The photo is sourced from Nikolay Kovalenko/Unsplash
The efficiency of ultra-supercritical coal-fired TPPs, i.e., the efficiency of converting thermal energy into electricity, ranges from 44% to 46%, whereas it hovers around 37% to 40% for supercritical TPPs and from 33% to 37% for subcritical ones. The higher the efficiency, the less coal is required to produce a certain amount of electricity and the lower the greenhouse gas emissions are.
The difference in efficiency is caused by the differences in the operating conditions of steam boilers at coal-fired TPPs. The technological threshold is critical water pressure (221 bar), at which the water is converted to steam. At subcritical coal-fired TPPs, pressure in steam boilers remains below 221 bar and the temperature doesn’t reach 550 degrees Celsius, whereas at supercritical ones the pressure and the temperature cannot be higher than 243 bar and 565 degrees Celsius, respectively. Meanwhile, at ultra-supercritical TPPs the pressure reaches 320 bar and the temperature goes up to 600–610 degrees Celsius.
China is well ahead of all other countries in terms of bringing ultra-supercritical TPPs online. According to Global Energy Monitor, the share of ultra-supercritical TPPs among the existing coal-fired power plants outside China by early 2024 was only 10% and made up just 19% in the segment of generating facilities under construction. Moreover, China is the world leader in the overall pace of bringing new coal-fired TPPs into operation: the country’s share in the global capacity of existing coal-fired power plants is 53% (1,136.7 GW out of 2,130.1 GW), and it accounts for 71% of coal-fired TPPs under construction (139.8 GW out of 197.3 GW).
Coal remains a key source of electricity for China. According to Ember, coal-fired TPPs provided 61% of China’s power output in 2022, while gas- and fuel oil-fired TPPs made up another 4.1%, with the total share of low-carbon sources at 34.9%.
