Tuesday, January 11, 2005

How did the efficiency of coal-fired power stations evolve, and what can be expected in the future?

Generation of electricity using coal started at the end of the 19th century. The first power stations had an efficiency of around 1%, and needed 12.3 kg of coal for the generation of 1 kWh. This meant 37 kg CO2 emissions per kWh.

With increasing experience, in combination with research and development, these low efficiency levels improved rapidly. Increased technical experience with coal processing and combustion technology enabled a steady increase in the steam parameters 'pressure' and 'temperature', resulting in higher efficiency. In the years 1910, efficiency had already increased to 5%, reaching 20% by 1920. In the fifty's, power plants achieved 30% efficiency, but the average efficiency of all operating power plants was still a modest 17%. In the next stage, the use of cooling towers for the removal of heat that could no longer be converted to electricity became a requirement, in addition to the removal of SOx and NOx from exhaust gasses, resulting in a reduction of efficiency, since these facilities use energy. However, continuous development resulted around the mid 80's in an average efficiency of 38% for all power stations, and best values of 43%. In the second half of the nineties, a Danish power plant set a world record at 47%.

Power stations based on brown coal are a few % less efficient than stations using hard coal, because of the different nature of the fuel. Nevertheless, RWE's brown coal optimised power station 'BoA' that started operation in 2002, reached 45.3% efficiency, the highest value ever achieved by a brown coal power station.

The average efficiency of all coal power stations in the world is around 31%. Hence, there is an enormous potential to reduce coal consumption and CO2 emissions. For the next 20 years, the EU-15 needs an additional 100,000 MW new capacity and replacement of 200,000 MW existing capacity. Hence, a significant development in coal generation technology is taking place. In the next 10 years, efficiencies up to 55% can be expected. This means 223 g coal equivalent (CE) per kWh2.

Current and future efficiencies for coal-fired power stations, using comparable terms of reference, are in the upper ranges of all electricity generation technologies.

Download article

No comments: