The photo is sourced from the rechargenews.com
Nearly all coal-fired TPPs use the technology of pulverised coal combustion, which involves grinding coal to a powder as fine as talc and burning it in order to heat up water so as to subsequently produce high-pressure steam and activate the power generator. The key parameter for classifying coal-fired TPPs is critical water pressure (221 bar), at which water is converted to steam.
Subcritical coal-fired TPPs are equipped with boilers, in which the pressure does not exceed 221 bar and the temperature does not go above 550 degrees Celsius. In the steam boilers of supercritical TPPs, the pressure reaches 243 bar and the temperature goes up to 565 degrees Celsius. Finally, in case of ultra-supercritical TPPs, these figures go as high as 320 bar and 600–610 degrees Celsius, respectively.
As a result, the efficiency of converting thermal energy into electricity differs as well: the Massachusetts Institute of Technology (MIT) estimates that the efficiency of subcritical coal-fired TPPs is 34.3%, while supercritical and ultra-supercritical ones have the efficiency of 38.5% and 43.3%, respectively. The higher the efficiency, the less coal is required to produce a certain amount of electricity and the lower the greenhouse gas emissions are. This is why making changes to the structure of coal-fired power generation in favour of ultra-supercritical TPPs could help reduce specific emissions.
However, the pace of implementation of ultra-supercritical TPPs varies in different countries and regions. While by early 2023 the share of ultra-supercritical TPPs in the capacity structure of operating coal-fired power generation facilities was at 29% in China, it was at a mere 1% in India. The difference is even starker in case of coal-fired power generation facilities under construction: in China, ultra-supercritical coal-fired TPPs in that segment accounted for 87% of the overall capacity, while in India they represented just 5%. Consequently, China and India will demonstrate slightly different dynamics of greenhouse gas emissions from coal-fired power generation in the coming years.
