Analysis: Efficiency of coal-fired power stations – evolution and prospects

  

According to Hans-Dieter Schilling (Energie-Fakten), the average efficiency of all coal power stations in the world currently stand at around 31%, leaving a vast potential to reduce coal consumption and CO2 emissions.

With countries like the USA and China looking set to continue relying heavily on coal for their energy needs, efficiency gains in electricity generation from coal-fired power stations will play a crucial part in reducing CO2 emissions at a global level. 

China and the EU have signed a partnership on climate change in September last year at the conclusion of a bilateral summit in Beijing (EurActiv, 5 Sept. 2005). The two agreed to build a demonstration near-zero emissions coal-fired power plant by the year 2020 as well as to cooperate on reducing the cost of key energy technologies.

In this analysis, Hans-Dieter Schilling (Energie-Fakten) looks at how technological progress in coal-fired power stations can lead to significant energy-efficiency gains and reduced CO2 emissions.

In the early days of electricity generation from coal at the end of the 19th century, the piston engines that were used at the time operated at about 1% efficiency, according to Schilling. This meant 12.3 kg of coal was needed for the generation of 1 kWh, resulting in 37 kg CO2 emissions.

Experience and R&D developments such as intermediate heating, increase of steam parameters (pressure and temperature), cooling towers and the removal of SOx and NOx from exhaust gases have allowed for remarkable efficiency improvements, the study reports. 

According to Energie-Fakten, coal amounted to 23% of the global energy sources in 2002, using 3.4 billion tonne coal equivalents (tCE), the major part of which (2.8 billions tCE) produced 7000 billions kWh of electricity. Nowadays, with a world average efficiency of around 31%, coal-fired power stations is said to compare favorably with the upper range of any other power generation technology. 

Nevertheless, there remains significant potential to reduce consumption and CO2 emissions in many areas, the author underlines. In the EU-15, the future need for an additional 100,000 MW new capacity and replacement of 200,000 MW existing capacity in the upcoming 20 years should be seen as a unique opportunity for further developments in coal generation technology, says Schilling. 

In that perspective, H-D. Schilling lists the most relevant options:

  • Going on with increasing steam parameters ; 
  • Development of CO2 sequestration techniques in order to overcome large storage difficulties ;
  • Combination of coal gasification (with steam generation) and coal combustion, in order to use the advantages of gas turbines 
  • Direct combination with coal combustion under pressure – targeting 60% efficiency

While experiments in those directions are in their infancy, and still encounter major technical difficulties, Energie-Fakten considers it feasible "to have 55% efficiency available for the necessary replacement and addition of coal-fired power capacity."

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