China’s power supply structure is dominated by coal-fired power. As China’s renewable power expands, coal-fired power units are required to improve flexibility to balance power system. However, more flexible operation of coal power units increases energy consumption and pollutant emissions. This paper examines the energy efficiency, CO2 and pollutant emissions characteristics of China's generic wind-coal combined power generation system, and discusses pollution-minimizing dispatch strategies by modeling three hypothetical scenarios of wind-coal combined power generation systems. For day-scale analyses, we find expected displacement rates of coal consumption and CO2 emission decrease by wind fraction rate, indicating reduced energy savings from wind power per unit of increase in wind capacity. For NOx emission, we find that expected displacement rate reaches maximum value of 112% when wind fraction rate is equal to 0.27.For week-scale analysis, we simulate the coal consumption rate and emission factors with and without an operation of shutdown and startup of coal power units in the system. We suggest future study on dispatch decisions of startup/shutdown of coal power units to optimize power generation economically and environmentally.
China has proposed an ambitious development plan for renewable energy (NDRC and SERC, 2011; NDRC and NEA, 2016; NEA and NDRC, 2017; Yuan, 2016a, b. The goal is to achieve 15% non-fossil energy supply by 2020 and 20% non-fossil energy supply by 2030, and the goal will mainly be achieved via expansion of wind and solar energy (Yuan et al., 2007, Yuan and Xu 2014a,b; Yuan, 2016a, b; Yuan and Na, 2016; Yuan and Lei, 2016; among others).With strong support of national policies, renewable power generation has experienced rapid development in the past decade (CEC, 2018). By the end of 2016, China has become the world's largest investor of wind and solar power capacity. Due to intermittency of wind and solar power generation, large-scale wind and solar integration onto power grid inevitably requires other generation sources to balance demand load (Denny and O’Malley, 2006; Valentino and Valenzuela, 2012; Lu et al., 2011; Lu et al., 2014; Liu et al., 2015; Na et al., 2018). China’s power supply structure is still dominated by coal-fired power, and the more flexible power sources such as gas turbine power generation and pumped-storage power generation account for only a small share. Many existing studies have studied the CO2 emissions scenarios in China’s energy and power system, but few works have addressed the impact of renewable integration on CO2emissions in the power system (Chen and Cai, 2017; Su and Fang, 2016; Liu et al., 2017; Peng and Xie, 2018; Zhou and Wang, 2018; Ye and Ren, 2018; Tang et al., 2018). In the three northern regions of China (North China, Northwest China, Northeast China), wind and solar power generation account for a larger proportion, and the system load is mainly balanced by coal-fired power units. Although wind and solar power can be considered to produce zero emissions, their intermittent and uncertainties can impose negative impacts on economics and emissions of peaking units in the system.