Thermal Performance and Fossil CO₂ Emissions of Coal–Wood Chip Co-Firing at the Timor-1 Power Plant: A Cycle-Tempo Simulation Study

Coal-fired power plants contribute to CO₂ emissions, highlighting the need for strategies to reduce fossil carbon emissions. This study investigated the effects of coal and wood chip co-firing on thermal efficiency and fossil CO₂ emission intensity at the Timor-1 Power Plant using Cycle-Tempo simulation. The baseline model was validated against Heat and Mass Balance (HMB) data at 100%, 75%, and 50% load, with deviations below 5%. A total of 105 simulation cases were evaluated across three load conditions, five excess air ratios, and seven wood chip co-firing ratios, all of which converged successfully. At 100% load and 20% excess air, co-firing with 30% wood chips by mass reduced net thermal efficiency from 32.64% to 31.95%. Fossil CO₂ emission intensity decreased from 1.0134 to 0.8144 kg CO₂/kWh, representing a reduction of approximately 19.64%. Increasing the excess air ratio from 10% to 30% reduced net thermal efficiency by 0.4–0.5 percentage points and increased fossil CO₂ emission intensity by 1.46–1.57%, depending on load. Each 5-percentage-point increase in wood chip proportion was associated with an efficiency decline of approximately 0.1 percentage point, while 30% co-firing increased fuel mass requirements by approximately 15%. Wood chip co-firing can reduce fossil CO₂ emission intensity with a relatively limited efficiency penalty. However, this reduction does not necessarily indicate lower total direct emissions or life-cycle emissions. Heat rate performance and fuel handling requirements should also be considered when determining suitable operating conditions.