ARC E-Newsletter 12/5/24: Achieving Turn Down Ratio (TDR) in Cooking and Heating Stoves
Aprovecho Research Center
Achieving Turn Down Ratio in Cooking & Heating Stoves
Do not burn the rice!
A stick fed cook stove can achieve a ~three to one turndown ratio (TDR) by burning more or fewer sticks per unit of time. In a low mass Rocket cook stove, ~five small sticks can boil the water/food and ~two to three small sticks can simmer it (without, hopefully, burning the rice).
The gas burner in a conventional furnace comes on when heat is needed and turns off when the thermostat indicates that the room is warm enough. The old style gas heater is either on or off.
A 10 to 1 TDR modern gas furnace can more economically run at higher and lower firepowers. Insulated, airtight homes can use more BTUs to heat water than to warm the home! Leaky houses can require a lot more energy to replace constant losses. (Reminds me of constantly bailing an old boat I used to own before it sank).
Batch fed, automated pellet heating stoves can have an adaptable ~five to one turndown ratio, burning 5 pounds of fuel per hour or one pound.
In cook stoves (and heating stoves), effective TDR can be achieved in several ways:
- The operator puts more or less wood into the combustion chamber (Rocket)
- Decreasing air entering into the stove slows the rate of combustion (TLUD)
- Simmering with just the made charcoal provides lower firepower (T-CHAR)
Trying to widen TDR while maintaining very low emissions, very low Black Carbon ratios, in affordable products, makes life fun!
Find the 2nd edition of "Clean Burning Biomass Cookstoves," resources, publications and information about our work at www.aprovecho.org
Find archived newsletters online at aprovecho.org/newsletters
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