Table 1. Design criteria and evaluation metrics considered throughout design and development of the semi-gasifier cookstove and pelletized biomass fuel combustion.
| Design Criteria | Evaluation Metrics | Target Performance Indexes | Achievement relative to Target |
|---|---|---|---|
| High energy utilization | Stove thermal efficiency (expressed as %) | >35% | >40% |
| Low pollutant emissions | Mass emitted of fine particulate matter (PM2.5) and carbon monoxide (CO) per mass of fuel burned and per energy unit delivered, and per task, under conditions of controlled and uncontrolled stove use | CO emission ≤9 g/MJd, and PM2.5 emission ≤168mg/MJd, matching the highest performance targets (Tier 4) set by the ISO International Working Agreement Tiered Cookstove Guidelines (ISO, 2012). | Achieved Tier 3 when including all data; excluding two high-emitting households, Tier 4 stove pollutant emission performance metrics met. |
| Ease and convenience during use | Duration and effort required for stove operation, including fuel loading and ignition before cooking; flame and firepower adjustment during cooking; ash removal | Cooking can begin within 3 minutes following ignition; firepower can be easily adjusted between the conditions of low power (30% of the maximum achievable power) and high power (100% of the maximum). | Met and exceeded goals for ignition speed and power variability. |
| Safety | Smooth surface and stable stove body; electrical safety; burn prevention in compliance with Biomass Stove Safety Protocol Guidelines (Gallagher et al., 2016) | Achieve the safest level (tier = 4), based on performance with respect to ten standardized protocols. | Achieved Tier 4 |
| Adaptability | Capacity of stove to perform multiple tasks, including diverse cooking activities and water boiling | Perform more than 80% of daily cooking activities and water boiling. | Intervention stoves used for many, but not all, daily cooking activities. |
| User acceptability | Users’ attitudes toward the new stove; initial and long-term choice to use (or to not use) the stove; use of the gasifier stove in replacement of, or in addition to, the traditional cookstove | More than 50% replacement of the traditional cookstove over the long-term (6 months) deployment. | In homes using the intervention stove, traditional and interventions stoves were used separately and for a similar number of meals per day. |
| Material cost and durability | Anticipated years of operation, under conditions of normal use; Initial cost and annual cost of repairs | Anticipated years of operation for more than 10 years under conditions of normal use; similar initial cost level to traditional cookstoves (RMB 1500 (US$215)); annual cost of repairs will be zero in the first three years, and less than RMB 70 (US$ 10) annually in the following years. | Durability yet to be determined. Initial capital cost < RMB 1600. Repairs cost < RMB 50 |