Coal-fired power unit efficiency varies widely across different fleets, not only around the globe but often among different utilities in the same country and sometimes among individual units in the same utility or the same plant. Many factors impact unit efficiency, including design and operating parameters and coal quality. The current global average is 37.5 % (LHV, net), whereas state-of-the-art plants achieve efficiencies of over 47%. This means that around 2 GtCO2/y emissions could be saved if the gap between the average and the state-of-the-art power plant was closed. Several technological pathways are available, and they are often combined. However, the greatest results are achieved by increasing the steam parameters. Massive increases in both steam temperature to 700°C (760°C in the USA) and steam pressure to 35 MPa are targeted to create advanced ultrasupercritical (AUSC) power plants, and research and development (R&D) programmes on this topic are ongoing in China, India, Japan and the USA, and to a lesser extent in Europe. Such high steam conditions will allow around 50% efficiency but require new materials such as advanced austenitic steels and nickel-based alloys that need intense testing and engineering code certification before they can be used commercially. Research on AUSC technology is cutting edge and is applicable to different energy technologies including other fossil fuels, nuclear, and
renewables.
Double reheat, which is experiencing a revival in China, is another route to push efficiency towards the 50% mark. The Master Cycle 2, which is a modified double reheat cycle, yet to be applied in practice, and also conventional double reheat cycles with elevated turbine configurations, currently explored in China, both have potential to achieve 50% efficiency and more if advanced Ni-based alloys are used.
Significant increase in coal power plant efficiency can also be achieved by the recovery of flue gas heat, especially by using low pressure economisers which are becoming more popular and can increase plant efficiency up to 2 percentage points.
The development and deployment of cleaner, more efficient coal technologies require both relevant and predictable policies and government support to make it into the global market.
