According to “Taipower 10610 project”, the installed capacity of coal power plant increases 3.8GW from 2015 to 2025, but the generation mix of coal-fired including private owned company decreases from 45.4% to 30% during 2016–2025. Thus, it is expected part of coal-fired units newly installed will be idle after 2030 due to the carbon reduction. The paper proposes the replacing coal with bi-coal (co-firing of coal and bi-coal) as alternative to solve the idle coal-fired units by scenario studies and TIMES-ED simulation. The influence of emissions of particulate matter (PM) by co-firing of coal and bi-coal on the generation mix is also considered in terms of external cost. The scenarios proposed in the paper include business as usual (BAU), scenarios 1, 2 and 3 in terms of ratio of co-firing, in which the BAU does not consider the carbon reduction, but scenario 1–3 takes the “NDC” and “Greenhouse Gas Reduction and Management Act” into account. Among the scenario 1–3, scenario 1 does not consider the co-firing of coal and bio-coal, but it is assumed 20% in 2020 and increases linearly to 40% and 80% respectively in scenarios 2 and 3. Based on the results, the 60% of co-firing in 2040 and 80% in 2050 in scenario 3 can be as alternative for the idle coal-fired units, but it is not in scenario 2. In scenario 3, the emission factor of coal-fired generation with co-firing is more beneficial for carbon reduction than the gas-fired generation after 2040; on the other hand, due to the limitation of the available zero-carbon technologies and installed capacity, the generation of co-firing by bi-coal and coal correspondingly increases. Therefore, it shows that in order to achieve the target of carbon reduction in 2050, the development of zero-carbon generation technology, such as wind power and PV, is the first priority and then is the low-carbon co-firing technology. If the external cost of PM is considered in scenario 3, the mix generation of coal-fired is larger compared with the one in scenario 2 (40% co-firing in 2050). It can conclude the ratio of co-firing of coal and bi-coal is one of the key points for the development in the future. The insufficient for biomass and cost is the main issue for increasing the co-firing ratio. The results in the paper can clarify the role of bio-coal and coal co-firing technology in the carbon reduction path, and provide the reference for future technology deployment.
power sector, biomass, TIMES-ED, coal-fired generation.