, gasifier stoves can reduce particulate matter substantially, averaging 90% improvement over the three-stone fire. Five forced air stoves reduced fuel use by an average of 40% and emissions by 90% over the three-stone fire. Traditional charcoal stoves use about the same amount of energy as the three-stone fire to complete a task (not counting the energy lost in making the charcoal, which can be as much as 70%) and produce up to two times more carbon monoxide and 80% less PM. A rocket-type charcoal stove can reduce this energy consumption by one third and CO emission by at least one half. Liquid fuels generally exhibit less energy use and emissions. Kerosene can emit higher levels of PM than some improved wood stoves when not operating properly. Well-designed stoves with chimneys remove smoke from the kitchen while fuel use is generally directly related to how much of the pot is in direct contact with the flames.From this data, it was possible to recommend benchmarks of improved cookstove performance. Benchmarks were suggested at levels that were achievable using known materials and manufacturing techniques, yet still aspirational, ensuring each stove design is carefully tested and optimized for highest efficiencies. It is hoped that these benchmarks can be used as the first step toward international performance standards for cooking stoves. Five of the stoves presented here were also tested at the US EPA, with results agreeing within 20% or better on all fuel and emissions measures, suggesting standard evaluation at various locations is possible. © 2010 Elsevier Inc. Source

Bentson S.,Aprovecho Research Center | Still D.,Aprovecho Research Center | Thompson R.,Aprovecho Research Center | Grabow K.,Aprovecho Research Center
Energy for Sustainable Development

Researchers at the Aprovecho Research Center tested 14 charcoal cookstoves using the Water Boiling Test 4.1.2. The protocol does not specify how much fuel should be loaded into the stove, and most stoves could not boil 5. L of water without a lid. The amount of fuel loaded was suspected of affecting stove performance, and the use of a lid allows the stove to be tested over a greater range of firepower. Each stove was tested at the maximum fuel load as defined by the volume of the combustion chamber, and minimum fuel load needed to complete the modified test. A lid was used in all tests, a modification to the WBT4.1.2. The study finds that fuel use to complete a water boiling task is reduced by decreasing the amount of fuel that is loaded into the stove. When each of the stoves was loaded with the minimum fuel required to complete the cooking task, the range in fuel consumption was small (150. g-300. g). When the combustion chambers in the stoves were fully loaded, the range in fuel consumption (200. g-1600. g) was dramatically larger. The initial fuel load used during a WBT was found to be an important and determining variable influencing the performance of the stove. © 2012 Elsevier Inc. Source

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