Tier 4 and Beyond!(We’re closer than I thought…)

Dean Still Aprovecho Research Center

The International Working Agreement Tiers: Lots of different calculations

Thermal Efficiency is easy!

Increasing Heat Transfer Efficiency

• TARP-VE• Temperature• Area• Radiation• Proximity• Velocity• Evaporation• Don’t stop optimizing until the stove has 45% thermal efficiency

Forced Air Stoves, TLUDs, New Rockets, and a Charcoal Stove scored over 45% thermal efficiency by following Baldwin/Winiarski

Low Power Specific Consumption does not match High Power Thermal Efficiency

(MJ/min/L) Low Power Specific Consumption is influenced by the turn-down ratio

Not much CO when burning wood!

IWA CO and PM Metrics are based on the effect on health

Tier 4 for CO on all three measures

Forced air stoves can be Tier 4 for High Power PM

Low Power PM is different! (mg/min/L)

Stoves with chimneys and Indoor Emissions

Tier 4 and Beyond! • Over 45% thermal efficiency is made possible by following the heat transfer 

techniques described by Baldwin and Winiarski! • TLUDs, Forced Air stoves, Rockets, and charcoal stoves stoves can meet the Tier 4 

standards on all three metrics for CO (High Power, Low Power, and Indoor Emissions)!• Fan stoves  with superior mixing of gases, smoke, and fire reduce PM to Tier 4 

levels! •  Stoves with chimneys can be as fuel efficient as single pot stoves and the indoor 

emissions were essentially nonexistent! • Batch fed stoves often do not turn down enough at Low Power. Metering the fuel 

can remedy the problem!• Surprisingly, a charcoal burning stove met all the Tier 4 levels of performance!

Closing in on the solutions

• Envirofit agrees that stoves should cost $20 retail. ($10 wholesale)• Need 3 to 1 TDR in batch fed stoves• Add ease of use in metered fuel Fan stoves• Rockets: Smoke and gases go into tall flame until fully combusted• Optimize no cost stoves• Fan Side Feed: The answer ?• Only sell chimney stoves ? • Durability: Two years ?• Tier 23333 or Tier 44444 ?